I bought the junk yard 1991 Husqvarna WMX 610 suspension more than a year earlier, but it took me a while to decide what to put it on. The possibilities seemed endless. Upgrade the 1992 chassis with my old 610 motor in it to make a 1991 Husqvarna WMX 610 with the 1992 sub frame and exhaust system, upgrade the 1986 Husqvarna 400 two stroke to make a smoker race bike or upgrade the White Power suspension on my 1991 Husqvarna WXE 350 chassis? It was a tough choice. I felt like I really needed three more sets of 1991 WMX 610 suspension, but I was pretty lucky to have gotten the one set that I did.
Junk Yard Parts
1991 Husqvarna WMX 386
The Lifan 150 Husqvarna goes WP
I have managed to purchase just about all 1991 Husqvarna four stroke specific parts that I have seen advertised for sale. Every complete, or nearly complete, 1991 Husqvarna four stroke I have ever seen advertised for sale is now sitting in my garage, and the few 1991 Husqvarna four strokes that I have seen parted out on eBay have also ended up largely in my garage. The 1991 Husqvarnas that I have seen parted out were mostly only partially complete, and I managed to get many of the important parts off of them. Buying used parts from salvage companies does tend to be rather expensive. Even when the prices are reasonable compared to other salvaged used motorcycle parts it is still a lot more money than complete, non-running bikes sell for.
Of the four 1991 Husqvarnas I have seen parted out on eBay two were 1991 WXE 350 Enduro bikes. I got a bunch of parts off of both of them, but mostly it ended up being the plastic that was such a good score. A lot of that 1991 plastic just hasn't been available either as original parts or aftermarket reproductions. The front fenders are available, as they are interchangeable with just about every year of Husqvarna. There are lots of front fenders around. The 1991 through 1994 radiator shrouds are also available as aftermarket reproductions, albeit at a rather steep price. That's it though. The rest of the 1991 plastic just hasn't been available, so snapping up some nice original plastic parts off of the 1991 WXE 350 bikes was a good score. I also got a complete exhaust system off of one of the 1991 WXE 350 bikes to replace the dented and actually worn out pipes and muffler on my 1991 Husqvarna WMX 610 that I have been riding off and on since 1998. That exhaust system was beat up when I got the bike in 1998, and it has only gotten worse over the years with lots of funky repairs to get it to hold together for just a few more rides.
The two 1991 Husqvarna 610 bikes that I have seen parted out on eBay were not very complete, really only a selection of the parts were listed. One was a WXE 610, and there was not much of it listed for sale. Just a few things, but not the motor and none of the suspension. The other one was a WMX 610, and the entire suspension system was listed. I bought it right then and there, as soon as I saw it advertised. I got not only the WMX 610 White Power forks and the WMX 610 White Power shock, but also the shock linkage, triple clamps, front brake caliper and front wheel. Everything required to do a complete suspension retrofit. The total price was $572 including shipping. A lot to pay for junky looking old parts, but I knew it was a jewel in disguise.
Then the parts just sat there in my garage for well over a year waiting for inspiration.
The easiest bike to upgrade would of course be the 1991 Husqvarna WXE 350, as the 1991 WMX 610 suspension parts would slip right on without any modification required. I toyed with this idea month after month, but what I kept coming back to was that my 386 stroker motor just didn't run well enough to justify the higher performance race suspension. When going slow on tight trails the 1991 WXE suspension was actually capable of delivering a smoother ride under certain conditions, and I kind of liked the idea of keeping the 1991 Husqvarna WXE 350 as close to stock as possible.
Throughout the summer of 2015 and much of the time during the winter of 2015 and the spring of 2016 the 9.7:1 386 stroker motor just wasn't running very well. It was requiring too much spark advance which caused a dramatic lack of low end power and a narrow and actually rather weak powerband. When I could get the spark timing down to 27 degrees BTDC the 386 stroker motor would sort of work, but only when the spark timing was down at 21 to 25 degrees BTDC did the 386 stroker motor really shine. A few times during the winter of 2015/2016 I happened to get some lower pressure gasoline in the 1991 WXE 350, and the 386 stroker motor was fun to ride with spark timing values of around 23 to 27 degrees BTDC. Most of the time though it was 29 to 33 degree BTDC spark timing and the 386 stroker motor was a turd very nearly just as bad as the stock 1991 Husqvarna WXE 350 motor had been with spark timing from 30 to 36 degrees BTDC.
I sort of just gave up on the 9.7:1 386 stroker motor. It wouldn't work most of the time, and I figured that I would need to split the cases again to have the stroke increased to 2.75" so that I could get the compression ratio up to 11:1 or 12:1. How high though? It depended on the gasoline. Sometimes the 9.7:1 386 stroker motor was just a hair away from working. With 28 degree BTDC spark timing it was so close, but it just wouldn't quite make torque at 3,500 to 5,000RPM no matter how carefully I adjusted the spark timing. When that was happening all I needed was a slight bump in the compression ratio. Just moving the crank pin out 0.020" for a 2.72" stroke length would yield a 10.4:1 compression ratio which would have done the trick. Then other times the 11:1 hot rod 610 motor would only run with huge 29 and 30 degree BTDC spark timing and the 9.7:1 386 stroker motor wouldn't run at all at any spark timing value up to 40 degrees BTDC. Just nothing, no torque and no top end power. Smooth and consistent with instant throttle response out to 7,000RPM, just hardly any torque at any engine speed above about 3,000RPM. When that was happening I would have needed to go beyond 11:1 on the little motor by stroking out to 2.75 or even 2.78 inches of stoke length.
Then the big shift came in the late spring to summer of 2016. All of a sudden I was very often able to run 23 or 25 degree BTDC spark timing in the 9.7:1 386 stroker. I took the small displacement bike out for some substantial rides, and it was really a blast to have less displacement to work with. There is no way around it, 577cc is way too much for a dirt bike. Even when the weight, size and bulk is exactly the same 350 to 400cc is a whole lot more fun on the trails. Instead of the game of "can I keep the tread blocks on the rear tire" like it is with the 610 the 386 stroker motor allowed a much better game of "how fast can I go".
What I ran up against though was that I couldn't go all that fast on the 1991 Husqvarna WXE 350. The suspension wasn't up to the task. After many months and many great rides on my resurrected 1991 Husqvarna WMX 610 the WXE suspension just wasn't cutting it anymore. When it really hit home that I couldn't ride the stock 1991 WXE suspension anymore was when I did the same long trail ride first on my 1991 Husqvarna WMX 610, and then a while later on the 1991 WXE 350 with the 386 stroker motor. With the 9.7:1 386 stroker motor delivering respectable torque everywhere from 3,000 to 8,000 and even 9,000RPM thanks to a 23 degree BTDC static timing setting there was just about enough power on tap to go fast. For the most part I wasn't even revving the 386 stroker motor out. I was just torquing along at around 3,500 to 7,000RPM, and it was just barely enough power to do the large heavy chassis justice. Acceleration certainly wasn't as fast as on the 610, but the 386 stroker motor was putting enough power to the ground to get the bike moving up to similar speeds on the trail.
What really hit me was that the 1991 Husqvarna WXE 350 White Power suspension just wasn't fast enough to handle those higher speeds I was used to on the 1991 Husqvarna WMX 610. I was having fun riding the 386 stroker motor, but I wasn't covering ground as fast and it was a lot more work than on the 1991 WMX 610. The 1991 WXE 350 White Power suspension works well at low speeds on tight trails, but when the single track opens up a bit and the speeds pick up or if there are some challenging bumps it is a different story. In 2014 when the only bike I had to ride was the stock 1991 Husqvarna WXE 350 it was pretty good. In direct compression to the 1991 Husqvarna WMX 610 though the WXE Enduro suspension is just not unacceptable. Dangerous even.
There are three problems with the 1991 Husqvarna WXE 350 White Power suspension compared to the 1991 Husqvarna WMX 610 White Power suspension. Medium to high speed harshness, lack of bump absorption on impacts and landings and poorly functioning rebound damping. The differences are rather slight, but they are there. Particularly on bigger faster rocky trails or rough dirt roads the WXE suspension is a bit harsher at both ends than the WMX suspension, and this is the problem that tends to be most obvious. It means the WXE simply is not as comfortable to ride. The lack of bump absorption on impacts and landings can seem like it is only an issue on a motocross track, but trying to go fast on trails on the WXE runs into similar problems. When there are some big bumps in the trail the WXE suspension becomes very demanding and the Enduro bike just won't cover ground as quickly. This is true even when the speeds are still rather moderate on tight trails, the WXE suspension just can't smash into bumps like the WMX suspension can. The last problem is the dangerous one. When the 1991 Husqvarna WXE 350 does get going fast on more wide open trails the rebound damping doesn't keep the bike in control as well as the 1991 Husqvarna WMX 610 White Power suspension. The WXE Enduro suspension has more of a bouncy feel at speed over bumps and can get out of hand considerably more easily than the 1991 WMX 610 White Power suspension.
I started with the fork swap. The junk yard 1991 WMX 610 White Power 4054 forks were obviously leaking out the seals, so I tore them down for new seals and new 5W fork oil. The big surprise I got was that the fork springs were cut off very short and the difference was made up with huge 1.75" long spacers on top. Wow, that just didn't look like a good idea! What was left of the springs was just 38 coils. With 0.312" between each coil these cut-down springs would only be able to compress 11.8" before coil bind sets in. That's not enough. With the stock 8mm of pre-load (13mm of pre-load spacers) the coils would bind before the forks bottom, not good for spring longevity and reliability.
At first I was very disappointed, thinking that I would have to buy new springs before proceeding with the project. Then I got the idea to use the springs out of the 1991 Husqvarna WXE 350 White Power forks. They are nearly identical despite the difference in travel between the two models.
I took the springs out of the WXE 350 forks, and sure enough the length was just right for setting the usual amount of pre-load on the 1991 WMX 610 forks. When I carefully compared the WXE springs to the WMX springs I found that the only difference was the coil spacing. The diameter of the wire was the same 0.187", and the outside diameter of the helix was the same. The only difference is the wider 0.335" spacing between the coils. A wider spacing between the coils results in a stiffer spring rate, and also a lighter weight. About a 4.5% stiffer spring rate for the WXE spring. That's more of a difference than I had expected.
I got to thinking about this difference, and I remembered that the springs in my long time 1991 Husqvarna WMX 610 don't look exactly the same in both legs. Someone must have put one WXE spring in to slightly stiffen up the overall spring rate. That would be hardly more than a 2% difference, but it certainly is a stiffer spring rate than stock.
The next thing I thought of was that the wider spacing between the coils was a very distinctive look, and I remembered seeing that look to the springs in my 1990 Husqvarna WMX 610 when I had those forks apart last year. The funny thing though was that it didn't feel like a stiffer spring rate. It felt like a softer spring rate if anything, but really it felt like the same spring rate. I decided to pull a spring out of the forks on the 1990 Husqvarna WMX 610 just to see what it was. When I got a spring out I saw right away that something was different, it looked a lot smaller! When I measured the wire I found a substantially smaller 0.180" diameter. Smaller diameter wire, but I also found a wider 0.370" spacing between the coils. The big difference with the 1990 springs is that they are lighter in weight. About 70g lighter than the 1991 WMX springs and 58g lighter than the 1991 WXE springs. A total weight savings of nearly a third of a pound for the 1990 springs over the 1991 WMX springs. Pretty substantial.
I am guessing that they decided to go with the heavier springs for the 1991 model to increase reliability. With tons of pre-load the spindly 1990 WMX springs might fail.
To equalize out the spring rates in all four sets of 1990/1991 WMX 610 White Power forks I have I decided to put one of the 1990 WMX springs in the 1991 WMX 386. One 1990 spring plus one 1991 WXE spring equals two 1991 WMX springs? Maybe.
The freshly serviced WMX forks worked great. I set the tops of the WMX forks extending up above the tops of the triple clamps as I have been doing on the 1991 WMX 610 bikes, and the front end of the 1991 WXE 350 came up only slightly. The balance of the bike felt good, and the increased plushness and comfort at the front end was evident right away. At higher speeds and over sharp bumps the smoother ride was quite dramatic. The forks were a huge improvement, but the 1991 WXE 350 shock became a thorn right away. Compared to the increased plushness and comfort at the front end the back end started to feel very harsh with unexpected kicking over sharp bumps at higher speeds. The back end also felt bouncy and out of control on landings from jumps. It was obviously a severe mismatch, and after just a few short test rides I swapped the shocks also.
The 1991 WXE and WMX shock linkages are exactly the same, so the shocks just swap directly without any modification. Once I got the 1991 WMX 610 White Power shock on the 1991 WXE 350 it immediately turned into the 1991 Husqvarna WMX 386. On the first test ride I noticed right away that the forks and the shock work best when used together as a matched set. All of a sudden the 1991 WXE 350 rode and handled pretty much exactly like the 1991 Husqvarna WMX 610. It wasn't a WXE anymore, it had truly become a WMX race bike.
I did have trouble with the junk yard shock though. There were signs that the shaft seal had been leaking, and when I first rode with it I could tell that the oil level was low. The shock seal wasn't leaking when I first rode the 1991 WMX 386, but the compression clicker didn't work and even the rebound was a bit spotty. When I pushed down on the seat I could hear air squirting through the compression valving, and the rebound damping sort of worked on and off. There was rebound damping most of the time, but then up near the top of the stroke even the rebound damping disappeared.
When I pulled the plug out of the bottom of the reservoir there wasn't any gas pressure behind it. The first thing I did was just take the reservoir off and add some shock fluid. This got the rebound damping to work consistently all the way to the top without any of those squirting through sounds, but the compression clicker still didn't work.
The oil that was in the shock was also too thick. I had the rebound clicker all the way out at the #1 possition and there was still quite a lot of rebound damping. The WMX 610 shock was actually sort of working like this. It was already faster, more comfortable and better matched to the WMX 610 forks than the 1991 WXE 350 White Power shock had been, but there were obviously severe problems. It was somewhat harsh with that thick oil and the compression clicker didn't do anything.
Next I sort of half ass changed the shock oil by dumping the reservoir out several times and replacing the oil with fresh 3W shock oil. Each time I dumped the contents of the reservoir out and replaced it with fresh 3W oil the 1991 WMX 610 White Power shock got closer to how the shocks feel on the 1991 Husqvarna WMX 610 bikes. After about four of these partial oil changes I was back up to the #7 rebound clicker position I usually run on the 1991 Husqvarna WMX 610, and the excess harshness was pretty much totally gone. The compression clicker still didn't work though. It needs gas pressure under the piston in the reservoir for the compression clicker to actually deliver increased compression damping. But first another side project.
I had a similar problem with the 1985 Ohlins shock I was using on my new Lifan 150 Husqvarna creation. See The Lifan Husqvarnas.
The 1985 Ohlins shock was leaking oil, and when the oil level got low the damping disappeared. The 1985 shock was leaking very badly, and really needed to be serviced or replaced. That was going to cost some bucks, and I don't really like the old 1980's Ohlins shocks all that much anyway. They work well at very low speeds, but then they get harsh at higher speeds. I decided to try to upgrade the 1986 Husqvarna chassis on the Lifan 150 Husqvarna with a White Power shock. The one that seemed like it was close to fitting was the 1991 Cagiva/Husqvarna 125 two stroke White Power shock. It is the same model of White Power shock as on the 1991 Husqvarna four strokes, but the linkage is Cagiva derived and the bottom mount is different. That Cagiva bottom mount looked close to being compatible with the old Ohlins shocks. The 1991 Cagiva White Power shock turned out to be a bit too long overall, but I decided to give one a try anyway. Quite a few used 1991 Husqvarna 125 two stroke White Power shocks were listed on eBay at that time, so I snapped up the cheapest one. I should have paid the $160 asking price for one of the ones that were advertised as being in good condition, but the slightly discounted shock I got turned out to work fine also.
When I got the 1991 Husqvarna 125 White Power shock the reservoir was loose and it was low on oil. It looked like the shaft seal had been leaking slightly in the past, and someone had probably been topping up the shock fluid. I did the same thing, but first I had to get it mounted on the 1986 Husqvarna chassis.
The upper mounting bolts are the same 10mm diameter and the width of the tops of the Ohlins and White Power shocks are very similar. All the top needed was a washer as a spacer and it bolted right into the 1986 Husqvarna shock tower. At the bottom though it was not so easy. There were actually two separate issues that had to be overcome.
The real problem is that the 1991 Husqvarna 125 White Power shock is too long. The 1986 Husqvarna chassis should use a shorter shock. The funny thing though is that the 1985 Husqvarna XC Ohlins shock I had been using was too long also. At first I thought there might be some difference between the shock towers or linkages between the XC and WR models or between the 1985 and 1986 models. Nope, all exactly the same. It turns out that the XC model just uses a longer shock for more rear wheel travel and a higher overall ride height. I thought the shorter WR Ohlins shock fit better overall, but those are apparently somewhat hard to come by. Even the 1986 Husqvarna 250 WR bike I had picked up had been retrofitted with a longer XC Ohlins shock.
The 1991 Husqvarna 125 White Power shock was even a quarter inch longer than the 1985/1986 Husqvarna XC Ohlins shocks. Way too long really, but I was determined to make it work somehow. To get that quarter inch of extra length off I knocked the lower shock bearing out and replaced it with an offset bushing.
The next problem I ran into was that the shock spring bottomed out on the swing arm with the shock mounted low like that. Actually the 1991 White Power shock just doesn't fit on the 1986 linkage, with or without the offset bushing. It is quite far from fitting, but I realized that there were actually several differences that could be used to cancel each other out so to speak.
The linkage ratios are different. To get the stock 13" of rear wheel travel the 1991 White Power shock has a longer throw at the shock shaft than the 1986 Ohlins shocks. Putting the 1991 White Power shock on the 1986 Husqvarna linkage tended to result in increased rear wheel travel. Too much rear wheel travel really, and the shock spring bottoms out on the linkage.
What I figured out I could do was just move the shock spring up on the 1991 White Power shock. I fabricated a custom lower spring mount to mount the spring up farther where it doesn't interfere with the swing arm, and there was plenty of range of adjustment on the pre-load rings to move the top of the spring up. Since there is so much range of pre-load adjustment on this Cagiva two-stroke version of the 1991 White Power shock I didn't even need a spring compressor. Even with my custom lower spring mount it just went right together without needing to compress the spring.
The final result on the 1986 chassis is a bit more than 13 inches of rear wheel travel and a lower effective spring rate than on the 1991 Husqvarna 125 two stroke. On the 1986 Husqvarna linkage the 1991 White Power shock moves a shorter throw distance to deliver more rear wheel travel than on the 1991 Husqvarna 125 two stroke.
This turned out to be great for the lighter weight Lifan 150 Husqvarna. Both for the spring rate, and for the damping. When I first rode the 1991 White Power shock equipped Lifan 150 Husqvarna I was nothing less than blown away. Wow, plush and comfortable at high speeds like the 1991 Husqvarna four strokes, and also with rather substantial rebound damping.
At first there wasn't enough oil in the 1991 Husqvarna 125 White Power shock though. The rebound damping only worked way down at the bottom of the stroke, and up near the top it was bouncy. Since the reservoir was loose it was easy to add oil. With the oil topped up the rebound damping worked consistently all the way though. I set the rebound clicker at the stock #3 setting, and this seemed just right for the lighter and less powerful Lifan 150 Husqvarna.
The 1991 Husqvarna 125 White Power shock felt pretty good on the Lifan 150 Husqvarna, but the compression clicker didn't work. It needs gas pressure under the piston in the reservoir for the compression clicker to actually deliver increased compression damping.
As the 1991 WXE White Power shocks have Schrader valves on the bottom of the reservoir this was easily remedied. I just pumped the reservoir up a bit with a tire pump and headed out. Wow, compression damping. Lots of compression damping with the clicker turned in! Huge amounts of compression damping like I have never seen on a 1986 Husqvarna chassis. With the huge 14 or so inches of rear wheel travel and 1991 White Power compression damping I could actually jump the Lifan 150 Husqvarna. And it was a nice planted feel on the landings, with that great 1991 White Power damping that just soaks up the landings without the bouncy and out of control feeling of many other dirt bikes.
I had thick oil in the 1986 Husqvarna conventional forks also, so it was not bouncy at the front end either. Interestingly though the front end was feeling extremely excessively harsh compared to the 1991 White Power shock out back. Even the rebound damping up front was too much for the lightened bike. I had put ATF in the forks, and this turned out to be too thick. When I switched to 5W fork oil there was a hugely dramatic difference. Gone was the harshness, and so was most of the rebound damping. For the under powered Lifan 150 Husqvarna the conventional Husqvarna forks felt good with the thin 5W fork oil. The rebound damping was minimalistic, but it was enough. When paired with the very effective rebound damping on the 1991 White Power shock the Lifan 150 Husqvarna felt easy enough to control over bumps at the highest speeds I could get it up to.
It is a very old fashioned sort of feel with under damped front forks and very substantial damping at the rear, but it works well for casual cruising. It actually reminds me a lot of the suspension on the 1980 Kawasaki KZ400, just a lot more of it. Like three times as much of it really and without the excessive sport bike style rebound damping at the rear that packs up severely over any sort of small to medium sized successive bumps.
Overall the modified suspension on the Lifan 150 Husqvarna seems pretty good, but it also feels like it could use some 40mm USD White Power forks. Even with the flexy conventional Husqvarna forks the bike is pretty good for casual cruising. The reduced weight takes some of the stress off of the forks when cornering and it all works pretty well together. A shocking success.
Adding pressure under the reservoir piston on the 1991 Husqvarna WXE 125 two stroke White Power shock had been fairly easy with the Schrader valve. The 1991 Husqvarna WMX 610 White Power shocks don't have Schrader valves on them though. How the heck are you supposed to get gas in them with no valve? Without gas pressure the compression clicker didn't do anything and the bike was basically stuck in dirt road casual cruising mode. I had to get some pressure in the shock somehow. I thought of different ways to get some pressure in the shock, but nothing seemed easy. Could I put it in a pressure vessel with the plug cracked open a bit? Could I make an adapter to pump pressurized air onto the entire bottom of the reservoir? Could I just drill and tap the bottom of the reservoir for a fitting with a Schrader valve?
What I finally came up with was just to use the reservoir off of the 1991 Husqvarna WXE 350 White Power shock. They are exactly the same other than the valve. The 1991 WXE White Power shock has a Schrader valve, and the 1991 WMX White Power shock just has that little 4mm threaded plug.
With the WXE reservoir installed on the WMX shock I pumped it up and headed out for a test ride. Yes, that got the compression clicker to do something. It still seemed a bit wrong, but turning the clicker in a few clicks certainly did deliver some increased compression damping. It was probably just some residual little air pockets limiting the compression damping action. The response from the compression clicker was not nearly as dramatic as I was used to on my 1991 Husqvarna WMX 610, but going up to the #3 compression clicker setting on the shock certainly did increase hold up on rolling bumps and on jump landings. Going farther to the #5 setting didn't seem to do much of anything, but there was a substantial difference between the #1 position and the #3 position. Then I noticed that the shock shaft seal was leaking. It hadn't leaked a drop with no pressure in the reservoir, but once pumped up to 80psi the shock fluid was slowly leaking past the seal.
When I lowered the pressure to about 10psi the leak completely stopped, but the shock didn't work as well either. With the lower pressure I could hear air squishing through the compression valving, and the compression damping felt a lot lighter at the same clicker settings. I then brought the pressure up to 25psi, and the compression damping came back substantially. At 25psi a small oil leak came back also. Time for real shock service I guess.
I also found that the shock on the 1991 Husqvarna WMX 610 with the stock bone stock 10.2:1 motor and the Czech Republic CDI ignition was flat. I hadn't rode that bike much for a few different reasons. One was that the surging at 3,000RPM had been extremely bad for a while. The other was that the fork seals were leaking and the front end felt harsh. The front end had been somewhat harsh when I first got that bike running last year, so I had changed the fork oil. With the new 5W fork oil the front end still felt somewhat harsh over small bumps at slow to medium speeds. Decidedly harsher than the 1991 Husqvarna WMX 610 that I was usually riding. The fork seals had also started leaking shortly after I changed the oil, which was discouraging. It needed new seals, but I didn't feel like taking the forks apart since I had just had them apart to change the oil.
For quite a few months I didn't do much of anything with that bike, mostly because the surging around 3,000RPM was just really annoying. When I found that a large part of the severe surging at 3,000RPM was just that I had accidentally put the needle clip in the stock 3rd groove (See A Tail of Two Huskies) one of the main obstacles to riding that bike was removed. With the needle clip in the first groove the surging at 3,000RPM diminished so substantially that I started to consider the bone stock 10.2:1 Czech Republic CDI 610 motor actually fun to ride. That gave me the motivation to replace the fork seals, which is actually a rather simple little job. It just tends to get oil all over the place so I avoid doing it more than absolutely necessary.
With the new seals installed the forks didn't leak anymore, and the excess harshness was also gone. It had just been some really spectacularly crappy old seals that wouldn't seal despite dragging severely. It was actually a really rather big difference that the new seals made on that bike. The excess harshness was totally gone. In fact the front end felt perhaps a bit plusher even than on the 1991 Husqvarna WMX 610 that I usually ride. It felt more like on the 1990 Husqvarna WMX 610 with the one modified damper cartridge (See A Tail of Two Huskies). I thought that extra little bit of plushness had to do with the damping cartridge modification, but it turns out that some of it is just better fork seals. Both of those bikes have Italian made ARI brand fork seals, and they seem to run a bit smoother. The Parts Unlimited fork seals I put in my main "daily driver" 1991 Husqvarna WMX 610 with the hot rod 1997 motor were also made in Italy, but they were the cheaper $16 a set parts. The ARI seals are the premium ones that retail for a whopping $20 a set. I guess they are worth that extra four bucks though. Any little bit of increased plushness and comfort over small bumps at low to medium speeds is welcome on a dirt bike. Especially when it can be had without giving anything else up (other than the $4 of course).
The next thing I noticed with the forks serviced and working at their best was that the rear end on that 1991 Husqvarna WMX 610 with the bone stock 10.2:1 Czech Republic CDI motor felt a bit harsher than the other 1991 Husqvarna WMX 610 bikes. I hadn't really noticed this much when the forks were also somewhat harsher over small bumps. With the forks delivering supreme levels of plushness though the rear end stood out as problematic, and interestingly this turned up an even worse problem.
I cracked open the 4mm plug on the bottom of the reservoir, and there was some gas pressure behind it. Not huge pressure, but probably at least 20psi or so. That should be enough to keep the piston up against the oil, but something obviously was not working. I hadn't noticed that the compression clicker wasn't working, and I am not even entirely sure that the compression clicker was out of commission. I seem to remember thinking that the suspension felt a bit on the harsh side when I was out riding this bike, but when I turned all the compression clickers in one click I said to myself "at least the compression damping does work". In any case just now when I rode this bike with the express purpose of seeing if the compression clicker worked, I found that it didn't. There wasn't any difference between the #1 position and the #3 position. Even going up to the #7 position didn't seem to do anything. It all just felt like the #1 position.
Normally the way the rear shock compression clicker works on the 1991 Husqvarnas is that all the way out at the #1 position is rather loose and floppy, but going in just to the #2 position makes a substantial difference and delivers quite a bit of hold up over rolling bumps and on jump landings. The way I usually ride the 1991 Husqvarnas is to stay at the #2 position most of the time, but for extended cruising on bumpy dirt roads or even some types of rough paved roads I go out to the #1 compression damping position on the shock to get that little bit of extra comfort. For those old beat up paved back roads with lots of small uneven patches and broken edges of asphalt going all the way out on the compression clickers fore and aft on the 1991 Husqvarnas tends to work best. There are times though when I actually go in a click on the compression clicker on the shock just for pavement. It is over the long rolling bumps found on some small highways that substantial damping is required to rein in 13 inches of suspension travel. On the 1991 Husqvarnas I don't go in on the rebound clicker on the shock. It is fairly hard to get at way up under the bike, and there tends to be just one setting that works best for all conditions. I do set that rebound clicker on the shock way in at the #7 position out of ten clicks of rebound damping where it works well under all conditions, but I don't go beyond that. What I do adjust are the rebound clickers on the forks. On the 40mm USD White Power forks they are big red dials on the top, and they are fairly easy to turn while riding along. I usually leave the rebound clickers at the stock #3 setting, but I do also go in to the #4 setting if I think of it before heading out on the highway. The other clicker that can be reached while riding is the compression clicker on the shock, and I find that I do actually go in on it sometimes while riding along on the pavement. If I get caught on a section of big undulating bumps that gets the suspension moving too much I can just dial in the #2 position on the compression clicker on the shock, and that quiets down the movement of the whole bike quite substantially. It is those rather long bumps in the roadway that need a lot of damping for elevated rates of travel. The long undulating bumps that get many 1980's Japanese and American cars rocking and rolling like a Pirogue in a Sirocco. Those are the ones that get me to reach down and turn in the compression clicker on the pavement. It is not that lots of suspension travel can't work at high speeds over those rolling bumps, it is just that it has to be sufficiently damped in some way.
I also go in all the way to the stock position of #3 on the compression clicker on the shock sometimes, but that is really a very large amount of hold up that I don't usually feel the need for. The 1991 Husqvarna WMX 610 might be a bit faster over some types of terrain at the #3 compression clicker position than it is at the #2 compression clicker, but it takes pretty aggressive ridding to make use of that #3 compression clicker position on the shock. Only a very few times have I actually ridden the bike with the compression clicker on the shock at the #4 setting, and that really is too much compression damping. I have also run the compression clicker in farther just to see what was there. Basically hard as a board at the #7 maximum compression damping setting. Hardly any suspension movement. Even the #5 and #6 settings seem totally useless, just way too much compression damping. I prefer the #2 setting for most purposes, but a motocross track or really big whoops often calls for the stock #3 compression clicker setting on the 1991 Husqvarna WMX 610 White Power shock.
On the bone stock 1991 WMX 610 with the Czech Republic CDI I was sort of surprised to find substantial pressure in the shock with the compression clicker not working at all. In fact I was sort of surprised to find pressure in there at all considering how weathered and neglected that bike looked when I got it. The problem is likely a low oil level. The shock shaft hasn't been leaking while I have had the bike, but there is evidence that it was leaking in the past. There is some dried up old shock oil residue around the seal area, so it was probably leaking many years ago. There is still some oil in the shock though, and the rebound damping still works. The damping circuits at the lower part of the shock even work enough to deliver a noticeably harsher ride over small sharp bumps than the other 1991 Husqvarna WMX 610 bikes, so there must be some oil down there. The harsher feel and very substantial rebound damping despite the low oil level probably indicates that the 27 year old oil has dried up and thickened over time. Obviously time for an oil change.
That's easy enough, but how to get some gas pressure back in under the reservoir piston after putting it all back together? There isn't any mention of shock servicing in any of the manuals I have. There doesn't seem to be any information at all about shock servicing. Just that ominous sticker that says "DO NOT DISASSEMBLE".
Interestingly the somewhat flat 1991 WMX 610 White Power shock on the 1991 WMX 386 is still a lot faster under pretty much all conditions than the stock 1991 WXE 350 White Power shock. In fact even the completely flat 1991 WMX 610 shock on the stock 1991 WMX 610 with the Czech Republic CDI ignition is faster than the 1991 WXE 350 White Power shock. The WMX motocross shocks are simply better for nearly all purposes, and they still remain faster than the WXE Enduro shock even when they go flat and the compression clicker stops working.