after riding some 600k odd last weekend, I noticed my front suspension was a bit stiff.....on one piece of slab my head was being shaken so badly I could hardly focus on the road no matter how much I relaxed my arms and it got me thinking about pulling my folks apart and seeing what could be done to improve them, after all they have done 19,000ks to date since new. Hearing comments about our folks being cartridge type and not serviceable I wasn't quite sure what to expect and the workshop manual wasn't much help and you can't even find how much oil they should hold (did I miss it somewhere??). With both folks out I notice the right one is sticky and the left one seems low on oil. Draining them both of oil I notice the factory volumes are different, one had about 500mls and the other had 650 odd, what withs that I wonder??.....there’s a problem, or is there?. Getting the folks apart required a rattle gun on the bottom cap screw, with this out and the top cap nut off, the entire cartridge can be removed as one. Both internals looked ok but there was a bit of crud in the bottom of one leg. I was about to reassemble when I decided to completely strip the internals and its then I find the right piston was full of crud and different to the left one....what? have they been assembled wrong??,……No, one is compression dampening and one is rebound, thats not mentioned any where that I have seen?! Ok so the right folk is Compression and the left is Rebound,... the manual doesn't say that!!. I give them a good old clean and reassemble, but how much oil do I put in them? Using Motul 5W which seemed a lot lighter than factory, I decide to put 700ml in each leg and try it, well it was terrible, way to stiff. Ok, so let’s try and make them as soft as possible, a quick volume calc. and 400ml (this is about 273mm) is minimum needed to cover the intake holes in both legs. A quick test ride and its feeling pretty good, but I'm thinking I want more response, so when I get some more time I’m going to try 2.5W in the right leg only to increase response and adjust the oil volume to give enough progression to stop bottoming. 2/9/15. Right folk changed to Motul 2.5W, 550ml or 188mm to top of outer, response feels better, and progression seems ok, all left to do is ride it. One very important tip. Clean all the loctite out of the bottom cap screws and DO NOT use loctite to reassemble them (unless you never want to pull it apart again), because the bung/nut they screw into is not held and can turn and if it does, your in real deep, deep shit,....and you wont be able to get it apart or tighten it up.
Previous threads on forks: http://www.cafehusky.com/threads/options-for-improving-tr650-forks.41767/#post-408461 http://www.cafehusky.com/threads/knocking-at-front-end.35890/ There are others.
Thanks those links are on quite different tangents .... I'm more wanting to share, understand and service our folks to get more comfort and handling...hope its of help to some.
RuggedExppsure did an awesome pictorial on replacing the fork seals. Very good info in the several posts he wrote up. http://advrider.com/index.php?threa...uestions-thread.850525/page-141#post-23286707
Yes it has been Marzochi practice to use the different legs for compression and rebound, they have been doing it for over 30 years, even on road bikes. The BM owners have been swapping out the components to full cartridge set ups or swapping to WP or YZ forks as a result of the same el cheapo systems use by BMW, there is a lot of info on Advrider if you look over there
Many thanks Mr. kiwiape, for the information about the service of the front fork.. I changed the oil to 5W and 2,5W, as you wrote. The viscosity in the fork legs from the factory was much higher, 10W or 15W. The front fork works much better now.
Hi Jac. Thats excellent news. One thing I noticed when riding a friends Terra with factory oils is, if you brake moderately hard on the front mine will dive some and spring back immediately when the brake is released, but his was is slow (as mine was) to return and unresponsive, which gives a harsh ride and the wheel will be off the ground more......
I am a novice at forums (not sure about etiquette), but thought I'd try to reply on this old thread. Are you saying add a comp shim stack on the rebound side and a rebound shim stack on compression side? Can you do this with the existing pistons? Finding parts-shims and such -seems esoteric. If you made both comp plus rebound, you'd have to cut the shim stack stiffness in half compared to the factory arrangement. I tried to disassemble the cartridge but think I missed the smaller circlips shown in one picture above.
