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1989 RM250 FORK ADJUSTMENTS

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Hi,

Old guy (55) here that has pulled my old 1989 RM250 out of the mini barn to get ready to ride again after a 17 year break. I installed new bushings and fork seals but have some questions about the damping adjustment. Haven't found much information on these forks. I think they are KYB inverted single open chamber forks used on the 1989 and 1990 RM250 bikes. Forks should be the stock ones since I purchased this bike about 25 years ago. I don't seem to have any clicks on the top fork adjustment. I feel the lower clickers for the compression adjustment and it seems to work fine. Taking the top fork cap off I don't see a way for any adjustment. There is a 13mm nut with an air bleed screw that can be turned but no adjustment seems to be made. Looking at diagrams it doesn't seem to be missing any parts. There is an inner push rod that I can depress about 1/8 inch but see no way for the cap adjuster to depress or rotate the inner rod as the top nut is turned. Have purchased service manuals online only to find information is not correct for these forks. Most manuals show a different fork, Showa dual chamber. Please help and any upgrade to these stock forks would be great. Been out of the riding loop for awhile and getting the fever again.

Have a great day,

Bob

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Thanks for the very quick reply. I work out of town but maybe I can find a picture on the net somewhere tonight.

Have a great day,

Bob

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Work out of state and will not get home till weekend to take a picture of the top fork caps. Found an ebay listing of the forks (121472379306 ) These are the correct forks. The center screw is just an air bleed screw. The 13mm center nut can be turned but no adjustment appears to be made. Thinking I'm not looking at things correctly or cap is broken. Both right and left caps are the same.

 

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR0.TRC0.H0.X121472379306.TRS0&_nkw=121472379306&_sacat=0

Edited by highvolt
added link and information

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Never seen anything like that

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Darn, was hoping you would know all about these forks. I can't even find a parts diagram showing these forks correctly, close but not completely. Was beginning to think my forks had been altered until I found the ebay listing.

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I remember the 125 having the right side up showas?

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I think I read that the rm250 and the rm125 used the same forks in 1989. The old manual, I bought and lost to mice, said both Kayaba and Showa forks were used in 1989 for the rm250.

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3 hours ago, mog said:

I remember the 125 having the right side up showas?

It was my understanding that the legendary 1989 RM250 forks were HUGE 49mm conventional with awesome cartridges, possibly the best conventional off road fork of all time, other than being understandably HEAVY.

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A quick Google search has shown most 1989 RM250 wearing USD forks while the 1988 has conventional.  1989 RM125 have conventional still.

On ‎6‎/‎11‎/‎2017 at 8:44 PM, highvolt said:

I don't seem to have any clicks on the top fork adjustment.

As for this question, sounds like you installed a cap or nut too far onto a threaded post or bolt.  The clicker screw just clicks when it is turned but it is turning a screw which is closing off a small passageway.  By over tightening or installing the cap/bolt too far onto the threaded part, you have limited the distance the screw can travel so only a few clicks of movement.

The top adjuster is for the mid-valve so I think you installed the cap too far onto the damper rod.  Remove it and reinstall not so far onto the damper rod but also make sure you install it with the screw turned fully counter clockwise, fully out, full soft.

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1 hour ago, MetricMuscle said:

It was my understanding that the legendary 1989 RM250 forks were HUGE 49mm conventional with awesome cartridges, possibly the best conventional off road fork of all time, other than being understandably HEAVY.

Those 49mm conventional Showas with gold coloured lowers were fitted to the 96, 97, and 98 RMs. The 97 and 98 having a slightly shorter under-hang below the axle mount area so less likely to catch on rocks.

I see you have also worked out that the 89 125 had conventionals before going to USD in 90 to 95. Whilst the 89 to 95 250 used USD.

Sorry can't be of more help regarding the OPs adjustment issue.

 

 

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Looks like I'll remove fork cap and take some pictures. Can anyone tell me what fork I have, Kayaba or Showa for sure? It is single open chamber inverted fork.

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Fixed

Took off the fork caps and went to Dreyer Suzuki in Indianapolis today. Spoke with a service tech "Brian" and he confirmed the caps were broken. After cleaning out the caps I did start feeling 4 clicks per rotation of the 13mm nut. Since the caps were broken, I drilled out a pin holding the 13mm nut in place and disassembled the cap unit completely. Looks like the cap was installed to far onto the damping rod at one time and someone had forced the 13mm nut smashing the tip of the adjusted screw and causing damage to the 13mm nut internally.  After filing and cleaning things up the caps work as they should now. Will have to modify things a bit since I drilled out a special pin that also held a spring and ball bearing for the detent but all is good. The caps new are around $170 each and only one in the country.

Thanks for all the help. Didn't want to drill out the pin to disassemble without knowing how things should be working and possible destroy a good part. Once apart it is very clear how everything works and the damage. By design these caps are much more involved than they need to be to work but it is what it is. Looks like I'll be heading out to the trails.

Have a great day,

Bob

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