Forks sticking

[ranton_rambler]

As part of test riding to try and sort carb setting, I thought the front end felt stiff. Sure enough, the right leg of the forks was stuck at about 2” compression.
Is this a known issue, with a known fix?
Having stripped the slider off, the only thing I can see is a bit of crud on the stanchion above the slider, so I think a bit has got down between the slider and stanchion. At least a bit of it seems to be rust off the spring.
The bike is a 175 with the standard forks.
Ian

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[Jordan]

Unparallel legs can cause forks to stick.
It happened to me recently, when I mixed up some wrong axle spacers.
It wasn't on a Ducati, but has a similar design.
What happened was that on fitting the wheel, instead of allowing the clamp side at the bottom of one slider to float to it's natural position before clamping, a wrong spacer did not allow it to do that. Very stiff fork action was the result.
The same thing can happen if the clamp is tightened on the axle, before the axle nut on the other end is tightened.

[Bevel bob]

Clean the sliders out and check that the Dampa assembly is still intact in the bottom of the leg. Mine were all broken up with bits everywhere.Passed 6 MOT'S like that!.

[ranton_rambler]

Unparallel legs can cause forks to stick.
It happened to me recently, when I mixed up some wrong axle spacers.
It wasn't on a Ducati, but has a similar design.
What happened was that on fitting the wheel, instead of allowing the clamp side at the bottom of one slider to float to it's natural position before clamping, a wrong spacer did not allow it to do that. Very stiff fork action was the result.
The same thing can happen if the clamp is tightened on the axle, before the axle nut on the other end is tightened.

I can imagine that, but my problem only affects one leg. Photo....

F18C9961-82DF-4624-919E-7440961D721D.png

[ranton_rambler]

Clean the sliders out and check that the Dampa assembly is still intact in the bottom of the leg. Mine were all broken up with bits everywhere.Passed 6 MOT'S like that!.

Damper is all good in the stiff leg.
It just seems that the slider and stanchion are not sliding nicely.
Ian

[Duccout]

Are you sure that the slider and(or) the sanction are not bent?

[Bob_Matthews]

Hi Ian,

I think you should pull the fork legs from the yokes and then strip them - or you can never be quite certain. I know there is an issue to pull them back up into the yokes once the headlamp brackets are in place, but Laurie Richardson sells a puller for £10 and it works great.

The other problem once the fork leg is removed is removing the bolt from the bottom of the leg to release the damper. Some recommend to use an impact driver but on mine the damper was still spinning inside the leg and I had to improvise and make a tool to stop the damper from spinning whilst the bolt was undone - I'll see if I can find it and take a picture of it.

Once you have the stanchion out it's quite an easy task to check for straightness with either an accurate straight edge or by rolling it on a flat surface like a kitchen worktop. Stanchions can be straightened - so long as they are not kinked - and several firms will do this for you if you do a Google search...... https://www.google.co.uk/search?sxsrf=ALeKk01wIjJhmqG5VUmt7xiFS5fL_eN5MA%3A1609927719332&source=hp&ei=J4z1X8eeEoSYlwTkr7XwAg&q=motorcycle+fork+leg+straightening&oq=motorcycle+fork+leg&gs_lcp=CgZwc3ktYWIQARgHMgUIABDJAzICCAAyAggAMgIIADICCAAyBggAEBYQHjIGCAAQFhAeMgYIABAWEB4yBggAEBYQHjIGCAAQFhAeOgcIIxDqAhAnOg0ILhDHARCjAhDqAhAnOgQIIxAnOgsILhCxAxDHARCjAjoICAAQsQMQgwE6DgguELEDEIMBEMcBEKMCOgUIABCxAzoICC4QsQMQgwE6CAguEMcBEKMCOgIILjoICC4QxwEQrwE6BAgAEApQsxBY_Fpg8YsBaAFwAHgAgAFaiAGHC5IBAjE5mAEAoAEBqgEHZ3dzLXdperABCg&sclient=psy-ab
I have always used Motoliner - who are brilliant - but they are within a half hour's drive from me. They have not straightened any stanchions for me but I have had two frames done and a set of yokes.

Good luck.

[ranton_rambler]

Fairly sure nothing is bent, but can try and check. Maybe will take the stanchions out one at a time to avoid too much disturbance to everything else.
Getting the sliders off isn’t too bad. I made a long tool to hold the damper rod when I initially stripped it.
The stanchions were reconditioned as part of the original build, and I’ve only done 2000 miles. No drops or crashes.
I have a cunning plan to compress the springs so I can start the bolts at the bottom...

[Duccout]

Ian, do you remember if the slider slid easily up and down the stanchion without the spring fitted when you refurbed the forks? When you take them apart it will be easy to see where the tight spot is. I'm wondering if the casting could have distorted in use and has created a tight spot?

[ranton_rambler]

This leg was a bit sticky when I first assembled it, but once it had been "worked" on the bench a bit it was sliding nicely. Over the 2000 miles I've ridden since, the forks seemed to be working nicely.
I pulled the stanchion out last night and it's dead straight, as is the slider as far as I can tell.
There were some shiny areas on the stanchion and according to my digital caliper, it's possibly slightly oversize. About 31.55mm, but I accept that it's not the most accurate measurement method.
A little experiment was to leave the slider on top of the boiler while I had my dinner and then it was nice and free on the stanchion, until it cooled down.
I suspect that during nice weather, there is just enough clearance for it all to work. Last week when it was cold (about 3C) the fit has perhaps just flipped to slight interference. I think the alloy expands/contracts more than the steel.
I've polished the shiny areas (high spots?) on the stanchion with some fine abrasive and it all seems OK now, so I put it back together.
My cunning plan to compress the spring worked - ratchet strap over the bottom yoke and hooked round the studs for the mudguard.
Only problem is that I forgot to put the little steel washer under the spring so I'll have to do it again tonight!
Ian