My forks are not happy

[Jumbo J]

Any suggestions out there on what might be causing this severe fork gouging problem. (TM250L forks)
I had PD valves fitted and after the first race deep gouges started to appear on the stanchions. Got RAD to re-chrome them, same problem. Tried a different set of sliders, re-chromed again-same problem. There was also fair bit of fine alloy particles floating in the oil when i drained them, possibly came from the emulators by the look of the marks on them.
- quality 10-15wt Motorex oil used. 120mm air gap.
- damper rods modified (but shortened  ) to take the emulators. 
Suspect the material being stripped off the emulators may be getting lodged between the stanchion and slider which could be causing the deep gauges - but why?
ideas anyone?

[Momus]

Dislodged seal gaiter spring?

[smed]

I'm no expert but am thinking the emulators are too tight a fit in the fork leg.

[Jumbo J]

Dislodged seal gaiter spring?

meaning? - you got a bit more detail Momus

[pokey]

Im trying to visulise this in my head and Umm. why shorten the rods? Wouldnt you have to shorten an internal spacer or spring as thats the part that the valve is going to replace the space as far as My head sees it or your spring is preloaded a lot more.. if thats the case try it with new rods unshortened. I wouldnt rechrome again untill you sorted this

[Noel]

Looks to me like the emulators are not  " located"   on top off the damper rod
 which would allow the spring to push it to the side of the staunchion which probably has a fairly course surface finish

[David Lahey]

what is the surface finish like inside the fork tubes where the damper rod pistons and emulators run?

[fred99999au]

Doesn't the damper rod go inside the stanchion? Looks to me like the stanchion is rubbing on the slider, so maybe a slider bush?

Having said that, the chrome is bloody hard stuff. Is it maybe a deposit of slider material on the stanchion instead of gouging?

[evo550]

when you re assembled these, was there two brass bushes included in that assembly ?

[pokey]

Bingo David, thats what i think..

the emulators are suppose to be inside the staunchions then the spring sits on that.

if the em is inside the leg on a shortened rod. I guess it will still dampen but the spring preload will be out so its loose and not holding the valve and rod tight. Then it rattles around and rubs on the inside of the leg..


 have i got it arse up? id ask myself this question like i just did.

[Jumbo J]

Looks to me like the emulators are not  " located"   on top off the damper rod
 which would allow the spring to push it to the side of the staunchion which probably has a fairly course surface finish

Yes Noel, the emulator can float on top of the damper rod, there is nothing retaining it in place. furthermore the OD of the Emulator is .6mm larger that the OD od the original springs - i don't have a relscopic vernier to get an accurate measurement of the ID inside the fork tubes

what is the surface finish like inside the fork tubes where the damper rod pistons and emulators run?
[/quote
 there are scuff marks on the swept area inside the fork tubes David

Doesn't the damper rod go inside the stanchion? Looks to me like the stanchion is rubbing on the slider, so maybe a slider bush?

Having said that, the chrome is bloody hard stuff. Is it maybe a deposit of slider material on the stanchion instead of gouging?

No bushes in this old sliders fred, alloy ID of the slider runs up against the OD of the staunchion.

and on top of all that the original oil gallery the holes in the damper rod have not been enlarged or drilled out, nor are there any additional holes drilled in there.

[Tim754]

My forks are not happy also, tried to tidy them up with the bench grinder- polisher   The knives were pretty pissed off too     and the spoons ...................

[David Lahey]

When I fitted emulators to some forks of mine that are very similar to the TM250 forks inside (1976 TY250 forks), I realised that my emulators were going to operate further up the inside of the fork tubes than the damper rod pistons do. Because of this, I smoothed out above the original swept area to avoid damaging the sealing rings on the emulators (Gold Valve) when the forks get close to bottoming. I figure your setup also puts the emulators above the old swept area

[Jumbo J]

when you re assembled these, was there two brass bushes included in that assembly ?

Well i didn't assemble these, at the time i didn't know enough about it so i paid someone "who did"
if you mean were there two brass bushes included in the emulator kit , then no. the photos show all there is re: the damper and emulator assy. if you mean where there brass bushes in the slider - also no just alloy agains hard chrome.

Pokey they are assembled in the correct place, inside the fork tubes on top of the damper rod with the spring on top of that with pre-load. the standard variable rate springs with replaced with linear one as part of the conversion job.

There were also no top out springs in there, but i'm not sure if that is standard or not on 74/75 TM250 forks. there was a holed spacer and washer set up located inside the tube at the bottom which could be for a hydraulic top out mechanism instead of a spring - if anyone knows?

[pokey]

 If they are assembled like above then chopping the rod just reduced your travel and as said alows the fork to run on a different part of the staunchion 

the spring and internal preload spacer needs to be reduced to allow for the valve dimension. this will hold things correctly with the correct spring preload. i would remeasure everything

if not assembled as above then ther's the problem.

if the spring isnt correctly loaded  its going to allow things to move around.