My forks are not happy

[Jumbo J]

If the tubes have been rechromed they would have to be straight as they are ground between centres as part of the process.

Bent axle or triple clamp?

No. The front wheel spins true, tubes slide up between upper and lower triples no hesitation or misalignment. There was no issues with the front end before the forks were sent off for the conversion. no gouges no weird noises. there have been no frontal impacts or crashes since the job was done.

[Nipper]

Hey Jumbo I have sent you a pm

[Jumbo J]

Please tell me that this bloke is not a member here. or anywhere?

...Sadly Fred, he is in fact member here ...!
 
After taking into account all the feedback, i'm still uncertain as to what the root cause might be, so I will revert to the stock setup prior to the conversion. Remove the YSS PD valves, springs and my original shortened damper rods. Then re-chrome the inner tubes again  (the fourth time !) use the correct length damper rods, original compression springs, plus the "missing" top out springs. Then see if the problem still occurs, and whether there is any foreign matter in the oil. 

Will probably have to sleeve the top of the alloy sliders now too . So if anyone knows who could do that i'd appreciate a name - thx

[evo550]

Jumbo might be far cheaper to just get another pair of forks, than try and repair those.

[Jumbo J]

Jumbo might be far cheaper to just get another pair of forks, than try and repair those.

True not that easy to find tho - 74/75 model TM250. You got a set, 35mm  

[smed]

Theory No 565 , I have been studying the pics of the std damper rods v the modded ones, they have been shortened to have the same overall length with the valves fitted so as to have the same spring preload,I think this is wrong, the spring needed to be swapped out for a shorter one or if there is a preload spacer pipe it should have been shortened to suit,I don't think this is the cause of the damage though but will affect travel,The other thing I noticed is the piece removed from the original damper rod top to allow the valve to be fitted is quite a bit smaller diameter than the valve,could that be causing a problem at full bottom/top out

 

[fred99999au]

If this is the photo you are referring to:


I cant see a lot of sense in what was done. Can anyone explain why it may have been modified like this? Rebound damping would be impacted as well I guess.

[smed]

Yep, thats the one, my guess is to have the same spring preload as before

[Nathan S]

Hmmm. Shortened damper rod with no top-out spring is longer than stock damper rod with top-out spring, meaning there's probably insufficent overlap (depending on how heavily preloaded the main springs are, but I'm pretty confident in saying they're nowhere near that heavily preloaded).

[Jumbo J]

Theory No 565 , I have been studying the pics of the std damper rods v the modded ones, they have been shortened to have the same overall length with the valves fitted so as to have the same spring preload,I think this is wrong, the spring needed to be swapped out for a shorter one or if there is a preload spacer pipe it should have been shortened to suit,I don't think this is the cause of the damage though but will affect travel,The other thing I noticed is the piece removed from the original damper rod top to allow the valve to be fitted is quite a bit smaller diameter than the valve,could that be causing a problem at full bottom/top out

Actually you are right the head piece is a different diameter on the modified/shortened damper rod to the std one. Compare a close up of the modified rod to the std one which has two upper oil holes, the modified one has three holes, the ctr one is filled with a rivet and blocked off- maybe he miscalculated when he was doing the drilling. Then have a look at the piece of rivet material in the ctr hole in the rod on top, the same piece is missing from the rod underneath it, and compare that to the round piece of material the that came out with the fluid on the gauze in the bottom pic




Re the springs: Remember there were no top out springs when they came back to me. The new main springs that were supplied fitted up approx 15mm shorter than the std ones from the top of the inner tube - Fitting the correct top out springs brought them back to the same level as the std spring but reduced the travel by the same amount . 

[Jumbo J]

So i removed the shortened damper rods / PD valves / compression springs that were supplied with the emulator conversion job. Had the fork tubes re-chromed again (for the 4th time since this saga began!) as well as fitting bushes into the top of the fork legs that were now badly scored by this time.  Fitted standard damper rods (no emulators) rode the bike at a couple of meetings one club round and Broadford GP track, and the problem of gouged fork tubes has miraculously disappeared . Front end feels much better now in standard trim than it did after the emulator conversion job!   

[fred99999au]

That is a good outcome to return everything to stock and have it work as intended, but I am still intrigued as to what the issue was after the conversion, if only to avoid making the same mistake in future.

I did a MikesXS 35mm cartridge emulator conversion to my IT175G front end and had to make adapters because the valves didnt fit in the top of the damper rods. Worked a treat and fitted in well.