Fork Rebuild??

[shed]

Hi,
Ive got a 97 RM250 that I bought 2 years ago from a guy that did very little maintenance on it. So far the only part of the bike that I havent rebuilt myself are the headstock bearings (which are notchy - but thats just like running a steering damper isnt it?) and the front forks. The fork legs have always seemed incredibly stiff and not at all plush, but I just thought it was because I wasnt used to an MX bike having only really ridden my XR600 andXR650 at any speed off road. I had a set of softer fork springs put in, and at the time the shop said they had replaced one of the sliders, but the forks were still way too harsh. I tried a (standard) 96 RM250 at the weekend and the forks were great - much nicer than mine.

In January I put the original fork springs back in and lowered the oil level. This made the front end a bit better, but still nasty. Whilst I was doing this, I realised that the forks had side to side slop in them of 0.5-1mm, and were binding up when any fore/aft load was put on them ie all the time I am riding. I attributed this to worn bushings, but cant figure out if replacing them will sort the forks out.

I am a reasonbly competant mechanic, I think I could replace the bushes myself. Alternatively I could send them to a UK based specialist to get them done. Trouble is when they came back from the last "specialist" they were no better than when I sent them and I was £140 worse off.

Any further suggestions about whats wrong with my forks? Or does anyone know a really good shop in the UK that I can send them to?

Cheers

Shed

 

[moto242]

shed,

it sounds like the tubes may be bent, if they were binding whilst setting the oil height (purging oil by sliding the tubes up and down)this may be your problem. the forks will always have a touch of play even with new bushings.if you do replace them, check the tubes because bent ones will thrash your new bushes. as for the steering stem - binding does the OPPOSITE of a steering damper-it does not restrict abrupt steering changes as a damper would, hence actually promoting headshake as well as other problems
hope this helps,
MOTO242

 

[marcusgunby]

The Showa fork is actually fairly easy to rebuild.MX-TECH web site on the left has a download section with rebuild instructions on it.I would install new bushes as then you are starting from a known point.You can use different wt oils to achieve a softer ride.A 2.5 wt will make it slightly softer on low speed compression and rebound, where about in the Uk are you?I know a few Uk tuners and can help you choose.

 

[shed]

Cheers for the info...

Its definately not an oil viscosity problem, they have 5wt oil in them at the moment. The forks just have loads of stiction. From what I remember when I last changed the springs, the tubes slide in and out really easily - good tip though I will have another go tonight. With the forks out of the bike, I can load them up purely in compression ie no bending (you cant avoid putting them in bending when you are on the bike and "testing" them by holding onto the front brake) and they dont seem to bind. Thats why I thought it was the bushings.

Im in Oxford, but dont mind sending the forks away for a rebuild.

Shed

ps I was joking about the headstock bearings - im an engineer with a sense of humour (until it come to stiff forks that is).

 

[Mark Hammond]

Hi Shed
It may be that when you put the front wheel in the right hand fork leg is pushed over when you put the spindle through, when you then tighten up the clamp bolts the fork leg is at an angle and will get very stiff as it goes through its travel. Make sure the leg is in line before tightening up the pinch bolts. Alternativly I have found that the bushes wear in these forks and cause binding. If you still have a problem or need someone to rebuild your forks give me a call 01225 811583.