Front fork pinchbolts
Posted: Tue Apr 17, 2018 7:36 pm
No help required but just an observation.
I thought I'd replace the front fork oil seeing as how I'd just done the gearbox, engine and chaincase oil (suction). Got my SAE 20. Drained 5 FL Oz from nearside slider. Filthy and of course less than the 6 that I should've got. I did thoroughly work the forks but with hindsight had unscrewed the cap bolt first
When refilling oil poured out of the headlamp shrouds.
The pinchbolts weren't pinching!
The tube had dropped.
Fortunately I had long ago made up a tool for drawing the tube back up and did so. Then the problem of how to tighten the pinchbolt as this was custom made with an extension for the Avon handlebar fairing. I didn't want to remove the fairing because it was a nuisance refitting it.
Some time ago Colin Farrington had made me some custom pinchbolts out of hexagonal stainless steel which he'd turned down to round at the yoke end. Unfortunately the threads were now tired (stainless is hard to work with and had a difficult time when I came off on the way to Nijmegen and then repeated the trick on the way to Stirling the other year) and the engagement into the bottom yoke could've been greater.
A local engineer had made up some further ones for me providing more engagement into the yoke but made them from round bar and machined two flats for a "C" spanner. I'd shunned these flats and as the extensions for mounting the fairing were quite long enough wound a nut to the bottom of the extension thread and tightened with that using a ratchet, two extension bars and a socket!
On releasing the fork tube puller the tube dropped again.
I didn't know why but the only answer I could come up with was that the pinchbolt thread was bottoming out in the yoke. Rather than shorten the thread I found a washer in my box of washers and filed down the outside diameter to match the pinchbolt, put it in and when tightened up the tube remained in place! The difference can't have been much more than a turn but it seems that was all that was needed.
Why this happened I can't guess, but it worked. Ironically, the fork leg other side was a doddle with no movement of the fork tube, although the custom pinchbolts were a matched pair. Also, the oil out of the offside (second) leg was so clean that I doubt if it really needed doing.
The whole lot is coming out next winter as the nearside leg seals are weeping and the slider extensions (which I had re-chromed 30 odd years ago) are flaking. I know from when I replaced the bushes quite a long time ago that there is quite a bit of pitting on the tubes above where they enter the bottom yoke although not so much as to be a hazard as yet (I hope). Saving up now.
Johnny B
I thought I'd replace the front fork oil seeing as how I'd just done the gearbox, engine and chaincase oil (suction). Got my SAE 20. Drained 5 FL Oz from nearside slider. Filthy and of course less than the 6 that I should've got. I did thoroughly work the forks but with hindsight had unscrewed the cap bolt first
When refilling oil poured out of the headlamp shrouds.
The pinchbolts weren't pinching!
The tube had dropped.
Fortunately I had long ago made up a tool for drawing the tube back up and did so. Then the problem of how to tighten the pinchbolt as this was custom made with an extension for the Avon handlebar fairing. I didn't want to remove the fairing because it was a nuisance refitting it.
Some time ago Colin Farrington had made me some custom pinchbolts out of hexagonal stainless steel which he'd turned down to round at the yoke end. Unfortunately the threads were now tired (stainless is hard to work with and had a difficult time when I came off on the way to Nijmegen and then repeated the trick on the way to Stirling the other year) and the engagement into the bottom yoke could've been greater.
A local engineer had made up some further ones for me providing more engagement into the yoke but made them from round bar and machined two flats for a "C" spanner. I'd shunned these flats and as the extensions for mounting the fairing were quite long enough wound a nut to the bottom of the extension thread and tightened with that using a ratchet, two extension bars and a socket!
On releasing the fork tube puller the tube dropped again.
I didn't know why but the only answer I could come up with was that the pinchbolt thread was bottoming out in the yoke. Rather than shorten the thread I found a washer in my box of washers and filed down the outside diameter to match the pinchbolt, put it in and when tightened up the tube remained in place! The difference can't have been much more than a turn but it seems that was all that was needed.
Why this happened I can't guess, but it worked. Ironically, the fork leg other side was a doddle with no movement of the fork tube, although the custom pinchbolts were a matched pair. Also, the oil out of the offside (second) leg was so clean that I doubt if it really needed doing.
The whole lot is coming out next winter as the nearside leg seals are weeping and the slider extensions (which I had re-chromed 30 odd years ago) are flaking. I know from when I replaced the bushes quite a long time ago that there is quite a bit of pitting on the tubes above where they enter the bottom yoke although not so much as to be a hazard as yet (I hope). Saving up now.
Johnny B