35 mm fork still good?

[wherearewe]

Couple of quick questions about forks>

1. What is the purpose of the grey material on the inner of the fork lower? What is it made of? Either myself or the PO scratched it when removing the fork seal on one of mine. All good? In the photo it looks like a rust patch, but its not. Its actually a scratched off section of what looks like grey paint or teflon tape. The material underneath is copper coloured and quite porous.

2. One of my two fork uppers is bowed. I suppose its around 2.5mm. The other is only a little off true. I know they all bow a little from braking over time and you can rotate them, but is this too much? Should i replace? You can clearly see it when rotates against some glass.

Thanks in advance!

 

[jd750ace]

The internal bushings have a soft bearing materical over red bronze. Most are in the self-lubricating plastics family of products but could not say for sure what it is. The soft material does not abrade the chrome slider, and it allows the smallest particles to bed into it and keeps them from making longitudinal scars. On the tubes, I'd find someone to straighten them. If they can't be straightened to within aroud .2 MM or so, I'd scrap them. That number does not come from a manual, but is based on "some" experience with bent 35MM tubes. Since everything is apart, I'd be inclined to change those bushings as well. A well serviced, damaged front end is still a damaged front end. A well serviced and fully serviceable front end is a beautiful thing.
Just my 2 cents worth.

 

[gggGary]

Thought I'd chime in here. Can the bushings be removed? Are they available separately? I have straightened a tube or two back in the old days.... I think with a proper set up and careful work straightening a MINOR bend is not beyond the pale. It is pretty easy for the tube to be oval as well as bent. Oval might be a deal breaker. The last thing I straightened was a post hole auger for my skid steer, not quite as critical.

The OP being in New Zeeland Makes a difference too, you can usually get a good complete "needs seals" fork leg stateside for $50 ish.

 

[jd750ace]

If you can get enough access to measure the bushings, here's hope for finding them.

http://www.racetech.com/HTML_FILES/FMB-ForkBushings.html

Gary is right on the tube being oval. Probably should check that it is round first before attempting to straighten, then check it again afterward. Oval does not work well at all.

 

[650Skull]

This is a long time ago, (could be 650rider), I remember some one trying to take that bushing out thinking it was the seal. I don't think that is a repairable part that can be bought. Some one else might know for sure. Sorry to be such a help

 

[Scrambled]

If you can get enough access to measure the bushings, here's hope for finding them.

http://www.racetech.com/HTML_FILES/FMB-ForkBushings.html

Gary is right on the tube being oval. Probably should check that it is round first before attempting to straighten, then check it again afterward. Oval does not work well at all.

My experince with bent tubes is even if you straighten them they will soon bend again , once they bend they lose some structural integrity . I think once they have been bent to the point where your seals are failing it would be best just to get new tubes . As for oval tubes , gggGary and jd are right, have you ever tried to solder a copper pipe that is out of round ? It is impossible ! No matter how much solder you get in that fitting it will never seal . No one ever said motorcycles was an inexpensive hobby. Some times you just have to fork out (pun intended ).

 

[wherearewe]

Thanks for the feedback guys!

First of all will measure up to see if one of those bushings might work. But...From the look of it that bushing isnt intended come out (well it def wouldnt be easy - i think damaging the lower would be likely...). Its not shown as a sep part on any parts diagrams.

No one has any ideas for a patch up?

The other option is replacement of the lower, but that seems so wasteful... of course i could just run it. I guess that would scar the tube pretty quickly.

Re tube replacement - Ill check mine for roundness, but with that kinda bend i am leaning towards replace. What are mikes ones like? A new OEM tube is gonna set me back about 160US on Flea Bay.

There is an XS650 wrecker here in NZ who MIGHT be able to help with this but i dont know yet... old parts might not be in much better condition.

 

[gggGary]

Tell us a bit more about the 2.5mm? in US speak that's 1/10" or not very much if the whole tube is on the glass and the 2.5mm is the gap at the high spot. You might want to spend some quality time with a straight edge and determine if it is a kink (not good) or a bow and then mark the ends of the bow. with that knowledge and using V blocks to support the ends of the bow and on the plunger of a press, see if you can straighten it.

These guys showed up in a google search.
F1E Motorcycle Works
35 Te Puroa Road
RD1
Ngaruawahia
New Zealand
Phone +64 7 824 9433
Fax +64 7 824 9422
Mobile 0275 433 960
E-mail steve@rapidartnz.com


http://www.rapidartnz.com/Services/ForkS.htm



From another shop here are some "how they do it" pics

Which brings up the point that anytime you have a bent fork you need to check the lower yolk as well. the quick yolk check is to slide the tubes in, they both should slide through and right into the upper yolk holes with no fight or mis-alignment.

 

[wherearewe]

Tell us a bit more about the 2.5mm? in US speak that's 1/10" or not very much if the whole tube is on the glass and the 2.5mm is the gap at the high spot. You might want to spend some quality time with a straight edge and determine if it is a kink (not good) or a bow and then mark the ends of the bow. with that knowledge and using V blocks to support the ends of the bow and on the plunger of a press, see if you can straighten it.

These guys showed up in a google search.
F1E Motorcycle Works
35 Te Puroa Road
RD1
Ngaruawahia
New Zealand
Phone +64 7 824 9433
Fax +64 7 824 9422
Mobile 0275 433 960
E-mail steve@rapidartnz.com


http://www.rapidartnz.com/Services/ForkS.htm



From another shop here are some "how they do it" pics

Which brings up the point that anytime you have a bent fork you need to check the lower yolk as well. the quick yolk check is to slide the tubes in, they both should slide through and right into the upper yolk holes with no fight or mis-alignment.

Well gggGary more good advise as per usual.

I know Steve, he actually did some work for me on this bike already! He does a great job and is fairly priced. He could get the bushing out, and we could replace or re-teflon. Dont know cost yet though...

Yes that 2.5mm is a bend at the apex when rolling on glass. Its fairly gradual, begins just above the knurled portion and continues to the end.

Finally, yep lower seems ok? It was a mission to get the tube back in. Tried the other tube too just to be sure - no joy- so I loosened top, removed, greased, placed back on and aligned. Forks slide in easy. Tightened it back up. Picture shows how far off it was.


Still leaves the question about the small tear on the inner bush lining...what to do....

 

[wherearewe]

So i picked up an entire left side fork assembly missing only the drain screw for about 55US. Pretty good for NZ... cheaper than messing around with trying to find a bushing or recoat the old one. The upper is good so hopefully im back in the game!

 

[wherearewe]

So er, i now know that there were a few differences between years inside the forks... The wrecked single i tracked down didnt have the pre-load cap mine do and the inner tube was about 1" longer. It was straight as an arrow too. Damn. The lower is fine though. They were the same throughout all years correct?

 

[gggGary]

From the factory parts fiche the part number is different for both the inner tube and the lowers 77 #s are different and all the later years are the same. (color different in 82) 5twins mentioned there were some internal differences. But this is the first I knew the tubes and lowers are somehow different. Don't know if they will interchange or not.

Part # for the tube
77 1G3-23124-50-00
78-83 2F0-23110-00-00

Part number for the lower
77 RH 1T3-23126-50-00
78-83 RH 2F0-23126-00-00

77 LH 1T3-23136-50-00
78-83 LH 2F0-23136-00-00

 

[650Skull]

Reason would say the lower, 77 and 78 and later was the same.......Yea right.........Now you have the 2 different forks it would be great if you can post your findings on the differences.

 

[wherearewe]

In this thread 5-twins does a pretty good comparison.

http://www.xs650.com/forum/showthread.php?t=17623

From what info is there - both forks are from 78 on, as the dampers etc are all the same.

The differences i can see:
- my original forks from my 81 had adjustable caps, this mystery fork does not.
- The upper is 1" longer. The knurled area near the bottom is smaller. Inserting a depth gauge, the depth is different from the end to the washer?? inside.
- Didnt have a spring so cant compare that.
- Maybe someone has been in this fork, as the fork seal had what looks like some sort of sealant around it when i pulled it out and didnt look 30 years old. Could be a Mikes 1" longer upper? However, ive never seen one so i can't compare it to anything.... Also the chrome looked really nice.

I have looked over the lowers and cannot see any difference. I put my original uppers in and there was no obvious difference in fitment.