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Discussion in 'Some Assembly Required' started by Luke, Sep 6, 2012.
Lookin good! So what are you going to do where its cut by the swingarm pivot?
I envy that seat (drz owner) !
try slowing down your spindle, you shouldn't see orange sparks or chips while machining. it dlls the carbide if the surface speed is too fast and travel too slow.
subd, great project
Are you sure you want those sprockets?
Don't forget what a harder-than-stock sprocket did for me.
I'm 90% sure that I'll cut the whole back of the frame off and replace it. I'll make new shock mounts first and if those look good then I'll do the replacement. I need to resize the shock mounts and want to move them as well, so there will be major changes of some sort.
Vintage seats are great. Modern foam is fine on woods or MX bikes where you're mostly standing but that's about it.
Thanks for the tip. I'll have to try on the other lathe. The Sherline doesn't do well at turning slow, not enough torque when the speed is turned down.
No, I did forget. It's a good thing it's much easier to replace that shaft on a CB than an XR.
Hmmm.... I wonder if it's possible to remove the hardening from the sprocket. That'd solve two problems.
A little creative heat/quench work might do the trick if you knew what temps you needed, but it would probably be easier to just buy a new sprocket.
Mortimer; what was the time frame or usage that led to the pictured damage? Did it occur relatively quickly or over a longer time span or more usage? How were you able to confirm a harder sprocket as the culprit vs. a possible softer shaft (or even just a poor fit on the spline)? You may have already covered all this with Luke in different place, but you definitely have my attention on this concern. Thanks!
I didn't keep track of the time involved, but once it got started it seemed to get worse at an increasing rate. I have no proof of cause, but this is a fairly common problem, at least on XRs, and the consensus on the XR forum seems to be that hard a aftermarket sprocket is the culprit.
I bought the bike used, and the sprocket that was on it was hard to get off. I didn't think to inspect the shaft at the time, but I think the damage had started with that sprocket.
After a season (two?) on the new sprocket, the damage was obvious, but less bad than in the below pic. I noticed the keeper had strange wear on it, so I pulled the sprocket, and found the damage. I foolishly hoped it would not get any worse, but after not-enough-hundred miles more, it looked like this.
I knew it was doomed, so just put it back together and kept riding. After an even shorter period of time it looked like it did in the first pic.
At that point I figured all was lost, and with nothing to lose, I welded the sprocket to the shaft to get some more mileage before changing the shaft.
The first sign of danger is a keeper that looks like this. But, I think that once the destruction starts, it will continue until it strips completely no matter what you do.
Though I can't be positive the sprocket caused this, I think it is likely enough to warrant never using aftermarket primaries again. The OEM sprocket for the XR is not only the proper hardness, but it also has a wider cross-section, or so I am told.
The xr650r sprocket has at least double the surface area on the shaft. the xr650l guys use them on their bikes.
I have no idea if that helps you or not.
Sweet build bTW!
It's a moot point, OEM sprockets are unavailable.
Absolutely. Easy. You should be able to anneal that with a torch or a BBQ or something. Just heat it up and then let it air-cool. Then send it out to have it heat treated after you're done. Hate the idea of custom consumable parts though. Might also try giving any of the custom sprocket mfgs a call?
There also is no cush drive on XR600s or XR650Ls to dampen this kind of wear if the bikes are being used for a lot of street miles. I would love it if there were A) someone with a hardness tester to prove the varying hardness of the shaft and stock/aftermarket sprockets, and B) a more affordable cush-drive sprocket than the one made by RAD Manufacturing.
You're really going all-out by lengthening the frame, Luke. Great job. I hope to check it out in-person in a few months.
No one has accused me of being too conservative with this build.
You're coming back to Portland? Any guess when? It'll be good to see you.
A little more work got done today.
I pulled the bushings from the shock and measured them. I'll replace them with spherical bearings which should work better.
Ohgood had the right tip on cutting the sprocket. I put it in the big lathe, set the speed as slow as possible and it cut quite nicely. Slowly, but nicely.
I put a countershaft in the engine cases that are mounted in the frame. Then fit and adjusted the chain.
This is with the chain tension adjusted and the wheel at full extension. The slack looks pretty good, there won't be too much work for the rollers and guides to do.
It's a long bike.
SWEET!! tall enough for us normal people almost! ;-)
You can check hardness of stuff with a good file.. if the edge of a good "mill" file cuts a piece easily, the piece is usually soft or not yet heat treated. If it "screams" or "sings" off the piece, its harder than a preachers dick in a ..... well you get the idea.
You can use that to check areas around welds, or welds themselves. If it gets too hard, watch out! There's a whole bunch of hard vs tough vs strong vs black magic I can't remember anymore... but it matters sometimes.
This project isssssss great!
Its looking good, You'll be finished by next week at this rate.
I bought a brand new 94 XR600, put an aftrmarket 13t c/s sprocket on and had this happen in 450 miles of two track dirt riding. I bitched to Honda USA about a having a soft c/s and they told me they have never sold a XR600 c/s. I replaced my c/s and ran the OEM 14t with more teeth on the rear sprocket to gear down without any more problems. Since I have seen 5 other c/s wearing the same way, fixed two of them...each and every one was running an aftermarket c/s sprocket. Still bugs me that Honda USA told me they have never sold a XR600/650L c/s.