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Repaired Frame discovery
http://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=21&t=4702		 Page 1 of 1
Author:  MT250GUY [ Sun Nov 06, 2016 6:34 pm ]
Post subject:  Repaired Frame discovery
Well, the 74 MT250 I bought has had a couple welds done to the frame. I'm not happy about that. My intent was to do some mild trail riding and also right around the country side from time to time. That fact is I've no idea of the quality of the welds or the skill of the person that did them. The front sprocket wobbled a lot an I just figured it was shot and needed replaced. But now I wondering if it was by necessity since maybe the frames not true and the chain was binding up on it a bit and damaged it. Also, the thing appears to have thrown a chain at one point and busted the left side case lip near the sprocket. There's also some lateral slop in the rear sprocket. This leads me to wonder:

Could it all be related to a tweaked frame?
Should I feel comfortable riding this thing not knowing if some yahoo welded in his barn?
Getting everything checked out properly is probably just not worth it for the value of this bike... :evil: :evil:
Author:  rayivers [ Sun Nov 06, 2016 8:36 pm ]
Post subject:  Re: Repaired Frame discovery
If you're concerned about the frame welds and know a good local welder, take in in to them once the bike's running and have the welds re-done. I've had broken motor mounts, cracked swingarms, shock mounts, drilled holes, etc. fixed this way, plus I've added chain guide mounts, swingarm stiffening bars, custom exhaust pipe mounts, etc.

The rear sprocket slop may be caused by the 'cush hub' rubber bumpers inside the LH wheel hub, which get squashed and dry-rotted. I'd just replace the front sprocket (PBI's are $12 shipped on eBay) and use a new fixing plate & bolts, as the sprocket that's on there may not be correct (at least they didn't weld it on).

If your motor mounts are good, the swingarm's straight, and your sprockets are undamaged & mounted correctly, your chain alignment should be fine. I'd get both your sprockets tight first, then put the chain on and see.

Ray
Author:  MT250GUY [ Mon Nov 07, 2016 5:32 pm ]
Post subject:  Re: Repaired Frame discovery
With the rear wheel off I rigged up a laser collimator and speed square; projected a beam from 2.5 cm inside of the left swing arm (approximate center of rear sprocket), and the beam hit the center edge of the front sprocket. Of course, I made sure my setup was orthogonal, etc... So, at least it's not tweaked in relation to the sprocket alignment.

Thanks Ray. I appreciate your input.

Al
Author:  Rick [ Fri Nov 11, 2016 10:30 am ]
Post subject:  Re: Repaired Frame discovery
I use my eyes as I don't have one of those things. What is it called again? :)

Rick
Author:  MT250GUY [ Sat Nov 12, 2016 6:07 am ]
Post subject:  Re: Repaired Frame discovery
Rick wrote:
I use my eyes as I don't have one of those things. What is it called again? :)

Rick


Hey Rick,

It's a small machined cylinder with a laser diode housed in it. It's really meant for aligning optics in telescopes (an expensive freakin hobby of mine). Anyway, using it and some hillbilly engineering saved the day.

Al
Author:  fasteddie [ Sun Nov 13, 2016 8:03 pm ]
Post subject:  Re: Repaired Frame discovery
If you're interested and anywhere near Texas..I have a 74' MT parts bike I bought that I thought I would use the cases for to rebuild my project 73' CR..frame is in good condition..its missing the top end..pipe.. tank..seat..turn signals and tail light assembly..I decided to use original CR cases so I won't be using the cases or sidecovers. until I get mine torn down I'm not sure if I will need the crankshaft..but if I do theres still a lot of parts and the frame I'd be willing to sell. Drop me a line if you're interested. Eddie Williams 3456 Sam Houston Rd. Willis Texas 77378 936-524-6877 or 6877ew@gmail.com
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