1980 cr250r swingarm pivot elongated

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2/28/2018 11:09 PM

So as I am disassembling this bike and noticed a lot of play in the swingarm. Further investigation revealed the swingarm pivots in the frame are all wallowed out. I can actually move the bolt almost 3/16" in the frame hole! Has anyone ran into this before? I was thinking of welding it up and recutting the hole but not sure if it would be centered correctly. I am thinking the best fix would be to enlarge the hole until it is round and fab up a bushing and source a new pivot bolt.

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When in doubt gas it! It may not cure the problem but it will end the suspense!

3/1/2018 4:44 AM

wertman194 wrote:

So as I am disassembling this bike and noticed a lot of play in the swingarm. Further investigation revealed the swingarm ...more

Ouch, they rode it to death! The reweld and bushing idea seems reasonable. On center is another thing. Perhaps you can obtain the chassis blueprint or a fiche, engineering draft of the hole locations and sizes. Most likely all in mm...As long as the frame is not twisted I am thinking a tall drill press / vertical boring machine... I would go for it imho. It can only get better ! Also, what about a good replacement frame? Cheers

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3/1/2018 5:09 AM

I really wanted to save the frame as I have the title which can be hard to come by on these older bikes. The left side is not as bad as the right so I think I can keep it pretty centered. I could probably take some dimensions from that side of the frame to ensure I am close on the right side. This bike was a one owner trail rider that appears to have only done maintenance when needed (everything is worn out). Cracks me up when selling a bike and the buyer asks if it was ever raced. Most racers take extremely good care of their bikes and they are not all beat up from rocks and trees and the like, but the buyer always considers it a negative point. Ignorance is bliss!

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When in doubt gas it! It may not cure the problem but it will end the suspense!

3/1/2018 5:16 AM

wertman194 wrote:

I really wanted to save the frame as I have the title which can be hard to come by on these older bikes. The left side is not ...more

For sure ignorance is bliss. Never raced translation, most of the time equals "never maintained" and beat to death" . "Fast bike too"... Gotcha on the originality thing. I was checking out that CAD swingarm post and I am sure you guys will get done what needs to be done. Hard parts / major components design and manufacture. I cant believe i even get to read about that, let alone converse with folks that have that kind of knowledge and experience. So cool... Good luck and keep us updated... ☺

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3/1/2018 7:07 PM
Edited Date/Time: 3/1/2018 11:33 PM

The left hand side is better than the right.

You can perhaps use measurements from 'mirrored points' from one to another to achieve accuracy in the mount hole placement. And use the advice I give further on.

Or, If both sides have a 'healthy' section of the original bolt hole left, you can use a Engineers Washer ( goodness only knows if that term applies in the USA) or a machined washer / spacer to use as a drilling guide.

If you can find enough of a segment of the original bolt hole arc, you can 'match' the washer / spacer to that arc (and perhaps the 'mirrored point' measurements I mention above) and tack weld said Washer / Spacer to the Swingarm mount plate. This given my assumption that an 80 model has just plates as the swingarm mount area, and not a three dimensional section as later bikes did / do.

The tack welded part then gives you a guide for accurate drilling, even with a hand held drill. Just go in small steps as you go towards the ID you are working to. If it's a hardened Engineers Washer, you'll need good drill bits, and a bit of cutting fluid / lube as you go through to the size you want to achieve. The drilling for either, making a much larger, 'completely circular' hole for then welding in a 'top hat' type spacer that you then weld in, or if you just infill with weld the flogged out plate on the inside of the frame. But, infilling the weld will require you to then make sure the resulting face is filed / machined flat to mate with whatever swingarm spacers / end plates the bike used. It's Very important for the inner face to be perfect! A 'top hat' type spacer welded in obviates the need for what can be a Very tedious chore. And, will be much stronger. Of course, you will probably have to source a longer SA pivot bolt. I very much recommend that you go the machined 'top hat ' spacer route.

Of course, a full weld around the circumference of the Washer / Spacer / 'top hat' insert is to be done. A 'top hat' insert can also have the inner , swingarm side circumference welded.

I write from having a TIG (for decades, so I guess I'm a bit blaze' about it) , and I urge you to Not f**k around with any other form of welding. Cripes, every man and his dog can get a few hundred dollar TIG, from their local Hardware store now, so it's not hard to get access to one. Whether or not the bloke / blokette that has it, knows how to weld well with it? There's so many people with "all the gear, and No idea" now. It's not hard to find someone who has a TIG, and Knows how to use it.

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3/3/2018 12:39 PM

Had this exact same problem. I made up some top hat bushes.
I think I went up to 17mm dia I made the heads quite thin, only 1mm. So the stock spindle length was fine. (we make new spindles by the way).

If you fit the swingarm bearing pivot bushes, end caps and engine hanger bracket (you could bolt the engine cases in aswell) along with the spindle and new bushes it will hold everything in line. You can then tack the top hats in place.

Tig weld, or braze. DO NOT GAS WELD THEM!! Gas welding will make the weld and surrounding area brittle and much mire prone to cracking.

Stevie

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3/3/2018 12:47 PM
Edited Date/Time: 3/3/2018 12:49 PM

Thanks Bearuno and Stevie! That is what I figured and have the frame at the sandblasters right now. I guess I needed a reason to paint it anyway lol. Any progress on the CAD swingarm Stevie?

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When in doubt gas it! It may not cure the problem but it will end the suspense!

3/4/2018 9:54 PM
Edited Date/Time: 3/4/2018 9:54 PM

That looks a neat solution, Steve. Heard too about the possible issues with gas weld.

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