Worth it to rebuild a JDM bike? | GTAMotorcycle.com

Worth it to rebuild a JDM bike?

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Caboose87

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So a few years back I bought a 1991 CBR 250RR. The bike had been sitting for who knows how long, so over that winter I did a bunch of maintenance to it to have it in good working order. When it got closer to spring I started it and tried balancing the carbs. The bike was running like **** though and was blowing a bit of smoke. When I bought it it was cold out and I figured the smoke was just condensation, but obviously I was wrong. So I did a compression test and the compression was bad on 3 of 4 cylinders. I took the pistons to a mechanic and he said that the rings had failed probably from the engine not running for a long time (measured the pistons and they were within spec).

Anyway, so now I'm stuck with this bike, and I'm not really sure what I want to do with it. I can source the parts and do the engine for about $500. The carb also needs work though. The biggest thing is that the rubber vacuum diaphragms have all split, and there is also so corrosion on the jets. Diaphragms are $80 a piece, maybe the jets are still good? Other than that, it needs a new set of tires and a new chain.

I should have listened when I was told by a mechanic that I was buying a cat in a bag, but I was fascinated with the bike at the time (still think it's pretty cool, shrunk down supersport). The thing is, even if I sink the money and time into it, there's no guarantee how well it'll ever run (or for how long); but if I don't, what else do I do with it?
 
I'll buy it off you for $1 for every CC that bad boy has...
 
They are great little bikes and the engines are usually bulletproof. Nothing quite like the scream of a 250 doing 19000rpm with a pipe. Not sure how common they were in canada but in Aus these things were one of the most popular bikes on the road at one stage due to licensing restrictions.

Depends how deep you are into the project IMO. If you can sell it running for more then you paid for the bike + repairs then id say get it fixed. If not just part it out or sell it as a project to someone else and hope you get some of your investment back.
 
If you've "measured the pistons" then I take it you already have the engine out of the bike and the top end apart.

At this point, splitting the crankcases for a bottom end inspection will cost you nothing but some time ... unless you find issues, in which case, you are better off having done it. This is a no-brainer.

Get the cylinders honed (should be about $10 per cylinder), put new piston rings on them, put it back together with a new head gasket, and there you go!

I sure hope you have an English-language service manual (or can read Japanese!) ... or at least have access to the torque specifications. If you've never done an engine before, you need to follow the directions in that book to the letter.

If you do this job properly, it should be good for years and years ... provided that you ride the bike.
 
What Brian said. Also, parts are only going to get harder to find from here on out, so if you don't plan on fixing it, you're better off getting rid of it.
 
You guys are right, I should finished what I started (just like I learned when I was 13 :lol:). This bike will be a riot when it's running.
 
Fix it! I too have one (admit an older model) and the exhaust note at 19,000 rpm is worth the price of admission.
 
It's only worth it if you are gonna ride it or sell it to a collector as a mint unit which yours is probably not.

Your bike is good as far as parts availability and a manual in English. If you have the time do it, but inspect the bottom end as Brian said. I didn't and it has cost me more doing it later when my conrod bearing spun. It's a cheap insurance as they say when you buy a bike of unknown origin.

Good luck..... There's something about redlining those little 4 cyl. devils.
 
My co-worker has one of these bikes, a 1994 model though. I took it for a spin and it's a wicked little bike. I say fix it and keep it, or sell it to me! :)

You can maybe source a set of carbs for it on the 400greybike forum classifieds if you're lucky. There's also ebay.co.uk for aftermarket stuff and to check if people are breaking bikes. Used parts might be a cheaper option. If you do rebuild it properly it should run for a long time. The engines are pretty reliable if they don't sit.

Where are you getting the engine parts from? I'm pretty sure you could order new rings, diaphragms and a jet kit from these guys:

http://www.elliottmc.co.uk/products/95

There's also www.cmsnl.com/

Just did a quick browse on EbayUK, there's all kinds of MC22 spares on there right now.

The best option is buying a set of FCR flatslides from Japan. Free shipping on those!!! haha

http://japan.webike.net/products/1228124.html
 
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Apparently, if you contact this seller he can get most parts from Japan for JDM bikes.

http://myworld.ebay.co.uk/wwwisicarcom/

He's got rings for my bike (NC30) for $225. I'll bet he can get a jet kit too. Trick is to buy as much as possible from 1 place/person to minimize shipping costs.
 
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