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I just bought a 1979 kz 250 from an old friend. I saw the bike years ago and it looked great but have not seen it recently. I trust the friend so I bought it on the phone. About 5000 miles on it. Yes, only 5000......
She says it runs well but has a leak around the head gasket and the top speed is about 55 MPH.
She does not know if the leak is a weeping leak or something serious.
I'm just looking for information about this particular model.
Any known common problems?
Were head gaskets a common failure?
Parts easily available? Does 55 for a top speed on level ground with a 150 pound rider seem slow?

Will I have a problem with the rubber parts in the fuel system if I use gasahol? That is the only fuel easily available here.

Anything else I should know? I'm an experienced mechanic but have not worked much on cycles.

Thanks for any help! Al.

Where is "here"? My guess is yes, you'd have problems with the rubber lines using e85 unless they were made to withstand it. And I'm not too sure how recent e85 is so maybe in 1979 they didn't have it.

Its only 10 percent ethanol. Not e 85.

I had a few problems with my '70s cars and bikes when I first had to put alcohol tainted fuel in them. Composite floats would sink and certain types of fuel lines would swell from 1/4" to the size of a hot dog. Floats and fuel lines were the only problems I had.

55 mph for the KZ250 sounds a little slow. In good condition you should be able to get at least 70 mph out of it. Since the bike has only run 5K miles in the last 27 years, it's likely that the carbs have gummed up. If the main jet is partially blocked, that'll cut your top end. Since you're mechanically inclined, I'd recommend pulling the carbs for a thorough cleaning as the first order of business. A compression check wouldn't be a bad idea either. Lastly, you might want to check in with the folks at KZRider.com. There are a lot of KZ knowledgable folks and several KZ250 owners on their forums.

Good luck with the new bike!