Vintage Dirt Bike Q & A

Hi, I was wondering what everyone thinks about rechroming a cylinder verses sleeving it. In particular, have heard that sleeved cylinders run hot. Is this true?

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Joe

72 Yamaha CT2

Technically the heat transfer properties of the chromed cylinder are better than an iron liner, hence the chrome finish being chosen in the first place. That being said, many engines came with iron liners stock, and I have good experience with both types of cylinder on the same '79 CR250R. In a National with an expert or Pro rider back in the day this might have been a make or break difference, but with a novice in a 5 lap vintage race? However, what I have noticed is that the LA Sleeve sleeve does not line up with ports well on the CR. One might expect a little mis-alignment that could be cleaned up with a grinder, but in this specific case something else is up. The '79 has a bridged intake port and the hole in the cylinder for the secondary port is significantly larger on all sides than the port in the sleeve. To be perfect the resulting step would need be filled in and/or the sleeve opened up some. So if you pass me, that's the reason right there.

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

Thanks for the help. I had my cylinder reseeved using a wiseco sleeve. Your comments got me thinking, so I took a close look a it. My cylinder is a 79 so there is no intake bridge. I did notice that there is some extra material around the intake port (1/32"). Should I try to remove it or just leave it. Also, the sleeve does not line up well with the exaust bridge. the bridge is shifted amost a 1/16th of an inch to one side. Do I dare do any grinding to try and fix it or would this do more harm than good? The exaust bridge seems to be a problem area on these bikes.

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Joe

72 Yamaha CT2

A couple of things to bear in mind. If you change the fundamental size and shape of the ports, you are of course changing the timing etc. You are also making the sleeve and cylinder a "mated" pair that will make it difficult to re-sleeve without more work. I can't imagine removing any material from the exhaust port bridge is going to help it dissipate heat. I have left my cylinders alone, except for a little clean-up work LA Sleeve did at my request. I can live with the nominal power losses and have kept a special chrome cylinder for any porting work I want done.

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF