78 CR250 cylinder material

[jumpingjoe628]

I was wondering if the 78 CR 250 cylinder wall was plated or sleeved. I want to hone it out and install a new set of rings. I already have the rings, and the piston and the cylinder looks to be in good shape. But there are a few scuff marks that concern me.I plan on racing this bike in ACR events pretty hard as an expert, but I will do regular topend maintenence on it so I just want to get a few more practices and a couple of races out of this configuration before I start replacing parts. I took a couple of pics to show as well. These were taken on both the intake and exhaust sides.

http://wopr.myftp.biz/pics/10 Vintage/IMG_0592.JPG
http://wopr.myftp.biz/pics/10 Vintage/IMG_0593.JPG
http://wopr.myftp.biz/pics/10 Vintage/IMG_0606.JPG
http://wopr.myftp.biz/pics/10 Vintage/IMG_0610.JPG

 

[TimberPig]

Steel sleeved. I believe it was 87'ish (?) before they went to plated cylinders.

 

[jumpingjoe628]

Hey Timberpig, did you see the pics? I guess I can go ahead and hone the cylinder then because the scuffing isn't too bad. Thanks for the info.

 

[jrm]

The 78-79 CR250s had a chrome bore from the factory. Can't tell from the pics if yours has been resleeved with a steel sleeve or not. The bore does look like it needs some work on it. Plenty of places can fix your cylinder up for you, either with a sleeve or a slight over-bore, re-chroming, and use of an oversize Wiseco or Vertex piston. Good luck.

 

[TimberPig]

I thought they were steel until the late 80's? Or was it chrome until they switched to Nikasil in the late 80's?

An easy way to check is to look at the bottom of the cylinder, the sleeve will be very dark grey next to the aluminum. The line will be readily evident. A magnet will also stick to a steel sleeve.

Sorry if I was incorrect, not trying to steer you wrong, I was just under the impression they were steel sleeved back then.

 

[jrm]

Honda (at least) went back and forth during this period. Up to 78 they used a steel bore. From 78-80 they used a chrome bore. With the introduction of water cooling in 1981, they went back to a steel bore, at least through 1985. You are right that sometime during the mid to late 80s Honda went back to a nikasil-type bore.

 

[TimberPig]

That makes sense, thanks for straightening that out.

 

[jumpingjoe628]

Well, a magnet dosen't stick to the bore so I guess it's plated. Is it that bad according to the pics or can I carefully hone it a little. I can't even catch my fingernail on any of the scuffs. If it was real bad I was going to send it to Eric Gorr, I know he's good.

 

[TimberPig]

If it won't catch a fingernail, hone it, make sure the piston to wall tolerance is acceptable, set the ring gap and run it.