Vintage Dirt Bike Q & A

I bought a cylinder and head off Ebay awhile back and didnt realize how much bigger it is than the 2nd one I purchased for my 1974 CR125M. It appears to have been highly ported and polished, whats really confusing me if the addition of the 2nd plug hole. Can anyone tell me what it is or came from?






Heres a few more pics, theres a strange symbol and a number (388)on the bottom of the head. The stock cylinder measures 56.4mm, the red one measures 57.3mm bores. Red cylinder will mount to the CR125M bottom end. Maybe the symbol will help here. Thanks Again
Vin

Maybe a compression release??

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1974 Honda CR250M
1979 Honda CBX SS

That doesn't look like any CR125 head I've even seen. Could it be off an MR175? Maybe the MT or MR guys would know.

The second hole in the head could be used for either a compression release or a spare spark plug. If the head came from an MR the compression release would make a lot of sense since they were used for steep downhills among other trial related terrains.

It is not an MR175 head because the bolt holes are not lined up in a square pattern like the CR125. Maybe a later CR125 like a 1980?

Thanks Guys, Guess were all stumped on this one. What about the little symbol I found on the head, what is that? A Honda symbol? Aftermarket? Anyone, Anyone?

Great site Nathan maybe some day I can post the pic's of this monster I'm restoring.

Vin

My next project I'm buying parts for now is a AZ600 Coupe, the first model car that Honda sent to the united states in 1970-71. It has a 600cc twin cylinder motorcycle engine in it.
Check this lil puppy out.