Vintage Dirt Bike Q & A

I have just pulled the cylinder on my 79 resto project , i think that it is still in good shape. after removing the piston from the rod i checked the rod end play it moves from side to side a little but seems to be tight up and down the crank bearings seem to be tight as well. the rist pin however is wore some. do the mfg still make stock pistons and ring sets ,and is the rist pin and bearing still avalible ? or will i have to go with a wisco or after market ? now for the cylinder , it still looks good it has some ware lines but their is nothing that you can feel what would be the ring gap tolerince and where would you take the measuments. thank s in advance ,

Hi fudge. A little side play is normal and necessary on your rod. Up and down is bad, very bad. Roll the crank around and make sure there are no tight spots or noises. Check the rod for play in a few places of crank rotation. You can take the generator cover off and check for play there too. That'll give you a better idea of the shape of at least one main bearing and is easy enough to do.
Does the small end of the rod look smooth? A nice clean bearing surface? I'd put a new wrist pin and bearing in with a new piston anyway, cheap insurance.
Not sure if Honda still has pistons for this one. You'll probably have to go with a Wiseco piston. They're good quality though. No worries!
The 79 CR had a chrome plated cylinder. Is yours still plated or has it been sleeved? Probably be a good idea to take it to a good shop and let them measure it to make sure its still straight. If it has been sleeved, you may need to have it bored. If it's still plated, does it look OK with no peeling or flaking?
Hope this helps a little!

Wiseco has everything you need to re-build the top-end on the '79 CR250R. You do need to watch for a couple of things. First, there are two types of rings - one for cast iron sleeves and one for the original chrome bore - so you need make sure you know what you have. Second the piston will come ready for a 1978 cylinder that had a single exhaust port. The 1979 has a bridged exhaust port and you need drill some oil holes in the piston to match up with the bridge. (The instructions come with the piston.)

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

Thats interesting I have a 79 and i put a wiesco in it i have only had it runnig one time and when it was running it was not running right i never looked at the directions would you happen to know what the symtoms would be if you did not drill it. by the way girls read directions.

It might sieze at the exhaust port bridge and cost you a lot of money. Your wallet, your gamble.

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

would you happen to have a set of directions you could send me a picture of so i do not blow the bike up. thanks

I don't have the specifics. I remember three small holes and that each needed to be counter-sunk and cleaned up with a file to ensure there were no burrs. I would go back to where you got the piston and have them open up the box of one that is un-used. Or call Wiseco. Sorry. I guess only real girls keep the instructions...

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

If you can't find a copy of your instructions, pm me and I can fax a copy to you or send it.