Vintage Dirt Bike Q & A

Hi, I have a 74 CR 250 I'm finishing restoring and I was wondering if anyone has proven results on how the best way to break in a rebuilt 2 stroke. My engine has all new bearing, seals, fresh 2 over bore, and new wisco piston. Also should I start with the stock carb jetting or does it need to be changed because of the overbore.

Thanks for any help,
Matt

Hi Matt! Jetting should be the same, because you haven't really changed much with the bore.
This is one of those questions that have as many answers as answerers!
Anyway, I ride for about 15 min at a moderate practice pace, then let the engine cool off a while. Then 15 again and a cooling session. Then 15 again and a cooling session. By then you'll want to ride it! Biggest thing is not to get it hot right away.

Also once you get the bike hot and let it cool down re torq the head bolts.

there is an interesting article about break-in on this site.

http://mototuneusa.com/

It is a free newsletter site, but you'll have to enter your email to look around. It has a wealth of "outside the box" knowledge to check out

Cheers,
Ryan

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1980 CR250R Elsinore

I remember coming accross that article about a year ago. It seems pretty convincing by his photos. It suggests that you use a non synthetic oil to break in and seat the rings. Does anyone know a good 2 stroke oil that is not synthetic? Most of the quality race oils are all synthetic.

Matt