Vintage Dirt Bike Q & A

I got my mt running today nos cr cylinder everything was replaced except the crank it didnt get a rebuild but all other bearings are new. I havnt ever had a two stroke before and am not sure how to break it in. I was told to run it at 20:1 and am but it fouled the plug in about a minute or two. What should I be running it at and what plug should I be using? Havnt been able to ride it yet as I still need a chain anyone know how many links? It runs really nice or did until the plug fouled. I didnt have any atf for the crank case so used some 10-40 oil yes it made the clutch drag im gonna take it out as soon as I get some atf. The speedo cable almost didnt fit after the fork upgrade anyone know of another cable thats about two inches longer that will work?

I wouldn't run 20:1 premix unless the oil manufacturer recommends that. The main concern on a break-in
is not to over rev or over load the engine.

The shop that built my race engines used to send an "owners" manual that spelled out in detail how they
wanted the engine broke in. They even sent me a quart of special Kawasaki break in oil for the job (I guess
Honda doesn't make any). I imagine any quality petroleum base two stroke oil will do for your MT.

What they said was to use the break-in oil mixed at 32:1. Ride the bike on firm terrain (no deep sand)
at no more than 1/4 throttle then let it cool back to ambient then do the same at no more than 1/2 throttle.
Then again at no more than 3/4 throttle allowing it to completely cool off each time. The rings and bore
should be used to each other by now. Also, you should be using the standard spark plug for break-in.

Change to a new spark plug, switch to a good synthetic oil and go for it.

As far as plug type and chain links, both of those items are specified in your owner's manual. If you don't have
a manual, let me know what year and displacement your bike is and I will forward that info.

dogger

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1973 CR250M
1979 CR250R
1993 CR250R
2008 CR500R
2009 CR250R