4 speed 250r

[ATC NUT]

I bought a 83 250r engine..I was told it was a custom DG race engine ..the jug was ported and DG logo scribed in the top fin ..it had a sunburst head on it ...but the guy sold it before I bought the engine ...he told me it had a four speed gearbox..he said the engine was in a shifter cart he had bought..anyone ever heard of a 4 speed 250r?..was this custom...I'm trying to restore a second gen 250r ...just wondering if anyone ever heard of any racers changing the gears ..I had a 83 growing up and it was a 5 speed ..so any info would be helpful

[Footy]

Any chance that the engine could have been a 1982 CR480R engine?
Those are 4speed and also have the counter shaft out put on the right side of the engine like a 1st and 2nd gen ATC250R does.

[350for350]

That's what I was thinking. I couldn't remember for sure if it was the CR480 or the CR450, but I thought that one had a four speed trans.

[ATC King]

Finding some numbers on the engine and going from there would be a good idea.


Beyond that, it's not uncommon for certain competition engines/transmissions to have gears removed. If those gears aren't needed it's just increased rotational mass and friction, slowing it down. Motorcycles and ATVs have a sequential, constant mesh transmission, all gears spin all the time. Without getting into the mechanical details, that's why they don't need synchronizers like automotive manual transmissions, especially for higher RPM use.

Fewer gears also take less space, so if the engine is built to a point it's damaging a stock transmission, a new one can be made with fewer, but wider gears to stand up to more power.

If you'll find out by the numbers, or pictures, of what engine you have, then you can go from there to tear it down and see if they done anything permanent or you can just add back the missing gears/gear.