stroker rods.

[Dude]

Since we can use some select honda rods has anyone ever bothered to see how much of a stoker rod we can use before trenching +2 +4? any ideas?

[Sixdays]

You are actually talking about the crankshaft stroke not the rod.

You can also use a custom rod with a smaller dia big end so you donr have to trench the cases.

A 2mm stroker only moves the rod end 1mm out on the crankshaft.

[Dude]

So do any of the trx250 or cr250 cranks fit in?

[Sixdays]

I dont know but doubt it.

[GMP]

Cranks are not interchangable, rod kit is same as Honda CR250 thats all.

[Dude]

You can buy cr250 rods that are 4mm and 6mm longer eye to eye on the rod.

[noobi]

You could put in a longer rod if you made up an appropriate spacer to raise the cylinder up however much longer the rod is over stock, however I cant think of an advantage of doing that, other than to change port timing??

The rod length doesnt determine stroke length, the crank offset does. So a longer rod with the same crank doesnt increase capacity, it just moves it to a different portion of the cylinder.

[Dude]

I guess i figured it would add case volume

[Sixdays]

Most of the time a smaller case volume is better. It builds more preasure to push the fuel and air up the transfers.


But a long rod makes a smoother powerband and a short rod makes a snappy powerband. But a short rod side loads the piston much worse. It also raises the piston speed.

[socalscott]

Long rod gives a mechanical advantage. Early 90's YZ 250 kit was a winner, but they liked the drop in negative(case) compression.