Question on a Rossi 21

[jeff246]

I've got my rossi 21 outboard all broken in...its the one with the silver 4 bolt head. It had the fat head shim it came with in...should I now change it to the smaller one, or should I take the head shims out all together? I've been runnin between 30%-40% nitro through it.

Thanks,

Jeff

 

[topfuel443]

What head button do you have in it? The stock one that takes a turbo plug? If so, its not a good volume (too large, even for your lower nitro) for that engine.

What is your head clearance? "Fat" and "smaller" is not the best way to describe a headshim. I havent had much luck with the stock headbutton, but with a new headbutton, we usually run about 6-8 thousandths of clearance.

Find out what clearance you currently have, then measure your shim thicknesses, and determine what shim (if any) you will need to get to your desired clearance.

~James