os .21 vg advice needed

[meno222]

hello i just got a used os .21 vg. that was run with 30% nitro fuel. what i want to do is run it with 20%. the engine has one silver shim, do i need to remove it or change it to a differernt size shim. i would really aprecciate your advice.

 

[ajames942]

Not sure what a Shim is but if you would go to 20% all you would have to do is retune it. Dont keep switching though

 

[MrClean]

Most engines have shims between the cooling head and the engine, for sealing purposes. They do make shims for installing 'long glow plugs'. I'm not 100% sure, but I don't think you'd need to remove/change shims if you stick with a standard sized plug.