Tweaking 7900 without cylinder porting

[4492011]

Hi I would like to tweak my 7900 without cylinder porting. I think that the biggest question that I have is if I remove the cylinder gasket to get more power what would be the minimum squish measurement if it were run on premium pump gas using 40:1 mix of mobil 1 2t oil. I have messed around with snowmobiles a little has anyone tried to just take a little off the intake skirt of the piston? I have modded the muffler at this point just looking for a little more.

 

[Peacock]

You'll gain a bit of torque doing that but will likely lose some rpm and some cutting speed due to the change in port timing.

You could go to .020-25" pretty safely imo.

I don't think I'd take anything off the piston without porting the rest of the motor. I doubt you gain much if at all. You're just going to increase intake duration and wouldn't likely benefit without opening the exhaust as well.

I'd just mod the muffler if it were mine.

 

[drmiller100]

muffler mod, mod the top cover on the intake, remove the base gasket, advance the timing, and you are going to see a noticable improvement.

i would certainly consider an 8 pin wheel as well.

 

[4492011]

Thanks for the help what kind of mod to the intake cover? and can you advance the timing without grinding off the flywheel locating boss?

 

[drmiller100]

take the air filter cover off. turn it upside down.

see the shelf wiht all the little holes??? make another BIG hole.

to change timing easy way is ot remove flywheel boss.

 

[4492011]

Thank how big of a hole?

 

[rbtree]

better to get the new style cover....unless you already have it.. Seems to breathe well enough to me......and one of mine is woods ported.

 

[drmiller100]

what he said. get the updated filter, i'm gonna ask my dealer for one.

but, if not, then 1 inch????? big ugly huge hole. Why not???

 

[William Balaska]

If you pull the base gasket on a saw that allready makes 180psi you will probably have to run race gas in it, Rule as far as I know is 180psi on pump gas max

 

[Meadow Beaver]

You can keep the head gasket if you just deck the cylinder a little.