Hi fellows.
Maybe this winter I'll get the head of my shee shaved. It will higher the compression (Someone stop me if I'm wrong) and if I do it up to a certain point, am I not going to have to run race gas?
What's the maximum shaving I can do keeping running on pump gas?

 

Do you also plan on changing pistons at all? Any good machine shop should be able to tell you how far you can go. It doesn't take much to raise compression levels drastically. So you want to be careful and have someone experienced do it for you.

Depending on your altitude, I wouldn't go much over 10:1 (for a compressin ratio) if you want to stick with pump (premium) fuel. Once you get up to 12:1, to run to it's utmost effeciency, you're looking at 108 octane.

It all determines on the bore (if it's been bored or honed at all) and the cc size of the head.

You may want to check out www.rageperformance.com

 

I spoke with a representative with Team Alba about the same subject before. Call those guys and they will steer you clear on taking too much off of the head and killing high rpm power. Do a net search to get the website. Good luck!

 

I've taken 75 thousandths off before as a max. This only bumbed up the compression to around 165 or so and you can still run pump gas. If you go more than 75 thousandths you risk breaking through the water jacket on the backside (side towards the taillight). If you take 60 thousandths off you will be safe, then all you need to do is cut the squish back into the head 10 thousandths and it will leave with the right amount of squish once you install the head with the head gasket. I've done around a hundred of these and it's about the best you can do to raise the compression up to around 160-165 or so. Any higher and you will need an aftermarket head with domes.

Jeff

 

I want to get my head shaved this winter and I want to still run pump gas. I talked to rage performance and he told me that I would have to run race gas if i had it decked by him. Can you Deck my head or do you know someone who can do it right so I can still run premium gas?
Thanx
scotch

 

Thanks for your answer...another question(s).
When I shave the head, is it gonna make a difference if I change pistons/rings or if I keep the old ones (assuming that they are not used too much)?
Will I have to change my premix (I run 50:1 now)?
Will I have to rejet my carb?
I guess I'll have more power, but where? low end? high end? everywhere?

thanks

 

Whether or not you're shaving the heads or decking the block you're still accomplishing the same thing...lowering the combustion chamber size. Which in turn also raises compression ratio. When you increase compression ratio you need to increase octane to reduce the amount of pre-detonation of fuel.

There is no other way around it, if you want higher compression (above 10 or 11:1) you're gonna have to run a higher octane fuel.

 

Well, the majority of my experience comes from 4-stroke engines...So by increasing compression you see a broad increase of horsepower (througout the powerband).

However I'm uncertain if this is true with 2-strokes as well.

Macdizzy will most certainly be able to answer your question.

www.macdizzy.com

 

40:1 might be better

Jetting: possibly, the increase in compression creates more heat.

Power: Low to mid range is where it will be most noticable.

 

OK.
Someone tell me if everything is right.

I can shave the head 0.075", keep running on pump gas, modifying what should be (premix and jetting), and it will work fine (even better)

Is that it?
Sorry if I'm boring but I don't want to scrap my engine because I didn't read a post accurately enough.