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Hi Guys,
I have got a head for an L9, I am sending it for porting and polishing.
Having the head down I could do sometimes with the pistons.
I am thinking about changing the rings, but maybe put some hight compression pistons.
I have no intention on reboring, but maybe just put some hight compression pistons that are the original size.

What do you suggest?

cheers
Ruben

I think that the "standard" compression is 12:1, so how much higher do you want to go?!!
Do you realise that a new set of rings will set you back a significant amount of money? I suggest that you wait until you have your head done, install it and check the compressions. That will tell you if new rings are needed. To raise the compression, you can leave out the base gasket, BUT you must check the clearance of the valves as the pistons rise an fall. I don't know the details, but am aware that if there isn't sufficient clearance, then valves and pistons could meet at 14,000 revs.

thanks for your reply,
I read that Hight compression pistons have a compression of 13.1
the cost of the rings is about EUR120 plus shipping on ebay for genuine Kawa parts, not the end of the world.

As you suggested I could fit the new head, and check the compression and then decide.
How would you check the clearance, if i decide to leave the base gasket?
what is people using to seal the base of the base of e piston with?

but I think the question now would be, what does this mean in term of performance?

thanks a lot in advance
R

Go to Forum - Downloads - Race manual page 3. That gives details of piston to valve clearances. Something like Plasticine can be place on the valve cut-outs to measure the amount of "squash" between valve and piston when the engine is turned over. Something like Black silicone sealant can be used to seal the barrels to the crankcase...which is what would have been used either side of the gasket.