lowering compression

Anyone having knowldge in the compression ratio??

Im running a 1197cc/76mm but wanna lower the compression - anyone knows approx how much what, will give??
EG. 1mm ticker gasket gives around 0.5 ???? from 1: 10.5 to 10....???

just a rougly idea where to start

/Lars

What pistons /head are you using,how much are you trying to lower it? Has the head or block been milled/how much?

The head is a stock lz1000a head with stage 1 done by joe/PSP
yes the cylinder top and head has been planned

i know i cant have anything direktly but just a guide line

Pistons is from a company called REC-tuning in germany (horrible service) -ordered to be around 1:10.3-5 compared to Wiseco's 10.25

I've read that on a 810 kit for a 650 every .010 cut on the head will pick you up approx 2 tenths of a point...... totally diff animal I know so maybe I should stay outta it........ I've also read that checking the cc's (volume) of the head and piston is really the way to know for sure what you have...... and one more use less hear say I've read that Wiseco's are slightly less in comp than they state also.(why a head cut is recommended on the 650/810 build.

What are you trying to achieve here? I run 10.5-1 compression pistons on most of my bikes with no issues. I could see lowering the compression if I had detonation or other cylinder issues but if you have no running issues then why go through the trouble?

Yes i have small detonation on the low rpm

Have you tried using high octane fuel and retarding the ignition timing a bit? Ed

My ZX750 motor has a Wiseco 10.25 comp. 810 kit with about 010 off the head and in will
run fine on 93 octane pump gas if it's not 100 degree's out and I don't pound on it's ass.

I do have an advantage over most on here as most have a stock ign. advancer
with my Dyna 2000 ign.. box I can plug in the laptop and program a timing curve
and set the adv. degree's every 100 rpm from idle to 16,000 rpm.

IIRC.....Mr.Turbo said on a 1015 an extra base gasket would lower the CR 0.2 or was it 0.5

There should be a formula to figure that out somewhere

Stacking base gasket's work's but tend to leak but I bet Cometic would
make a thick one if you called and asked.

Hmmmm. I don't think you should be having any detonation or pinging with any 10.25:1 engine, correct ignition timing and +91 octane.
Something is wrong.

Well i have always been running on 99octan/v-power and sometimes with boost. The ignition is a DynaS and the springs on the advancer has been tighten to 'hold' the ignition a bit. It has the green 3ohm dyna coils and tayler plugs. Cams are K410 timed to their standards. Head has been done by PSP. and the guy who help me run it on the Dyno is a guru around this (MJP)
it has a 'hole' around 3000rpm and at 3500 the curve rises like a wall ending at around 10k rpm and 120Whp
MJP said i should change the exhasut a tiny bit to get rid of the 'hole' 3000rpm - i did and it helped, but it still has a tiny bit of detonation around the 1500-3000rpm
Only thing that actually help a little bit was iridium sparks!?!?!

the things is the guy who did the pistons wanted me to run with CNC fitted GPZ1100UT headgasket due to he said that the Cometic was crap.. I can see the UT headgaket is slightly thinner than the fiber version...
I didnt do a compression measure do to it 'only' was a street engine where i ordered the pistons not to be to agresive (10.3-5) and with a 'mild' version cam
I know that cylinder and head hight is a big play in this game, same as how deep the valves are in the seat and all those things (the cylinder was taken of a stock runing bike and the head Joe found me)

but but