Safe squish for pump premium.

[Master of Faster]

Can anybody tell me about what the tighest squish would be safe to still run pump premium?

This would be on a 92 750

[IZZ]

Hey Master I Dont anything about it, I just remember doing alot of reading on this before the site crashed and I vaguely recall someone saying 65thou.
But dont take my word for it!!

[Brakes]

master, I do believe the stock squish is 83 but what you really need to know is your ratio determined by volume. I know that 12:1 is still safe for 93 oct. but just taking the squish down will help figure this out. 65 is safe but I think you can go lower. Check volume by putting pto cylinder to the top, pour in trans fluid and measure how much to the bottom of the spark plug hole by cc's. Then use this formula to figure ratio: total cc (ie. 800 is act. 792) divided by # of cylinders (4) plus # of cc poured in divided by # cc poured in. you can run 93 up to 13.3:1.

[Master of Faster]

Got it, thanks!

[YAMMIEGOD 3:16]

.058. NO LOWER. 3:16 (tony)

[Brakes]

I have one of my 96's at .055 with a 12.25:1 and runs on 93.

[Master of Faster]

I wonder if the shape of the head is different from my 92 to your 96? I know if the outside edge of the head is steeper you can get away with running a tighter squish without detonating. I just had a head for my quad re-shaped on a CNC and it let me run tighter, maybe I'll see about having the v-4 heads done.


Thanks guys!

[toydoc]

I wish I could even be 100% sure it's prem fuel I pay for now days!
To be safe I add a touch of race fuel or AV gas on my sleds that ran for years fine on just pump prem.

[YAMMIEGOD 3:16]

GOOD MOVE CHRIS. MY 2002 SRX DCS LITE CAME ON AT THE END OF THE 1/2 MILE STRIP WITH JUST ABOUT ANY PUMP GAS PREM I BOUGHT. I DECIDED TO RUN 100 OCTANE SUNOCO, LITE HAS NOT BEEN ON SINSE. WHAT THAT TELL YA !! 3:16 (tony)

[toydoc]

Yep, one time. Just one run down the track and you need one piston or more. I'd like to have a lite just like that on every 2 stroke I have!

[toydoc]

One thing everyone needs to remember to ask is.
How much hp will I gain?
With most trail sleds with few mods going from .070 to .060 squish will pick up 1~2 hp. Thats added to all the power band with maybe a 10% chance of a poss problem from that mod.

Now go from .070 to .050 and gain 2~5hp and now the odds jump to say 40% to 60% that some problem or issue may come from that mod.

Same with jetting. Going from 143's to 141's is a 2~3hp gain, 10% odds some issue may come from it.
Going to 143's to 135's is a 3~5hp gain, but the chance of a problem went WAY up.

Going to the edge on both may give you a total of 10hp gain, keep it safe and still have 6hp.