tuning and oil mix question.

S

snakecorleone

Location
Indiana
if yamaha states 50:1 ratio, why are people mixing 40:1, wouldn't that affect tuning? just to be extra safe? does that affect the tune, or not?

I recently picked up a square nose with a 760 in it, with a b pipe. The motor starts perfect, very strong all the way through the rpm range if I'm steady with the throttle. I can hammer on the throttle as hard as I want past a certain rpm/throttle range and it rips up to top speed, no issues. The only problem I've noticed, is, when I set up for a wave or bring rpm/throttle low, and hammer down to jump a wave, it will basically stall out. I read in the tuning section, if it feels like its getting punched in the stomach, the low speed mixture screw is too lean. I haven't adjusted anything yet, but plan on trying to adjust the low speed adjustment tomorrow. I'm hoping that cures it, but I'm somewhat curious, have I potentially damaged the motor having a lean condition that low in the RPM range?
 
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snakecorleone

Location
Indiana
Barbieri972 said:
What carbs are on it and what kind of set up is it, does it start easy or do you have to crack the throttle
Click to expand...
Not sure on the dual carb size, and yes, I barely crack the throttle and it starts right up. I'm running 40:1 and premimum gas(93oct) Compression is around 155 in both cylinders. I don't know much, not a mechanic, but have been reading as much as I can in an attempt to learn more. Any info/advice is greatly appreciated
 
mbrick

mbrick

Location
Los Gatos, CA
People run 40:1 because more oil is better. 50 to 40 isn't enough that it really needs to be re-tuned (but still should be double checked). They aren't a small displacement WOT 2-stroke so more oil than that is probably not needed.

I have buddies who raced karts with a 125cc or smaller and it's WOT 98% of the time. They'd run as much oil as it would take before it won't run any more, usually around 20-24:1.

But, this is a timeless debate and everyone has their own opinion. I think more lubrication can't hurt, and the oil is cheap.
 
bored&stroked

bored&stroked

Urban redneck
Location
AZ
Mys girls ski is a ported 760 with 195psi and b pipe, dual 44's. Guy we bought it from said he couldn't get it to run right using standerd jetting so he reverse jetted it. Runs great and we've never had to adjust anything all summer.
 
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