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I am currently running 32:1 on torco gp-7 full synthetic race mix, it runs good with a little spoo thinking about switching to 40:1 to save oil/ reduce spoo my bike is an 02 and still has not been rebuilt ( going to at the end of this season) I only get to ride it about 4-6 times a year, so I dont think it will beat the rings up to bad. what happens to the jetting when you go from 32:1 to 40:1? I know you are richening the mixture( more gas versus oil) so would you reduce jet sizes by one and up the clip on the needle one notch or just play with it until you get it right? thanks guys really appreciate your help.

Yes...Less oil = more fuel = richer

Read up on here concerning jetting....There is a weath of info. If you have not jetted your bike at all yeah, you're most likely looking at leaning it down anyway...Both on pilot and main. Race gas and 32:1 have probably gotten you by (race gas will run a little leaner).

Re: 'just play with it until you get it right?'

That works.

There isn't an empirical formula to follow, and the math can be confusing. Consider you're increasing the amount of fuel relative to the amount of oil..from 32 parts to 40 parts.

A difference of 8 would mean you are increasing the fuel part of the mix by 25% (32/8=4=25 out of 100)?

Wow...that's a huge increase! Are you going to decrease your jet sizes by 25%?

Except..that math is wrong.

Consider that a 32:1 premix ratio in five gallons (640oz.) of fuel takes 20oz. of oil, a 40:1 ratio in the same quantity of fuel takes 16oz. of oil. That's a difference of only 4oz. in the fuel volume....or .6%

That's far from huge, 'eh?

Which gets us back to, 'just play with it until you get it right?'

Sounds better all the time!!

Whew...glad that got sorted out.


...except..re: 'it runs good with a little spoo..'

Never jet by spoo. Never ever. Spoo is not necessarily an indicator of an incorrect air/fuel mixture. Jet by performance response and/or plug reads.