I have a stock 2008 s40 carb. I am very interested in changing the jetting on it except i dont know which jet set to buy, and if ill be over my head trying to re-adjust everything. I worked as a mechanic and im very inclined as a mechanic, but sometimes dont know where to start or stop.  any suggestions???

well last week i bought a dyna exaust and it very much eliminated the sputtering/backfiring and what little bit it does, doesnt bother me any more. It did blue my new exaust a little but that is what has led me to the carb. I know i need a jet kit but not shure which one. I think I need a stage two kit and ive read the info in the tech section (good info) but still a little confused on which kit to buy?

I could of sworn Lancer had a thread in the marketplace dedicated to his jetsets, but I cannot find it now.  Anyway, Lancer's the go-to man for jets and carb upgrades.

Moofed wrote on 03/16/10 at 12:25:28:



It may be too old now.

Quote:
Which one will you need ?  It is difficult to know for sure before you actually have the muffler/air filter installed and begin the tuning process.  
Only then will you know if a particular jet is too lean, too rich or just right.
There can be variations even among two engines with the same intake and exhaust installed.  Different engines may require slightly different jetting/tuning from each other.  Yea, strange but true and proven over many years of folks posting tuning and performance info on this site.
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IMO, Lancer says it right ! Not that I'm any kind of an expert on these bikes, but I have much mechanics experience from years passed. And I do know that these bikes do not all tune the same, nor do we all ride the same, or ride at the same altitudes.

From my experience w/ my bike, (no open exhaust) and 6-8 months reading here, I can only add this,.......
Don't start jetting,...carb modding etc etc just because it seems like everybody else does it. Have a reason for doing it. In my case, trimming the needle spacer was all that was needed to correct a low end lean condition. I can't find any evidence of a lean condition at hi speeds or WOT. But if I did a lot of hi speed or WOT in hot weather, I would take another look at the plug etc, and possibly open the main jet a little, especially if I opened the exhaust more than my drilling it.
I'll also add,...IMO, a blueing exhaust could be,...but is not necessarily proof of a lean running engine.

bill67 wrote on 03/18/10 at 05:52:55:


If its already rich ?
Where do you draw the line,....when you get a big stumble when backing off, or wait for black smoke ?

you can keep going up on the main jet, and when it gets TOO RICH it will stumble at WOT.
do the testing in 3rd or 4th gear