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How dangerous is a lean mid section


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So, I am pretty sure having a pilot that is too lean won't really hurt your engine.

Having a lean main can obviously melt things down.

How dangerous is it to try a variety of needles.

My pilot is not overly rich, and my main is pretty close, but it smokes a lot in mid throttle and splooges some out the exhaust. (runs OK though with the stock needle on the top clip)

How much do I need to worry about putting a fat needle in there?u Is there much chance of melting the engine from a lean needle?

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Not sure that exactly answers the question...

The issue is not dropping clip positions, it is that the currently used needle is not going to work to get a good mixture, so I will be trying alternate needles.

The question is basically, weather going too lean on a needle has real potential for a melt down if I go too fat.

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Not sure that exactly answers the question...

The issue is not dropping clip positions, it is that the currently used needle is not going to work to get a good mixture, so I will be trying alternate needles.

The question is basically, weather going too lean on a needle has real potential for a melt down if I go too fat.

Any lean condition could cause problems. too fat a needle can lean out the main too much or the pilot too much.

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A lean condition is always something you have to watch but running lean in your midrange is less risky than running lean at WOT. Remember heat is the problem so the longer you spend in the lean part of your fuel curve the more things are going to heat up. When in Doubt blip the throttle and vary the RPMs to help keep things cool.

I have done a lot of dyno work and tunning on both snowmobile and dirt bike two strokes and I have found that most two strokes run leaner in the mid than they do at WOT. The EFI snowmobiles are really lean in the midrange (damn EPA crap) but they generally don't have a burn down problem.­čśĆ

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After trying a much fatter needle that I was told came out of my year bike, I was able to get it to work pretty well with a few exceptions. After all my experimenting, I found out that someone I know has a whole range of needles for my bike for me to try that are all in the correct range. Back to the drawing board.

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You didn't mention which bike and year . . .

if it's a 250 and your talkin' this century, try a N3EJ first if your buddy has one, probably 2nd clip position.

BTW, if neither your pilot or your main is lean you probably are just fine on the needle unless you go with something outrageous . . . but then your bike would run like poo so you should know it anyway.

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