Sunday, January 8, 2012

Do you HAVE to rejet after installing new pipes?

I just ordered some Vance %26amp; Hines 4-1 pipes for my '96 Nighthawk 750, mainly for better sound and a lose some weight. I know it's recommended to rejet the carbs, but is it absolutely necessary?|||ONLY and I mean ONLY if you find it running lean. This is not an automatic thing to do and without knowing what jet size or needle position you are running it is impossible to tell. You need to look up "plug chop" and as an alternative you can always raise the needle a notch which results in a jump in jet size by about 4. Too rich? Lower the needle and rejet. You're new at this so get all the information before you go running off to bolt on farkles you know nothing about.|||I am not familiar with the 96 nighthawk. If it has a fuel/air set screw you can just reset the carburators. They normally become lean after installing aftermarket exhaust. This will cause you to run hot. If you run hot for prolonged times it will harm the rings and valves. If it is bad enough you will melt the piston. But, not likely, it would more than likely just lead to using excess amounts of oil and premature wear of the rings.|||Normally molitor and I don't agree but this is one time where he and I do. First off, just because an exhaust system makes more noise, that doesn't necessarily mean if flows more air. And more noise does not equal more power, although your seat of the pants perception is that it does.





A system that flows more freely won't make enough difference at small throttle openings to make much difference. That doesn't mean your bike doesn't run too lean now, because many bikes of that era do. So whether you change exhaust or not, you may want to adjust the pilot screw. There may be plugs or **** on the screws that prevent or limit you making any adjustments, but the plugs can be popped out and the **** cut off.





You're going to need to run the bike at wide open throttle with the new exhaust and see how it runs. If it seems to surge or miss, or you hear pinging at full throttle or when you crank open the throttle, it does need to be rejetted or jetted and the needles adjusted. You might check to see if V%26amp;H has any recommendations for your bike.|||I agree with some of the previous answer. Running better pipes will lean your motor. A leaner motor will actually give you a bit more power. The kicker is that if you run leaner, you also run hotter. This could result in burned exhaust valves or even a holed piston. I have to admit, I'm not familiar with your bike and the 4-in-1 pipes. Hope you make the right decision. Take care!|||If you don't, you will run lean, with a probable decrease in actual power. They recommend rejetting your carbs for a reason.|||you must re jet,the air fuel mixture screws only affect the idle circuit.And anyway on a 96 those screws are under a plug that you would have to drill out.|||Yeah man. Re jet it. It will run like crap. They recommend things for a reason.|||As said so back to it and get it right b 4 you trash it.

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