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yamaha426

Yet another jetting problem

2 posts in this topic

I know that you guys are tired of answering questions about jetting and I have used the serach and read until the wee hours of the morning about jetting but I think I still need more help. My 2002 is still stock and runs fairly well. It can be kind of hard to start sometimes but most of the time is starts on the first or second kick, I have to use the choke to start it first thing but after its warm I never use the hot start...it won't even try to fire with it out....but it starts fine with no choke and no hot start. When I first got the bike the fuel screw was a little too rich so I leaned it out and it ran better...but it seems that the as the temperature gets close to 100 the bike stutters when you gun the engine but not go past 1/4 throttle. Also the inside of my muffler tip is very black and my plugs have always been very black. It also dies occasionally if I don't warm it up enough. Should I go with a smaller pilot jet.....change clip postions.....mess with the fuel screw more? :) If you can't tell I'm kind of lost here, jetting is way over my head.

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When it gets hot your bike will run richer. You will need to turn in the fuel screw and/or go to a smaller pilot.

I have a stock '01 and I am currently running a 40 pilot instead of the stock 42 pilot and one clip position leaner (higher). I don't know where the fuel screw is but it's somewhere between 1-2 turns out.

If you can't find the happy medium for your fuel screw position, that's when you need to go smaller. Turn it in 1/4-1/2 turn at a time. If the idle starts hanging before you get a nice snappy throttle response, then you need the smaller pilot.

So, probably smaller on the pilot and one clip position leaner ought to take care of it, at least for 0-3/4 throttle. I have a smaller main but haven't tried it out yet, that will affect 1/2-WOT but I rarely ride at WOT!

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