Fuel Problems - TwoWheelForum: Motorcycle and Sportbike forums
 
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post #1 of 8 (permalink) Old 07-05-2007, 05:27 PM Thread Starter
 
Join Date: May 2007
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Fuel Problems

Hey what up? Im having some major fuel problems, im running rich so rich its fouling out the spark plugs after about 3-4 weeks i installed a dynojet jet kit and that helped some i did the infamous float bowl mod if anyone knows what im talking about. I would like a lil word of wisdom from someone who knows what could help me keep my bike from running so damn rich...would adjusting the mixture screws help till i can afford to take it and have it completely dyno tuned? what can i do to keep it from fouling out my plugs till i can get it to the shop. Any advice is welcome, appreciated, and definately needed. Thanks Justin Laurent
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post #2 of 8 (permalink) Old 07-05-2007, 05:37 PM
 
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what kind of bike? zx7r? carb or fuel? you said float bowl so i'm assuming carb.

at what rpm range is it running rich? your mixture screw will generally only effect your idle up to about 25% throttle. upwards of that you might need to adjust your needle position, or change jet sizes. the only real way to be precise is to dyno tune it or at least put an air fuel meter on it and find out exactly what's going on. wha type of carb is it? i'm assuming it's a cv model. is it mikuni or khelin? they have different jet numbers. did you do a jet kit too, or just commander? the more info the better. good luck.
ok just reread your post, it said jet kit and not commander, sorry. did you change your main jet, or needle position. if so, try a different jet or try lowering your needle position, usually this will lean out your mixture. but mostly effects middle range and top end throttle positions. without knowing what type of carb it is, is hard to tell ya exactly what to do.

Last edited by bowb4me; 07-05-2007 at 05:42 PM. Reason: reread post
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post #3 of 8 (permalink) Old 07-05-2007, 05:38 PM
 
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what bike? make model and year would be helpful.
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post #4 of 8 (permalink) Old 07-05-2007, 08:03 PM Thread Starter
 
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its a 93 zx7 with cv keihin carbs the dyno jet jet kit came with 128/132 mains i lowered the needle position by half a slot so the needle is on the second slot with a washer under it i think its a problem with my mixture screw cause it idles realy rough and at times when i go to give it throttle it wants to die, it has become exceptionally hard to tune the idle its like it has only two settings 500rpms and like 3000rpms i can try to adjust the idle speed and blip it and it sticks at 3000 then i have to loosen the idle to get it to rev down and then it goes back to like 500 at times (very rarely) i can get it to stay around the correct idle speed. if you need any more info just let me know i appreciate all the help and concern.
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post #5 of 8 (permalink) Old 07-05-2007, 11:12 PM
 
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Bikes from the early 90's usually came with lean or correct jetting. Unless the main jets have fallen out of their holders I don't think your rich running is the jet's fault. I think one or more of your float needles is leaking or incorrectly set. Messing with the jetting doesn't appear to be doing anything. The first thing I would do is replace all four float needle and seats. Don't get them from the dealer. Search for K&L kits for your carbs.
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post #6 of 8 (permalink) Old 07-06-2007, 10:13 AM
 
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i agree with no worries, also make sure your float bowl levels are adjusted correctly. also do you have any other mods? exhaust, air filter? these can effect it too.

Last edited by bowb4me; 07-06-2007 at 10:16 AM. Reason: reread
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post #7 of 8 (permalink) Old 07-06-2007, 10:15 AM
 
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Sell it and buy a fuel injected bike.
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post #8 of 8 (permalink) Old 07-07-2007, 01:32 AM
 
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I think it sounds like your idle problem might have to do with your throttle cables. start by taking your tank off and adjust your idle screw out so that its not holding your throttle open at all then lube your 2 throttle cables then adjust them so there is very little or no slack in them. Whats your mixture screws set at? I would start by setting them at about 2 1/2 turns out from snug. then you should be able to get your idle set about right if not then you may have an air leak check your intake boots for cracks. I also try holding my hand over each one sealing it with the carbs off of corse and crank over the engine to see if it holds a suction. If it does then its ok be careful because you may have lines connecting them together and will need to plug them to isolate each one for that test. once you get your bike to idle steady then you should set your main jets. after you are satisfied with that then move to your needles. after those both check out and are to your liking then adjust your mixture screws the only control your very lower rpm. A good indicator is when you are at a steady idle blip the throttle to about 3000rpm and let off it should return to idle and not fluctuate. If it idles a little high then falls a few hundred rpm you are a little rich if it idles a little low then revs back up a then you are a little lean. this sucks because unless you have a fuel bag you can hang then its very time consuming pulling the tank for each idle adjustment. Also remember that if you each time you adjust your mixture screws then you need to reset your idle.

ok sorry for any and all spelling errors and for talking for so long but that should get you close for now

Oh and before you do any of this make sure your float heights are set to spec and your float needles are ok. Yes K&L make a good rebuild kit too!!

Hope this helps!
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