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2003 Yamaha PW80 wont run without choke...


the_ry_guy
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ok ok, it's not a quad, it's a kids bike, but it's still an issue I need solved lol. so with the choke on, it fires up first kick, but as soon as you take off the choke it dies. I removed the carb and sprayed it down with wd40, no help, maybe I need to actually soak it in a carb cleaner bucket for a night...I'm assuming it's a carb problem, but dunno? this carb is a little differant than the big quads i'm used to, it has some...apparatus lol...next to it with a very small air, fuel, or vacuum hose, not sure which, connecting it to the carb? anybody know what i'm dealing with here? I've never dealt with these little guys so don't know a lick about em... thanks in advance

Ryan

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Dream Car Giveaway

From the sounds of it your not getting enough fuel with choke off. So I personally would do a carb clean and check your jets and needle. Also if you can take a pic of the piece your talking about it would help out for people to see what your actually talking about and might be able to give you better advise. Quick question are you letting the bike warm up properly before shutting the choke off? I know my sons ttr90 has to warm up to running temp before I shut the choke off and then it runs perfect.

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ill do that then. I do let it warm up, let it warm up for about 10 minutes the other day on a 70 degree day (saturday) just to make sure that wasnt the issue. im going to pull off the carb again tonight and soak it overnight, ill take some pics of the "apparatus" lol and post them, thanks guys.

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So I'm stumped. I had the carb in the carb cleaner can for 24 hours soaking, pulled it out tonight after work, pulled the idle and primary jet off and sprayed the crap out of them and their respective holes, and just for good measure, sprayed the crap out of every orifice I could find on it, put it all back together, and nothing changed, still idles great on choke, and dies off of choke... I'm at a loss for words :(

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so you think adjusting the jetting out some would possibly do it, im no carb professional, so try to speak about it as if you were training a 10 year old and ill probably understand lol.

Right on man. Carbs are simple in principle…but can be complicated in execution ha ha ha. When you put the choke "ON", what you're doing is opening up an additional circuit through which fuel can flow. This gives the engine the additional fuel it needs for combustion to occur at lower temperatures. A properly jetted engine should have a hard time burning all the fuel it sucks in with choke on after it’s warmed up.

In your case it sounds like there isn’t enough fuel getting through to the combustion chamber without the utilization of an open choke circuit. That likely means that the idle circuit (the gas flowing through the pilot jet AND through the gap between the main jet and the needle in it) is insufficient. A larger main jet will put more room between its inside diameter and outside diameter of the needle, which is one way to increase the flow of fuel at idle. Increasing the pilot jet is another. Or there could be an unnatural blockage like sand, etc wadded up in the either of the jets or around the needle that is reducing the flow.

Edited by Senator
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  • 1 year later...

make sure when you put carb back on that you line up the Throttle Vaulve. ther are 2 slots 1 long and 1 short on the vaulve. look down inside the carb you will see a small pin on each side 1 high and 1 near the bottom align the slots accordingly( long slot high pin) let me know if this helps... coaachj

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