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I have a problem I have been chasing for some time, and it just got much worse. My current problem is that the bike cuts outs, and sputters to the point of complete loss of power, if I open the throttle above 3/4. I can roll on the throttle, and make and maintain speed 65-70mph as long as I don't go past about half throttle. It acts like the spark becomes intermittent under heavy throttle. I just tore into the carb, and cleaned everything I could, checked for vacuum leaks, and found none, checked plugs, and they are fine. Bike idles fine, has good throttle response if I rev it up "gently", but any time I open to 3/4 or full throttle, it acts like a car that is off timing. Checked some of the "gremlins" that affect these bikes, (loose battery cables, choke vibrating open), and it is none of them. Bike is primarily stock, rejetted to 58 pilot / 200 main jet, pair valve removed. Hope I can get some good ideas from the folks here before I knuckle under I take her to an $85/hr stealer! :banghead:
 

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If it is primarily stock, why was it rejetted? There was no need unless the air-box was modified to let in a lot more air. Anyway a 200 main seems small to me, but I'll wait until a more experienced person chimes in to confirm or deny.
 

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Discussion Starter #3
actually stock jetting is 55pilot/195main. These bikes are set up pretty lean from the factory. I do have a "reworked" stock exhaust, not a really heavy breather, but I don't think the 58, and 200 are too big.
 

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If there is an issue with the needle and the vacuum chamber on top of the carb I would suspect your problem. Check and make sure the vacuum boot is not torn and installed correctly with no leaks around the carb top seal.

Sounds like it is either starving for fuel or air.
 

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Discussion Starter #6
I hoped I would see you on this thread Charlie. Forgot to mention in my first post that I did actually inspect diaphram, and found no cracks. Any chance a broken, or almost broken ECM wire? The thing acts like it is getting an intermittent spark, but only just past 3/4 to full throttle. If I open it up all the way, it completely hesitates, or loses spark, and if I don't let up, it will crack and pop, but not accelerate, but as soon as I back off to about 1/4 throttle, it smooths out, and as long as I don't give it too much throttle (just roll on easy) it will accelerate to cruising speed 50-60. I'm just lucky there are no hills around here.
 

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It would seem unlikely that an electrical problem would "know" when the throttle is wide open so it seems unlikely that a problem associated with a wide open throttle would be caused by an electrical gremlin. What aspects of the bike "know" when the throttle is twisted to full open? The drive train doesn't know. If this was an rpm related problem, it could be drive train caused but you describe it as a throttle position problem so the engine is not the cause. The only part of the bike that "knows" where the throttle position is located is the carb. I would look there.

Okay, in all fairness, I believe there is a throttle position sensor on the carb and this will obviously send the computer some information. Despite this, I don't think it is the TPS or computer. If this was a random intermittent problem, I could see the ECM being a problem but as this has been solely described as a problem caused by throttle position, I vote carb.

G'day,

Vinish
 

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i have the same problem. i have had lots of issues with my bike all my our fault. i went on a deployment and didnt drain the fuel from my tank and it was in on the gulfcoast where everything rusts anyhow long story short 3 deployments and 3 kids i finaly was home for a riding season and wouldnt you know it my tank was all but destroyed all rusted and nasty. lines were dry rotted and so i relined my tank with kreem .... pain in the @#$ . i replaced some vent lines and vacuume lines and rebuilt my carb i know for a fact all vent/vacuume lines but now the bike runs great besides the full throttle bugging down. i love the bike and really want it 100%. i have blown compressed air through the tank vent and it was plugged and now is free. there is no lines comming off the tank vent and do not know where the lines are supposed to run
 

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Charlie D. you were right again! Tore into carb one more time, and re-inspected the diaphram on top of the slide. I still don't know how I missed it the first time, but it is definitely torn in several places. Waiting on the part, and can't wait to get back on the road. Thanks again to everybody here who puts up with my attempts to be a "wrench", usually with less than perfect results :cheers:
 

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Charlie D. you were right again! Tore into carb one more time, and re-inspected the diaphram on top of the slide. I still don't know how I missed it the first time, but it is definitely torn in several places. Waiting on the part, and can't wait to get back on the road. Thanks again to everybody here who puts up with my attempts to be a "wrench", usually with less than perfect results :cheers:
i took mine apart and mine looks good but too make sure you are talking bout the one on very top under the four screws !!
 

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i took mine apart and mine looks good but too make sure you are talking bout the one on very top under the four screws !!
Yeah, that is the one.

G'day,

Vinish
 
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