bike idles, but sputters and dies at 1/2 throttle

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cainen172
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Joined: Fri Sep 05, 2014 4:47 pm
Real Name: cainen miller
Sex: Male
Years Riding: 5
My Motorcycle: 1972/honda/cb100-----2015/yamaha/yz250f

bike idles, but sputters and dies at 1/2 throttle

#1 Unread post by cainen172 »

hi im new here, mainly because i am having the hardest time with this bike and i have exhausted all possibilities and i have no idea what do do anymore. the bike is a 1972 cb100 and there is waaay too much to type but you can look this post to see exactly what its been doing and what i have done to try and solve it. any and all help is much appreciated. :)

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Johnj
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Real Name: Johnny Strabler
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Location: Kansas City KS

Re: bike idles, but sputters and dies at 1/2 throttle

#2 Unread post by Johnj »

Hello Cainen and welcome to the forum. You either have a bad intake leak or a dirty little carburetor. Good luck.
People say I'm stupid and apathetic. I don't know what that means, and I don't care.
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BRUMBEAR
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Re: bike idles, but sputters and dies at 1/2 throttle

#3 Unread post by BRUMBEAR »

Ok lets start easiest first
1 pull the gas cap off and try it (vent may be semi clogged
2 check your air filter remove it and run it
3 check the fuel flow pull off the feeder line with petcock off, put a paper cup NOT STYRAFOAM under the line turn on petcock if flow is slow check screen at the petcock ( fuel flow may be limited by rust)
If this does not work and flow is good stop and check your ign points for proper gapping and loose connections and make sure the shaft isn't worn and wobbling wiggle it see the play.
The if all is ok remove your carburetor and pull the float bowl down remove and clean all your jets and needles clean em thouroly and replace you will need a gasket kit I am sure if the bike is 40 years old sorry the cork gaskets are done.
while the carb is off inspect the boot leeding into the engine for cracks but if its idling I doubt you have a intake leak unless the idle is super high.
Hope this helps
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GS_in_CO
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Real Name: Ron
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My Motorcycle: 1988 BMW R100GS
Location: Ft. Collins, CO.

Re: bike idles, but sputters and dies at 1/2 throttle

#4 Unread post by GS_in_CO »

I see no info about the bike and its history.
Is this new behavior? Is the bike new to you? Is this a barn find that's been parked since 1974?
If you think you've exhausted all possibilities we can't help much then can we?
Ron

Current: 1988 BMW R100GS (the 'numberplate' model)

Past: 1987 Yamaha XT350
1983 Honda CB900F
1980 Honda XL185S
1979 Suzuki GS425E

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