Vintage Dirt Bike Q & A

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 Post subject: Bike runs but dies
PostPosted: Sat Sep 22, 2007 3:54 pm 
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Joined: Wed Jul 19, 2006 6:40 am
Posts: 19
1978 KM100, bike will run perfect untill it is warmed up(run for 10-15 minutes) Then it sounds like it starts to miss then backfires and dies. Gas is premixed at 20:1 with the injector holes blocked off. New piston and rings put into it yesterday, along with new crank bearings and seals. When I first got the bike a month ago, it did the same thing and I checked the carb and everything is up to snuff. I think it has to do with the eletrical. Any info will be appreciated.

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1974 Honda MT250, 1978 Kawasaki KM100, 1993 Honda 300 4x4, Arctic-Cat Panther340/Jag275


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 Post subject: Re: Bike runs but dies
PostPosted: Sat Sep 22, 2007 9:45 pm 
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Joined: Sat Jul 21, 2007 9:03 pm
Posts: 39
Location: Sparta, Wisconsin
Some coils that are going bad tend to act up once they get warm. Are you still getting spark once it dies?

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Steve Amling

1976 CR 250M
1980 Yamaha DT100G
1980 XR 200
1981 CSR650


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 Post subject: Re: Bike runs but dies
PostPosted: Sun Sep 23, 2007 5:04 am 
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Joined: Wed Jul 19, 2006 6:40 am
Posts: 19
It seems to get smaller when it's warm.

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1974 Honda MT250, 1978 Kawasaki KM100, 1993 Honda 300 4x4, Arctic-Cat Panther340/Jag275


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 Post subject: Re: Bike runs but dies
PostPosted: Wed Sep 26, 2007 8:56 pm 
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Joined: Tue Mar 15, 2005 10:35 am
Posts: 254
It may sound silly but try taking the gas cap off when it happens. Sometimes the vent blocks and they pull a vacumn.

Rick


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 Post subject: Re: Bike runs but dies
PostPosted: Thu Sep 27, 2007 4:28 pm 
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Joined: Wed Jul 19, 2006 6:40 am
Posts: 19
Thanks, will give it a try. Also I just put new points in it, no change. But I have a condensor supposed to be coming in next week for it and if that fails, what next???

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1974 Honda MT250, 1978 Kawasaki KM100, 1993 Honda 300 4x4, Arctic-Cat Panther340/Jag275


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 Post subject: Re: Bike runs but dies
PostPosted: Thu Sep 27, 2007 8:54 pm 
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Joined: Sat Jul 21, 2007 9:03 pm
Posts: 39
Location: Sparta, Wisconsin
Here's a quote from Dan's On Line Motorcycle Repair Course

It is no substitute for the correct repair manual for your bike, but gives some sage advice on a lot of topics.

Quote:
Ignition coils. Measure the resistance between the primary (low-tension) wire and ground or ground terminal. It should be very low. Like .5 to 1.5 Ohms. The primary wire is the small wire going to the CDI box or points. Next measure the secondary (high-tension) wire and ground. (Note that on most bikes these days, the coil mounting bar, that passes through the coil and mounts it to the frame, is the ground for the coil primary and secondary wires.) This should be quite high, like 6000 to 13000 ohms. If the coil is out side the specs given in the shop manual the coil might be bad. Sometimes, a coil will work OK when cool but fail when it warms up. Let them cool and they work again.

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Steve Amling

1976 CR 250M
1980 Yamaha DT100G
1980 XR 200
1981 CSR650


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