Vintage Dirt Bike Q & A

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 Post subject: KD 80 power problem
PostPosted: Thu May 03, 2007 3:23 am 
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Joined: Tue May 01, 2007 2:50 am
Posts: 5
Hi everyone!

i have a KD80, with issues

it starts and idles great, but as soon as you twist the throttle quickly
she sounds like she's just sucking air (no acceleration)

i inspected the carb, when i rev (quick) it, i can see a vapor cloud
appear outside the venturi, along with no acceleration

carb seems to be swimming with fuel, so i dont think thats a problem

i can accelerate slowly, and the rpm's go up no problems
breaks up when its high a bit

i can ride it, but it needs a load of rev's and it doesn't have much torque

could this be that the timing is too advanced?

whats the best way to do it? from the points??


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 Post subject:
PostPosted: Thu May 03, 2007 12:05 pm 
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Joined: Tue Mar 15, 2005 10:35 am
Posts: 254
I've had similar symptons when the main needle gets loose. Clip or plate that holds it in place comes loose or doesn't get put back right.

Pretty easy to check. Just remove the slide and see if the needle moves up and down in it. You shouldn't have more then a few mils of movement.

Rick


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 Post subject:
PostPosted: Thu May 03, 2007 2:36 pm 
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Joined: Tue May 01, 2007 2:50 am
Posts: 5
cheers!, i will check that!


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 Post subject:
PostPosted: Sat May 05, 2007 2:34 am 
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Joined: Tue May 01, 2007 2:50 am
Posts: 5
carb seems to be fine :cry:


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 Post subject:
PostPosted: Sat May 05, 2007 10:53 am 
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Joined: Tue Mar 15, 2005 10:35 am
Posts: 254
Is it a reed valve engine? Other then carb issues that is probably the most hopeful thing it could be wrong w/o a major rebuild. It could also explain the back flow coming out the carb.

Doesn't take much, just a piece of crud holding the reed off its seat, to make trouble. They do break but kind of rarely.

Rick


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 Post subject:
PostPosted: Sat May 05, 2007 5:38 pm 
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Joined: Tue May 01, 2007 2:50 am
Posts: 5
i believe its rotary valve


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 Post subject:
PostPosted: Sun May 06, 2007 12:13 am 
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Joined: Tue May 01, 2007 2:50 am
Posts: 5
i retarded the points, seems to run alot better, still a bit saggy, nothin a top end rebuild wont fix i guess :lol:


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 Post subject: Re: KD 80 power problem
PostPosted: Thu Aug 14, 2008 8:59 pm 
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Joined: Fri Jun 02, 2006 11:12 pm
Posts: 158
Location: Salinas, CA
I bought a used bike with a similar problem once. The piston had bee put in backwards. The arrow that should be pointed forward was pointed backwards toward the intake.


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 Post subject: Re: KD 80 power problem
PostPosted: Tue Nov 04, 2008 8:24 pm 
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Joined: Tue Nov 04, 2008 6:46 pm
Posts: 6
Check the intake boot between carb and cylinder, if it is leaking it can cause problems...


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