318 issues

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Greenmachine225

Greenmachine225

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So I have my 318 running in my car and broken in but for some reason now when I give it gas it stutters and doesn’t want to rev any higher, I played with the timing a bunch but it’s still having problems. I checked for vacuum leaks and I can’t find any but when I put my hands over the carb it doesn’t change the idle at all, and I know it’s getting plenty of gas. I’m 19 and this is my first car build so I’m just a little lost. Any info would help.
Thanks, Carson
 
Carb floats not adjusted or our of whack? Maybe crud blocking a needle valve?
 
Greenmachine225 said:
So I have my 318 running in my car and broken in but for some reason now when I give it gas it stutters and doesn’t want to rev any higher, I played with the timing a bunch but it’s still having problems. I checked for vacuum leaks and I can’t find any but when I put my hands over the carb it doesn’t change the idle at all, and I know it’s getting plenty of gas. I’m 19 and this is my first car build so I’m just a little lost. Any info would help.
Thanks, Carson
Click to expand...
what carb? whats your timing?
 
Need some more background
  • car,
  • Year
  • carb
  • manifold,
  • type of ignition,
  • "broken in" suggests rebuilt engine, yes?




You say put "your hand over carb", do you mean you esseciently blocked all or most of the air flow and nothing changed?

If this is the case it seems like a major vacuum leak,
 
The only time I ever saw a SBM that would not take throttle from idle,was because the timing chain had jumped several teeth and I had advanced thechit out of the ignition timing while cranking it,to get it running. It idled very very very slowly with the curb-idle screw turned waaaay in, but would absolutely not run any faster no matter how far I opened the throttle, or what I did with the timing.
 
If it doesnt choke/die when you put your hand over the carburetor and say it even speeds up or smooths out. ... you have a vacuum leak.
 
I had a similar condition come out of nowhere with stock 73 model 2 brl. Something had came apart in that carb but I forget exactly what it was, power valve? metering rods? I do recall it was a simple fix.
 
I had a bike that would fall on its face when you throttled it. It was a plugged main jet on the carb. Idled just fine. check for accelerator pump shot off idle and try shooting some carb cleaner down all the carb holes (bleeds, etc) with the little tube provided while ideling. Id also check your advance mechanism. pop the distributor cap and suck on the vacuum line, the plate should rotate smoothly and snap back when you release pressure.
 
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