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1978 gs750 exhaust feel(?)

  • Thread starter Thread starter randallscott
  • Start date Start date
R

randallscott

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Hi guys. I'm tuning the 750 and believe I've got it running pretty well. New rings, carbs done as per tutorial, vac sync, timing set. Still not right. When you put your hand a couple inches behind the right muffler you feel strong puffs of exhaust, but on the left the puffs are weak. Sound is different from one side to the other as well. Does this mean anything? How much does the internal condition of the mufflers effect the way the bike runs? Have put about 80 kms on since doing the rings.Compression is pretty equal across all four cylinders, at about 90psi. Seemed about the same hot as it did cold. I appreciate any thoughts you might have. Thanks for your time, Randy.
 
Hmm, 90 sounds kind of low. How did you check it, throttle wide open?
Other things to check are spark and carbs/intake system.
The only things that make the engine go vroom are spark, fuel and air.
 
Puffs of air at the bottoms of the exhaust may be leaking gaskets where the headers and mufflers join..or ,aybe smal pinholes rusted thru. As for the compression..warm the bike up well..little 10 minute ride, do the checks with the throttle wide open and then see what they read.
 
How does the bike ride overall?

Yes, check your spark on the weak side.
If you're getting spark, what color, white, blue?

Compression tests can be kind of "inconclusive", depending on how you conducted it.
 
:oops:Oops, I forgot about the wide open throttle part of doing a compression test! I'll ck again tomorrow. I have good spark thanks to dyna coils with the relay mod. I've sealed the airbox, replaced the intake orings, and adjusted the valves. The bike is running a lot better than when I started so I think I'm going to have to put plates on her and have some FUN!!! Your replies are greatly appreciated,as always! Thx, Randy.
 
Don't baby it during the break-in miles. Use the throttle aggressively without being dumb about it. The rings need pressure to press them into the cylinder wall so they can bed-in properly.
 
Also if you've not synced here carbs, that can factor in.
 
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