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77 GS 750 Carb Jetting

  • Thread starter Thread starter Phil D
  • Start date Start date
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Phil D

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Good afternoon all; I have finally pulled my bike out of storage (since 99) and am in the process of tearing down the carbs and rebuilding them. I have pod filters (K&N), Kerker 4 into 1, and a Dyna S ignition to install and would like to know where a good starting point is for jetting. Currently the carbs (VM26SS) have the stock jets installed. Thanks in advance.
 
Is it a stage 3 Dynojet? If it is I would follow the directions from the kit for stage 3. Except raise the needle one more notch from the directions. It tends to be on the lean side for the needle circuit.
 
If your stock mains are 102.5, then try 127.5 to 130 Mikuni mains.
If running stock jet needles (5 positions), try 2 positions richer by lowering the e-clip 2 positions. I don't remember if your '77 has the e-clip in the 2nd or 3rd position from the top straight from the factory, but lower it 2 positions. Place any factory jet needle plastic spacers in same factory order.
Try the stock 15 pilot jet, but richen the pilot fuel screws underneath. Initially, try 1 1/2 turns out from lightly seated. Test at minimal throttle position. If no joy by about 2 1/2 turns out, I'd go with a 17.5 pilot jet and return the screws to something close to factory...about 1 turn out.
The side air screws are always set by using the highest rpm method. They'll end up about 1 3/4 turns out on most bikes.
REMOVE the 2 floatbowl vent lines and leave the ports open. This helps avoid fuel starvation when running pods.
Be sure the valve clearances are set correctly, the carbs are bench synched, and the timing is set before vacuum synching. THEN, you're ready for re-jetting/tests.
I also suggest new manifold o-rings and of course, make sure the manifolds are good.
Test the mains at full throttle, the jet needles at 1/3, pilot circuit at minimal throttle.
 
Thanks for the info Keith, I'll let you all know how it turns out and what I ended up using for jet sizes. The stock position with the e-clip on the needle is in the middle by the way. Thanks again for the info.
 
Sorry I thought you mentioned Dynojet but it was Dyna-S. Doh!
 
Last edited:
No problem, I tried to find a Dynojet kit but it appears that theres not one available for the 77. Thanks for reading the post all the same though.
 
Phil D said:
Thanks for the info Keith, I'll let you all know how it turns out and what I ended up using for jet sizes. The stock position with the e-clip on the needle is in the middle by the way. Thanks again for the info.
Click to expand...
OK. Then the only chance (in my opinion) the stock jet needles have is to place the e-clip in the bottom position. Hopefully this will be rich enough. DJ hasn't made a 750 kit for years to my knowledge. Nor has K&N or Factory.
If the stock needles don't work well enough, then the performance will let you know at approx' 1/4 to 3/4 throttle position. If so, then you'll have to try richer needle jets or perhaps different jet needles, which can get interesting.
We'll keep our fingers crossed.
 
Thanks again Keith, I'll see what I can do with them. If push comes to shove I'll leave the stock air box in it and run the stock exhaust. Either way it's a lot cheaper than buying a new bike. Not many classics running around in Va Beach now days, there are however thousands of new Harleys. Why ride what everyone else has!
 
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