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No jet kit for 1977 GS-750?

  • Thread starter Thread starter TBC
  • Start date Start date
T

TBC

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Will be re-jetting due to DG pipe and EMGO pods. Can't find a jet kit for this bike. Source anyone? Dynojet has never made one. Will put the pods on when they arrive ( pipe has been on for years ) and do plug check as per what I have learned here and go from there. Barring availability of jet kit, it looks like buying individual jets. SUDCO lists Mikuni main jets for the bike but nothing for the VM26 pilot jet. Is there a starting point like maybe two sizes over on the mains? Also, when I put the pods on, what should I do with the breather hose that use to go to airbox?

Thanks,
Tom
 
ok Having gotten MY 77 750 KINDA sorted out, I can give you a couple pointers. With the pods and the pipe, you should NOT need to up jet the pilot circuit. Mine is, 17.5s instead of 15s and its RICH. 15s should be just fine. What you will need is a set of mains, and to drop your needle down a notch from stock. Mind you, i have NOT had this bike under load yet, but sitting at idle she is rich on the pilots, but running pretty smooth. Opening the throttle and hanging it around 3k in neutral is not really any GREAT indicator, but its not breaking up, so i think i am pretty close, and i jetted mine based off of numerous EDUCATED sources on here. I would suggest 127.5s on the main and dropping the needle down to the forth slot from the top, (technically, i guess its really moving it up.) I hope to have my sprockets and chain set soon, so then i can get some real plug chop tests going, but i think honestly this is going to be just about right.
 
TheCafeKid said:
ok Having gotten MY 77 750 KINDA sorted out, I can give you a couple pointers. With the pods and the pipe, you should NOT need to up jet the pilot circuit. Mine is, 17.5s instead of 15s and its RICH. 15s should be just fine. What you will need is a set of mains, and to drop your needle down a notch from stock. Mind you, i have NOT had this bike under load yet, but sitting at idle she is rich on the pilots, but running pretty smooth. Opening the throttle and hanging it around 3k in neutral is not really any GREAT indicator, but its not breaking up, so i think i am pretty close, and i jetted mine based off of numerous EDUCATED sources on here. I would suggest 127.5s on the main and dropping the needle down to the forth slot from the top, (technically, i guess its really moving it up.) I hope to have my sprockets and chain set soon, so then i can get some real plug chop tests going, but i think honestly this is going to be just about right.
Click to expand...


Okay. 127.5 is a ways up from the stock 100's but I am venturing into new territory here and haven't re-jetted before. Now, your best guess. If I were to order another set of mains just in case the 127.5's aren't quite right, what should I go with? Haven't heard altitude really mentioned here. I am at 3600ft.
 
Well at altitude, thats going to richen it no? Thiner air? or lean it out? Ive never had to tune for altitude so i have no idea. I would think the 127.5s should still be ok. If you were to order a SECOND set i would order the either step up or step down from that based on problems altitude gives you. Im not honestly sure, but SOMEONE here should know.
 
TheCafeKid said:
Well at altitude, thats going to richen it no? Thiner air? or lean it out? Ive never had to tune for altitude so i have no idea. I would think the 127.5s should still be ok. If you were to order a SECOND set i would order the either step up or step down from that based on problems altitude gives you. Im not honestly sure, but SOMEONE here should know.
Click to expand...

Air becomes rarefied with increase in altitude so mixture would richen.
 
If you're going to compensate for a higher altitude you're going to want a smaller jet, as the thinner air will mean you would be rich. If you will ride at altitude and sealevel and not be changing in between, you want to be rich at altitude and not very lean at sealevel (tune more for sealevel). This is because, as many tuners know, rich is "safe." Lean leads to higher combustion chamber temps, detonation, knock and ultimately engine failure. Don't melt a piston, run at stoich (right on mixture) or slightly rich. If you only ride at 3600ft you will probably need a step smaller jet than TheCafeKid, who is only at 700ft.
 
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