'78 GS750 / VM29 Troubles

[broquo]

Sounds like all good info.
Put needles on the 5th notch (5F21-5) before i sync'd the carbs back up and it feels a lot better, but after i get the mains in i'll be able to tell if i'll need to cut a 6th notch in. No nylon shims above or below the e-clip.
Already have #20 pilots. Which is why i think my pilot screws are so low. It will need a little fine tuning. Find someone with a colortune to get idle banging.
Noticed some minor arcing on my 2-3 point, so it's time to replace the condenser pending the Dyna2k. Damn points.

JETS R US says gs750's use keihin main jets. Wtf?

just found these jet specs on Allen's Performance:
Float Valve Assembly MRT-VM26/26-2.3 Main Jet MRT-N100604 Pilot Jet MRT-VM28/486-
There's no air jets on these carbs?
125 & 127.5 sound like a good start?
Series 182 needle jets?

[KEITH KRAUSE]

Sounds like all good info.
Put needles on the 5th notch (5F21-5) before i sync'd the carbs back up and it feels a lot better, but after i get the mains in i'll be able to tell if i'll need to cut a 6th notch in. No nylon shims above or below the e-clip.
Already have #20 pilots. Which is why i think my pilot screws are so low. It will need a little fine tuning. Find someone with a colortune to get idle banging.
Noticed some minor arcing on my 2-3 point, so it's time to replace the condenser pending the Dyna2k. Damn points.

JETS R US says gs750's use keihin main jets. Wtf?

just found these jet specs on Allen's Performance:
Float Valve Assembly MRT-VM26/26-2.3 Main Jet MRT-N100604 Pilot Jet MRT-VM28/486-
There's no air jets on these carbs?
125 & 127.5 sound like a good start?
Series 182 needle jets?

Don't know about cutting a notch into the jet needles (that isn't the factory needle to begin with.) Doing that may compromise how the tapered needle transitions to the main jet. Might cause an overlap problem.
I suggest you look up a parts diagram for your carbs. If you're missing the two nylon/plastic jet needle spacers then that will allow the needle to raise even higher than intended and cause a much richer mixture throughout the needle range. With all the mix 'n match stuff you appear to have going on I'll be surprised if it truly does run well. You seem impressed by the 112.5 main jet performance which I KNOW isn't good so you need experience to know what's really right and what isn't. The plugs will tell you if you're getting close or even spot on.
20 pilot jets are probably too big.
Your air jets are pressed in and you shouldn't need to change them anyway.
Unfamiliar with "series 82" needle jets. You should run the factory Mikuni needle jets and the jet needles that are stock for your carbs.

[broquo]

Lol, not gonna cut a notch. just saying it might need to be richer. I'll look into those spacers, although it seems like the fit is pretty tight and my hayne's manual makes no mention of spacers. It actually calls the e-clip and needle a "sliding fit in the throttle valve". *shrug*

I DO need more experience in judging the proper fuel mix...So I came here! Experience is the only teacher, man. No, I don't think the top end power is where i want it. I understand engine theory pretty well, so i saw a few things which led me to ask on here in the first place.
I wasn't "impressed" at its performance but I wasn't displeased. I am keeping the bike after all. She'll get on it though, don't underestimate the old girl. I surprise some people, just under 60 and above 10 mph =-] Keep up with cbr600's doin city riding.
What mixy match?

Maybe the rich pilot value is the cause for my bogging passing quickly through 1/4 throttle? Dunno what i was going on about the needles. Just looking at jetsrus.com.
5F21 is the stock needle listed in my Haynes. Stock needle jet as well.
I can't find any charts comparing size and taper to needle part numbers so I dont know if resizing those will help me in any way. I mean i could swap 'em around for shirts and giggles and see how it runs and maybe find a better combo, but that's impractical as hell.

I am always ready to tear into these things so i got some 125 & 127.5 mains in the mail.

[KEITH KRAUSE]

"Mix n match" is just the feeling I've had here. Kinda like just making what you have work.
It sure sounded to me like you were planning to cut another groove in the jet needles. It also seemed at the time that the needles weren't even stock which would just make the jetting more difficult. Same for the needle jets. I tell you 17.5 pilot jets should work but you say 20's is what you've got. No mention about the synch or if other tuning is done. When wiredgeorge touched your carbs was the red flag went up.
Just trying to help is all but you have to help us. We need plug reads. That's one of the first things we'd do if the bike were in our hands. You tune it first (valves/ignition timing/good spark/clean carbs...) and then you jet. Short cuts just waste everyone's time.

[broquo]

WEll this is getting confusing, but I actually put up another thread with a different title to correct my carb identification deficiency:

http://www.thegsresources.com/_forum/showthread.php?t=174683

the end to this story, it seems.

I also found a little surprise wiredgeorge left for me...

"Mix n match" is just the feeling I've had here. Kinda like just making what you have work.
It sure sounded to me like you were planning to cut another groove in the jet needles. It also seemed at the time that the needles weren't even stock which would just make the jetting more difficult. Same for the needle jets. I tell you 17.5 pilot jets should work but you say 20's is what you've got. No mention about the synch or if other tuning is done. When wiredgeorge touched your carbs was the red flag went up.
Just trying to help is all but you have to help us. We need plug reads. That's one of the first things we'd do if the bike were in our hands. You tune it first (valves/ignition timing/good spark/clean carbs...) and then you jet. Short cuts just waste everyone's time.

True that, Keith. It actually turned out to be more of a mixup than i had originally thought...

As for all the info I was providing, I was kinda just going off what i knew / had in front of me. I REALLY do appreciate all the info, cuz i would have tried 10 different jet sizes with no avail. I wasn't trying to be standoffish, just a smarta$$. :-)