750GT Carb Settings

2

2Types

Junior member
Location
Wales
My 750GT came with VHB29 carbs with the following internals.

Pilot Jet 55
Main Jet 175
Atomizer 265N
Needle V3

I have ultrasonically cleaned them but cannot get the bike to run right. (not sure if it ever run on these carbs as off road since 2014)

I can set it up to start easily and tickover fine but once off choke it will not pick up under load and just misfires, if I put a bit of choke on the bike picks up and runs much better and rides fine when cold and on choke. All ignition is good,

With the above settings I would have expected it to run rich not be fuel staved.

I understand the book settings are

Pilot Jet 50
Main jet 112
Atomizer 256N
Needle V2

Before just going back to factory settings anything else I should check which would mean the current internals were used or are there any recommended changes.

Thanks
 
Hi,
No Airfilter and open Exhaust?
Then 55/175 could work.
Airfilter and Exhaust are Factory-Stile, 50/112.
Needle same, right ( standard) Position of the Needle ( 2nd carb ).
Regards
Rainer
 
Forgot to add needle was in slot 1 not 2.

Factory exhaust supplied by Slaters.

N9t factory air filter but should not be particularly restrictive.
 
I don't know about the V2 needle, I'd need to check. I have some 29 carbs in the attic. Needle on middle notch.
175 mains would suit an F16 with an afterburner, not a GT. Spec is indeed 112.
Pilots 55 but you might find that you need to come down on that with modern fuel.
No major difference with or without an air filter.

Should work on factory specs.

Paul
 
Re your comment on the 175 main and also with the larger atomizer and and more angles needle I would have thought I was getting way to much fuel rather than not enough so I am.concerned there could be another issue as well. Or is it that this set up just does not work together to flow enough air to amek the rest work.
 
Main jet won't affect off-idle. And I doubt very much that your needle and needle jet will allow any more fuel through than a 150-ish main jet (ie you could take the 175 out and have nothing there and find no difference). Is there a slide cutaway? Sorry, not familiar with VHBs.
 
I have the following in mine:-
Pilot - 55 (Had 50's in it but runs better on 55's)
Main - 115 (Closest I could get easily to 112's which were in it, just to put new ones in, shouldn't be any real diff)
Atomizer- 265N (Always thought the mention of 256 was a typo??)
Needle V3, middle notch (Thought these were correct?)
Runs well however did have an issue with missing recently. After dismantling to clean air filter it started missing at higher revs when put all back together. Took apart again and resynced, checked float heights etc, still not right. Had a few more goes pulling apart, cleaning, adjusting etc but each time would be slightly different such as missing at different revs. After a rub of the head (no hair to pull out) thought could be condensors, so swapped a complete points plate over but didn't help. Went back to basics and redid tappet gaps and timing as well. While all seemed to be perfect still would miss when revving out (but perhaps less so) Anyway, after spending a lot of time on this, finally found the problem. The tank is quite a tight fit and each time I refitted, it was ever so slightly catching one choke cable and raising the plunger, obviously a slightly different amount each time. I had suspected this prior and had been careful in ensuring chokes were seated correctly and cable was not being pulled, however it must have just been catching it at the last moment. (I was aware of this potential as had previously happened with throttle cables but that was rather obvious!!) Loosened both choke adjusters as much as possible and tried to hide the cables as best I could and more care placing tank and bingo all fixed.
I guess at least I know the whole tune up has been done.................
Now, this may not be your problem as I note you say it runs a bit better when applying choke, but maybe that is just evening up both carbs? Anyway fwiw, just thought I'd relay my tale of woe which ended happily ever after!
 
Mains are enormous but runs better on choke- my GT likes 55 pilot jet not 50 - check for air leaks at manifold , does mixture screw make any difference, fuel tap filters not blocked, tank breathing and ignition- mine pops and bangs off idle if points are wet/ oily .Is the air filter original paper or aftermarket?
 
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