GS750 stalling at full throttle

[gs750e]

The Haynes manual covers '77-'79 models generically. Trust me the '78 should be 23mm.

Cool! I'm gonna try it right away, I'll post the results

[chuck hahn]

Where are the bottom and side screws set?? bottom should be 3/4 to 7/8 out and the side 1 1/2 to 2 out. Needle clip on center groove.

Since you dont know what the problem is, I would suggest getting the floats set as was stated and setting everything back to the stock default positions.

The bottom ones wont need any more adjustment..so set and forget them. NOW, verify the valves are adjusted within spec and vacuum sync the carbs to the engine AFTER the valves are inspected.point is that youre chasing a gut off tail till you are positive the valves are right, carbs are synced, and your sure there are no air leaks like the orings in the intake manifolds ( carb holders ). Also stretched clamps wont tighten well and theres another source of contention.

Check the timing too...while your doing all the required stuff.

Moral of the story is that until and unless all the engine maintenance is done your just wasting time and energy.

[gs750e]

Damn, I set the floats to exactly 23mm, but the problem stays. Any more ideas?

[gs750e]

Where are the bottom and side screws set?? bottom should be 3/4 to 7/8 out and the side 1 1/2 to 2 out. Needle clip on center groove.

Since you dont know what the problem is, I would suggest getting the floats set as was stated and setting everything back to the stock default positions.

The bottom ones wont need any more adjustment..so set and forget them. NOW, verify the valves are adjusted within spec and vacuum sync the carbs to the engine AFTER the valves are inspected.point is that youre chasing a gut off tail till you are positive the valves are right, carbs are synced, and your sure there are no air leaks like the orings in the intake manifolds ( carb holders ). Also stretched clamps wont tighten well and theres another source of contention.

Check the timing too...while your doing all the required stuff.

Moral of the story is that until and unless all the engine maintenance is done your just wasting time and energy.

Hello,

I set the valve clearances 5,000 km's ago, and I set them on the loose side (when there was a choice between 0,04 and 0,09 I chose 0,09) The last time I did synching was last week. The intake boots and clamps are in very good condition. But as I don't have any other leads I'll check the valves tomorrow. Thanks,

Jim

[chuck hahn]

No need..if they were on the loose side just 5,000 K ago theres no reason to think they are tight. So the intake manifolds and clamps are good, new orings in them and all that..ok.

So what are the screws set at?

[gs750e]

The air screw is at 1 turn out, I've never touched the fuel mixture screws, I could set them all at 3/4 to be sure? I'll check the intake o-rings when I'm back from work today, thanks.

When the engine is cold and I rev it, sometimes I can see a little bit of white smoke coming from where the exhaust meets the flange, so it's not 100% sealed I think (I used new original gaskets) Is that bad?

[chuck hahn]

We dont need to be concerned with the exhaust side..its of no meaning as to how the intake side sucks fuel and air INTO the engine.

Yes I would set the bottom pilot screws at 7/8 so you know they are really really close. Then set the side mixture ( air ) screws at 2. At 1 there isnt enough air mixed into the fuel to help it ignite..so its basically trying to fire ALL the fuel but cant...follow the theory here?

[gs750e]

We dont need to be concerned with the exhaust side..its of no meaning as to how the intake side sucks fuel and air INTO the engine.

Yes I would set the bottom pilot screws at 7/8 so you know they are really really close. Then set the side mixture ( air ) screws at 2. At 1 there isnt enough air mixed into the fuel to help it ignite..so its basically trying to fire ALL the fuel but cant...follow the theory here?

Damn, I can't take the intake rubbers off, the crews are incredibly stuck, like bending tools stuck. I tried spraying starter fluid from all angles onto the intake rubbers when the bike was running. The revs did not go higher when doing this, this means the rubbers are airtight right?

The fuel screws were at +- 1 turn out, I set them at 7/8.

With the air screws at 1.5 turn the problem persists, I can't 'open' them further because one of the screw heads is worn too badly, I ordered a new air scew for that carb.

Can the problem lie anywhere else than carbs? I remember when one of my coils wasn't working the bike couldn't rev beyond 4000 revs. Since then I replaced the coils, plugs, plug wires, timing advancer, points and condensers.