77 gs750 tuning ?

[Guest]

ok after following all the advice ive recieved from this site as far as carb cleaning, valve clearances and such ive fired up my 77 750 and it seemes to be idling fairly well. havent had it out on the street yet. one problem is when i twist the throttle hard it will kill it, if i ease it open it seems to rev up nicely. obviously i need to do some carb tuning, wondering where to begin

[tkent02]

That's fairly typical of the VMs without accelerator pumps. Does it do it when it's fully warmed up? Is it just cutting out a little bit or is it so bad you can't really ride it normally?

It can be tuned out but it's usually not necessary unless you just can't open the throttle smoothy.

And, what is your intake and exhaust?

[maddoghoek]

intake and exhaust is all stock, gonna take it out for a spin in a bit, and see what happens

[tkent02]

re you sure there are no air leaks in the intakes? Could help to go a tad richer on the piiot circuit, they came lean from the factory. Yeah go give it a good test ride.

Don't change anything until you know what it needs.

[Griffyn]

Full throttle issues are usually main jetting. Although you shouldn't yet rule out a vacuum leak as those are tricky devils.

Rule of thumb in carb tuning is that 0 to 1/4 throttle is pilot jets, 1/4 to 3/4 throttle is needles, 3/4 to full throttle is mains. Not hard and fast rules, but should get you pointed in the right direction.

EDIT: Oh, 1977. VM carbs. I was thinking CV carbs, so I'm probably wrong.

[tkent02]

Full throttle issues are usually main jetting. Although you shouldn't yet rule out a vacuum leak as those are tricky devils.

Rule of thumb in carb tuning is that 0 to 1/4 throttle is pilot jets, 1/4 to 3/4 throttle is needles, 3/4 to full throttle is mains. Not hard and fast rules, but should get you pointed in the right direction.

NO, that's not it. It's fine at full throttle, it's the transition from idle that is weak.