80 gs750 general performance

[saltykunk80]

inherited an 80 gs750 last winter and instantly began tearing it down and built a cafe racer. majority of the changes were cosmetic only, dropped about 50 pounds of it, did install vance and hines 4 to 1 pipes and rejetted as recommended. changed plugs/oil and filter new o ring chain etc. Am curious how this bike should perform if anyone else has got one. Mine seems underperforming but ive got nothing to base that on. Am getting about 15-20mph in 1st, 35 in 2nd, 50 in 3rd maybe 70 in 4th and have not been able to see where it tops at in 5th and these speeds are at high rpm. Was reading factory specs and say this bike should do 130 mph? seems no way in hell mine is capable of 130. I realize the bike is 29 years old but has only 14,000 original miles was always garaged. seems i am not getting close to redline before ive got no more acceleration and have to shift am shifting at about 6,000 rpm in every gear and redline on gauge is at 9500. Did also remove original airbox and put on individual cones but vance and hines recommended opening the airbox anyway? I do believe the 80 is slower than previous 750's ,78,79. Just wondering if im performing around par or underperforming as i suspect.

[tkent02]

Was reading factory specs and say this bike should do 130 mph? seems no way in hell mine is capable of 130. I realize the bike is 29 years old but has only 14,000 original miles was always garaged. seems i am not getting close to redline before ive got no more acceleration and have to shift am shifting at about 6,000 rpm

130 may be optimistic but it should go well over 100 very easily, the power really starts at around 6,500 so you are missing out on most of it. Just a guess, most likely something is causing you to not have enough fuel flowing for full throttle high RPM operation. Could be a problem in the carbs or in the petcock, it could also be something clogging the exhaust?
What size jets did you put in and how did you determine the correct size?
Pods and a pipe would require major rejetting.
It should not be any slower than the previous two valve 750.

[salty_monk]

I suspect your not jetted correctly. The "Emgo" style filters are not much good, I recommend getting yourself a set of K&N's & a DynoJet kit.... That will sort it out.

Dan

[saltykunk80]

vance and hines recommended changing main jet to a 130, previously had 115, recommended changing pilot jet also can't remember the size but size recommended was already in place.

[tkent02]

vance and hines recommended changing main jet to a 130, previously had 115, recommended changing pilot jet also can't remember the size but size recommended was already in place.

What V&H recommends and what your bike needs have little to do with each other. They never even rode your bike let alone doing a series of plug chops or dyno runs. They are guessing at it from averaging out what similar bikes have used in the past, no two are alike when it comes to jetting, engines are all different.

[GregT]

Put a timing light on it & check you're getting full advance - nothing kills performance like a sticking advance mechanism

Greg T