1980 GS750 Massively underperforming

[Guest]

Hey guys. Awesome forum, I can't wait to learn all about the GS (just bought my first one).
That being said, my 750 is massively under-performing. I was hoping to get some diagnosis help.
Basically, the bike seems to run nice, but can't break 90kms/hr...crazy right? The guy I bought it from was trying to make it into a cafe racer or something and he had pods on the carbs instead of the airbox. When you give it some throttle, these pods even flex, like it's starving for air.
Am I correct to assume that maybe he just threw these pods on without rejetting the carbs and the bike is just being starved of oxygen? Would that cause a 200km/hr bike to be a 90km/hr bike?
I really appreciate any information I can get on this issue, as I love the bike and want to be able to take it out of the city. lol

[theresthatguy]

This may help. http://www.thegsresources.com/_forum...=199275&page=6

[sokocanuck]

This may help. http://www.thegsresources.com/_forum...=199275&page=6

Great, thanks for the link. If it is rejetting, I'll definitely poke around that link some more. Unfortunately, I'm not sure if that's the issue.

[theresthatguy]

Yes, you'll have to do some digging to find out. I don't what condition your bike is in but perhaps it needs a valve adjustment and carbs cleaned as well.

[duaneage]

Sounds like the slides are not going up. How are the intake boots and clamps?
Might be a fuel supply issue too, have you tried it on PRI instead of On or RES?

[sokocanuck]

Sounds like the slides are not going up. How are the intake boots and clamps?
Might be a fuel supply issue too, have you tried it on PRI instead of On or RES?

The boots are all just clamped on instead of screwed on like I've seen in the manuals but the condition of the rubber is good. I am concerned about the K & N pods because they're quite small and I notice they have inner threading...yet it isn't being used. The boots are just clamped over them. I tried to check the product number on them and as far as I've found so far they don't exist...

Good point about the prime. I'll give that a try tomorrow!

[sokocanuck]

Sounds like the slides are not going up. How are the intake boots and clamps?
Might be a fuel supply issue too, have you tried it on PRI instead of On or RES?

Opps, didn't notice the slides part.
Probably no easy way for me to check this, is there? Is that related to the amount of air coming in? They are sitting 3/4s the way down when I just took a peek.

[Jcgonzal]

Very easy to check since you have pods. Just take all the pods off and look into the carbs as you rev the engine. If everything is working correctly and the carbs are synched, all 4 slides should move up at the same time/same distance.

[mrbill5491]

Too much air will kill your power big time and that is what it sounds like, very lean conditions. does your bike have a 4-1 pipe? Last time the valves have been adjusted? Gonna have to take the carbs off and see if the main jets have been changed out. Lots of things to look at here.

If you were to take the stock air box off one of these bike and try to throttle up the engine with out it, you would be hard pressed to see 4,000 rpm. You gotta have some air restriction (and the right jetting) for these CV carbs to operate properly.
A few pics would be nice.

[sokocanuck]

Very easy to check since you have pods. Just take all the pods off and look into the carbs as you rev the engine. If everything is working correctly and the carbs are synched, all 4 slides should move up at the same time/same distance.

I checked it out and they seemed to move up at the same rate when i hit the throttle. They do a little stutter and move about halfway up.
I did notice that one of them was spitting some gas back out. Any idea about that?

[sokocanuck]

Too much air will kill your power big time and that is what it sounds like, very lean conditions. does your bike have a 4-1 pipe? Last time the valves have been adjusted? Gonna have to take the carbs off and see if the main jets have been changed out. Lots of things to look at here.

If you were to take the stock air box off one of these bike and try to throttle up the engine with out it, you would be hard pressed to see 4,000 rpm. You gotta have some air restriction (and the right jetting) for these CV carbs to operate properly.
A few pics would be nice.

Here are the pics, Mr.Bill.
Also, the pipes are 4-2

[sokocanuck]

More pics

Here is the whole bike.

[sokocanuck]

More pics 2

Here is the K & M filter next to a 12 mm wrench. Seems too small, no?

[ShadowFocus603]

I'd ditch those pods and get a stage 3 dynojet kit from z1 as well as a set of ape super pro pods from pingel. Otherwise you are going to rip your hair out chasing your tail trying to dial those in. An alternative is get a stock air box and take her back to factory. Option 1 is about $160. Option 2 depends on whether you can find a use able air box and for how much. Either way I wouldn't ride it til its sorted or you risk overheating it from being massively lean.

[sokocanuck]

I'd ditch those pods and get a stage 3 dynojet kit from z1 as well as a set of ape super pro pods from pingel. Otherwise you are going to rip your hair out chasing your tail trying to dial those in. An alternative is get a stock air box and take her back to factory. Option 1 is about $160. Option 2 depends on whether you can find a use able air box and for how much. Either way I wouldn't ride it til its sorted or you risk overheating it from being massively lean.

Ugh, it just rained for a week and it's going to be nice for a week. Terrible timing to put it away.
You could be right about it being lean. I really don't know and am just learning. It seems to run and idle fine, doesn't stall or sputter or anything though. I do notice a "tick, tick, tick, tick" noise when I'm driving though.

I'm thinking I should start by cleaning the carbs (though I already ran seafoam about a month ago) and then sync them. Possibly a valve tuning?
Uh, I'm pretty lost here, boys. lol