won't rev past 5k

[Dubweiser]

well...i'm finding more and more issues with my "good deal"

....i took it for a test drive for the first time since i got it home, so, here's the issues i can't figure out

... its an 84 GS750EF


....it won't rev past 5grand....and when its sitting at 5 grand or thereabouts, constant throttle...it starts to act funny and backfire, it's really sputtery


...it has a Vance and Hines Header and KN pod filters, probly never been jetted either, which i'm sure is causing some problems, i'm not sure where to go from here

[chef1366]

You are going to have to open those carbs up and have a looksy. If the carb jets are stock I'd go with a Dynojet stage 3 jetting system. Any way you look at it you need to do some rejetting and you can curse the PO for not jetting it with all the extra airflow.
These guys have good deals on the Dynojet kits. http://www.mawonline.com/

[tfb]

....it won't rev past 5grand....and when its sitting at 5 grand or thereabouts, constant throttle...it starts to act funny and backfire, it's really sputtery

Have you put a fresh set of plugs in it? Always a good starting point with a new acquisition that has mis-firing problems.

[Dubweiser]

i forgot to mention that..i did put new plugs in and fresh gas...it was sitting for a while i think.....but i don't know what to think now that everthing they guy told me when i bought it is a complete lie

[tfb]

Even if they're not outright lies :---), they're often the musings of someone who doesn't know their stuff. :-\"

So, don't assume anything. Not a thing. Check and eliminate everything yourself, and then you know what has and hasn't been done!

It's time for carburettor removal, dismantling, cleaning, reassembly, & synchronisation.

While you're at it, let's do a compression check. If you've got one or more cylinders below 100psi, let's do a top-end rebuild and take it from there.

All the best,
Mike.

[Cassius086]

If it acted up like that when the engine was cold, dig into the carbs, and clean 'em. Then research a jet kit. If it only started acting up once it got warmed up, check the coils and the CDI/igniter box.....if it proves to be the CDI box or coils, clean the carbs anyway :-D

[Dubweiser]

took the carbs apart....all 4 boots to the head were cracked and tore, and the jet sizes seem to be 130 and 55....i'm guessing stock, gotta look into that to make sure though