gs750 sputter and popping

[vintageacat]

hello there. my dad has a 78 gs750 that he bought last summer. it had 6k on it when he bought it. original mint condition. anyway it has a funny sputter on the middle right cylinder. it also doesn't seem to have much power and does not
impress him at all. he is in fear that it is a bad head gasket making a lean mixture. I was thinking it could just be the carbs are out of sync. so I was wondering if this is common or if anyone has experienced something similar. once we can get this figured out then I will be able to talking him into pod filters and a new exhaust. right now it's so gutless my dt400 walks all over it at all speeds.

[tom203]

"middle right cylinder" - does the petcock vacuum line connect to this same cylinder? maybe it's not in original mint condition and is not flowing enough gas to carbs and/or leaking down this vac line fouling this cylinder out.
Did you take a peak at air filter element- lots of maintenace issues need checking.
Take a visit to this link- running right, this bike should scare your dad with its power.

http://members.dslextreme.com/users/bikecliff