Topic: 74 750 acceloration/power problem

[Big Cobra]

I just got my 74 cb750 on the road for first time this summer.  It seems weak.  It doesn't want to go past 60mph very easily...and not at all when going up hill.  When I try to get it going up hill, at a certain point it just stops increasing in speed no matter how hard I crank the throttle...sometimes it revs really hi in gear when trying to get up hills...like it's slipping outa gear.  It seems like I'm getting a low percentage of each gear.  Sorry, it's kinda hard to explain this.  My diagnosis is first:clutch is going out...but it still seems like something is at foot here...any suggestions?

[Johnie]

Can you give us more info here? Have the carbs ever been cleaned? Tank clean? Petcock screen cleaned? Any tune-ups done like points, plugs, condensors, timing, cam chain, valves and sync? Just trying to rule out some issues here. Is this a new bike for you? If you think clutch would an adjustment help? Let us know how you come out.

[Big Cobra]

Cleaned and rebuilt carbs last year, it's been jetted several times for pods, has a dyna electronic ignition, plugs are fine, I'm going to toy with clutch adjustment today, carbs probably need to be synced...but I don't think this where in-lays the problem...it's just sooo hard to explain what's happening on paper it just feels a little gut-less all of a sudden.  Last year when I first did some work on it...there used to be a pause in acceleration and then a jolt!!!...now there's a pause without the jolt.

[Johnie]

Could the carb intake rubbers be leaking? Run the bike and spray some carb cleaner or WD40 on the intakes and see if the engine speed changes. I would also check that sync as you mentioned.

[Big Cobra]

Cool, I'll give it a shot.  When I'm trying to get up a hill and I push the bike as hard as it will go and it doesn't want to do it it revs up really high, like it's slipping outa gear...so should I suspect clutch problems?

[Johnie]

Cool, I'll give it a shot.  When I'm trying to get up a hill and I push the bike as hard as it will go and it doesn't want to do it it revs up really high, like it's slipping outa gear...so should I suspect clutch problems?

Yah, it sounds like clutch from that description.

[TwoTired]

Are all the head pipes getting hot (about equally)?
What kind of deposits are on the spark plug tips (check all spark plugs)  If they are sooty, replace them and check for effect.

Are the RPMs racing while the bike doesn't accelerate?  (This is a clutch issue.  If you have been doing this a lot, the steels may warp and get heat damage.)