Topic: Accleration Stumble

[wilinfla]

My 1976 CB550K has a very slight hesitation when you accelerate through 2500 to 2900 RPM. It's not real bad, just enough to annoy me. It runs fine everywhere else in the powerband, just that one spot. Do you think it's dirty jets or maybe the carbs need to be synched?

                                Will

[TwoTired]

I think we need to know if the bike is still in stock configuration.

And, when the last complete tune up was performed.

[wilinfla]

The bike is totally stock. I have only had it for a month or so. It had 6000 miles on it when I bought it, it is very clean, the inside of the tank even looks brand new. I'm not sure when the last complete tune up was done. I suppose I should probably start there, but  I have been too busy riding it  , I have put about 600 more miles on it so far. The stumble is very slight, you wouldn't even notice it if you were riding aggresively. It bothers me because I know it's there and it really shouldn't be. Thanks.

                                                             Will

[TwoTired]

If you don't know the tune up history, it needs one.  Every 3000 miles.  If you don't do the tune up at 3000 mile intervals. It is just plain neglect. 

Quite possibly a new air filter, could solve your woes.  At any rate, corrective tuning procedures should be preceded by a full, complete, thorough tune up.

These bikes do not have the modern auto technology that allows 100,000 miles without maintenance. 

Cheers,

[OldSchool_IsCool]

Throwing in 2 ounces of Seafoam per gallon of gas wouldn't hurt.  Also, if you have an in-line fuel filter, either mount it vertically so that it doesn't trap air or remove it and trust your in-tank filter. 

The in-line filter probably isn't your issue since the stumble is at such a specific range.  More likely it's dirt in your idle or main jets which are transitioning right around the RPM range you specify. 

Also, check your timing advance unit.  It too is transitioning right around that RPM range too.

[wilinfla]

Thanks, I'll have to park it long enough to do the tune up I suppose.

                                                                Will

[736cc]

Replace spark plug wires and caps if they show any signs of cracking anywhere. Those are calssic symptoms you are describing of old wires shorting out. Run your bike in a darkened garage and watch for sparks around the head. Might as well replace plugs, too.