Bike stumbling off idle & missing under hard(er) acceleration

[ThrottleJock]

Hey guys, newbie here. Been riding/racing various bikes for 20yrs but this is my first foray into bikes as old as I am. I picked up a clean little '76 that was nicely taken care of, and I'm having a ton of fun with it so far.

I do have one issue I'd like advice on where to start -

Bike starts 1st kick piece of cake, settles into a decent idle once warm, rides around nice at low throttle openings, but it occasionally stumbles and dies when taking off from a stop, and when I run it hard it misses a little bit and doesn't pull all that clean. Seems to get worse when it gets hot. Also, it seeps a little fuel thru the carb overflow if I leave the petcocks open when I'm done riding. Not sure if that's a clue.

Previous owner recently changed plugs, wires, points, condenser & battery. He didn't touch the electrical system or carbs.

What do I check/clean/replace first?

THANKS!

 

[mrkil]

sounds like it's running lean.

is it real hot when your riding? does the exhaust crackle after a good ride?

what colour are the plugs?

check your float levels for the fuel coming out of the carb.

 

[ThrottleJock]

AWww I didn't think about that.

It's been 95 degrees every day here, and it does it worse when the bike's hot. Gonna go check the plugs now!

thanks!

 

[ThrottleJock]

Yeah they look like they've been running a little hot

 

[5twins]

You'll have to learn to get into the habit of shutting your petcocks off. The float needles were meant to meter the fuel flow, not act as an on/off valve for long periods of time. A full tank of gas pushing against them can overpower them.

 

[ThrottleJock]

Yep on the petcock shutoff, that's no biggie and def solves that prob.

Went for another ride today to further diagnose miss, and it stalls & misses less when lights are OFF. Also, it seems to run better if I kick the everloving shit out of it.

I think I'm going to start by replacing all old/corroded cables and giving the carbs a nice soak & cleaning, that'll eliminate some of the variables. Any of you guys use that Seafoam stuff? Bandit/air cooled Suzuki guys (world I come from most recently) seem to swear by it.

 

[5twins]

Check your timing and points gaps. These bikes like that set dead nuts. It can be a chore on the dual points set-up. Basically, you're setting 2 single cylinder engines and need to match them to one another as well.

 

[remmy1101]

I've used sea foam just running it through my gas tank before im not sure if it did much to be honest with you.
Your best beat is to do a full tear down carb clean I always buy gumout carb clean. The name brand stuff really works better.

 

[Tech7]

If it runs better with the lights off, it's time to check the charging system.

 

[yamaman]

Old iggy coils will do that! And get worse the hotter it gets!

 

[IllusiveJack]

I had exactly the same problems and thought the carbs were the fault until I put a Hugh's Hand built PMA on it, then bam! Haven't had a misfire since best thing I ever purchased to the bike.