Picked up a 76A that had been warmed up before i went to see it........it is a bugger to start when it is cold, will crank, then after a few mins start to missfire then eventually start, when it has started it is easy to re-start while warm, exactly the same issue as this one:
http://youtu.be/oqrznIyy9TY

Took the carbs off, cleaned them, changed the 4 o-rings in each, checked float heights, set mixture to 1.5 turns (one was fully screwed in!

Put carbs back on.......exactly the same......got it started, checked balance, miles out, balanced them all, still no better.

Other thing i have noticed is if you adjust the idle screw to get decent idle speed, the revs will hang up after a throttle blip. If i wind back the idle speed to almost stumble the revs don't hang up.

Has new plugs fitted and battery seems very strong. All the band clamps on air intake side of carbs are missing but all in place on engine side, could it be too much air getting in?

Any ideas, i am about out of them!

Chris

Had a look at the spark tonight, seem to get continuous sparking instead of any firing order.... cdi?

sorry, i cant help you on this...
after seeing the video, i noticed that @ video 2, the exhaust sound was like running rich, mine was like that (sound like a scooter!!) but video 3, it sounds better after its been rode for 5mins. as i'm using stock exhaust so i'm not really sure how that exhaust should sound like. i'll post a video how mine sound like. scooter... unable to idle well. once i on the headlights, it died straight. have to adjust the idle screw to let it idle higher. even stalled as soon as i stopped @ traffic. had to kep rev.
your coils to plugs are correct? plug 1&4, 2&3.

http://www.youtube.com/watch?v=LKIS7fD90q4
above is mine running rich. the exhaust sound sluggish, running very rich with black smoke. did yours have black smoke? i'll post 1 more when it sound normal, its stronger & dry.

now you listen to this 1, although its with no exhaust but its the same bike with different sound. its dry & strong.
http://www.youtube.com/watch?v=nOBdEOqf9xs

Fairly convinced that my bike is smelling rich when trying to start due to not starting and now reasonably confident that the CDi is nacked as not sparking in sequence, still can't work out why it would start with the CDi the way it is but guess that is the mystery of electrics. It actualy starts a bit better after sorting the carbs but still not right. Time to hunt down a CDi.

Chris

why dont you try double check on the parts inside the carbs? make sure everything is in place, then if still cant, look for a cdi. are your 2 coils ok in the 1st place?

The fact i have a near continuous spark needs fixing before i go through that pain of taking the carbs off again.

Chris

hello,
could ye resolve the problem already?
have exactly the same problem when cold start.
I still have not found errors.
cleaned carb. 2x spark plugs replaced.
everything no improvement.
if she runs again, it is ok. then jumps to problems, even after 2h.
next morning, nothing goes back.
need urgent help

Have you checked the petcock? My petcock on my GK76 is worn and doesn't fill the carbs on prime. I have to crank the engine to apply vacuum to the petcock so that the float bowls fill. It will fire, and runs on two cylinders, and continues to misfire for several seconds, but eventually smooths.