New owner

Thanks for the replies, I have been running the bike with a temp tank feeding the engine with no petcock,and vacuum pipe plugged, and as I have good equal compression i,m guessng that the valves and pistons are good.
Hoping to balance carbs and get improvements will let you know.

[Big T]

#3 misfiring means your petcock is bad.
Test by removing the vacuum line at the petcock and plugging the line
Run the bike using the Prime setting and see if #3 doesn't start to fire.

You need to go back and properly sync your carbs
Have you adjusted the valves yet?

[hannibal]

What's the history of the bike? How long have you owned?

It's possible the carbs need a good, thorough cleaning. Also, you should check the valve clearances and adjust the clearance with new shims if the clearance is too small.

The work you described on the carbs sounds like an so so attempt at carb syncing. Typically, this is done after cleaning the carbs and preparing to reinstall on the bike. Once reinstalled, you should be a proper vacuum sync.

Read this guide to learn how to properly clean the carbs: http://members.dslextreme.com/users/...rb_rebuild.pdf

[Mikey82]

Hi I,m new to the forum and from the Uk..Please be kind👍👍
I have a 1977 Gs750 had long term problem of firing on 3 cylinders and number 3 cylinder staying cold until after 5 mins of running time.
Compression test shows 100-105 psi in all 4 cylinders.
i found that some of the wire sheath had been worn away and missing in small sections of the wire from points to coils, so replaced the wires. Slight improvement in cylinder 3 but not much.
Next stop I checked the carb settings I loosened the locknut on top of the carbs (after winding out the throttle tick over screw) and screwed all the screws in until they stopped, and then tightened the locknuts I now have no.2,3 and 4 getting hot immediately and no.1 just warm.
Took bike for short run, very sluggish with a top speed of 70mph checked plugs and very black and sooty.
Going to tune carbs tomorrow, and wind out air screw ( presently unscrewed 1 1/2 turns from closed.
Any further tests you could suggest would be very useful.
New coils, plugs (ngk8es) points capacitor, carb kit. Battery,
Thankyou in advance.