77 GS750 - Valves or Timing?

[Spaceecho]

I have a project 77' GS750 that I'm having a hard time getting to run.

First off, I've done the following: starter relay (was old a crusty), Points & Condensers, plugs & wires and rebuilt the carbs (the floats were off and there were huge 27.5 pilot jets in there).

The bike seams to be trying harder I'm getting huge "bangs" every few seconds when holding the starter. The plugs are getting spark. I've checked the point gap setting like 10 times. I most recently changed the plugs and wires, after when I tried to start the bike flames shot out of the carbs lighting the air filter on fire?!

I'm now looking for help on next steps... I've been told it's timing, if so any tips on how to set the timing when the bike isn't running? I've also been reading it could be valve clearance, if so please send tips on setting the valve clearance.

Any advice is welcome and appreciated.

[hikermikem]

make sure the plug wires are connected to the correct cylinders...

My son's project 1100L looked correct, but the PO had the switched the coils so the left coil actually went to cylinders 2/3, instead of 1/4. Had the same flame shooting going on as yours.

I pulled the points cover (this one had the sig gen ignition) and verifed which coil was being energized based on the 1/4, 2/3 marks on the timing plate. That's where i saw it was backwards.

Hopefully your is just as easy.

[Nessism]

Check the newbie mistakes thread linked in my signature. It might help.

[Spaceecho]

Thanks guys. I'll try these out.

Definitely a newbie but I do try to do as much research as possible before starting a job. I think the only thing on the newbie list I missed is the valves. Tips would be appreciated.