‘80 KZ650: cyl 1-4 not firing but have great spark

Cleaned out the carbs recently and the bike was running great. Had a hard time starting yesterday on the way back from work which has never happened but eventually warmed up and did fine. Went to go to work today and it sputtered but wouldn’t stay running. I kept it sputtering for a minute and felt the exhaust. 1-4 are freezing, 2-3 are warm. Tested spark on all 4 and all four looked great. Compression between 145-150 on all 4 cylinders. Not sure why it suddenly decided to not run on those two cylinders, simultaneously. I can’t help but look at the ignition coil since it’s both 1 and 4 but the spark looked good on both so who knows. I know I should consider carbs but how did 2 cylinders stop working at the same time?

Note: I swapped some valve shims last week but it ran just fine for a few days afterwards.

Figured it out but don’t know how to delete thread. Just ignore.

What was the problem?

jekyllman wrote: Figured it out but don’t know how to delete thread. Just ignore.

Sorry jekyllman that's not how KZR works!

KZR is a community of enthusiasts who share and learn. You asked a question and then apparently learned the answer on your own. I'm sure that there are others who would benefit from your lesson.
If you're interested in this community, please let us in on the "Rest of the Story"
Bill

Been trying to post a response to this for days but this forum constantly gives me errors when I try to post.

Well the solution is somewhat "unrelated" to the issue brought up but here's what happened:

Decided to remove the carbs to see if there was something blocking the jets on the cylinders that weren't warm. When I opened the drain plug nothing came out. I gave the #4 a few good taps with a wrench and voila! Carb float unstuck and the bike has ran great since! Stupid solution for a stupid problem.

Thanks for the update. It’s common. I had it happen on a fresh rebuilt rack. They preformed flawless then one afternoon during my pre ride inspection i smell gas. Pulled that bowl and everything seemed normal. Put it back together and haven’t had another incident yet to date.

Usually the floats stick down and the gas won't shut off! It happens.

Sometimes it is the simplest of things.