3-4 fire...1-2 won't..HELP/It's Alive!

[showtime]

1 and 2 cylinders will not fire. 3 and 4 do and the bike will idle (slightly) on them. I have spark in all 4. i have totally rebuilt the carbs. Float bowl's were full. I pulled them again and am pretty sure everything is clean. Checked cleaner through all the holes and it came out all the ones it was supposed to. And when I pulled them they looked wet on the head side but the 1 and 2 plugs are dry. What are the chances my intake valves are stuck shut on 1 and 2 ? Anything else I should check first ? The pipes stay cold as a stone. I'm completely flummoxed...It's an '80G and everything is stock. It hadn't run in a couple of years when I got it, was sitting on the side stand, and the #1 carb was pretty gunky. The rest were nice and clean tho..

[Snow]

Is this a standard by chance? I'd check to make sure your left fuel petcock (if standard) is functioning properly - try turning it to "prime" to see if perhaps the vacuum diaphragm may not be working.

[showtime]

petcocks flow freely, float bowls filled right up. It's not that I lose the cylinders when they start to starve from fuel....they don't appear to be getting any period..

[Snow]

Oops, didn't notice that you had said that. I would think if you had stuck valves that it would have lots of trouble turning over, perhaps even breaking a camshaft. If you are worried about the valves, you might be able to see the end of them through the #1 spark plug hole with a flashlight while turning the motor over (by hand would be best)...I'm not certain though as I've never tried.

Have you verified that your plug wires are connecting correctly? As in 1&4 are connected to the same coil and 2&3 are connected to the same coil? It's possible that if 1 & 2 are switched that not only will it not fire, but it might actually backfire - I could be off base there with the backfiring, but it's certainly easy to check the wires.

[Snow]

Also, you mention cleaning the carbs so you've had them off recently? If the plug wires are correct, then I'd also pull off the carbs and make sure nothing had gotten into the carb boots on the head while they were off... it does concern me a bit that #1 and #2 plugs don't even get wet...

The only thing in common between those two cylinders is the fuel line and tee between the 1&2 carbs...and of course the camshafts for all 4....

[Ken Talbot]

Pinched fuel line

[Ljay40]

Says floats are full..
How bout running a compression test to test your valves
just a thought may help you get a idea whats going on.

[79XS11F]

It is likely fuel starvation but might also be very low compression on those cylinders. Check compression and if that's good start looking for a fuel supply issue. Sticky floats etc. My carb floats were working great when I had the carbs on the bench but they would stick when back on the bike while on side stand. also make sure those 2 cylinders are not flooding.

Rob

[shutchis]

Try sparying a little starting fluid in the #1 and #2 carbs. You may have to loosen the air box so you can shoot a small squirt into the air intake. Starter fluid (either) is available in a spray can at any auto parts store.

Be careful when cranking the engine, you might get a backfire and it can catch fire. Keep your face away from the carbs, and keep a wet towel handy to pat out the flames.

What you're trying to do is start those cylinders. If they start, then you have a carb problem, which is my 1st guess.

As you know, carbs can give you problems after sitting for a few years.

[showtime]

It's Aliiive !

Reference my last post about #1 and #2 cylinders not firing, y'all were right about fuel starvation. I don't know where the problem was but i pulled the carbs again, checked the intake ports, checked the petcocks and gas lines, and tore the 2 carbs all the way down again. I poked, brushed, and sprayed it all clean, and put it back together. Of course everything looked fine and I could find no gunk dirt or other issues. I reluctantly put the carbs back on not expecting any sucess. When I started it 1 & 2 started hitting about every 4th revolution. It back fired and spewed smoke out the pipes for a bit (from the oil I put in the cylinders to keep them nice). But then she coughed a few times and cleaned right out. I had my idle way way to high so when she cleaned out she went right up to ( I'm guessing cause the tach don't work) 4 -5 k rpm's. I shut her down and adjusted that. Ended up with the idle mixture screws out 2 full turns. Idles like a dream and revs up great. Of course thats in the garage and not under load but I'm happy...no ecstatic..with that for now. Well I just had to share the good news. Now I'm off the check the alternator per the tech tips to see if thats my tach problem. yahhoo !!!!

[kta]

That's awesome! Carbs can be so finicky. I love the grumble of these bikes. Get that thing on the road!!!

[eroellig]

I can't wait to holler that myself. The day is getting closer...

Eric