ledman_70

This is hard to believe, but yesterday I poured a little Marvel down #4 and ran it for 15 minutes and once the smoke started to clear #4 started firing. I set the timing today so I still have to sync the carbs, but it's running decent now. Once I get the carbs set I'm going to drag the 750 back into the garage and try the same thing with it, since it has the same problem seemingly. Can't believe all it took to clear #4 was Marvel! I would recommend that stuff for any bike that has been sitting. This is not the first time Marvel has fixed a bike for me, I guess I should have gone there first. Thanks for all your help guys!

I have 2 1000's and a 750 and I have swapped coils and carbs all around. Still the same issue.

After putting head back on I ran all the valve clearances again, but still nothing. I must have really pissed off the motorcycle Gods somehow!

I really appreciate all you guys pouring over my problem since I have obviously exhausted my abilities here.

New o rings on the intake boots, all 4 sync screws tight in the boots, tried starting fluid in the back of carb and around the boot. Starts on choke, but never runs smooth. Got the bike from the guy that bought it out of a closed shop with no history. New electronic ignition, i DO have a timing light, so I will try that suggestion. Bike hasn't ran smooth since I've had it. The only thing I haven't seen with my own eyes is the rings, and when the head was off I poured a couple ounces of Marvel in cylinders 2 and 3 and let it sit for 4 days. None of it leaked out, so that tells me the rings must be OK. I will also try the staring fluid in the #3 hose suggestion, too. The carbs are all open in back and 3 of them run, so I don't think that's the issue.

I have tried ALL of these suggestions to no avail. I have swapped the car bank between the 750 and 1000. Carb #3 from 750 bank won't fire on 750, but does on 1000. Same with carb #4. That tells me it's not a carb issue. Swapped coils and wires between both bikes with no impact, either. Also sprayed starting fluid into the non firing cylinder with effect. Covering the back of the carb on either bike will kill the engine, except for the non firing cylinder. The vaccum will suck my hand against the dead cylinder without changing the engine, but it will get gas on my hand like the carb is blowing instead of sucking! This just beats the hell outta me. I've wrenched on cars and bikes for almost 50 years and NEVER been baffled like this before!

If only, but no evidence of that, either.

So I pulled the exhaust off #3 and ran a snake through it, no obstructions. I have no idea which direction to go now. This is the same issue as the 750 has, just a different cylinder. If I can fix this one then the 750 should respond to the same repair and both bikes will run. The 750 has been restored except for this issue.

So are you guys as baffled as I am? I have no idea which direction to go here, the problem is obviously not the carbs. Compression is not the best, but certainly good enough to run.

I didn't replace the base gasket, after letting it sit for 4 days with cylinders full of marvel, I figured the rings had to be good since none leaked out.

Benn very busy with the bikes guys, but I appreciate all the input. Yes, new plus, yes swapped coil and wire. Tanks is removed, feeding from small can and vaccum hos on #3 is capped. Here's the kicker, I pushed it aide and dragged the 78 GS1000 in to work on it and it's doing the same thing on #4. Head has not been off, but coils swapped, new plugs, carbs swapped. Put my hand on the carb and the motor doesn't die, but it does if I cover 3. I will try swapping the 2 and 3 leads tomorrow as suggested. This whole thing is really blowing me away. I have wrenched on bikes since the 70's and never ran into this mess before!

Also forgot new electronic ignition.

I've been working on this bike on and off for several months, but I'm at the end of my expertise now. Motor has 32k and only runs on cylinders 1,2 and 4. I have tried everything I know, so here's the list. When the motor is running pulling wire 3 makes no difference, yet putting a plug in that wire and grounding it gets a great spark. I can put my hand over the other 3 carbs and kill the motor, but on 3 it sucks my hand against the carb, but has no effect on it running. Compression is 135-145 on each cylinder. Had tried 3 different sets of carbs, all have been cleaned, same result, no 3 not firing. Pull the plug and its wet. Pulled the head off, nothing obviously apparent. Reground the valves, new seals removed all the carbon on head, valves, pistons. With pistons 2 and 3 at bottom, I poured 2 inches of Marvel into the cylinders and 4 days later it was all still there. That tells me the rings are sealing. Put it back together, tried a different set of carbs which have been cleaned, no difference. Even changed the coil with no effect. I am really stumped here, I have worked on bikes most of my life and never ran into a problem yet that defies trouble shooting like this one. So tell me what an idiot I am and how I overlooked something obvious!