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Discussion Starter · #1 · (Edited)
After a top end rebuild I find the right cylinder not firing correctly ( plug is wet when pulled to inspect ) with corresponding smoke from that side. Head was reworked, cylinder honed and new rings. Carbs overhauled.

Since reassembled I set the valves, cam chain tension adjusted, timing set, carbs synched. Both plugs were tried on each side - no difference. I checked for spark and it is sparking as it should. New battery last year. Bike will run down the road. Had it up to 4500 rpm on a test run as I ran through a few gears.

What are other possible culprits? Thanks for your input.
 

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Verify your timing again (with a gun if you have it), reset your idle screws, and then do a vacuum sync on your carbs. Should clear it right up.
 

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Discussion Starter · #3 ·
Hi Pat. Thanks for the guidance.

Before I rechecked items I tried swapping coils. I discovered a loose/cracked connector (for the right coil) that feeds the two coils. So I replaced it.
I did a static timing. Prior to the carb cleaning last fall the idle screws barely made a change to the rpm. It is still the same now. That is still a mystery to me. After the sync the right cylinder still smokes and the plug is wet. Tried swapping the plugs and no difference. Bike runs great during a test drive up and down the block, however....

I have a bad feeling the rings aren't doing their job since the rebuild. It doesn't seem, though, that it is oil residue on the plug - too thin. On initial startup both smoked a bit, then both cleared up for a short while, now the right one continues to smoke.

I am leaving tomorrow on vacation for 12 days. It's gonna' bug me the whole time.
 

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Check/set your float heights and if you replaced the float needle and seat verify that it is actually shutting fuel off when closed - aftermarket ones tend to have a habit of not seating properly and allowing fuel to continue to flow into the bowls.
Based on what you've described I'd put my money on either float heights not being set correctly or a leaky float needle.
 

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Discussion Starter · #6 ·
The coils were swapped before my last post. I will take out the carbs and give them a looking over when I return. In the meantime my friend will do a compression check.
 

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Discussion Starter · #7 ·
The compression is within specs now since the rebuild, and the right one is slightly higher as well. I will be tearing up the carbs AGAIN, checking float level and fuel shutoff and other items in general to find the gremlin(s).
 

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My only thought is that there's gotta be something seriously wrong with the right carb for it to not be getting fuel from any of the jets in the RPM range and therefore firing. I'd be thinking like, float needle completely glued to its seat, float height set dramatically wrong, fuel line blocked, maybe a big hole in the diaphragm. If PJ's aboot, he knows these carbs better than just about anyone and would be able to tell you what to look for.

FWIW, every time I've had a one-cylinder firing issue, it's been either the carb sync, the idle adjustment screw setting, or not getting spark at all/when expected. My list would be:
- Verify timing with a dynamic gun, not a static light - I've had ignitions that didn't fire between the coil and the plug but look good at the points because it's a different wire run. This is especially true if you have an electronic ignition (do you have an electronic ignition?). If it's firing intermittently, you've got a weak spark for some reason, and if it's not timed exact, well...it's off. If your plugs are fouled, this is a good time to change em.
- The idle screws not making a change to your idle is concerning. If you screw them all the way in, does your engine die? You may want to pull them out and make sure the tips aren't broken or munged - there are cases on here where a bad idle screw or a broken tip prevented the screw from seating correctly and functioning. This would also, to me, explain wet right plug - if your screws or their seats are messed up, that'll dramatically affect your A/F mixture and give you that rich problem (which could cause the cylinder to not fire). For context, mine take about 1/8 turn before my idle starts to drop, quickly.
- Vacuum sync again after it's warmed up - never hurts to check again :) the more spot on your sync is, the less you'll feel like you just got off one of those old bumper boats after a ride.
 

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Discussion Starter · #9 ·
Pat,

I started a thread last fall about my carbs not changing the idle when the screw was adjusted, and another carb situation while running. I was waiting until the rebuild to finish that chapter. Unfortunately the idle mixture thing still exists, and now the wet plug/no run problem now.
I will get to the carbs when time allows this week and next. Work keeps getting in the way. As I last recalled the mixture screws were intact, equal length and all parts present - spring, rubber gasket. I'm not sure if the engine dies with it screwed in completely because I probably back it off before it would. I know the rpm gets low when it is almost fully closed. That's the only time there is a definite rpm change. Otherwise the rpm change through many turns of the screw is minor. The carbs are stock as well as all the jet sizes. I believe some jets were replaced prior to my purchase, but original size. Original ignition.
One new coil just purchased. It happened to be the right one. But both plugs have spark, and I interchanged the coils with no difference. Also interchanged the plugs. I did notice that the cylinder ran clean for a brief time after plug swap until it had enough of a chance to spew smoke once again (and get the plug wet again).
I used to have a timing light but gave it away years ago. So no dynamic timing.
I will take the carbs apart soon and compare. The diaphragms are original, I gather. Would there have to be a big hole, or would even a minor crack along an edge make a difference?
Duty calls. Time to attend a meeting.
 

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I don't have much experience but when I first started working on my 360, I had low power, running on one cylinder, and it was hard to adjust the idle correctly.

IMHO the 3 things that got the best results and made the bike rideable:
1. Clean the carbs
2. Fix the vacuum leaks - I'm primarily referring to the sync-port covers but I also tightened up the intake boots and air filter housings. I didn't have any issues with the diaphragms.
3. Replace the coils

I also replaced the points with a PAMCO and haven't had a single issue. I know there's a love/hate relationship around here about them. I'm on the love it side.

Anyway, I know you've done item 1 and item 3 partially. Just putting it out there that maybe there's another source for a vacuum leak.

Good luck
 

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Discussion Starter · #11 ·
Thanks to everyone so far for your inputs. I will keep your notes handy as I tear the carbs apart. I'll most likely start on it later today. :confused:
 

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Discussion Starter · #12 · (Edited)
It's been a frustrating week. Pulled the carbs three times. The only things I found were an obstruction in the pilot (slow) jet, and later I realized I lifted the needle jet last year and figured I'd take the shim back out. Both items produced no change. I rechecked all jets and channels and confirmed they were all open using carb cleaner and air. The carbs are clean enough to eat off. Also installed new plugs. Plug sparks when pulled and grounded to the head. Timing rechecked and synch done. Floats are set at 19.5 and float shutoff valves work correctly.
The idle mystery still exists. The idle mixture screws are identical - the needle tips are both 3mm long on them (for reference). I'm assuming that is the correct length. When screwed in completely, individually, the engine does not stall. It gets close right near the end. The right one coughed a time or two but that's it. Otherwise, through the adjustment range there is very little RPM change until they are screwed out quite extensively. Then the idle falls off somewhat noticeably. So I set them about 3/4 of a turn out from closed.
No matter what the right side is still smoking. I am thinking it must be an oil leak fouling the plug and burning oil. I will be pulling the head cover and possibly the head since I suspect a valve seal could be causing the smoking. Whitish smoke. As I mentioned earlier the head was reworked and he replaced the exhaust valve guides and seals. The compression on the right cylinder is 160, slightly higher than the left. So logically it's not the new rings.
The engine runs well in the range I tested it to date (up to 4500 rpm), despite the smoke and the idle concern. So I am still baffled.

More background info: All original parts except for the new reg/rec combo. Rubber collars to the intake ports are flexible, no suspicion of vacuum leaks. Before taking the engine apart last fall the engine ran well, despite the low compression 125/130 caused by worn rings and maybe some exhaust valve leakage, and the idle adjustment problem. Back then it would also stall sometimes when the engine was hot and idling the engine coming to a stop. No telling if that is still an issue until I get these two things (idle and smoke) squared up first.
 

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Discussion Starter · #13 ·
I just received some input from my 'head' guy. It is possible the rings aren't seated yet since I put the engine together, hence the smoking. Most of my running of the engine has been in the garage. So the next step is to do a break-in run when I return home in three days.
The other item - the idle mixture not adjusting - may be from aftermarket mixture screws which are not quite the same caliber as originals. The ones I have look too new to be original. They seem to fit well and are snug like they should be, O-rings and all. But I have no idea if they are Keihin level quality. Does anyone have experience with that situation? Is there a supplier for those items only vs buying an entire rebuild kit?
 

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Discussion Starter · #14 ·
The break-in run has been completed. Most of the smoke is gone. Maybe some regular runs will clear up the rest over time. Some advice on the idle screws did not pan out. Still very little rpm variation when tuning.
Now I have an overflowing left fuel bowl. Don't know where that came from. Yet another carb removal coming up.

Work, work, work, work on moto, work, work, work on moto, work, work on moto, work, work, work, work on moto, work, work......
 

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Discussion Starter · #15 ·
I replaced the pilot jets with Keihin jets and there is a bit of an improvement. I am done fiddling with Moto for now and will run up some miles to see if the rings and carbs 'settle in'. After all, it is August and the engine runs great.
 
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