I am stumped

[79XS11F]

sure it's not carb related Rob, the carbs you have now, came right off my SF that morning and it has never had a miss, ever. Same carbs, same jetting, same fuel levels, and while I never get mine up to 10k, if anything was a miss in the top end, you'd have known it within that 20 second interval while you were running and crapping at the same time!

I would agree Mack but... if it was not carb related, why would the miss that returned within 24 hours of when we switched them out not move to cylinder #4 when the plug leads were switched out between #1 and #4? Unless there is something going on inside the coil itself or within the plug lead that is corrected by the direction that the lead is twisted the miss should have went to #4 when I switched them.
The issue is of course that it makes no sense. It does not appear to be carbs and it does not appear to be electrical???? I am going on the idea that with no fuel filters on the carbs we switched out, perhaps something went from the fuel tank into the carbs and plugged some tiny opening but cleaning has not been helpful.
Are you still anticipating being in Ottawa on the 30th?
Rob

[79XS11F]

With that funny pic and mrssage, take apart and clean coil plug-ins on upper right side of frame under tank, Then REMOVE completelty the KILL switch and completely clean it shiney/ Best way is to drop ALL pieces including switch itself into a little cup of ' Evapor-Rust overnite. Nezt morning it all WILL all look like new includin switch itself. Wash all pieces with water and blow dry, then re-assemble. You and bike wikk be smiling.

I haven't used or heard of Evapo-Rust? I took all the switches apart as part of the restore and cleaned them up nicely using spray-able brake cleaner and tooth brushes to clean out all the electrical goo that was built up inside them around the connections. I don't recall seeing a ton of rust in them.
Rob

[motoman]

Ever since I crushed the original brass floats in Betsy by shooting air through the fuel lines I'm pretty paranoid about putting any air pressure on carbs with brass floats with the bowls attached. That's part of the reason I switched to plastic floats. I just fill the gas tank with a heavy dose of seafoam in it, and run the carbs dry, and that's always worked for me. But taking them off and draining them good sounds like the most effective way. Course then I'd be afraid something would make a nest inside the carb hangers. Around here the mice like to come inside when the weather turns cold, but they have to navigate my "mine field" to get to Betsy.

With that funny pic and mrssage, take apart and clean coil plug-ins on upper right side of frame under tank, Then REMOVE completelty the KILL switch and completely clean it shiney/ Best way is to drop ALL pieces including switch itself into a little cup of ' Evapor-Rust overnite. Nezt morning it all WILL all look like new includin switch itself. Wash all pieces with water and blow dry, then re-assemble. You and bike wikk be smiling.

[mack]

Pretty damn

sure it's not carb related Rob, the carbs you have now, came right off my SF that morning and it has never had a miss, ever. Same carbs, same jetting, same fuel levels, and while I never get mine up to 10k, if anything was a miss in the top end, you'd have known it within that 20 second interval while you were running and crapping at the same time!

[dbeardslee]

I've got an old inductive timing light, and every time I hook that thing up I have to hold my mouth just right to get it to work. I can get it to flash enough to set the timing, but it's not very consistent with its flashes - and that's with a bike that's running right. I just bought a new DMM that has a tach with an inductive clip, and that clip is adjustable for sensitivity. It seems to do a much better job of reading the pulses than that old timing light. But with a colortune plug (with a clean window) you should be able to see exactly what's happening in the chambers.

[79XS11F]

Yikes! (wrong engine for YICS) If there was a weak spot that would have found it or created one. You can do a compression/leakdown test but with all the work you've already done, I hope it's just really wEiRD luck with the carburetors and the Colortune plugs will help you ferret it out.

"Calling upon my years of experience, I froze at the controls." – Stirling Moss

.

I have fired her up a few times since then and there has been no change. She starts up and lumbers along missing about every 3 to 5 seconds. If nothing else, the color tune plugs will tell me if the issue is # 1 or #2.
Given that the timing light goes on #1 and I see it missing in the light, I am guessing it’s #1. The timing light is however, an inductive type and I’m not sure if I really trust it. Maybe I should test 1 and 2 with plugs on the head with this light to confirm it as well.
Rob

[dbeardslee]

Calling upon my years of experience, I froze at the controls." – Stirling Moss

That's right up there with the old Combat! episode:

Lt.: Kirby, you know what to do if the Germans attack.

Kirby: Yes sir. Panic.

[3Phase]

I was in a bit of a panic so I don't remember if she was missing.

Yikes! (wrong engine for YICS) If there was a weak spot that would have found it or created one. You can do a compression/leakdown test but with all the work you've already done, I hope it's just really wEiRD luck with the carburetors and the Colortune plugs will help you ferret it out.

"Calling upon my years of experience, I froze at the controls." – Stirling Moss

.

[79XS11F]

Rob,

I think you've said that the problem has stayed with the engine through two sets of carburetors and that it's been the same cylinder that misses or misbehaves.

Maybe there is a burned exhaust valve/seat, a weak or broken valve spring or a valve/valve bucket is sticking.

I'm trying to think of simple problems that would let the engine pass a compression test and valve shim clearance check but would still cause the engine to miss at all RPMs when it's actually running. There really aren't very many options, eh?

.

If I had a head gasket here I would pull the head and check it out.
Rob

[79XS11F]

Yes the entire bank of carbs was changed out around this time last year. She fired up and appeared to run well until the next time I fired her up. The miss had returned. Compression is good at 150 - 148 - 151 - 150. The top end was rebuilt as part of the restoration. Everything on the top end was cleaned checked and compared to the specs. Everything was good and the bike ran like a top for 2 years. Shims were checked last spring and all was within spec. Top end noise is minimal. I fired her up on Thursday and I guess the throttle cable was routed a little off and while I was in the kitchen I heard her jump to very high RPM. When I got to her she some 15 to 20 seconds after hearing her jump she was at just over 10K on the tack so I think if I had a sticky valve it would have revealed itself. I was in a bit of a panic so I don't remember if she was missing.
The bike is stored in a heated garage and I have been lucky to not have any critters in there since I moved into this house.
So the spring of the 3rd. year after the restoration was completed she was missing like she is now and I didn't sort her out because she was trapped in the garage by my camper which took up the entire laneway from within 2 feet of the garage door to the end of the laneway. She sat that summer and winter. Last year with my camper out of the way I cleaned the carbs checked the wiring, coils, plugs, plug caps, TCI unit, pickups etc. to no avail. And that's pretty much where I'm at now.
As soon as I can find the time I was run her with my color-tune plugs in her and see what that reveals. I also still need to run all the electrical tests for this issue that are listed in the factory manual and hope to find the problem.
I still think this issue is carb related because when I switch plug lead 1 and 4 the miss remains on number 1.
Rob

[3Phase]

Sorry Guys, I have calmed down now. My rant is over. I'm not sure which is more disappointing, not being able to figure this out or not having the time to really get into it and figure it out or just not having my bike running.
I am if nothing else, convinced that this is something simple and likely silly that I am overlooking. I don't have time today or tomorrow but hope to run the electrical tests on Monday or Tuesday.
What ever happened to having MORE time when we get older????
Rob

Rob,

I think you've said that the problem has stayed with the engine through two sets of carburetors and that it's been the same cylinder that misses or misbehaves.

Maybe there is a burned exhaust valve/seat, a weak or broken valve spring or a valve/valve bucket is sticking.

I'm trying to think of simple problems that would let the engine pass a compression test and valve shim clearance check but would still cause the engine to miss at all RPMs when it's actually running. There really aren't very many options, eh?

.

[jetmechmarty]

Rob,

Did you ever swap the entire bank of carburetors? I didn't see that on the list.

[79XS11F]

Sorry Guys, I have calmed down now. My rant is over. I'm not sure which is more disappointing, not being able to figure this out or not having the time to really get into it and figure it out or just not having my bike running.
I am if nothing else, convinced that this is something simple and likely silly that I am overlooking. I don't have time today or tomorrow but hope to run the electrical tests on Monday or Tuesday.
What ever happened to having MORE time when we get older????
Rob

[79XS11F]

That's a WRAP. Carbs are as clean as carbs get and the miss remains. I will run all the indicated electrical tests that are in the factory manual for this issue sometime next week when I have time.
All I can say at this point is that if those tests can not pinpoint an issue, I will consider it a "ghost in the machine" and the bike will be parted out in an effort to capture as much of my money back as is possible.
I just don't have the time to be messing around with this bike anymore. I should be out riding on a "turn key" machine that I'm not afraid to leave the city limits riding.
Rob

[79XS11F]

Yes I did spray cleaner through those holes and it exited somewhere on the carb bodies. I didn't check where but I saw an atomized mist be created at an out of view area location.
Rob