Very Strange Carb Sync Problems

[Steve]

Huh? can't you just get them from your local spot like Iron Pony?

Sure, he can get them pretty much anywhere, but it's not his bike.

SHE is the one that is going to have do to the purchasing, or at least the re-imbursement.

.

[cowboyup3371]

Huh? can't you just get them from your local spot like Iron Pony?

Yes I could but as Steve and I both said - it's her bike now. When she told me last year she wanted to take on the registration and all other responsibilities then my role has become nothing more than her mechanic

Of course it is okay as it still keeps me somewhat involved in her life (she's pretty busy with other things)

[Sandy]

So it looks like maybe the carb sync is settled though we didn't really do anything special as both my Carbtune and Steve's mercury sticks show the same levels. However, the engine is still dying after it warms up. After verifying the ignition timing (maybe a degree or two retarded), valve timing (where it is supposed to be), voltages at the coil (12v when cold but seemed to drop to 9-10v after it warmed up), and even a valve clearance check (done when slightly warm - one valve potentially out of spec and will be rechecked later when the engine cools off), we are left with not knowing for sure what's going on. So, after talking with Steve, I will do what I don't want to do and just throw parts at it. I'll first replace the coils with spares I received today and ride it for a day or three to see how it acts. If we still have problems then I'll try to put the ignitor from my bike onto hers.

More to come later

I've been following this with interest and this sort of jumped out at me. If the voltage drops that much at the coils it probably drops that much throughout the bike and most automotive/motorcycle electronics can get flaky or just stop working when things are near or south of 10VDC. Might be worth a check, that's a huge voltage drop and could be very well be the result of something like bad/dirty contacts in the ignition switch and I'm assuming you've gone over all the connectors.

[Brendan W]

I've been following this with interest and this sort of jumped out at me. If the voltage drops that much at the coils it probably drops that much throughout the bike and most automotive/motorcycle electronics can get flaky or just stop working when things are near or south of 10VDC. Might be worth a check, that's a huge voltage drop and could be very well be the result of something like bad/dirty contacts in the ignition switch and I'm assuming you've gone over all the connectors.

Good point. I was wondering about those voltages and what were the corresponding battery terminal voltages.
Rather than get hung up on the number at the coil another way to look at it is no more than 0.5 Volt below battery as measured at the same time.

[bwringer]

Just sitting here miles away thinkin'... you guys have your mitts and eyes on the problem!


I'm fuzzy on exactly where things stand at the moment, but I'm also wondering about a couple of other things:

- Air leaks around the enrichener slides? The little pads at the end, and the seals around the little actuator shafts? Are they all seating all the way when off?

- I can think of several other physical issues the carbs could have, but I also feel like these (and many more) are things Steve would have already looked for as a matter of course:
Wrong/drilled-out/aftermarket jets and needles and slides and such.
Bad/soaked floats -- could one or more floats be soaking up gas over time?
Some sort of twist in the bracketry? But then again the carbs wouldn't work at all if they were twisted.


And yeah, coil voltages that low are A problem. Whether they're THE problem, I dunno. I do know a GS coil will typically stop firing somewhere around 10V.

[Wingsconsin]

Yes I could but as Steve and I both said - it's her bike now. When she told me last year she wanted to take on the registration and all other responsibilities then my role has become nothing more than her mechanic

Of course it is okay as it still keeps me somewhat involved in her life (she's pretty busy with other things)

Carl's Rules of Vintage Motorcycles
Prime Addage -- "No such thing as a cheap motorcycle"

[cowboyup3371]

Just sitting here miles away thinkin'... you guys have your mitts and eyes on the problem!


I'm fuzzy on exactly where things stand at the moment, but I'm also wondering about a couple of other things:

- Air leaks around the enrichener slides? The little pads at the end, and the seals around the little actuator shafts? Are they all seating all the way when off?

- I can think of several other physical issues the carbs could have, but I also feel like these (and many more) are things Steve would have already looked for as a matter of course:
Wrong/drilled-out/aftermarket jets and needles and slides and such.
Bad/soaked floats -- could one or more floats be soaking up gas over time?
Some sort of twist in the bracketry? But then again the carbs wouldn't work at all if they were twisted.


And yeah, coil voltages that low are A problem. Whether they're THE problem, I dunno. I do know a GS coil will typically stop firing somewhere around 10V.

All jets are stock and in good shape with no twists or any other sort. Ran into a small problem with my reading skills tonight so the valve cover is not on yet but I'll finish it and put the replacement coils on tomorrow night so more news to come by Thursday I hope.

[cowboyup3371]

Plug caps are cheaper, and can present strange symptoms.

Thanks Dave; I'll talk with her about ordering some.

Huh? can't you just get them from your local spot like Iron Pony?

Yes I could but as Steve and I both said - it's her bike now. When she told me last year she wanted to take on the registration and all other responsibilities then my role has become nothing more than her mechanic

Of course it is okay as it still keeps me somewhat involved in her life (she's pretty busy with other things)

Called Iron Pony twice today (first time got the typical useless parts monkey) and ordered the new plug caps which should be in Friday or Saturday after she transferred some money to my account. I'll swap those out first this weekend then try swapping the coils.

Thank you all for all the thoughts on this one and to Steve especially for being willing to scratch his head on this for me.

[cowboyup3371]

Replaced the spark plug caps this morning and so far the bike is running fine - at least in the garage. I had other things to do this afternoon and wasn't able to get it out for a ride myself but one of us will test ride it tomorrow for sure. Thank you for the suggestion Redman and keeping my fingers crossed

[Rob S.]

I'm confused...so it might not be a carb sync problem at all? Or the old plug caps were causing the carb weirdness? And how does the cold tail pipe fit in?

[cowboyup3371]

Got off work a bit early today and took Charmayne's bike out for a 20 mile test ride. Although it seemed to run better at first, by the end of the ride it died out twice - once at a light (behind a person who sat through almost 3 lights before they found the right gap in traffic) and then back at the garage. It restarted fine at the light and I did have to blip it a few times throughout the ride. However, the most telling moment came back at the garage fortunately when I could not restart it to save my life. Went back over an hour later and it fired right up. So, I'll replace the coils tomorrow evening then give it another test ride this weekend (have to work Saturday though). If that doesn't fix it I'll consider finding a replacement ignitor.

[tom203]

My local guy with same bike model and similar odd running issues still hasn't solved things. He's got dyna ignition,dyna coils new plug caps and feels that bike loses a cylinder or two after some running. He "felt " some improvement with cleaning connections, but not right yet.

[cowboyup3371]

Steve and I are stumped by a problem with Charmayne's '81 550L that we'd like to give to the Hive Mind for consideration.

Since we got her 550L on the road a few years ago, she's experienced problems with the bike cutting out at lights/stops. The plugs are looking slightly lean on the pilot circuit but the mixture screws for 1, 2, and 4 were set for over 3 turns out while number 3 was at 2-1/8 (it actually looked richer than the others). The intake boots and o-rings were replaced within the last two years and still look/feel good (no obvious cracks, cuts, or tears - visually and physically checked by running a finger around them inside/out). I also confirmed the air filter is still in good shape and doesn't look dirty or overly oily in my opinion.

With that, I asked Steve to come over this morning to help me troubleshoot the problem further. After not getting the carbs to synchronize at all and continuing to see the bike cut out even on the center stand, he recommended that he take the carbs home and re-clean them himself. We found that one pilot jet was definitely clogged from what looks to be bad gas so he re-cleaned all of the jets (full carb dip was done for the second or third time last year). All floats were set to the correct setting and all jets visually re-verified to be stock (40 pilot and 92.5 main; 150 air). The carbs were then reassembled and bench sync'd then re-installed on the bike; mixture screws are now all set to over 3 turns out.

Does any one have any suggestions as to what could be causing the issues here? I'm sure Steve will be by later to add/clarify anything I wrote here but I tried to explain it as best as what I saw the bike doing while we worked on it today/tonight.

So an update to this. After picking up replacement coils from Tom Witt (forum name is Witttom) this week, I took the bike out today for another short ride but one that should produce results and it did, again. It started and idled properly at about 1200 RPM once off of choke so once my gear was on I took off on a ride down to show Charmayne (she was in her truck) a location she didn't know how to get to and then to Lenscrafters. At that first stop, I noticed the idle had climbed up to 2000 rpm and sat there but didn't adjust it at first. However, once we got close to Lenscrafters, I turned the idle back down to about 1200. As we pulled away from that stop, the bike died one time but I quickly restarted it with no obvious issues. However, once we got to Lenscrafters (another 4 miles), the idle seemed to drop below 1000 rpm and so I raised it back up slightly to 1200.

Leaving Lenscrafters, Charmayne went home and I decided to ride over to Steve's to talk about what I had seen so far. That 4 miles or so to his house involved two stop lights where, at each, the bike would drop idle to almost nothing, raise back up to 1000, drop again to almost nothing then finally raise back to 1000 right as I started off. After talking to Steve for maybe 20 minutes and letting it run a short couple of minutes twice during that discussion, I decided to head home and go about the evening. Unfortunately as I got to the edge of his driveway at the street the bike died and refused to start back up. After Steve pushed it back up to his shop, it continued failing to start until after it had cooled off (maybe 15 minutes) about the time we loaded it up onto his trailer. I say about the time we loaded it as I was able to start it and ride it up onto his trailer then again once it came off of his trailer and into my garage.

I know I named this thread as a strange carb sync problem and it did give us that symptom when we were trying to get the carbs back together to further troubleshoot this issue earlier this month. I also now that someone asked about the valve adjustment and while we were troubleshooting this, we confirmed all valves are set to a 0.08mm clearance. However, now that the carbs are sync'd and we are back to the original issue, does any one have any ideas as to where I should look now? I already reached out to Tom Witt to ask for the ignitor he had on the 550 that provided the replacement coils. However, I just don't know where else to look to find the cause for this. Has anyone else experienced the bike dying even after replacing coils and with or without replacing the ignitor?

What other things should I check for? I want to reiterate too the problem only shows up AFTER the bike has sufficiently warmed up which, both on her previous rides before we really started looking into this and my test rides, has been after 20 miles of riding. It also doesn't just suddenly quit but instead the idle drops to about 500 rpm then 100rpm then dies.

[Nessism]

Wonder if the carbs could be sucking false air from the throttle shafts? I know you like to soak carbs for 24 hours but that's bad on rubber parts.

Maybe try some spray ether on the front of the carbs after the bike is warm to see if the idle stays stable? Replacing the throttle shaft seals isn't a hard job you just need to fabricate a tool to stake the butterfly screws.

[cowboyup3371]

So I understand you correctly Ed, you're saying to spray the ether onto the airbox boots or onto the carbs directly?

Also, I don't see a seal listed in the parts fiche for the throttle shaft; are they a part of the screws themselves already?