Very Strange Carb Sync Problems

[Nessism]

Spray the carbs Scott. Around the throttle shafts.

Here are the seals...https://www.partzilla.com/product/su...71cdb39560a272

[bobgroger]

Just a thought, is the gas cap vent clogged? If it dies and you open the gas cap is there a whoosh sound? Happened to my 850. Would run fine for 1-5 miles then die. Eventually it would start up again. If I opened the gas cap it would start and run fine again.

[cowboyup3371]

After a few attempts at trying to get over there this week, I finally made it to Steve's garage so we could go through the troubleshooting together. Here's what we found. First, we believed the vacuum line, despite being what I received from Parts Outlaw last year, might have been too big as it measured about 5 or 6mm. So after changing it out for a slightly smaller diameter one that he had I took the bike back out for a quick ride under the condition that I don't get out of cell range. Of course luck would have it that was only as far as the Police Station on the corner because I left my phone back at his garage as I discovered when my headset said cell phone disconnected .

However, it was fortunately close enough it didn't matter since once I put the kickstand down the bike died. Okay, vacuum line is not the problem. Then we followed Ed's advice he gave:

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.

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?

Spray the carbs Scott. Around the throttle shafts.

Here are the seals...https://www.partzilla.com/product/su...71cdb39560a272

But with no noticeable affects on the operations. As we sat there and discussed other options and possibilities, Steve remembered that the pipes on her bike have all of the holes opened in the ends of the mufflers instead of just the center one. On a whim, he started adjusting the mixture screw settings going up from 4 turns out to a final 7 turns out from lightly seated. In the garage the bike started to run a little better so rode directly back to my garage as I left my keys in the door earlier this morning. Leaving the bike running while I was there (no loss of power), I grabbed them, remounted, and left for his place the same way I went this morning with no ill effects. In fact, when I returned to his garage I left the bike running for another 5 minutes or so without it dying for the first time in forever.

Now, we verified when we had the carbs apart that the bike has the stock pilot jets (40) and air jets (150) in all 4 carbs. However, we are thinking that the extra holes drilled in the mufflers of both exhaust pipes might be the cause of the issue. I am going to let Charmayne ride as she has time over the next few weeks and see how well it runs for her at the setting we have now. If it all works without causing her issues, I will probably try to increase the pilot jets to a 42.5 and reduce the mixture screw settings accordingly.

After he explained how the changes in the pipes can affect the intake of air, I wonder who changed them and why. It lines up with the problems the PO told me she had and could never figure out. I think we found the true reason for it only because Charmayne rode much more than the PO might have and is not one to accept problems without wanting them fixed. For that I applaud her and hope she carries that desire through everything in her life.

[Nessism]

People run headers and pods without having to touch the pilots. Something doesn't seem right...

[Steve]

That's what I was mentioning, too. Main jet changes, definitely. Needle changes, probably. Pilot changes, no need.

So, ... we are still stuck here.

Scott has gone through the carbs and replaced intake boots and o-rings in the somewhat recent past. I went through the carbs to double-check them, so we are reasonably sure that carbs are not the problem, even though all the symptoms sound like carbs.

We are getting good voltage to the coils and ignitor. Most electrical problems I have experienced showed up as suddenly not running, or at least running poorly, because one or more cylinders was not operating. This bike will fade a bit, then come back, fade again, then finally stop. Sounds more like it's running out of gas than having electrical failure. Equally puzzling, sometimes it starts running BETTER, rather than fading.

And it only happens when at operating temperatures, meaning after about 15-20 minutes of riding. Sitting in the shop with fans blowing on it, it would not fail. Faded once or twice, but did not fail. This was with tank off, running on aux. tank, two fans blowing on engine.

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[Rob S.]

I'm with #2 emoji: bang your head against a wall.

Still, it's got to be something. It's like I used to tell my computer classes: "broken mouse pad." And half of them would go, "Oh..."

I'll certainly keep tuning in to this one. Same Bat-time, same Bat-channel.

[Steve]

I'm with #2 emoji: bang your head against a wall.

You like that one? The next one will be this:

It's like I used to tell my computer classes: "broken mouse pad." And half of them would go, "Oh..."

You need to tell them that they have a PEBCAK error.

Problem Exists Between Chair And Keyboard.

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[roeme]

Inconsistent fuel delivery from tank?

The way I read it, you had it on an separate Tank in the shop...

[Grimly]

I had one that made me scratch my head for a while. Full tank - perfect; half tank, it would sputter and fart and occasionally die.
Turned out the vertical filter assembly in the tank was partially varnished, but the fuel flow through it was sufficient when it was all covered, so gave no hint of trouble until half-full. This was a couple of years after I'd thoroughly cleaned the tank, petcock and filter, but obviously the filter wasn't as clean as it looked, because the bike certainly wasn't sitting neglected once it was back on the road.

[gustovh]

I just read all this and not one mention of a compression check. hmmmm another question one might ask, does the exhaust flow the same on both sides....ls it possible that there might be a plug up on one side of the exhaust or other? Remember Sandy, John’s problem?

V

[Steve]

Don't have a compression gauge.

Part of what is so confusing is that when it's running, it runs PERFECTLY. Nice, smooth, as powerful as a 550 can be, can't ask for much more. Then it warms up, stumbles a bit, fades out and dies.

If it only happened with the regular fuel tank, I would suspect the vent in the cap. I might also suspect the petcock losing vacuum and shutting down fuel flow. That's because it gives the impression of running out of gas and slowly dying. However, we are feeding it with an external tank, so those two suspects are eliminated.

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[Sandy]

Don't have a compression gauge.

Part of what is so confusing is that when it's running, it runs PERFECTLY. Nice, smooth, as powerful as a 550 can be, can't ask for much more. Then it warms up, stumbles a bit, fades out and dies.

If it only happened with the regular fuel tank, I would suspect the vent in the cap. I might also suspect the petcock losing vacuum and shutting down fuel flow. That's because it gives the impression of running out of gas and slowly dying. However, we are feeding it with an external tank, so those two suspects are eliminated.

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Have you guys done anything to address what could be a heat soak problem on the ignition/electrical components? A full can of canned air sprayed upside down makes a really good refrigerant, or go buy the proper stuff if you can find it. This is getting pretty crazy.

[cowboyup3371]

Coils were replaced last week with a working set I bought from Witttom. The only thing that hasn't been touched is the ignitor but I am not swapping it out yet until we put some more miles on it and see if setting the mixture screws out so far really did fix the problem. After we set them to the 7 turns, I rode the bike about 10 miles around the block and didn't have an issue. I then rode it from Steve's house back to mine without one single fade at any stop light (previously I would have had to at least goose the throttle). I told Charmayne she could ride it this week but to let me be in a position to come get her if needed (meaning to be sure it was later in the PM when I can get away from work). I'll also try to get it out and see what happens.

[Wingsconsin]

Through most of this I have been thinking -

Heat related electrical problems -
On some old bikes I have seen the Main fuse get hot and open up and kill the bike -
The fuse is cracked not broken and the temp change eventually cause the crack to be too wide to conduct electricity.

Now I am just confused --

[cowboyup3371]

Unfortunately the bike died three times during Charmayne's ride to work today so it's not fixed . Mom and I are going to meet her at work shortly and ride back to the garage. I'll do some more investigating this week and will check your idea out Carl. Plus, I'll put the ignitor from my bike over to hers and see what happens.