Very Strange Carb Sync Problems

[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.

.

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 -- :hopelessness:

 

[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.

 

[cowboyup3371]

So this has been on hold since September for various reasons but I started thinking more about different causes and figured we'd swap the petcock from my tank to hers (her problems originally started around the time we replaced her petcock a couple of years ago) for a test. However, we removed the carbs during the winter so I first had to re-install them a few weeks ago when I realized the clamps wouldn't tighten properly. So, I then transferred the clamps off of my bike then noticed the airbox side boot on the number 3 carb wouldn't cover the carb intake properly. I got home that night and ordered new airbox side boots which I just finished installing. All four carbs are now sitting very nicely in both the intake and airbox side boots.

Unfortunately she is out of town this weekend and asked that I wait until she returns before putting everything else back together. Once she returns, I'll put her petcock back and test to see if the boots were the problem. If not, I'll try my petcock in her tank and then go from there.

 

[cowboyup3371]

Took the bike out today for a test ride and it seems to finally run better. We do have a rear brake problem we need to investigate but at least it didn't die on me at any stop today. More testing to come but I wish I had replaced the airbox side boots some time ago.