On the road and stumped: hesitation/lurching during acceleration (among other things)

[60ratrod]

My guess is you were running rich for the increased elevation. Less air(thinner), less fuel and more air(denser), more fuel. Just remember, richen it back up when you get back up here

[klylor10]

Ugh. Strangely as soon as I headed home from my workspace the problem started up again. I guess it's carbs tomorrow...

[jsandidge]

Your fuel starvation could simply be because of the inline filter. These low pressure gravity fed systems don't usually work well with them. There's already a filter inside the tank on the petcock and screens on the fuel inlet of each carb. You simply don't need an inline filter. Try running without it. That's how they came from the factory. Most of us don't use them. There are some filters designed to flow well in gravity fed systems, but that's probably not what you have.

[azr]

Dip those carbs for 24hrs, spray every hole you can find with carb cleaner afterward to make sure they are cleared out. Make sure all your o-rings are in decent shape. At the same time take off your petcock and make sure the filter on the petcock is not clogged. How are you setting your float levels? measurement? Man this sucks, really need to get you back on the road.

[klylor10]

Dip those carbs for 24hrs, spray every hole you can find with carb cleaner afterward to make sure they are cleared out. Make sure all your o-rings are in decent shape. At the same time take off your petcock and make sure the filter on the petcock is not clogged. How are you setting your float levels? measurement? Man this sucks, really need to get you back on the road.

I'll double check the o-rings, but I got a complete set from cycle o-rings when I rebuilt them 4,000 miles ago. The petcock filter looks squeaky clean, I took it out last night.

I haven't checked or set the float levels yet since buying this bike. I'll check that when I have the carbs apart.

24 hours in the dip won't harm the cast metal at all? I remember seeing something on the carb dip can that said not to have aluminum in for more than 4 hours.

I'm stumped here, if I dip each body and all small parts for 24 hours each that'll be 5 full days at a minimum! Guess the other option is to buy a bunch of cans... You don't think a few hours would be enough?

Jsan: I'll try running without the filter.

[OldVet66]

It will turn them dark, not a problem. If you leave them in several weeks like a friend of mine did, it makes a slime that sticks everything if you don't scrub it off with WD40 and hot soap and water. I have had good luck with the stuff at NAPPA, supposed to be a little more ECO friendly I think. When you put the carbs in as clean as you might think, you will still see a cloud of crud boiling out when the cleaner is still clear.

[eil]

Did you drain the gas from the float bowls and check it for contaminants? This is tricky to do with the carbs on the bike, but I've done it. Easier to remove the carbs if you can.

You can do 80% of a carb cleaning by just removing all of the float bowls, taking out the jets, and inspecting them under good light. Look for grit in the bowls, blockage in the jets, etc. Throw it all back together and test ride. If symptoms persist, it may be time for the more in-depth cleaning or look elsewhere for the problem.

Try adding a little choke the next time it acts up and see whether it runs better or worse.

[klylor10]

I don't get it...

Given time constraints, I dipped each carb body and parts for 1.5 hours each, sprayed through all passageways with carb cleaner, and sprayed out with compressed air. The carbs look like they just came out of the factory.

I synchronized the carburetors (which are absolutely spot on now), and adjusted the idle mixture screws using the method for CV carbs where you blip the throttle and observe the response. Screws are now set about 2.75 turns from lightly seated.

I removed the inline filter, and am getting solid gas flow. I dismantled and verified that my fuel cap vent is clear.

Yet: the problem persists, and does not get better when I turn the choke on a bit or turn the petcock to prime.

The problem is intermittent, and I hear some popping when it occurs, maybe backfiring? Also as the engine gets hot my idle climbs to 2-3k and doesn't want to go down. I thought this was a symptom of being too lean, but since the choke doesn't alleviate things I'm beginning to wonder if I've got an air leak somewhere. My intake boots are relatively supple, and I just put in new o-rings for them. I sealed my airbox with new side cover foam and foam where the filter seals to the box. Either there's another place in getting a leak or I didn't do the sealing properly.

Thoughts?

Edit: After a bit of reading I saw someone who discussed replacing gaskets where the exhaust tubes connect to the cylinder head. This reminded me of two small oil seeps I had from those connection points on both cylinder 3 and 4. I tightened down the bolts (a couple of which were not fully loaded right) and the seeps stopped. Maybe that's the problem? Could air sneak into the cylinder through there if they aren't sealing well?

[OldVet66]

There are no constraints, 24hrs or it doesn't work. The brass parts could be in there forever, but the crud lining the passages you are spraying through is tougher than the printing on your carburetor dip can. It all has to be cleaned out 100% or things don't flow correctly. Slides and diaphragms are not cleaned in the dip, it will eat the diaphragms.

[SlipperyPete]

I'm having similar symptoms on my 78 750. It was suggested I check out the points. I don't know if you have those, but I thought I'd mention it. The thread is in the carb section. Good luck!

[alke46]

I'm having similar symptoms on my 78 750. It was suggested I check out the points. I don't know if you have those, but I thought I'd mention it. The thread is in the carb section. Good luck!

His signature shows his GS is an 82 so no, he doesn't have points.

[azr]

Geez, this isn't getting any better. I can't remember for sure if you replaced the stock ignition with a new dyna or not, I know you've replace the coils, wires and caps already.

[OldVet66]

Refer to post # 23. He admitted he only soaked the carburetor bodies and parts for 1.5 hrs each because of some silly thing he read on the dip can. I haven't ever heard of any MY CARBURETORS MELTED POSTS. It might darken the aluminum some (mine included) but that's all. He needs to actually rebuild his carburetors properly and be amazed when those pristine carburetors go into the dip and crud comes boiling out and it turns the dip too dark to see through. The rest is a waste of time as to what could be wrong without having clean carburetors. 1.5 hours is not even enough to clean the jets.

[qcktvr]

Good morning,
I have been reading this thread and feel for you and your bikes problems, unfortunately I do not know the answer; but..
It's sounding to me as if you have been messing with your carbs trying to mask the problems caused by something else; this was/is a common problem with older marine and car motors with carbs.
My experience has been that they (carbs) rarely suddenly give problems, exceptions might be water getting into the float chambers or a cv diaphragm rupturing.
Carb cleaning/rebuilding after storage with old fuel is different.
I have not touched my carbs so cannot talk specifics, but with your high idle speed they are clearly, to me anyway, not adjusted correctly.. surely adjustments must be made on a warmed up motor to give you the correct idle speed and throttle response??
Typically they will not idle cold without choke, which also gives an increased idle speed, as it warms up you reduce choke and idle speed goes down to what you have adjusted it to??
My last problem was a completely dead spark plug, actual plug, there was good spark with spare/test plug..
Optical IR pyrometers are pretty cheap now and useful for monitoring exhaust temps as it warms up..etc..
Guess I'm trying to say, you should not rule out having an ignition problem, HT/plug wires touching/shorting, coils, voltage??
Anyone nearby with a spare igniter to try??
I think it more likely if intermittent and with various cylinders etc. maybe a pity that you got in to those carbs...
Good luck
Trevor

[Gorminrider]

if I dip each body and all small parts for 24 hours each that'll be 5 full days at a minimum! Guess the other option is to buy a bunch of cans... You don't think a few hours would be enough?

I have never had any luck merely soaking things to clean them. It doesn't work for my (admittedly!) filthy laundry and it doesn't work for bubble-gummy deposits stuck in tiny holes,IMO. Jets have to come out wherever possible and all the tiny holes cleared-in the carb bodies too. As in laundry, Soaking helps, but it still needs scrubrush, washboard or even agitation (sonic cleaners?) to move the dirt off the surface.
IF it's a carb problem, soaking alone may not fix anything...it might move stuff around, or begin to dilute the gums but as soon as you dry it out, it reconstitutes and gets sucked back into place when you reassemble and start the bike.
No doubt what I say is not exactly true for all solvents in all situations, but where I am, it's easier to dissassemble and completley clean things mechanically or with air than it is to keep buckets of toxicity agitating...