inconsistent starting and possible fuel delivery 81 550T

[Guest]

Hi all,

have been struggling for a few weeks with my 81 550T to get it running. has pods and 4to1 exhaust, new jets have been put in (although def still needs to be tuned), needles shimmed, o rings replaced in carbs, and intake boot o rings replaced. carbs were dip cleaned as well. I also have spark in all plugs. did a valve adjustment and all valve clearances in spec. cam timing is correct too.

couple days ago I installed a brand new petcock because the original petcock had issues with fuel flow on prime (very slow, inconsistent flow). Put the carbs back on, wouldn't start (was using 12v car battery to jump).

The next day, after sitting overnight, I put the petcock to prime for about a minute when I woke up and then the bike roared to life. It seemed like it finally got fuel - It was idling at 4,000rpm!!! attempted to adjust idle screw counter clockwise and would not change idle. Also changed pilot/mixture screws and had them turned out only .5 turns and the bike would still start up and immediately roar to 4,000 rpm and stay there. If my pilot jet was too big could it cause this crazy high idle??

I thought might be an issue with pilot jet, so took it apart and inspected the pilot jets. When I took the carbs off there was fuel visible in front of the butterfly valves, not sure if this indicates too much fuel? (checking my spark plugs they still show a lean condition and are not wet??)

ALSO, there was some fuel that got into the far left air filter, seeming to indicate a bad needle valve/seat...? but I don't see how this would stop the bike from starting...

Put it all back together today, replaced the needle valves, and suspecting a fuel delivery problem I left it on prime for about 10 minutes. Then turned the petcock to on, tried to start it up (battery fully charge), and it cranks and cranks but does not start. Is it possible there is still not enough fuel in the bowls after 10 minutes of prime?? given the history of starting issues this is my guess but I'm really not sure where to go from here. I don't want to leave prime on too long and run the risk of flooding the engine.

Debating tearing the carbs apart and doing another deep dip clean and start from the beginning.

The weather has been too nice for me to be spending so much time with these starting issues

 

[Guest]

UPDATE

left prime on for another 10 min or so to test my lack of fuel theory. Started on the first try, shot up to 4,000 rpm again. I pushed the choke in and rpms slowed a little to slightly under 4,000. Then returned to hovering just above 4k. idle mixture screws are now at 2.5 turns out

White smoke is also coming from exhaust headers... Any ideas?

 

[Big T]

The dumb question is = did you try to drop the revs with the idle screw?
The typical issue with high, hanging idle is air leaks

And, 10 minutes on Prime is too long. 30 seconds is about right. Check your petcock for fuel flow

 

[Guest]

yup, unscrewed the idle screw fully with no change to rpms.

I just replaced the o rings on the intake boots, only thing that changed since the last time it held a normal idle. cleaned and inspected intake boots at that point and didn't see any issues. can't imagine this would make things worse and create an air leak?

I literally just bought this petcock. Fuel flow is good when I tested it on both prime and on. it would be a bummer if there was an issue with it after spending 65 bucks for it new :/

 

[1948man]

http://members.dslextreme.com/users/bikecliff/images/carb_sync_notes.html

Did you "bench sync" the carbs after the cleaning and before you remounted them?

 

[cowboyup3371]

Why are you using prime to run the bike at all? You don't need it unless the bowls are dry because the bike has been sitting for weeks and even then like Big T said you only want it on for about 30 seconds AT MOST

 

[BigD_83]

White "smoke" is usually caused by excess fuel or water in the exhaust stream. Could also be too much fuel stabilizer and/or gas treatment in the tank. Is the smoke coming from around where the headers fit to the head, or at the joint between the headers and the muffler?


Such a high idle is a sign that the butterflies are open too much/massive air leak. This can be caused by:

a) master idle screw turned in too much
b) throttle cable too tight (easy enough to do when popping the carbs off and on repeatedly)
c) old intake boots not sealing well
d) related to c), stretched out clamps that don't apply even pressure around the carb ----> poor seal (normally, I'd think about the inlet tubes from the airbox, but in your case, this wouldn't apply)


I'm confused though. You said you still suspect a fuel delivery problem, but you have gas in front of the butterfly valve AND a high idle. That sounds like it is delivering gas. I'd be concerned about leaving it on PRIME for 10 minutes, that could flood the cylinders.

 

[Guest]

thanks for all the input, ill answer these in order

1948man yes, the carbs have been bench synced according to your link.

cowboyup3371 I replaced the valve needles when I took off the carbs, so I used prime to fill the bowls. I was worried that it took so long for the bike to start on prime. I discovered fuel dripping out of the fuel line when the petcock is on the on position, so clearly its no good. I'm going to look into returning it and getting an oem one.

Bigd

the white smoke is coming from where the headers fit to the head. given my newly discovered leaky petcock, fuel in the air filter+in front of the butterfly valves, I'm going to play it safe and do an oil/filter change before I start the bike again. Is there anything else to do to get gas out of the engine/oil?

- master idle screw is turned all the way out
- I made sure the throttle cable was extended out all the way and was not hanging up the throttle linkage.
- the intake boots were sealing fine and idle was good for a couple removals of the carbs UNTIL I changed the o-rings this past time,, wonder if I disturbed a seal on something and the boots are too old? or.. I only have 3 clamps for the intake boots and one of them is a little loose. I use a zip the on the 4th which hasn't been an issue in the past. seems like this is likely the culprit