Bike stalls at stoplights

[comatt]

Thanks for everyone with the help on the throttle cable.  It was routed wrong and I didn't have enough slack in cable.  Beginners mistake and stupid. 

Well since that is not a problem anymore and new one has seemed to take its place. 

Once the bike warms up at idle (~1500rpm) and the temp gauge needle gets to about 3/4 of the way across, the bike starts to stutter and will just die.   If I give it gas it will keep going for a short while.  I first noticed it while I was at a stop light on a test drive, the idle just kept going down until it almost died then I would keep the throttle open a bit.  Now if I just leave it running in the driveway it will do it.  Once it dies it will start right up with no problem.

I have POR'ed the tank, added a fuel filter, dipped and rebuilt the carbs (3x's) and fuel pump with kits from Sirus.  Gas tank is full.  I checked the stator and it seems to be charging the battery.  I just moved the RR to around the rear foot peg.  I sprayed the TCI w/ WD-40.  I cleaned all of the electrical connections with cleaner and an emory board.  Sealed the carb boots w/ liquid electrical tape.  Synced the carbs as best as I could.  Changed the oil, I have not done the rad yet.

I haven't soldered the stator wires b/c looking at the conector and the wires they look brand new.  I think a previous owner replaced it, but I'm not sure.

So does anyone have any ideas on the cause?  I tried looking in the archives, but could not kind any info. 

Thanks, Matt

[Lucky]

sounds like fuel starvation..

there is a vent in the fuel cap that can clog producing similar symptoms.  when fuel is used from the tank, air has to replace it (thru the vent). if the vent is pluged, at some point there will be enough vacuume in the tank to prevent fuel from flowing.

next time it happens, try removing the cap (a spare key helps here) see if it stays running.  if so, take the cap apart (it unscrews) and clean it out.

[comatt]

Thanks I will try that tomorow, it's supposed to be 70 and sunny.  I love CO!
Did I also read sometime ago that most yamaha tank caps ar the same.  When I POR'ed the tank I took the gas cap apart and cleaned it.  I also replaced the cork gasket with one that I made out of gasket material, maybe that is the problem?
Thanks, Matt

[comatt]

Thanks Lucky for the info, but unfortunately it did not work.  I tried it this morning, let it warm up and then it died.  As it was dying I opened the cap and nothing changed the idle just kept going down until it died.  I then restarted it and with the cap lose and it died after a couple of minutes left at idle. 

[vision_chris]

I don't really know anything mechanically, but it kind of sounds like what mine does if I have the fuel in the 'on' position.  It runs a little while ok, then sputters and dies.  I have to keep it in 'prime' all the time to keep the bike running.

I'm getting ready to attempt to take the tank off, clean it out, disassemble the petcock, see if its just clogged up or if i need to get an '82 rebuild kit and send it to Lucky to make it work for my '83.

[ps2/bikevision]

sounds to me like it is the fuel pump. dont know if it is actually a fuel pump. its the hose that comes out the other side of petcock. make sure it is in good shape. mine did that to me all it would run on was the prime position. i started looking at it and found the last time i pulled the tank off i forgot to unhook that hose and riped it at the carb. after replacing it she ran fine again.

[h2olawyer]

The second hose from the petcock is the vacuum hose that opens the petcock.  Without vacuum, fuel won't flow through the petcock.  This is so we don't have to remember all of FINE-C (from the MSF basic course). Fuel, Ignition, NEutral, Clutch - the recommended starting  procedure.  Many bikes made after about 1980 don't have an "OFF" position on the petcock.  That hose should connect to one of the vacuum ports on the front intake manifold.

H2O

[comatt]

Well I guess the next step is to check to see if it will run in the Prime position.  Then maybe I can track down the problem.  My fuel and petcock vacuum lines are really long, may that be the cause?

[h2olawyer]

If it runs OK in prime, I'd suspect a petcock / vacuum line problem.  Low fuel has been found to create similar problems.  How full is your tank?  One other thing to check is the enrichment plungers (choke) on the carbs.  If they are staying open even with the choke lever in the off position, you could have the same symptoms.

The fuel and vacuum lines from the petcock should be just long enough to reach their destinations and still have a little slack in them.  If the vacuum line is getting kinked someplace or collapsing under vacuum, it could be causing the problem as well.

Keep at it & you'll get it figured out.

H2O

[YellowJacket!]

Hmmm, this makes me think of a similar problem that I have.  Although mine is not a regular problem, it does occur from time to time.  Also, I have an 83 tank and petcock on my bike.  I put a deadender on the vacume port on the petcock to cover it up since there is no connection for it on the 82 carbs.  Could this be the problem and is there a way to fix it or is my setup ok?

Thanks,

David

[Lucky]

Dave you can't have capped off the vacuume line. (small line) the petcock would only work on 'prime' if you did...  you capped off the 'return' line(& tha's fine with 82 carbs)

[comatt]

Is there any problem with leaving the bike in the prime position if I have another inline shutoff valve?

[Lucky]

not as long as you remember to shut it off & NEVER plug the overflow drain.  (Because if you do plug it & forget to close the inline shut off, you'll end up with a crankcase full of fuel)

can you say 'nice clean bearings'?

[YellowJacket!]

Dave you can't have capped off the vacuume line. (small line) the petcock would only work on 'prime' if you did...? you capped off the 'return' line(& tha's fine with 82 carbs)

Yup, You are correct.  My mistake

David

[Lucky]

I think we are all missing the obvious solution for Comatt's problem:

Don't stop at the lights!!!   ;D

[h2olawyer]

I think we are all missing the obvious solution for Comatt's problem:

Don't stop at the lights!!!? ?;D

Best advice yet!!

H2O

[comatt]

Not stopping would be an option, but I don't trust people talking on thier cell phones to stop for me.

I tried to run it only in prime, but it still dies.  I cut down my fuel and vacuum lines and put my cone filter in between the carbs so the hose wouldn't kink, still dies.  This is really starting to tick me off. 

If I bumb up the idle to about 2500 it will run and not die, but I don't want to keep it at that high idle. 

My tank is about 2/3 full so I know I have gas and when I was cuting down the fuel line I let it in prime the fuel poored all over my engine case, not good. 

I don't know were else to go.  Could my mixtures screws be too lean?  I have both at about 4.5 turns with updated 82 carbs.  Is there a way to check if the fuel is working?  I just rebuilt it a month ago.

I don't know, the rebuild was going so well until now.

[h2olawyer]

It could still be mixture or synch - or both.? Set your mixture by letting it idle and turning the mix screw one way until it idles rough, then turn it back until it idles rough again.? Then turn it to half way between these positions - then turn it right (lean) about 1/8 turn.? Do it to each carb individually.? I know mine are not even close to the same setting front to rear.? As I remember, the front carb is closer to 2.5 - 2.75 turns out from lightly seated & the rear is close to 5 turns out.? Each bike will have its own settings where it will run best.

Then check the synch.? You can build a manometer easily & cheaply - see Lucky's site - www.xz550.com/art_files/4dollarmano.jpeg.? It's what I use and is very accurate.? Clamp the YICS hoses closed with vice grips to make the synch easier.? You may have to set the idle screw higher with the YICS deactivated to keep the idle at 1300 - 1500 RPM.

If the weather is nice next week, I may be able to take a ride south to give you a hand if you're still having troubles.  Hopefully you can get this bug ironed out by then.

H2O

[YellowJacket!]

have you checked your carb jets?  is carb dirty?

David

[comatt]

Thanks for the offer H20, I may have to take you up on it. 

I still want to mess around with the mixture and I'll have to recheck the sync in the next couple of days.  I built a manometer which works great.

I think I have the correct jets.  I remember seeing a post months ago from I think H20, who is also in CO, and they stated what jets they were using at high elevation.  I think they are the same that are included with the rebuild kit. 

I have dipped the carbs 3x's in the last couple of months and I really haven't riden it so I think they are alright.  I also added a filter and POR'ed the tank so they should not be clogged.  The last time I did it  I sprayed out each opening with carb cleaner just ot make sure. 

I also checked the spark plugs before I started messing with the mixture and they looked good with the nice light brown color and no residue. 

So were would be a good place to start to check the mixture on upgraded 82 carbs?  Should I start at about 4.5 turns for both or 2.5 front and 4.5 rear? 

Then set the idle to about 1500 w/ YICS and then turn them until the engine studers?  Then back the other way until it studers again, then go halfway?  About how many turns between each studder?  or is each bike different?  Some 1 turn other 3 turns? 

It is nice that I can get all of this help from some good people who all seem to know what I'm going through.  Thanks Guys.