Idling issue's after carb sync

[mack]

I had a

similar issue with my LH, it tuned and sync'd just fine, ran really well until the motor got hot during a ride. Then at lights and stop signs, the idle would drop to 400 and stall. It would start right up again but same thing the rpm would drop and it would stall again. I had a bitch of a time finding the issue. Turns out the new intake boots were the problem. Can't remember right now who I bought them from but it might have been parts n more. What the problem was , once the motor got hot and the heat blown back on the boots, the brass metering nipples became loose. You could pull them right out of the boot with just your fingers. Friggin tiawan crap again. Replaced the boots with OEM and haven't had an issue since.
I find that the 80/81 carbs work best at 3 turns out. I used a colour tune for a bit but now I just watch the plugs. They give you a better indication of whats happening through the idle , middle and holy s..t range of the tach.

[Bonz]

Air bubbles in the fuel lines would seem to be inconsistent fuel coming from the tank like maybe there's a pinched line or something of that nature? Is the vacuum going to the pet cocks on nice n tight and not leaking?

I know this stuff seems elementary but may as well ask the questions.

Have you had any luck getting it fixed?

[ccogswel]

For the carb boots I bought. I got them from that motorcycle carbs website. And the brass pieces on those are tight. But I'll double check to make sure. As for the petcocks they are not vacuum operated. I didn't notice the air bubbles in the lines until after I shut the bike off and went into the house and came back out after like ten minutes. Before I shut the bike off I do remember looking at the fuel lines and I didn't see any air bubbles and at that time the bike was idling come to think of it before I shut it off. And when I went back out and started the bike up it didn't want to idle. I just couldn't see it being air bubbles in the lines but this is my plan. I want to narrow the problem down so it may help another member on here if they have a similar issue as I.

1st I noticed on my carbtune the vacuum lines that came with it gets really mushy after they get really warm next to the head. So i bought some new vacuum lines from Napa yesterday to replace the original ones just in case they were getting warm enough to close up and cause a misreading. So I'm gonna check my sync again with the new lines with the air bubbles in the fuel lines.

2nd if trying number 1 shows nothing and my sync is on the money then I'm gonna figure out why it's getting air bubbles in the lines and fix that. Then I'll check the sync again and do any adjusting if needed.

Right now I'm just waiting for it to warm up to go out to mess with it.

[GLoweVA]

Just to throw something else that may be related,
Once while trying to sync my bike, I had a hard time getting one of them to get dialed in, turned out the 2 mounting bolts for the carb boot were loose and it was sucking air in thru the joint there.
JAT.

[Bonz]

Sounds like a good plan please keep us posted!

[ccogswel]

Ok this is what I came up with. The vacuum lines for the carbtune or the air bubbles wasn't the issue. What it was and I'm guessing here so bare with me. The idle screw was turned in so far that I believe it kept the throttle plates open enough to allow the pilot circuit to suck extra fuel loading it up as I turn the idle screw all the way out and started over. And low and be hold it idled. Re checked the sync which was off. Got it set back and now it will idle at about 600 rpms. Now the problem is I can't get it to idle any higher then that. But it will idle at 600 rpms. It sat there this after noon and idled for 30 minutes. The only other issue I have is it won't idle until it gets good and warm. Anyone else have this issue? Thanks for all the advice. I'm gonna keep working on it to see what I can get out of it.

[mack]

This might

be a stupid response but have you adjusted the mast idle screw at the bottom center of the carb bank?

[ccogswel]

Any question isn't a stupid one to ask. But to answer that question yes I did. It cause's it to idle higher then I like. And when you hold the throttle open above 4000 grand and let it go it kind of hangs for a bit. But when it's idling at the 600 it is now you can rev it up and hold it and let it go and it falls back like it should.

What I'm thinking I may have to do is hook up the carbtune again and adjust the idle screw while I keep a check on the sync and fool with the idle mixture screws again. Right now there somewhere between 21/2 to 3 turns out. I took it out for a quick ride yesterday and it seemed to run fine. The only thing I seen with it was if you came to a real quick stop it would try to die down on the idle. I'd like to get it to 1100 rpm. Something to mess with a bit more.

The only other issues with the bike is a few oil leaks. The main oil leak coming from the timing chain tensioner, the other is one of the cam caps on the left front of the valve cover and I think there is one coming from behind the shifter cover as it drops onto the exhaust every now and then. Which might be from when I had the tranny apart fixing the 2nd and 3rd gear issues it had. Then the only thing I need to do is repaint the tank and side covers. Just wished I knew the color code for the yamaha black with the red speckles.

[yamtom]

color code

I had a similar question that I presented to a paint man at the auto store, he said, that if you can bring him a sample of the paint, he can match it, unquote. He also said he can put it in a spray can if needed. Minimum cost was about ten bux for the spray as I recall. It seemed kind of low for all the work that must go into it, but thats what I recall.

[ccogswel]

Yeah thats what I thought too. But I went down to my local paint shop who says they can color match any paint using this special machine. Which is the only one in town here. But anyways I took the gas tank in and they guy said he couldn't do it. Said he couldn't do it cause it was a motorcycle color and not a auto color so the machine wouldn't work. Some BS like that. I figured my next trip to Nashville I'd check with one of the larger paint shops down there. The only other thing I can do is find a really nice shade of black and then look for some red speckle flakes to mix with it.