New boots! Still won't idle.

[UncleMike]

At the suggestion of many, I bought new carb to engine and carb to airbox boots for my 750. Installed them yesterday after cleaning out the jets in the carb again and the bugger still won't idle!

As before, I can keep it going by blipping the throttle, but it won't idle by itself.

Before I replaced the boots, it would idle after being VERY warmed up, but it would idle high and would creep a bit, suggesting an intake leak.

Keith(KGB) thought that perhaps I could have a clogged screen on my petcock, so I'm checking that now.

Anything else I should check before I go nuts? I'm thinking to re-synch the carbs first, but that's not easy when she won't idle!

Thanks,
~Mike

 

[UncleMike]

Screen on petcock is fine. Should I take it apart and clean it?

 

[UncleMike]

Carbs are re-synched. That #1 carb was WAY off. Mercury was three times the height of the other three. Guess it came loose since synching earlier this year.

Now, let's see how she starts after cooling down.

 

[DimitriT]

I used a little blue loctite on the carb sync screws to keep them from moving.

Once its cleaned, synced and air tight from the motor to the airbox, you should try using the pilot mixture screws to richen the mixture. It sounds like your idle mixture is a bit lean. Once you richen it (by turning the screws counter-clockwise) it will idle at too high an RPM. Then you use the throttle stop knob to bring down the RPMs and you got yourself a nice solid idle.

There's a technique some people use on the BS carbs called the "highest RPM method" in setting the idle mixture. You basically warm up the bike, and then for each carb turn the idle screw out until the RPMs stop increasing. The RPMs will increase very slightly as you slowly turn that screw out. Do it very slowly and wait after each adjustment. You then repeat this for each cylinder. Once you are done, you use the thottle stop knob to bring the RPMs back down.

I think I got that right, but its been a while. Maybe someone who's done it recently can add something I left out.

 

[UncleMike]

I don't know, I'm just getting very frustrated. She's synched now, and I've played with the airscrews according the the highest rpm, method, but I just don't trust it very much.

The adjustments I'm making don't seem to be making a whole lotta difference. There is definitely a point where one is either too tight or too loose, and the bike tries to stall out. But there aren't dramatic increases or decreases in rpm when adjusting them otherwise.

If I rev the bike up to about 4000K for a little bit and then back off, she'll try to stall out. And she's was kicking a bit of white smoke when I would rev her up a bit. What the hell does that mean? Overheating? Rings toast? I had a box fan on her.

I just want to ride!

 

[mark]

I apologize in advance for suggesting this, but I did this once and it screwed me all up. When I did the synch my vacuum line to the petcock wasn't plugged. Possibility?

 

[UncleMike]

And in the time it took me to type the above message, this is what happened:

I went back down after typing the last message to mess with her again. She wouldn't idle anymore, with or without choke. I had to blip the throttle constantly to keep her running, with or without choke. White smoke was gone though, so I'll assume it was overheating. Must need more fans.

Once I got her going again, she was idling nicely, but I took her up to ~4000K again, and then released throttle. She'd stall out and refuse to idle. I barely got her going again with a weak idle and shut her down. Put the tank back on and hooked up all the lines, and started her up again. Idling nicely at 1100.

Please help me?

 

[UncleMike]

I apologize in advance for suggesting this, but I did this once and it screwed me all up. When I did the synch my vacuum line to the petcock wasn't plugged. Possibility?

Mark, never apologize for assuming I'm an idiot when it comes to motorcycles.

But I'm using my tank just propped up on a table higher than the bike, and using long fuel and vaccum lines, so both are still hooked up.

 

[Jethro]

I apologize in advance for suggesting this, but I did this once and it screwed me all up. When I did the synch my vacuum line to the petcock wasn't plugged. Possibility?

LOL, I have done that more than once . Even worse is wondering why the heck it hardley runs after a perfect synch- forgot to put the synch plugs back in the intake manifolds after removing the synch tool adapters.

I have never had a huge difference setting the micture screws at idle either. Never seemed to make much of a difference unless I bottomed them, then the bike would stall of course.

Man, I sat here for a couple of minutes desperately trying to think of a way to help- after all, I want you to come to Moosehead! But I don't have any ideas that you haven't been over already?

 

[UncleMike]

I'm trying my best to go through this logically.

Can't be the petcock, right? Because the float bowls are getting fuel.

I know I've got spark.

What if one cylinder was low on compression? Possible?

Bottom line is I don't have enough experience to really go through this very well.

Is it possible I just don't have the cables hooked up correctly? Clutch? Choke? Throttle?

How about we move the Moosehead ride to my place instead? We can ride around all the Finger Lakes in one day, and all you experts can take a look at my bike!!!!

Sounds good, right?

 

[Jethro]

The petcock is not likely if you are having idle problems, and not problems on the needle circut. Possible, but less likely.

Yes, poor compression on one cylinder could cause problems, but it should still idle ok, unless it has very, very poor compression in that one cyl.

Have you checked valve clearances or did someone in the past 7000 miles?

 

[Jethro]

How about we move the Moosehead ride to my place instead? We can ride around all the Finger Lakes in one day, and all you experts can take a look at my bike!!!!

Sounds good, right?

Sorry man! Can't mess with tradition! Get in the cage and head on out! You can rent a kayak and explore the lake while we are out riding!!

 

[UncleMike]

The petcock is not likely if you are having idle problems, and not problems on the needle circut. Possible, but less likely.

Yes, poor compression on one cylinder could cause problems, but it should still idle ok, unless it has very, very poor compression in that one cyl.

Have you checked valve clearances or did someone in the past 7000 miles?

I just went down and checked the petcock again and it pours nicely when vacuum is applied to the vacuum line.

I started her up again while I was down there. Not sure if this is normal or not, but she won't start without me gooseing the throttle. So that's what I did. Hit the starter and goose the throttle a bit and she idles nicely at 1100 for 10 or 15 seconds, then slowly starts to die.

If I apply choke at that point, or any throttle, it will save her, but she'll try and die again after a couple of seconds.

If I turn her off and wait thirty seconds, she'll start and idle nicely at 1100 again, but then go through the same process.

I have not checked valve clearances or compression. Don't know how on the valve clearances and don't have a compression gauge, but I can get ahold of one.

 

[UncleMike]

Sorry man! Can't mess with tradition! Get in the cage and head on out! You can rent a kayak and explore the lake while we are out riding!!

Sounds like SO much fun.*

 

[Jethro]

Sounds like SO much fun.*

Ah, I see the *...

 

[UncleMike]

Ah, I see the *...

It's handy, no?

Now quit f*ckin' around and give me the magic piece of advice that will fix my bike!*

 

[UncleMike]

I refuse to believe someone smarter than me hasn't read this yet.

 

[Guest]

Sounds like your bowls are running out of gas. Try richening your float height. Do you have a 5/16" fuel line that doesn't have a kink when you lower the tank the last few inches?

 

[UncleMike]

Sounds like your bowls are running out of gas. Try richening your float height. Do you have a 5/16" fuel line that doesn't have a kink when you lower the tank the last few inches?

No kink. Could the carbs really starve the bowls after filling them on prime for 30 seconds or more, just by idling for 10 seconds or so?

 

[Guest]

If your float adjustment is off, yes. But I'm just throwing out suggestions because as many times I've had my carbs on and off I feel I should be a pro. When your bike stalls pull your plugs and see if it's rich or lean.