Fast idle

[86Royale]

Okay, I've done some research on this. I've been looking for a vacuum leak, tomorrow I'm going to pull the air box and look at the butterflies, the choke seems to be closing all the way with the lever positioned off. What I'm running into is that recently the idle has started increasing on its own as the engine warms up. It starts out at about 900-1000, and by the time it's warmed up in about 10 minutes, it's run up to about 2000 rpm. If I goose it quickly, there's no hesitation, and it'll come back down to about 1300 rpm, then ease its way back up to 2000. I don't have any tools to adjust the carb sync, but is there anything else I may be able check on my own? Thanks

[86Royale]

Okay, tried looking for the vacuum leak today, no luck, but now it's giving me a little bit of a backfire on startup, any additional thoughts.

[Marcarl]

I got more or less the same problem. A carb sync would be in order first in order to make sure the carbs are at least close. If you don't have a carb sync, what I would do is to pull the air box, then visually turn the idle screw until #2 is just fully closed, then do # 1 with the sync screw, then # 4 then# 3. Now turn the idle screw back in some and then fire it up. That's about as close as you will get it without a measuring tool. I know the numbers don't seem to go the right way, but it should work, I'm thinking. Others may call me wrong, but it's what I would try.

[hipshot]

i replied to this post earlier, and it didn't make the trip!

so , here goes again.

some of us , have been chasing this ghost for months!

i haven't got a clue what the answer is YET!

i will be following this thread, for more updates!

just jt

[muffinman]

This is a problem that I chased for months on the blonde.I finally fixed it when I replaced the carb boots.Not because they were cracked but because they were cracking.I have since installed them on another of my bikes and they are not causing any problems.So I think that the root of the problem is in the area where the carbs set into the boots not the boots themselves.At one point I had a vacuum leak with these boots and what had happened was the carbs came out of the boots on #s 3&4 and after I reset them no more problems.That was the day I ordered the new boots.

I hope this helps some of you.

As for the way Marcarl told to sinc the carbs without a carb tune I would do this instead you will get closer start with # 3 with the motor running and adjust the idle screw untill the scoot sounds best then do #4 then do #2 It can be done by ear if you go it slow and really listen to the motor but I would suggest that you be in a quiet area and alone so you are not distracted.

Jeff

[hipshot]

This is a problem that I chased for months on the blonde.I finally fixed it when I replaced the carb boots.Not because they were cracked but because they were cracking.I have since installed them on another of my bikes and they are not causing any problems.So I think that the root of the problem is in the area where the carbs set into the boots not the boots themselves.At one point I had a vacuum leak with these boots and what had happened was the carbs came out of the boots on #s 3&4 and after I reset them no more problems.That was the day I ordered the new boots.

 

 

I hope this helps some of you.

 

As for the way Marcarl told to sinc the carbs without a carb tune I would do this instead you will get closer start with # 3 with the motor running and adjust the idle screw untill the scoot sounds best then do #4 then do #2 It can be done by ear if you go it slow and really listen to the motor but I would suggest that you be in a quiet area and alone so you are not distracted.

 

 

Jeff

thanks , jeff. i'm going to do the "boot swap", tomorrow, and see if that makes a difference.

just jt

[86Royale]

Thanks guys, that's giving me something to work with. I'm so new to these things that most of it's PFM! Oh, and does anyone have Chapter 9 of the manual on their computer, the troubleshooting guide? The one I downloaded here doesn't include it. Thanks.

[greg_in_london]

I would investigate the fuel level if you have a problem with tickover rising like that. Obviously balance the carbs first, but if the screws aren't seized, it is not difficult to check if you use a bit of battery overflow/breather clear pipe. (The proper tool or glass tube would be easier to use, but only if it's available.)

 

Having said that, I've had funny results adjusting my fuel level (see the petrol/gas mileage thread) - I'd now check the level two or three times on different days to make sure I'm getting a true reading. If the fuel level is too high, then that my be your problem.

 

If you're taking the carbs off anyway, though, it's certainly worth checking.

 

NB - check the fuel level on the bike to decide whether or not to adjust, and clean out the pilot air jets while you're at it.

[86Royale]

I haven't read the thread, but if the level was set incorrectly, wouldn't that be detrimental to the mileage. I've been pulling down a consistent 39-40mpg riding 2 up. Oh, and another dumb question, which carbs are which. Where does the numbering start so I can check the sync?

Thx

[hipshot]

left front #2

left rear#1

right front #3

right rear #4

seems to be what i remember.

just jt

[Neil86]

question, which carbs are which. Where does the numbering start so I can check the sync?

Thx

 

On a Venture, as you sit on the bike.....left rear #1, left front #2, right rear #3, right front #4.

..^..

2....4

 

1....3

[86Royale]

Okay, I've been playing some more today, and now that I"ve finally got the airbox off (how I'm gonna get the hoses hooked up again, I'm not sure) I was poking around pulling vacuum lines with no change in the high idle, I did find that when I disconnected the vacuum line from the #2 intake (front left), the idle went back to about 1000. However, when i tried to accelerate, it would, but after a few seconds at around 3000 it would bog down and try to decelerate. Any thoughts? Maybe bad baro sensor?

[hipshot]

vacuum line to #2, is your PRIMARY source of vacuum. all other cylinders feed off of #2.

primary vac. comes from TCI. unit, i think. some one with more "savvy", will be here in a moment.

just jt

[Neil86]

The hose from #2 intake hooks to the pressure sensor....which senses the vacuum in the intake and sends a voltage signal to the TCI to alter the timing advance based on the engine load (vacuum). When you unhooked the hose...you capped the port? Vacuum leaks at the pressure sensor or its hose do happen.

[86Royale]

With the #2 vacuum disconnected, and my finger over the hose, which is pretty dry, and the end has small cracks in it, there was no change, lower idle, and doggy acceleration. WIth the hose hooked back up, immediate rpm increase of at least 500 and normal acceleration. All carbs seem to be in sync.

[greg_in_london]

I haven't read the thread, but if the level was set incorrectly, wouldn't that be detrimental to the mileage. I've been pulling down a consistent 39-40mpg riding 2 up.

 

I reckon it would affect your petrol mileage, but an overhigh fuel level can lead to a tickover rising in traffic/when warm. You can check the fuel level without taking the carbs out. You connect a clear tube to the drain hoses and open the drain screw a couple of turns. There's a mark halfway up the side of the carb housing. With the engine running, the level in the tube should rise to 14mm below this mark. You can check all four in ten minutes if the screws undo okay.

 

I wish I was getting 40mpg - US or UK. Some people are getting better, though....

[86Royale]

Okay, after spending the day playing with it, I ended up replacing the vacuum hose from #2 to the baro sensor and setting the idle down just a little bit. It now seems to keep the idle pretty close to 1000 rpm. Not too sure about that baro sensor, but I'll ride it for a while and see. However, I did notice some hesitation a couple times when getting on it from low rpms in 1st...when I set the idle down, I used the screw by the throttle cable over by #2, I'm assuming that was the right one?

[Marcarl]

I used the screw by the throttle cable over by #2, I'm assuming that was the right one?

Wrong one old boy, that's the one for syncing #1 carb to # 2. The idle adjust is in between #1 and #2 carbs but just below and hard to see. You have to look from the bottom up and it doesn't have a screw driver fitting, it's a thumb screw adjuster. I tried to post a picture but that wouldn't work.

 

 

[Neil86]

The throttle stop screw that sets idle has a larger knurled head that faces down...you can adjust with your fingers. The synch screw for setting #1 carb to #2 is a smaller flat blade screw head that faces straight out at idle, and throttle closed.

[86Royale]

Well, good thing I kept track of how much I turned it...I'm gonna go change that right now. Thanks, I'll learn one of these days.

[Marcarl]

Well, good thing I kept track of how much I turned it...I'm gonna go change that right now. Thanks, I'll learn one of these days.

No problem here, some of us are more interested in this sort of thing and tend to remember better how it all goes, or maybe it's just the age thingie, I'm not sure which. Hope you can remember the right amount of turns.

[86Royale]

Got the bike out yesterday for about a 70 mile ride and the problem seems to be gone. I set the sync back the number of turns I took out, reduced the idle correctly, and with the new vacuum hose to the baro sensor, it is running like a top and the idle is staying where it should. Thanks to all who helped keep me on the right track and turning the right knobs.

[spitfire9]

My 85 has been idling at 900 cold, 1400 hot so I searched and found this thread. Will check the same hose, boots etc. It does seem to run like a top, and after filling up today, I computed the mileage and came up with 46.2mpg on 93 octane. Is that possible? Thats better than my vulcan 900 gets. Anyway, seems there is a thread here for almost any q i come up with! Thanks, vr.org. :-)