High Idle

[Dizzle223]

I just got my bike back together after having the carbs gone though. When I took the bike to have the carbs sync'd the mechanic asked me why there were vacuum hoses connecting the manifolds on each side rather that having three of them capped. (See pics below)

 

I started combing the VR site and found that three of the ports SHOULD be capped. (I learn something new everyday )

 

Prior to having the carbs sync'd the bike would idle at 2500 rpm when warm and slowly fall to 1000 rpm after about 30 seconds to a minute. After the sync it does the same thing... idles about 2500 rpm then slowly falls to about 1000 rpm. Also, I did replace the diaphragms when the carbs were off.

 

Why would the PO connect the manifolds with vacuum hoses and would this effect the idle issue?

 

Thanks!

 

Brian

[van avery]

I believe this was called the "Jason mod". Here is a link to it.

http://www.venturerider.org/forum/showthread.php?t=501

[Marcarl]

Jason mod was done with the YICS hoses,,,, what happened here I have no idea, and why somebody would do such a thing would make no sense to me either. I would just undo those hoses and put caps in place, you might find that will help out with your issue big time. Keep in mind that there is a vacuum hose coming from the left front cylinder going to the TCI. It will be needed as well as a restrictor in that line.

[Condor]

For whatever reason it looks like the PO had all the vacuum bibs tied together and then to the booster. Maybe???

[Dizzle223]

Well I read the post regarding the Jason Mod and it indeed looks like that is what the PO did. I would be more inclined to think that was the issue if the bike had idled that way prior to going through the carbs but before it was just fine...

 

I have continued to read several threads regarding the high/fast idle and vacuum leaks seem to be the primary culprit. Can someone advise how many vacuum lines I should be looking for... so far I only see a couple. Also, I sprayed the manifolds with WD40 while the bike was running and no change.

 

And... thanks for the info!

 

Brian

[Trader]

I was told it could also be that the throttle cables need lube.

 

Mine would hang up....but if I gave it a quick rev it would settle down.

 

Just a thought.

[Marcarl]

Check all 4 carbs to make sure they are seated properly.

There is only 1 vacuum line that has any business being there. That's the one on the front left carb, and has a restrictor in it.

Just undo the Jason mod, you don't really need that YICS anyways, just pull the lines and plug the ports, you can always put things back later if you wish.

Did the sync go well or was it left with,,,, that's the best I can do!

[Dizzle223]

Check all 4 carbs to make sure they are seated properly.

There is only 1 vacuum line that has any business being there. That's the one on the front left carb, and has a restrictor in it.

Just undo the Jason mod, you don't really need that YICS anyways, just pull the lines and plug the ports, you can always put things back later if you wish.

Did the sync go well or was it left with,,,, that's the best I can do!

 

Carl, First of all silly question time... What is YICS? Guess I should know but :/

 

Carbs are seated securely and I pulled the Jason Mod plugging the ports as you suggested (Leaving #2 with the restrictor to the thingy up high) Still seems a little slow to come down from idle but it is better.

 

Funny you should mention how the sync went.... I couldn't have described the mech's look any better "that's the best I can do" was written all over his face! I've never sync'd carbs myself but I had just about memorized Skydoc's tech write up on how to do it so I knew they should have been a little more synchronized.

 

I really don't think the cables are hanging up but I will double check just to make sure...thanks for the advice Trader.

 

I'm going to check it again in the morning when the bike is cold. It seems to get worse as the temp goes up??? Perhaps after removing the Jason Mod they should be sync'd again.

 

Thanks for the help... I'll keep you posted

 

Brian

[Marcarl]

YICS= Yamaha Injection Control System.

Seems like there is a sync problem. My guess is that's it's a way out on one carb. Time to set them all back to fully closed and start again.

I won't argue with the cable hang-up idea. Best way to check that is to run the carbs manually, so remove the left side cover and using a flat screw driver move the half moon control that the cable hooks up to. You can increase the RPMs and when you let go of it the engine should return to idle. You can watch the mechanics by doing this and so make a determination.

 

Carl, First of all silly question time... What is YICS? Guess I should know but :/

 

Carbs are seated securely and I pulled the Jason Mod plugging the ports as you suggested (Leaving #2 with the restrictor to the thingy up high) Still seems a little slow to come down from idle but it is better.

 

Funny you should mention how the sync went.... I couldn't have described the mech's look any better "that's the best I can do" was written all over his face! I've never sync'd carbs myself but I had just about memorized Skydoc's tech write up on how to do it so I knew they should have been a little more synchronized.

 

I really don't think the cables are hanging up but I will double check just to make sure...thanks for the advice Trader.

 

I'm going to check it again in the morning when the bike is cold. It seems to get worse as the temp goes up??? Perhaps after removing the Jason Mod they should be sync'd again.

 

Thanks for the help... I'll keep you posted

 

Brian

[van avery]

If you get it started without the air filter on, look down the carbs and are the slides all moving correctly? If one is hung up it may have one cylinder keeping your idle up.

Yes you should re sync the carbs after removing the jason mod. You should be getting around 8-9 inches of vacuum when resyncing the carbs at 1000 RPM.

Not to ask a dumb question you have adjusted the idle screw ( under the left side) a knob you have to reach up from the bottom.

When you worked over the carbs did you check the float levels?

You can check the float levels on the bike by connecting a clear hose to the drain lines and then check that the level is .55 +/- .02 inches below the centerline of the carbs. There is a line on the side of the carb body that you measure down from. See page 4-8 in the service manual.

What was the condition of the rubber plugs in the carb jet block? I have heard if they are bad you will have idle problems.

Good luck

[Dizzle223]

I checked the cables by moving the linkage manually as suggested. Everything looked good and it did return to idle. One thing I did notice was if I gave a quick burst of throttle it would return to idle fairly quickly but if I held the rpm's at about 2500 for about 10 seconds and let off it would just stay there. It looked like the linkage was all going "home" though???

 

I did try and use the idle adjustment knob to correct the issue (not a dumb question I've been known to want to replace pistons cuz my tires were low )

 

I actually had a mechanic go through the carbs when I had them off the bike so unfortunately I can't be too sure about the float levels or the rubber plugs in the carb jet block. I'll have to read the manual to see if can tell the levels.

 

When I took the air box off the bike would idle but I wasn't able to give it any throttle without it bogging down and wanting to die so I couldn't see if the sliders were moving properly. I did check them manually and they seemed to move just fine though.

 

And as suggested, I will first have the carbs re-sync'd. Hopefully that will help narrow down the issue... Or fix it!

 

Thanks to all for chiming in. I really appreciate your help.

 

Brian

[Huggy]

When you pushed the slides up did they go Clunk when they closed? If not then you need to remove them and clean them up. I used carb cleaner and a scotch brite pad to do mine. I also cleaned up the carb where the slides sit. This can be done with the carbs on the bike.

 

[van avery]

Just another thought. Are the "choke levers" going completely in so the pistons are not held open letting alittle gas in. These dump a little raw gas in the system to get things started.

[Dizzle223]

Just another thought. Are the "choke levers" going completely in so the pistons are not held open letting alittle gas in. These dump a little raw gas in the system to get things started.

 

Good question.... I did pull all of the fuel enrichment valves off and clean them while the carbs were off the bike. I checked last night to make sure they all were completely in when the choke was off and they looked good.

 

B.

[Dizzle223]

When you pushed the slides up did they go Clunk when they closed? If not then you need to remove them and clean them up. I used carb cleaner and a scotch brite pad to do mine. I also cleaned up the carb where the slides sit. This can be done with the carbs on the bike.

 

 

They did Clunk when I let them go... I will be gone next week but when I get back I'll have the carbs sync'd again and let you know how it goes.

 

Brian

[Venturous Randy]

Carl, First of all silly question time... What is YICS? Guess I should know but :/

 

 

 

Brian

 

The bike in your profile is an 86. The YICS was discontinued after 85.

RandyA

[Patch]

if it were I experiencing this problem, I would remove the carbs using small drill bits I would measure the gap between throttle plate and housing 1st what is the gap and are they=, next I would remove each slide clean them with wd and a lint free cloth, I would roll each needle one by one insuring each is straight with no ware they should be shiny each should be reassembled the same, if not then let the group know, last I would change the gaskets for each manifold I would suspect them as a likely cause.

put all the caps back on the vacuum ports.

By checking the position of the throttle plate with the drill bits you will be starting the bike with synced carbs, it's rough and only the 1st setting of the plates but thats a must, after that you sink to the pressure differential by syncing them at rpm. That's how I do it and I do it often, I also use a vacuummate unit "I love that that thing"

 

you ruled out the enricher!

S/G