Very High Idle

[fatbiker]

Slowly fixing an old 86 Max that was not well cared for. Wiring was bad, ignition box wasn't firing on the #3 cylinder, carbs were nasty, exhaust was missing parts and wide open, etc. I've since fixed the wiring and ignition plus had the carbs cleaned by a local shop and replaced the bad mufflers with good stock ones.

Now I have a very high idle around 4k to 5k that I can't get to come down. The idle adjustment screw is set to it's lowest level and if I turn it anymore it will fall out. I found out the old carb main jets had been drilled out by someone who didn't know what they were doing so I replaced them with brand new 152.5 jets.

I turned in all of the pilot screws clockwise till they would not turn anymore then backed them out 2 complete turns each.

The carb diaphragms are not in the best condition and I have a new set on order. A few small holes in one diaphragm and a small tear in another.

The air box is stock with new rubber boots and hoses. I have used a can of spray ether to see if there are any leaks around the boots or intake. No indication of a leak.

I have a brand new MotionPro SyncPro which I have calibrated and used to sync the carbs. The more I get them into sync the higher the bike revs.

I checked to make sure the throttle cables were not stuck or sticking. The throttle moves freely and easily. Doesn't stick anywhere.

There is a grey-ish colored smoke coming out the exhaust especially heavy from the right side. When installing the 'new' stock mufflers I noticed that the silencer gaskets were shot and mostly missing. I have ordered new ones. Exhaust smoke leaks quite a bit from where the header pipes connect with the mufflers.

I'm hoping that the new slides with diaphragms will help some and maybe my problem is the lack of backpressure due to the mufflers having serious leaks. Anyone have any other ideas or am I on the right track?

Thanks in advance!

Fatbiker

 

[naughtyG]

Have you had the carbs off and apart? If so, are you sure they are refitted together as a rack nice and straight? Also, did you check for a rough sync on the bench as a starting point?
Have you check your coasting enrichers are in good nick? If the diaphragms are shot there's a strong chance the enrichers diaphragms are too. And finally, did you check the choke operation - are all four choke levers fully pushed in?

 

[fatbiker]

Hmm..good points all around.

I did take the carbs off the rack in pairs but didn't think to see if they were straight after putting them back together. I just assumed they would go back together correctly when screwing them back together.

I will also check to see if the choke levers fully close as well.

Where are the enrichers diaphragms located?

Thanks for all the advice! Will update later today!

Fatbiker

 

[adambweird]

On the sides of the carbs under a small (around 1.5") round cover is where youll find em. Have to split the carbs all the way apart to get at them though.

 

[sdt354]

Dannymax is the place to send them. You'll get them back right. Money well spent.

 

[fatbiker]

Took the carbs off and the rack was not on straight. Re-adjusted it and it fit better on the bike. This time it idled even higher at 5K instead of 4K.

Right now the mufflers are off the bike as I'm awaiting silencer gasket to come in. Wondering if the lack of back pressure is causing the high idle.

Also, the original CDI unit was not firing the #3 cylinder so I replaced it with another used CDI unit. I wonder if this unit could be faulty as well?

I plan to install the new muffler gaskets and slide diaphragms before doing anything else. I hope one or both of these will solve my high idle problem. Will update.

Thanks for all the help so far!

Fatbiker

 

[alorio1]

I think you should have done a bench sych while you had the carbs off. You could have checked the butter flys to make sure they were all completely closing off. Also make sure all butter flys screws are tight and the possibly one of the butter fly screws could be missing........

 

[m-cman]

Have you checked your idle adjustment screw?

 

[[email protected]]

lack of back pressure has nothing to do with it. A well adjusted bike will fire right up without an.y muffler and idle just fine.

Holes in the diaphragms aren't going to cause it. Slides shouldn't be moving at idle.

Look down into each carbs and look at the throttle plates. They should be nearly closed. Also, check the slides. They should be in all the way with the needle in the main jet. I'm guessing something is hanging open.

 

[fatbiker]

Installed the mufflers and you are right, nothing changed. As you suggested I checked the throttle plates and the are fully closed. Butterfly screws are all there. Slides barely move and if I push them in manually a couple of them stick open. I took the two sticking slides out and noticed they felt a little gritty. I had to lube one of them just to get it back into the hole. After doing this it now idles even higher at 6.5K . Still waiting for the new slides with diaphragms to arrive then will give another update. Thanks for all the help so far! Still open to advice.

Fatbiker

 

[[email protected]]

Not sure what would cause high idle if the throttle plates are closed. Bad synch would cause typically if it really bad it would be visible because the butterflies won't all be closed.

If the slides are sticking open, it could be a problem at idle but sounds like they are closed.

If the choke is open this would definitely cause a high idle. I see it was mentioned but I didn't notice a response from you. Maybe try spraying some lube on the plungers and work them a bit to make sure they are operating correctly.

 

[06VMAXIMUS]

I would check to make sure the needles are installed in the slides correctly.....especially that the infamous plastic *** is seated.

 

[tugla]

and little orings are im place before slide covers go back on.

 

[naughtyG]

Just saw you replaced the TCI unit - just checking your replacement came from a same year bike?

I would try swapping it back just to see what happens.

How are all your choke levers working?

 

[fatbiker]

Needles are seated just fine and have not been tampered with. Had a friend who knows something about them take a look.

All 4 chokes are closing fully.

Butterfly valves are closing fully.

The little O-rings near the slide diaphragms are still there.

I did change the TCI unit and while I cannot say for sure it's the same year model the part numbers and lettering on top of the box match perfectly. The wiring harness that came with the box was a perfect plug and play. Will swap boxes and see what happens. I know the old box only fires 3 cylinders.

My thoughts are that there is a huge air leak somewhere. The bike now idles around 6K and slowly tries to climb. I've sprayed ether every place I can think of but with the high idle I don't think the ether would cause the RPM to rise. At least not noticeably.

 

[DMAN999]

Disregard this post, I just re-read all of your first post.

 

[fatbiker]

Tried changing the TCI unit to the old one. Idle ran straight up to 4K but would have been faster if the #3 cylinder were firing. Not an electrical problem, not bad boots, must be something in the carbs themselves as many here have said. Carbs were cleaned and new gaskets installed recently but after talking to the mechanic that did the work he didn't delve to deep into them. Basic jet cleaning, major gaskets, and not much else. Going to take the entire bike to a known good mechanic and let them tear thru the carbs.

Fatbiker

 

[davesax36]

Shotgun and peashooter?

 

[jfeagins]

...and you are ABSOLUTELY sure the carbs are all four properly & firmly planted all the way down into all four rubber intake boots & their clamps tightened properly? If so, my bet is on something wrong in one or more of your choke assy's. Seems to me that'd be the only ways to get that much air past the butterflies.

 

[fatbiker]

Yes, all 4 carbs are as far down in the rubber boots as possible. I used a rubber hammer to gently tap the down then tightened up the clamps all the way. I did have to loosen the connecting brackets and re-align the assembly to make sure they were level. First time around they were not.

As for the choke assembly, it SEEMS to work just fine. Right now it's warm here in Houston so if I turn the choke on it bogs down the motor. Off, it revs up to 6K and beyond.