High Idle when engine is warm ***SOLUTION FOUND ***

I'm driving a '82 XJ750 SECA for 15yrs and had it parked for a couple years, (after accident) rebuildt it and also cleaned, disassembled the carbs. Started it and found out that when engine gets warm the idle will be stuck at 3-4K revs, it only will go down when letting the clutch come on.

This is what I did till now (without a good result);
-chg the airfilter
-chg the carb holders all 4, were in bad condition.
-sinc the carbs
-checked the choke and throttle cable, run without having it attached.

This what I didn't do yet (found some tips on the forum, have to try)
-no 'clunk test'
-didn't set the mixture adjustments to 2 1/2 turn from bottom.

I really want to ride my bike again, so if there'a anyone who can help me I would be gratefull. ;-)

 

Re: High Idle when engine is warm

Mine did the same, as a good starting point do the baseline 2 and a half turn adjustment of those pilot screws.

I won't say it's throttle cable / linkage related because she goes down when you engage the clutch and remains there.

 

Re: High Idle when engine is warm

Thanks, I'll give it a try tonight.

 

Re: High Idle when engine is warm

Definitely do the clunk test. That is a likely candidate. Another thing to check is for vacuum leaks. Take some starter fluid and spray around the intake boots and at the carb throttle shafts to check for leaks there. If you get a higher idle from that at the carbs, then the throttle shaft seals will need to be replaced.

A couple of other things to check is to see if the cable or throttles are binding. When you hit the high idle, between carb 1 & 2 or 3 & 4, try to push the throttle closed with your finger. If the idle goes down, you could be binding up somewhere in the linkage.

 

Re: High Idle when engine is warm

Hi Joefriday77,

I have checked the throttle cable, even without the cable attached the Idle stays high. Also pushed on the throttle lever but it stays high.
I have changed the intake boots with new ones.

First thing I'm gonna check or adjust are the mixture screws and see what effect that will be.
The so called 'clunk test' will be done after the mixture adjustment, because that means I have to disassemble the carbs :?

let you know

 

Re: High Idle when engine is warm

first turn idle adjustment screw down, then could make mixture screw adjustments then need to synch carbs, if rev and idle stays high for awhile than slowly comes down one or two cylinders are stealing fuel due to vacuum higher in those , thats why must be synched.And must use yics tool or make one to isolate each carb,they are easy to make.

 

Re: High Idle when engine is warm

Lean mixtures burn better hot. That's likely why your idle goes up.

Look for air leaks, plugged pilot jets/passages, pilot mixture, float level.

 

Re: High Idle when engine is warm

Update;

I've done the 'clunck' check and found one piston a little bit sticking, could not find the reason. Onces removed and installeb back into the carb it slided perfect.
Than set the mixture adjustments to 2 1/2 turns from full CW, 2 adj were set at 3 turns, re-adjusted and did a testdrive.
The revs still rising but not as strong as before, even when the engine is at idle it rises towards 3000-4000 rpm. Only get it down when release the clutch a bit.

An other thing I noticed was that 2 of the four exhaustpipes where hotter than the other 2 (see pics)



What els can I do?????

 

Re: High Idle when engine is warm

Nice!
Be patient, you're walking on the right way. 2 and 1/2 turns is just a baseline to start with. Do the synchronization again and check the plugs. Try to make them look tan. When they look tan and the synchronization is good you should have a proper idle.

If your exhaust developed that nice color recently, that should mean that your settings are way too rich so you need to make her lean. But check the plugs first.

Don't worry, just keep tuning. It needs a bit time to set everything correctly even when you're doing the right thing.

By the way, do you have any mods? (pods, open headers, god knows what else)

 

Re: High Idle when engine is warm

He,

What do you mean with 'check the plugs. try to make the look tan'?????

There are no mods on this bike, original as it can be

 

Re: High Idle when engine is warm

Firefox,
Blue pipes mean lean mixtures. You should start from scratch. Get the carbs back off and run a torch tip cleaner wire through the passages. Make sure your float levels are at the proper height. Someone suggested squirting starting fluid around your carbs. I would not do that in case of a backfire you could start a fire on your bike. Use an unlit propane torch and just flood the carb boots with alittle propane to see if the idle picks up. If it does check your boot gaskets and see if one didn't seal right. The other thing that happens alot is the throttle shaft seals dry up and crack which lets air in and that could cause a lean condition. Just remember if the engine has any vacuum leaks it will screw up your mixtures. If it continues to be lean major damage can be done to pistions and valves being overheated.

 

Re: High Idle when engine is warm

I agree with MN-Maxms blue pipes mean lean she is running hot, ask any snowmobiler when seals go and pulls in extra air goes like heck but then puff burns hole in piston. I know as happened to me.
I think i had my carbs out 3 times recleaning, setting float hieghts and synched .
NEVER USE STARTING FLUID for test -to flammable!

 

Re: High Idle when engine is warm

Ok I'm convinced, I'll take the carbs out and take them apart.
what should I check when disassemble the carbs??
At the cylinders who are running hot, is there anything that I can find/notice that caused the lean mixture?

How far do I have to disassemble the carbs, also take out all of the nozzles?

 

Re: High Idle when engine is warm

Hey guys, stop for a second. If he's able to set the mixture at idle there is pretty likely that she wont have any leaks anywhere. High idle at warm can mean a lot of things, but if you can fix with synchronization and idle mixture tweaking that should mean that your carb is in proper working order.

Or at least, that's my experience: a bit of off sync and a lean mixture setting can cause a high idle. High idle, doesn't necessarily an indication of air leaks. It can be a wrong setting.

If he's not running the bike just make her warm to be able to tweak with the sync - mixture it wont really harm the engine.

 

Re: High Idle when engine is warm

Ok ok don't get upset, I'll give it I try to set the mixture adj. and sync the carbs again.
when that doesn't work, I disassemble them and start all the way from scratch.

Turning the mixture screws CCW means a richer mixture?

 

Re: High Idle when engine is warm

Sorry about that, I just don't like the idea to remove everything again unless you have other options to try Let her idle for a while when she's warmed up and check the spark plugs. I'm assuming all the 4 will be different.
There is a link which is a good catalog for initial spark plug reading: http://www.dansmc.com/Spark_Plugs/Spark ... talog.html

You have to check the insulator and based on that information make small adjustments. Less than 1/4 turn at a time. It's time consuming but you should try.

And yes, CCW means richer mixture.

 

Re: High Idle when engine is warm

Friend of me gave me a Colortune device and going to try if I can adjust my carbs to the best.
He insured me that this would be the best way to adjust the carbs.

Anyone any experience with this?

 

Re: High Idle when engine is warm

Colortune is the best way to get proper idle mixture.

But the sync has to be right first.

Should probably bench sync them if you can.
(take them off and reset the butterflies mechanically)

 

Re: High Idle when engine is warm

I am very interested in the outcome of your work. I have exactly the same symptoms (I'm driving an xj750MK), but am inept at repair. If you solve the problem can you let everyone here know

Mine starts fine and drives fine , but will idle between 3-4k once it gets hot, which causes the exhaust to make some popping noises. The only way to remedy the situation is to kind of ease half out off the clutch.

 

Re: High Idle when engine is warm

Mine was doing the same thing.

Replaced the throttle shaft seals to correct the problem.

YMMV

 

Re: High Idle when engine is warm

Is replacing those a difficult job?
Something someone with 0 experience a standard house tool kit of ratchets and screwdrivers and the repair manual could do?

 

Re: High Idle when engine is warm

INVOLVED but not difficult as long as you take your time and read the manual AND ask questions if unsure.

S!

 

Re: High Idle when engine is warm

oddball is right, it's not rocket science but you have to get an understanding of what you are doing before you break the rack.

The screws holding the butterflies can be difficult to remove, and making sure everything is properly aligned when you re-assemble is imperative.

You can find all of the information you need on these forums to make the job pretty much painless.

 

Re: High Idle when engine is warm

RevChris, you are getting unwanted air in the system, check the carb boots & the shaft seals.
The popping is a lean condition. Wiz.

 

Re: High Idle when engine is warm

Yea, thanks for all the replies. Im glad to hear this is something that some work at home can be done on. However I'm not feeling too confident right now. I've been reading and don't even have the slightest idea on what most of thee things are ... breaking the rack, carb boots , butterflies , shaft seals..... no idea. And the manual doesn't relay feel like it helps , the carb chapter tells how to disassemble the carb but doesn't go into disconnecting it from the rest of the bike , it just say "disconnect from motorcycle"... yearg

Seem I have a lot of reading ahead of me. Given my inexperience I am worried that unless there is a chapter called "replacing X step by step" that I'm just gonna bust everything...

Maybe the best solution for me is to take it out to my Yamaha guy and tell him its running lean when it heats up.

 

Re: High Idle when engine is warm

Sounds like you need a good carb overhaul. You will need to find the right guy who will be honest and do a good job. You will pay alot to get this done. Just make sure your getting your moneys worth.

 

Re: High Idle when engine is warm

After a couple hours of investigation I think I found the reason for my rev problem. The throttle shaft seal on the outside carb was detoriated see pic.
At least I hope this is the cause.



Chacal; do you have these seals for sale????

 

Re: High Idle when engine is warm

I went out and noticed rubber seals that seem to connect the carbs to the engine. (I think) they have little cracks in them... could this be letting the air in?

 

Re: High Idle when engine is warm

RevChris:

Those seals are definitely in need of replacing. Yes, Chacal will have the seals. Thats where I got mine. The cracks on the intake boots should not be an issue until they go all the way thru the boot and actually allow air to enter. Some guys spread black RTV sealant over the cracks to help them seal.

 

Re: High Idle when engine is warm

Those could be just surface cracks. They don't go through most of the time.

 

Re: High Idle when engine is warm

He Revchris,

This is also causing problems, the engine sucks additional air through the inlet rubbers and cause the engine run higher.
I replaced these but that was not the reason for my high revs at Idle, as you can see above I found a bad throttle shaft seal. This could also cause high revs at Idle and I hope this is THE cause !!!!

 

Re: High Idle when engine is warm

Sounds like it could be one of many things causing my particular case. Or a combination of things. Hope its not too much money to have fixed.

Firefox I hope what you just found in your investigation solves your problem.

 

Re: High Idle when engine is warm

I've been reading through the Haynes manual and am starting to think I actually have a shot of doing this myself. Because I don't have a garage or anything I suppose I'm going to have to wait for a nice warm weekend day to get at it.

Just a couple of starting questions (I feel like sucha thread hijacker, but I have the exact same symptoms so Its okay right ) ,
If I were to apply this stuff http://tiny.cc/b3sXS to the cracks on the rubber boots (I think) as suggested should it stand up to the heat?
Is there anywhere else I can apply this stuff to keep air out or is its max temp too low to stand up to application in other areas?

Also because it might be pointless to take the bike apart without any spare parts around would a "Carb kit" be the right place to start in terms of spare parts being available.
Maybe something like this http://tiny.cc/AJbPa ?

I appreciate the assistance alot!

 

Re: High Idle when engine is warm

I was having the same symptom - idling around 3K when hot AND the exhaust smelling like it was running rich on a cylinder :? .

Mn-Maxims and I are tearing down and completely rebuilding my carbs. We're replacing pretty much all the rubber seals, gaskets and o-rings on them because some are brittle and falling apart, while some are just old enough that they're not sealing right and the rest are somewhere in between.

For example - When we had the carbs split, we shone a tiny flashlight in by the butterfly valve and could see small amounts of light leaking past the throttle shaft seals, even though they looked perfectly fine to the naked eye. Well, if light's getting through, so is air, and replaced they will be as soon as the parts order arrives.

Before you tear down your carbs and start ordering parts (in either order), read this first if you haven't already - In the church of clean
This wouldn't hurt either - THE SECRET LIFE OF CARBURETORS Covers the basics of understanding how the whole thing works together.

 

Re: High Idle when engine is warm

Correct CCW to richen. One other thing to look at. What kind of shape is the inlet system up stream from the carb inlets? Are there air leaks on the boots between the air box and the carb inlets? Is the seal around the air filter to air box intact? Old air filters with bad seals can allow raw unfiltered air into the carb inlets. This upsets the very delicate balance of airflow thru the XJs induction system

 

Re: High Idle when engine is warm ***SOLUTION FOUND****

Finally found what's causing my engine revs go up towards 4-5K from Idle when the engine is warm.
It was the throttle shaft seal, see picture in previous reply. After replacing it temporarly with O-seals it runs like never before, it's a perfect sound how it runs now, nice and stable Idle (never had that before).

What my experience is that when encountering the rev problem check al parts that can cause airleaks on the vacuum side 8)

I'm a happy camper again and can ride again

 

I seem to have fixed half of my issue, I adjusted the idle rpm dial down and haven't had the engine rev up anymore even after a good hot drive.

It used to idle around 2k and when hot head toward 3-4k , now it idles near 1100 and head upto 1500-2k when it gets hot.

The Exhaust pop hasn't stopped when I'm decelerating/higher rpms at speed but we will see if I can't remedy this when I replace the soiled air filter / check the seals.

 

Just want to add some of my experiences I had during this repair nightmare.
I found that the high rpm could by lowered by pushing on the sync adj screws, the rpm would go down and stayed for 10 sec down and started increasing again. This was when I still had the vacuum leakage.

After repairing the vacuum leakage, the rpm's were still high and I tried again to push on the sync adj screws but could only lower then 500-1000 rpm and when releasing the adj screw it raised instant.
At this time it was just a matter of adjusting the idle screw and mixture and it runs perfect now.

This was something I noticed and want to share with you guys, it took me too long to get the bike running as it suppose too and almost gave up on it.
But happy I didn't.

 

Turning the pilot screw CCW makes it leaner. You are opening up and more air is coming in. CW or in makes it richer. Rule of thumb is if the screw is on the engine side it regulates air, if it was on the air cleaner side it regulates fuel. Turn the pilot screw out from two and a half and get max idle, then turn it back in until it just lowers the idle a touch. This will give you a touch rich which is the way to go. Check all the plugs if you want, but your ear will tell you it is just a touch rich. Some say a half turn in from max, but I found that max idle is from 3 to four turns out, so I slowly turn back to about three, then slowly turn in a touch until I hear a slight change, but idle is still at it's max. A slightly deeper sound before rpms drop.

 

Hi,

I am in the process of trying to snyc my carbs. I have 82 Seca 650 with yics. i have put the mixture screws down to the bottom, turned them out 2.5 turns.

I have a carbtune hooked to all 4 carbs, yics tool in, and i am having trouble trying to get the carbs to balance.

1 & 4 are high, 2 & 3 low, when I adjust the balance screw the idle sneaks up, my idle seems to have no control, motor sneaks up and turning the idle down has no effect.

Is there a base point for the balance like the mixture?

Can I do this without the YICS tool?

 

Check your IDLE SCREW in the very center of your carbs. Turn it CCW to lower rpms. Take her for a short 10 min drive and then see where the RPMS are when you Idle, then try adjsuting the screw if your RPMS are above 1100. After your ride, then sync them. It works better if your engine is warm

 

Put another set of carbs on the bike, 4th was not firing right on the others. idle still high, but will run and adjust over the next couple of days.

 

Is it a maxium motor in the Seca?

 

I was thinking the same thing Hound...

 

No, I bought this bike two years ago, but serial numbers match.

This morning, it would not start. Pulled the plugs, they were bone dry. I squirted some gas down each cylinder and it started up, but the idle was all over the place. had to stop twice on the way to work to turn down or up the idle.

The vacuum line should pump gas down the fuel line, no? Am I drawing air from some other place.

 

The vacume pulls the diaphram in the petcock back so fuel can pass, run down.
I ask about the motor because the 650 Seca came with a non YICS motor.

 

I have two 1982 Seca 650's

The first is an XJ650RJ, silver with blue & white paint scheme, stock oil cooler, NON-YCIS motor

The second is an XJ650RJC, red with red & white paint scheme, stock oil cooler, YCIS motor

I am in Canada, and both these models were imported here in 1982. I do not think the Red was ever brought into the USA, hence the "C" in the model.

So this would point towards the petcock being a problem.

 

Very interesting I was under the impression that all 650 Seca's be it UK, Euro, US, Canada, were all non YICS.

To check your petcock.
Pull the fuel line from the carb.
Put the end in a container.
Turn the petcock to prime.
Fuel should flow freely, like fill a quart container in no time.
Fuel flows, good!
Turn petcock to the on position.
Start the bike, it idles quite a while on the bowls.
With the petcock in the on position, fuel should flow instantly.
If not check that the vacume line has not collapesed on it's self.
If line is good still no fuel petcock needs a rebuild but, you can run it on prime until you get it fixed, just remember to shut it off when you park.