Engine Idle trouble

I am having some itresting problems with my engine idle on my 82 maxim 550. The bike will idle at around 2000 - 2500 with the choke still on. If i take the choke fully off I will kill the bike. Eventhough the bike will idle at this rpm. When I pull in the clutch the engine will whine all the way upto 4000-5000, this happens when I am sitting still with the bike. When I am shifting and pull in the clutch I get no whine up. Last year I dealt with the same problems.
Things that were done with the bike all ready
-tried to put some fuel stabilizer in -------little to no effect
-when I bought the bike the previous owner said he had already cleaned the carbs.

I am looking for any help on this one.

 

You need to investigate to see if the Pilot Jets are clogged and the Pilot Jet + Pilot Air Jet Passages are clean and clear.

Until you have the Pilot Jets supplying the right Air~Fuel Mixture for Idle with Throttles closed ... you have cleaning and tuning to do.

 

Although I'm a noob, I gotta agree with Rick. I thought my carbs were clean too. Turns out some peoples idea of clean carbs and mine are just not the same.

 

Ok real big issues now. I took the bike out for a small trip and it had the same idle issues. This time when I restarted it something sounded different. It hessitated alot went a little then died.

It took me forever to restart it. I got it going and had very little power then it just died again. Good thing it was a short trip.

I didn't to push the thing the whole way home so I attempted to restart. It finally restarted only after I let it sit. It ran at 3000rpm and i left it do that so I could drive the thing home. I ran it like this and the thing died again.

This time when it died I lost all electrical power. I checked battery connections and they look good. Still no power I am really stumped.

How serious is this guys, I am really worried.

 

Let's start with the basics.
First, is your battery any good? Are the alternator brushes good? Is the battery being charged by the alternator?
You must have a full charge on the battery for these bikes to be happy. This happens when the alternator makes voltage through the brushes. They are regular culprits for lousy to no running of these machines. Check for at least 13 volts at the battery with the bike running over 2k RPM.
Then:Spark, fuel, air, compression.
Are you hitting on all four spark plugs? Pull them and verify each by grounding the body to the head and watching the spark dance when you turn it over.
Got fuel into all four carbs? Crack the bowl screws and verify fuel presence. Inspect the spark plugs for evidence of fuel (wet).
Is the air filter blocked perhaps? Check and renew as needed.
After you check for spark, disable the ignition system by unplugging the TCI. Run a compression test. In a pinch, just jam your thumb over the spark plug hole and push. IF it can force your thumb off the head, it's good enough.
This ought to get you started in the right direction. Verify the conditions I have outlined and let us know what you find.
Best of luck!

 

Okay here is what happened I had the main fuse blow. I had already looked at the fuses and this one didn't look blown, but was. However when i try to restart the bike it was not starting. I pulled all of the spark plugs and evaluated. 1 and 4 are both wet. and 2 and 3 are dry.

Does this mean that I have a bad coil for 1 and 4?

 

Oops me again does anyone know of where I could get a used coil? I really don't want to blow $100 on a brand new one if I don't have too.

Also could this possibly be some the reason for the idling trouble?

 

That would be the reason.
Among other things.

You need to test that coil.
Lift the tank and unplug the two coils from the wiring harness and SWAP the two connectors and see if the trouble shifts to the other two cylinders.

If so ... its the Coil.
But, it might be that the wiring connectors need to be cleaned.
Try spraying the Plug-in's with Contact Spray (Electric).

Be surue the Battery is fully charged; too.

 

I'm having the exact same problems minnMax described in the first post. I just put in a new, fully charged battery, cleaned the carbs meticulously, with some nice shiny new parts thanks to chacal, installed in-line fuel filter, new foam air filter, and got it going fine the other morning, but then when I tried riding later that afternoon, idle was all over the place, revving to 3 or 4000 when I pulled the clutch in and dying if I released the choke. After about 15 or 20 minutes of riding though, the idle evens out to around 1300 comfortably and I can let the choke off. No problems.

This morning I tried to start the bike and it wouldn't turn over. I still have to change out the alt brushes, and am hoping this solves some of it. But I'm vexed at the moment. The changes in the idle after I ride for a while is what's confusing me. Why does it even out after everything's warmed up? Any thoughts? Sorry about the long post

 

I recently got a NOS coil off eBay for 60 bucks, as good as new.

 

Scribe:

The Alternator Brushes are half the problem.
The Carb Adjustment is the other half.

Idle needs to be closer to 1,050 ~ 1,100 ... Tops.
Anything above that and you are feeding the Carbs off-idle.
Main Jet Fuel sneaking-in because the Butterflys are cracked-open too much.

Begin with the Alternator Brushes so you know the Charging System is adequately supplying enough current to run the bike and charge the battery.

Bench Sync the Carbs with strips of business card
Sync them with an appropriate meter if you have access.
Colortune them if you have the Tool.
Plug Chop if you don't.

You need to get the Carbs Idling the Bike with the Throttles closed so you can adjust the Pilot Mixtures.

Once you get to where you have the Bike Idling good we'll start a Thread for tuning and get you and everybody else dialed-in for the summer.

 

Thanks for the advice, Rick. I'm about to change out the alt brushes now, so hopefully that be half the battle, as you say. As for the idle, my manual says it should be 1200. Too high? I'll try to get it stabilized in the range you suggested.

Also, I did bench synch the carbs and I plan on picking up a Colortune plug from chacal soon, but just so I understand you correctly, are you saying I should be able to get the carbs idling the bike with the throttles completely closed, as in, the idle screw completely backed off? I have have my pilot mixture screws set 2 1/2 turns out. should I go with 3 turns out and then back the idle screw off completely? I don't know how else to close the throttles.

 

No. I just don't want you to substitute Main Jet Fuel for Pilot Jet Fuel.

Theoretically ... you should be able to adjust the Pilot Mixture Screw ... which Mikuni (you got Mikuni's ... right?) ... call Pilot Air Screws.

As you adjust the the Pilot Mixture Screw OUT ... you are letting MORE AIR into the Cylinder ... which draws-up Pilot Jet Fuel as the Volume of AIR allowed to enter the Cylinder from the Pilot Air Port which is married to the Pilot Fuel Jet.

There ought to be point where the Pilot Mixtures, adjusted for optimum Air~Fuel Ratio ... will allow the bike to run without the throttle plates open.

 

got ya. And yes, I do have Mikunis. So I should be able to adjust pilot mixture screws OUT while letting the idle screws OUT until the optimum idle is achieved? Sounds tricky but at least conceptually simple.

 

minnMaxim, Rick's suggestion of swapping coil input leads is a great way to narrow down the problem. If the problem follows the coils, you know it is the coil in question. If it remains on those cylinders, your pickup coils could be bad or the TCI is flaking out on you.
Be advised I have found (out of 4 coils tested and then disected) that the secondary leads (the ones you put on the sparkplug) tend to corrode and drop. They can be replaced with a little effort for very little coin. Check out the how-to on coil rebuilding in our XJ DITY under the links section.

 

Rick, can you clarify this?

Acc. to here: http://www.yamaha-triples.org/forums/th ... 587#M53587

the Pilot Mixture Screw controls only the amount of mixture - not the mixture itself:

"Ah, terminology. Pilot screw, or mixture screw. Mixture screw as in how much Richer Mixture is let into the engine. More or Less (mixture), as opposed to richer or leaner mix.
"Some of the fuel supplied to the needle jet by the main jet is diverted to the pilot jet. This is then mixed with air from the pilot air jet, and a Rich Mixture is fed" to the pilot screw. "The amount of Mixture allowed into the engine is controlled by the pilot screw, which has a pointed end partially blocking" the pilot outlet into the throat.

You can see by the position of the pointed tip that the screw controls not of what the mixture consists but the amount of Mixture itself, which is a richer mixture than normal.
This makes it easy to figure the pilot screw setting-- CCW, or Out of the carb throat, means a bigger hole and more of the richer mixture. (Also essplanes, I'm guessing, why a clogged pilot jet makes the pilot screw setting either useless or reversed.)

Someone put it thisaway: the pilot jet is fixed, the pilot air jet is fixed, they make the mix that goes to the only adjustable part- the screw. Different from the 2-stage choke, where air is fixed but fuel is adjusted."

Mikuni picture here:

http://xj900.kliwebdesign.de/vergaser01.php#

 

Finn,

You've been around the block enough that I'm sure you understand how a basic carburetor works, so:

The pilot circuit is essentially a very simple carburetor. Air comes in through the pilot air jet, it's being motion reduces it's pressure and fuel is pushed up through the pilot fuel jet into the air stream.

Now, because of the jets this fuel/air stream from the simple carburetor is extremely rich. This extremely rich fuel/air mixture is available to the pilot outlet and the by-pass hole above the throttle plate. The richness of this simple carburetor is controlled entirely by the pilot air and fuel jets. To change this mixture requires re-jetting.

Now, what happens when you are at idle -

The butterfly valve is almost sealed. The air moving through the carburetor throat is moving very slow and the needle jet is closed so it picks up no (or very little) fuel.

The pilot outlet is on the engine side of the throttle plate. Lots of vacuum there so the rich fuel/air mix from the pilot circuit flows through the pilot outlet to the main air stream making it richer. The pilot screw controls how much of the super rich fuel/air mixture gets into the main air stream, thus how rich or lean the mixture going to the combustion chamber is.

Now, why do the carburetor makers do that rather than just having a fuel supply with a flow valve (needle and seat) to control the amount of fuel? I can think of two reasons: 1) to give us more stuff to clean, or 2) it atomizes the fuel better to improve performance and reduce emissions.

Wow! That is as clear as mud. Perhaps a picture will help:

 

Thanks for the kind words, Micarl

Right - so the qouted statements in my post doesn´t exclude one another..

Actually when writing the above I came to think of that the air in the Pilot mixture surely couldn´t be the only stream of air entering the cylinders, even at idle - but still;

"main air stream": Does this come from the butterfly valves not being fully closed or?

Thanks for clarifying so far; we´re getting there

 

The Pilot Mixture Screw is an AIR Bleed Screw.
The Air Passage is married to the Pilot Fuel Passage.'
As the Air bleeds into the Cylinder ... it brings with it a small quantity of Fuel it picks-up at where the Air Passage meets the Fuel Passage.

The Main AIR is the AIR drawn-in to the cavity surrounding the Emulsion Tube.
This Air passes through the tiny holes in the Emulsion Tube and helps the Main Jet Fuel Supply reach the top of the Tube for blending-in with the Intake Air.

The holes in the Emulsion Tube break-up the stream of Fuel from the Main Jet and helt atomize that stream before it exits the top of the tube.

The Main Air Jet and Passage are under the Rubber Diaphragm most covered by an additional metal plate "cover" screwed into the top of the carb there.

The Main Air Jet on Mikuni is in the Outside diameter of the Intake Horn, covered by the Airbox to Intake side Rubber Boot.

When the Main Air Passage or the Holes in the Emussion Tube are clogged, performance off-idle ... particularly Mid-range and Wide Open Throttle are effected by the Fuel NOT being atomized and the stream too lean for conditions.

The Emulsion Tubes on BOTH Mikuni and Hitachi are held in place by the Main Fuel Jets Flat washer.
To service the Emulsion Tube:
Remove the Main Fuel Jet and washer.
Tap-out the Tube through the top of the Carb.

 

Rick,

Just for clarification, are you talking about swapping the primary (input) leads only or the primary and secondary leads also? Don't the primary leads come from a respective pickup for a particular cylinder?

Thanks, Ed

 

No. Just where they plug-in. The system works on WASTED SPARK. Even though the bike is on the exhaust stroke ... the Coil fires anyway.

All you have to do is swap the Plug-in's to the Coils from the Wiring Harness.
If the Coil is bad ... the problem shows-up by the other two Cylinders not firing.

It's the recommended test for a Coil not firing.

 

Hey sorry to keep whining but I just cleaned the carbs and made sure the coils are operating right and am getting the same problem. The coil for 1 and 4 were not fully hooked up, thats a long story on why they are not. The battery is fully charged too.

THe bike will just not idle with the choke off. The bike will run with half-choke. It seems like the idle screw for all for carbs does little to nothing. The bike fires right off now but when i try to run the bike with no choke it runs for two seconds then kills itself. Then takes a little cranking with the choke all the way open to get it going again.

 

Did you take the AIR Jets out when you did the cleaning?
The AIR Jets are under the Rubber Diaphragm?

It sounds to me like you don't have your Pilot Air Screws (Pilot Mixture Screws) ... opened enough, yet.

You should bring out the Pilot Mixture Screws until you get the Bike to run without additional Rich Mixture from the Chokes.
Those Screws are very sensitive. Once you get to the right spot, the Mixture changes very rapidly when adjusted in or out (My-nute-ly)*

Unless there is SOME contribution from the Pilots ... the Bike won't Idle or Pick-up when you try to give it some throttle.

 

Rick,

I changed the primary (input) connectors on the coils and it won't start. It cranks very fast and backfires through the exhaust big time and very loud. I thought it was going to blow the muffler off. I switched the input leads back and it fired right away but still misfires on #1.
Someone else told me that I would have to switch the secondary HT wires also. I don't think that they will reach because the wires are shorter. I didn't try to remove the wires from the coil.
If both coils have the wasted spark and both fire at TDC and BDC it seems that it would not make any difference where the wires were plugged in at all. All four fire at top and bottom.
Have you ever seen the CDI act like this? Now, I did reverse the spark plug wires between #1 and #4 with no effect. I checked the compression on #1 cylinder and it was somewhat low. It had 60 PSI. With a couple shots of oil it jumped to about 100 PSI. Today I rechecked the compression on the #1 cylinder. It checked out at 70 PSI and with a couple shots of oil it jumped to 115. The thing that I still don't understand is that i saw the bike run on that cylinder then lose it along with #4. Then lost #2 & 3, then started running on 2,3 & 4 again.
I am going to have to sit back and think about this.
Thanks for your help,

Ed

 

The Low Compression on the One Hole is killing you. That you passed the Wet Test (almost) ... means you have trouble with Rings or the Piston.

With the Compression so low you won't get the Mixture to Ignite. You'll just foul that hole out and make the situation worse.

You could try a hotter Plug.
You could try Leaning the Mixture a bit
All those quick-fixes don't really get to the heart of the matter.

If you did the Compression Test right, with the Plugs out, the Battery charged-up full and the Throttles cranked wide-open ... 60 PSI ain't gonna cut it.

Re-group. Make sure that you have accurate results from the Compression Test.
If you know, in your heart, you did it right and the 60 PSI is what you got; them you have to do some Engine work and I know you don't need to have anyone tell you.

What's with this Forum.
This is two or three people all having something making pulling the Head and getting nasty happening.

 

I saw a full gasket set on ebay for $85 plus shipping. I found a site that has .25mm rings for $40 plus shipping (all 4 holes). The bike has 31,000 miles on it. I find it strange that it would be worn out with that kind of mileage but running across that is nothing new for me.
A set of .25mm rings calculates out to be 0.00984". I have built enough engines in my life to be able to file the ring gap so as to use this ring in a standard bore engine. With what little increased ring tension from just .010", shouldn't be a problem so long as I have enough ring gap to compensate for the heat. From what I see, the top end should be able to be rebuilt in about a day, especially using air tools. The biggest problem I see are the irritating incidentals that always seem come along.
I really don't want to do this. If I could find a good engine reasonable I would buy it and get it over with.

Ed

 

Hey thanks again for the help. I took off the float bowl of the carbs and cleaned needle valve and i think the main jet. I did not clean any directly under the diaphram. I will have to do this when work and kids provide.

Can I do this leaving the carbs on the bike?

 

I have never cleaned the carbs leaving them on the bike.

 

I pulled out the pilot screw right underneath the bladder to make sure that it was clean and it looks fine. This leaves the only thing that I have not cleaned on the carbs is the needle jet. This is first time that I cleaned the carbs so let me know if i am missing anything.

I also checked the idle screws and they are set 2 1/2 turns out. Is this what they are supposed to be?

 

I think we have come to agree that 2-1/2 Turns Out is not enough Pilot Mixture.
Go closer to 3 if not beyond 3 toward 3-1/4 (not quite 3-1/4 but slightly beyond 3).

The best way to tell would be to observe the Mixture burn with a Colortune Plug.
Absent that ... tune for the best Idle and do a series of Plug Reads.

It took me quite a few Plug Reads to tune-in my 900 after cleaning the Pilot Screws and Passages. But, once I got the Plugs to where they were a very nice dark tan ... the bike is running and starting just fine.

It was fun doing the Plug Reads, anyway ... I found a nice Indusutrial Park with a long road around it and made the best of an afternoons worth of tuning.
The Pilot Mixture Screws are very sensitive to movement within the optimum setting range and don't need to be moved more than the with of a Nickel or so to obtain the optimum results!