high rpm when transmission isn't engaged

[87fz600]

I'm having a few issues with my 87 fz600. I get a horribly high idle in neutral or clutch engaged. I've tried adjusting the Idle screw to no avail. Anywhere from 4-6000 rpms. Any clues? Also while riding my frame gets hot. Radiator not working causing the engine to heat up too much and spread the temp to the frame? Or is this normal? Maybe another cause? Any way to check the radiator to be sure its in good working order? I've done a complete oil change, including filter. Any help is greatly appreciated. Thanks riders and posters.

 

[Jacobien]

Hi,

The high idle whilst in neutral etc. may stem from the carburettors. Try adjusting them and cleaning them.

In terms of the radiator, I am not sure but is there not some sort of liquid cleaner you can put into the coolant? There may be some blockage somewhere in the coolant flow cycle. After then draining the coolant and previously added cleaner, top up with nice clean coolant.

(Remember to drain some of the old coolant before applying the cleaning agent, to avoid over filling.)

Hopefully someone with experience will post shortly!

 

[Jugro]

When was the last time you changed the coolant? Could be something as simple as that.. And how warm does it get temp. wise, because on a good day my FZ6 gets a nice warm frame, so I don't think that's really an indicator.

 

[greg]

can't a vacuum leak cause this too?

 

[shuckle]

might want to check that your choke isn't stuck open also that the throttle cable isn't caught on something.

 

[FinalImpact]

can't a vacuum leak cause this too?

Bingo! +1

An air leak explains all of it. An unmetered air leak between the areas of the throttle plates and the cylinder head will make a high idle and make it run hot (A/F is off because there is no fuel with all that air). NOTE: this could damage your engine; fix it before riding it!

Check all vacuum tubing, carb mounts, intake manifold (if it has one). You likely need to pull the tank and get a good visual.

The other options are the throttle plate a not seating closed all the way. Look at that idle screw; if you back it out all the way the very tip of it is not touching anything, than the throttle cables (or something else) is keeping the throttle plates open. Find out what it is before you get into trouble.

 

[87fz600]

So I took the carbs off and cleaned them, basic quick cleaning removing the top and bottom of each one. Got them nice and pretty looking inside and out. Everything moves smoothly. Checked the throttle cable for hang ups anywhere, none. Took starting fluid near the boots betweenb the manifold and carbs and got a higher rpm result. Took all boots off and inspected them, no cracks. Put them back on being sure everything was tight. Still have the problem. I'm going to get back into the carbs today or tomorrow and start all over. Maybe a float sticking open? I was told there was a screw on each carb that adjusts the A/F mixture, which screw does anyone know?
As to the radiator, it is an oil cooled bike so no coolant. Tubes come off the radiator and go into the block on both sides of the oil filter. How would I check for clogs? I'm hesitant to take it off and use water but I'm sure I'll need pressure if there is a clog. thanks for the help every one.

 

[Motogiro]

Does your bike have one of those old type fuel valves that uses a diaphragm that is actuated by a vacuum line? If so the vacuum line may be leaking as well as the diaphragm.

 

[87fz600]

I don't think so. The fuel line goes from the gas tank to a fuel filter then right between the middle two carbs. I'll take pictures of everything when I get back to working on it.

 

[FinalImpact]

The fact that spraying cleaner near it changes it says you have an air leak. Try to pin point the exact location. Some times when rubber seals get hard, a simple thing like not returning a compression clamp to it original position can create an air leak as its no longer pliable.

All I can say about doing a sync is you need a manual to review the process for setting the carberator throttle stops correctly, setting the linkage between the carbs correctly, and lastly, syncing the carbs via idle fuel mixture control.

Find the leak and figure out how it got there. Also, for kicks, remove the plenum leading up to the carbs and confirm all slides are seated to equal depth on each carb.

Check for broken/cracked hoses too.

 

[FinalImpact]

Oh - a stuck float would make it run rich and make black smoke. It would likely slow the RPM down, not speed it up.

 

[87fz600]

So no leak but there are two hoses coming off the fuel valve from the tank to the carbs. One goes to the fuel filter then carbs. I'm guessing the other is a pressure release hose going that goes to the top of one of the carbs. Supposed to be like that or no?

 

[Jblk9695]

The other hose from the fuel valve is a vacuum hose to actuate the fuel valve, so yes it needs to be there. The other carbs should have nipples on them just like where the vacuum hose connects and they should be plugged so that no air can flow, they are used when synching the carbs. Air leaks are very hard to find as they can be anywhere in the system and drive you nuts. Good luck and let us know what you find.
Here is a set of carbs off my Connie, this is the set up I used to set the float levels. Carbs can be a real PITA at times but when they work, hang on.

Jerry

 

[87fz600]

I'm extremely thankful that you told me that. We were minutes away from taking that off also and putting a nipple on it. Whew! Don't know if that would've caused damage or not but glad we didn't do it. how exactly does this work and what does it do? I imagine its connected to the fuel valve for a reason...do we know the reason?

So the first time I used starter fluid there was a change, tightened it all up, used more fluid no change. Went for a ride and it did it again. Should I get complete access to the block and spray fluid everywhere looking for a change in the rpm? Should I remove the top engine plate(header?) and put down a new gasket in case the issue lies there?

I'm sure I could take it to a shop for a fix but 1) I wouldn't learn anything, 2) it would take away more money to put into the bike, 3) I wouldn't have the great satisfaction of fixing my bike and we wouldn't be in an as intimate relationship. I appreciate all the input in helping me and my baby get closer.

 

[Jblk9695]

Wouldn't have caused any damage it just wouldn't start for lack of fuel. The fuel valve is opened by the vacuum created when you crank the engine. You may want to replace all the hoses just to be sure, cheap enough at the local auto parts store. Then check the boots between the carbs and engine, they may look good but still have small cracks. When you had the carbs apart did you spray the rubber diaphragms attached to the vacuum slides with carb cleaner as this may have damaged them. Don't know if you've looked at an exploded drawing of the carb assembly but just in case you haven't--
OEM Parts Yamaha FZ600TC 1987 CARBURETOR FZ600T - TC - Cheap Cycle Parts
Might help identify if ever thing is in the correct place, hope this helps.

Jerry

 

[87fz600]

I did not spray the rubber inside for fear the cleaner could do damage. Mainly checked to be sure all parts moved freely. Used cleaner to get the build up off the insides of the metal and the needles and round valve(?) I checked the outsides of the boots and minor cracking due to age but no damage completely through. The bolts holding the boots on were finger tight and easy to loosen. Tightened all bolts down throughout complete engine.(stupid people owned before me) fixing leaks in gas tank to hook it back up and see what it does. I won't run it for long for fear of over heating. I'm going to remove the radiator tomorrow to check for blockage and will order a new one if needed. Hopefully not. Once the tank is sealed up I will fire her up and do the spray test for any more leaks. I figure random sprays to all engine parts will show me a leak if there is one. Sound plausible that this will work or does anyone have better ideas to find an air leak? Thanks for the help everyone.

@FinalImpact - is the plenum the boots between the Carbs and the intake manifold? I'm clueless as to what it is so I'm kind of guessing off a Google answer lol

 

[Jblk9695]

I think he means the air box where the filter is located as that can cause problems if it is sucking air through a crack in the box.
Sounds like your heading in the right direction as I still think it is an air leak somewhere. But still could be mechanical and caused by the throttle cables not allowing the butterfly's to close completely or could be the choke, which is actually an enrichening circuit and is controlled by plungers which if they are sticking could cause a high idle also, just more stuff to look at

Jerry

 

[87fz600]

I have no air box, just 4 k&n filters on each carb. Wish I had the box though. Also with the hose coming off the carb to the tank...I tried blowing through it to the valve and get nothing. Completely sealed. Took the valve apart and it is clean. How does it work in association with the valve so I know what to look for result wise?

 

[Jblk9695]

Does the valve have prime, run and reserve or does it have off, run and reserve?? I could be wrong about it being a vacuum actuated valve and how its marked should tell us. If its vacuum all that happens is when the engine cranks it opens a diaphragm in the valve that allows fuel to flow.


Jerry

 

[87fz600]

IT would appear off, run, and reserve. I'm getting a new tank soon so we will see on that one because my old one is super rusted inside with like ten holes. Could fix but its got a vicious dent and I don't want to deal with the bondo. We shall see what the new one has.