Help!

[85harley]

I have a 2000 Yamaha C70 that has a problem cold starting. The carbs have been cleaned and the enrichment pump has been rebuilt. If I remove the electrothermal valve and plug that hole with my finger and use my mouth to do the vacumn pulse part the system pumps gas as it should. If I replace the valve it shuts off the fuel circuit. Has anyone ever had an electrthermal valve go bad and not retract enough to open the enrichment system. Does anyone have any suggestions? That valve cost 180.00 and I do not want to take that gamble. I am new to the forum and I am looking forward to getting sme replies. Thanks to all.

[boscoe99]

When you turn the Primestart red knob to the ON position will the motor start easily when cold or is it the same problem as when the lever is in the automatic position? Is the red knob in the automatic position?

Is there any way that you can measure the distance from the tip of the needle valve to the point on the PS device where it mounts to the carburetor, and then measure the distance from the mount point on the carburetor to where the PS needle valve would rest to close off the supply of gasoline, to see if the distance of the former is less than the distance of the latter? Perhaps the needle valve is remaining extended and is not retracting.

If and when you apply voltage to the PS device does the needle valve extend?

[99yam40]

there are 3 positions on the red lever for the enrichment system. (at least it does on my C40)

have you tried putting it in the open position to see if it pumps fuel for enrichment?.

My C40 when in the normal(auto) position does not have liquid fuel going up into the line to the motor. It is just a heavy enriched vapor.
In the open position it does send liquid fuel

[85harley]

When you turn the Primestart red knob to the ON position will the motor start easily when cold or is it the same problem as when the lever is in the automatic position? Is the red knob in the automatic position?

Is there any way that you can measure the distance from the tip of the needle valve to the point on the PS device where it mounts to the carburetor, and then measure the distance from the mount point on the carburetor to where the PS needle valve would rest to close off the supply of gasoline, to see if the distance of the former is less than the distance of the latter? Perhaps the needle valve is remaining extended and is not retracting.

If and when you apply voltage to the PS device does the needle valve extend?

Yes, when I move the red lever it fires right up. The best I can tell by measuring according to my micrometer the needle is longer than it needs to be so it is not opening the fuel circuit. The service manual gives the resistance value and the valve passes that test, it also tells how to check with battery power supplied to it and it extends as it should. Is it possible the valve is not retracting enough? The difference in the measurement was almost 4mm to long.
Thanks

[TownsendsFJR1300]

Sounds like the "flow circuit" is clogged up as the rest of your system is operating properly..

A suspect a re-cleaning of at least THAT orifice will need to be done..

[99yam40]

Yes, when I move the red lever it fires right up. The best I can tell by measuring according to my micrometer the needle is longer than it needs to be so it is not opening the fuel circuit. The service manual gives the resistance value and the valve passes that test, it also tells how to check with battery power supplied to it and it extends as it should. Is it possible the valve is not retracting enough? The difference in the measurement was almost 4mm to long.
Thanks

seems like you need to find another one to measure to make sure. problem is usually the Yamaha part houses at local dealer do not keep everything in stock, so finding a new one may be a problem without buying it.

see if you can find someone with a motor like yours and see if they will let you measure it.
it will help if it happens to be someone you know well already.
cause I would not let a stranger play with my good running motor.

Just had a thought about what your start up procedure is.
these motors do not like it if you open/advance the fast idle lever any at all if you are doing that.
Usually pumping the primer bulb until you cannot get it to pump anymore.(making sure the fuel bowls are all filled)
hit the starter for 3 seconds or so, back to off for a few seconds and repeat till if fires off.
mine will fire up on second or 3rd turn of the key usually

[boscoe99]

If the motors starts easily with the override lever or with the PS removed and your finger plugging off the carburetor, then I would suspect the PS.

Take close look at yours. Do you see where one piece is threaded into another piece? I have seen folks that will break the threads loose and then screw the needle valve in or out in an attempt to make an adjustment, if and when the pin is not retracting to the proper length. Whatever that length may be. Yamaha does not tell that I have seen.

Can the pin be forced inward a bit more than its normal resting point? If so, push it in a tad and see if you can use something to hold it in that position. Then reinstall the device and cold crank it to see what happens. Leave the electrical leads disconnected if you do this.

[85harley]

seems like you need to find another one to measure to make sure. problem is usually the Yamaha part houses at local dealer do not keep everything in stock, so finding a new one may be a problem without buying it.

see if you can find someone with a motor like yours and see if they will let you measure it.
it will help if it happens to be someone you know well already.
cause I would not let a stranger play with my good running motor.

Just had a thought about what your start up procedure is.
these motors do not like it if you open/advance the fast idle lever any at all if you are doing that.
Usually pumping the primer bulb until you cannot get it to pump anymore.(making sure the fuel bowls are all filled)
hit the starter for 3 seconds or so, back to off for a few seconds and repeat till if fires off.
mine will fire up on second or 3rd turn of the key usually

Thanks for the reply. I will pump the primer bulb until it is hard and then turn the key. I never touch the control while starting.

[85harley]

If the motors starts easily with the override lever or with the PS removed and your finger plugging off the carburetor, then I would suspect the PS.

Take close look at yours. Do you see where one piece is threaded into another piece? I have seen folks that will break the threads loose and then screw the needle valve in or out in an attempt to make an adjustment, if and when the pin is not retracting to the proper length. Whatever that length may be. Yamaha does not tell that I have seen.

Can the pin be forced inward a bit more than its normal resting point? If so, push it in a tad and see if you can use something to hold it in that position. Then reinstall the device and cold crank it to see what happens. Leave the electrical leads disconnected if you do this.

Thanks for your reply. Mine does have threads so I might be able to turn it. Last night l placed an o-ring under the PS valve and the motor fired right up. It idled a little fast for a short time and then idled down to normal. It sure would have been nice if Yamaha had given the cold measurment specs. I think you are right about it not retracting enough to open the enrichment system. I do not know if there is anything in that valve that could cause it not retract enough.

[99yam40]

Ok now did the pumping the primer bulb until hard solve the problem or was it the oring spacer

[85harley]

Ok now did the pumping the primer bulb until hard solve the problem or was it the oring spacer

It was the o-ring. I always pump up the bulb good and tight. Do you see any problem with running with the o-ring in there? It is not leaking gas.

[boscoe99]

I forgot about the O ring/spacer trick. It has worked for some.

[TownsendsFJR1300]

It was the o-ring. I always pump up the bulb good and tight. Do you see any problem with running with the o-ring in there? It is not leaking gas.

I'd probably use some small SS flat washers so you can snug it down...

You can "fine tune" it as well with several washers...

[85harley]

Thanks to all who helped me. The ss washers could be used to fine tune the spacing I guess. That is a good idea. For all you that suggested the failure to retract enough I sure am glad you took the time to answer my questions. I would like to know what caused that thing to stop retracting enough to start with. Anyway I can buy a lot of o-rings and washers for $185.00, the cost of a new valve. If it does not give any trouble when the weather gets cooler I think I am good to go. If any one else has any comments I sure would like to hear them. Nothing like experience.