Ignition Timing Problem on 3zyl 2stroke 40HP Yamaha 40HET0

[Dataeater]

Hello Guys,
I work to repair a yamaha outboard engine of a friend - it is a 3zyl 2 stroke 40HP - Type 40HET0.

This engine has following problem:
The eingine works - but only in idle mode.
I checked many things (carburettor, fuel pump, compression, thermostat..) until I found out:

The Ignition timing is every time fix - approx 5 Degrees before TDC.
The changing of the Ignition time to earlier mode does not work.

Question
There is a connection from the overtemperature switch to the CDI. Does this switch open or close in case of over temperature? Is it possible, that this causes a problem like that?

Question 2
Or could be, that the intermal Potentiometer of the CDI is out of order?

The engine got the CDI - type: 6H5-01 F8T12773

Many thanks!
Dataeater

[99yam40]

not sure when that motor was built, and I do not get any info from searching for that CDI part.

but if it is like my C40TLRX there are 2 temp switches on the head.
one tells the CDI when the motor is warmed up , and the other tells when it is overheated.
these switches are normally open and close as the temp rises to the set points
Mine also has linkage from throttle to the CDI wiper telling the CDI where the throttle is positioned, instead of linkage to a timing base under the flywheel as the old motors had to control the timing.

time to test things.
hopefully you have a bad switch or wiring instead of a bad CDI

[BroderickQ]

I'm having the same issue with mine. I'd love to hear the answers and if you made any progress.

[99yam40]

Yes, but it was a long time ago. and I may have killed off those brain cells that had that info.
but let me think a little to see what I can remember.

seems like Ilet the motor idle ,disconnected the wiper from carb linkage and moved it to the WOT position while watching with a timing light to see if it hit the spec for wot.

RPM went up as the timing increased even tho the throttle plates did not move any

[Dataeater]

Hello,
I did not get a message, that somebody has replied...thats why with delay ;-)

OK, Yes, I removed the potentiometer arm from carburettor and looked with a timing light while the engine was running in idle speed.

When I moved the potentiometer - nothing has changed - every time the approx 5 Degrees before TDC.

That means - eighter the CDI is "not allowed" to change the timing - or the CDI is not able to do that.

I tested the wiring - evertything looks good - nearly like new.

But one wire is disconnected - with the colour Yellow/Red.
I could not find a wire wiht the same colour - what belongs to this.

Is Yellow/Red the output for rev counter?

The Part Number:

So far, as I found out the original part number should be:
6H5-85540-01-00
But it was replaced now to:
6H5-85540-02-00

If I take g*gle for F8T12773 I got 6H5-85540-02-00.