C40TLRX yamaha timing problem

[99yam40]

I set the throttle link like the manual said to and the pointer is pointing at 7 degrees ATDC in neutral low idle and 25 BTDC opened up but the actual timing is over 10 degrees ATDC at idle( maybe as much as 14 ATDC, no marks past 10) when checked with a timing light.
Does this make any since to anyone or have you seen this before?
I have not put it on the water yet to see how far it advances at WOT, if I adjust the linkage to get the 7 degrees at Idle I am afraid it will push the timing too far advanced at higher RPM, but it makes it run a lot better at idle.
Can anyone give me any advice on what it may do if it advances past the 25 degrees called for and or any information on how to solve this problem?

 

[99yam40]

Re: C40TLRX yamaha timing problem

Can someone tell me if there is something besides a bad CDI unit that would change (retard) the timing from what the pointer is saying?
I am able to move the pointer to the 25 degree mark with the linkage disconnected and the motor running and the timing light is at the 25 degree BTDC mark on the flywheel, but at idle and the pointer at 7 degrees the timing light shows over 12 degrees ATDC

I believe that a overheating problem may do this to keep the motor off of high RPMs, but I do not know how much of a timing change there would be. Does anyone out there know this?

My motor is not overheating. I am getting these readings right after starting up and idling for just a minute or two and there are no alarms.

 

[99yam40]

Re: C40TLRX yamaha timing problem

Just got back from running motor on the water. I had adjusted the retard stop screw to about 25mm instead of 20 mm just to get the timing to 10 ATDC instead of 14 ATDC and help with the idling. This still allowed for the TSP to move the timing a small amount before moving the butterflies
Checking the WOT timing with timing light showed about 28 BTDC, so I adjusted the advance stop screw to get it back to 25.
The motor still has some random RPM drops from time to time mostly 3/4 to WOT, but it is not due to timing change or fluctuations because I watched the timing while the RPMs were moving around and it stayed steady. I am only going by feel and sound, I do not have a tac.
I did notice that the RPM drops were not as bad when I removed the cowling and silencer from the front of the carbs and was running into the wind, was a little worse running with the wind. This sounds strange like it is running too rich or something with the little bit of restriction from the silencer. It did not help to adjust the mixture screws and it definatly killed each cylinder as I choked the individual carbs with my hand.

I have read most of the threads about timing, but I have not seen anything which states the retarded timing being this low with the pointer being on the 7 degree mark.
Even the treads about bogging and/ or surging do not give any definite answer to what finally fixed the problems.
I have been though the carbs, fuel pump, and fuel lines. The bulb stays firm and I have changed the plugs.

Any and all help would be appreciated.

 

[99yam40]

Re: C40TLRX yamaha timing problem

Rodbolt can you give me your advice about what could cause the timing to be off from what the pointer on the CDI unit is set at?
I set the throttle link retard stop adjusting screw to 20 MM like the manual said to and the pointer is pointing at 7 degrees ATDC in neutral low idle and 25 BTDC opened up. When checked with a timing light the actual timing is over 10 degrees ATDC at idle( maybe as much as 14 ATDC, no marks past 10). Even after I adjusted the screw to 25 MM it was just to 10 ATDC
I talked with someone at the Yamaha shop here but I do not think he was a tec and he said there are a lot of different things up under the flywheel that could affect the timing, which I do not think is correct.
I would like an experts advice.

2/12/2010
Just to let others know what I did to fix my problems that you will read about in this thread

I ended up changing the CDI and that fixed the timing problem and allowed me to get a lot better idling because I was able to get the proper RPMs with out having to open the butterflies as much.
I had to change the main jets to eliminate the high speed miss, because someone before me decided to drill out the old ones to get more fuel into the motor.

I hope this will help others as they do searches for problems they are having.When ever you buy used equipment you can never rule out anything as you troubleshoot because you never know what others have done.