1998 Yamaha 40 2 Stroke C40LTRW. will not idle. weak spark.

benptn

Recruit
Joined
May 26, 2012
Messages
5
1998 C40LTRW will not idle with lever closed. Performed the "sync and link" as the service manual said. (20mm gap at retarding stopper, adjust rod to align pointer with marks on CDI. 25 atdc when retarded and 7 atcd advanced. Also adjusted carburetor linkage as the manual said. All adjustments were minute, as the motor was close to factory settings.) After adjustments the motor improved. runs smoother. The motor dies when the throttle lever is about 1/4 open. Cannot get the motor to idle with the lever closed. The spark looks weak on all three cylinders. and i cant get a timing light to flash on any of the plug wires. but the plugs are getting fire. the motor runs! just very weak. Do i need to use a timing light to adjust the screws on the magneto lever (moving the pointer on the CDI)? Could a bad CDI or coil cause a weak spark? would it even run? Is it likely that all three ignition coils are bad? All help is very appreciated. New to the forum.


Thanks
Ben
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: 1998 Yamaha 40 2 Stroke C40LTRW. will not idle. weak spark.

Just for your info, ATDC is after top dead center which retarded, BTDC is before TDC so it is advanced.

Have you tried running with the red e switch in the normal sitting instead of the closed? That is where it should be in normal operation.

If you are using an inductive timing light, try turning the clip that attaches to plug wire around so that the arrow is pointing away from the plug. It worked on my C40TLRX
 

benptn

Recruit
Joined
May 26, 2012
Messages
5
Re: 1998 Yamaha 40 2 Stroke C40LTRW. will not idle. weak spark.

I usually have to put the red e switch in the middle position to get the motor started. then I move it back to the normal position. I will try the timing light again while moving the plug clip around. Im not sure there is an arrow on the plug clip. Thanks for the info and fast response.

Can something besides the ignition coils or a weak battery cause a weak spark? If the linkage or timing was off, I would assume the spark would be strong, just not sparking at the right time.

Thanks
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: 1998 Yamaha 40 2 Stroke C40LTRW. will not idle. weak spark.

If you have to move switch from normal to open to get it started then you need to clean the carbs, as they are not alowing enough fuel to start.

A spark tester set to 7/16" gap is the best way to test spark.

If it runs the it is getting spark, work on the fuel/carbs

The voltages to and from CDI can be tested with proper equipment to see if they are in spec.
Turning slowly will not give the proper voltage so weak battery can effect it.
 

benptn

Recruit
Joined
May 26, 2012
Messages
5
Re: 1998 Yamaha 40 2 Stroke C40LTRW. will not idle. weak spark.

Just checked the fire with a gap spark checker set to 7/16" and i got spark on all 3 cylinders. hooked my adjustable timing light and couldnt get it to strobe on any of the wires. until, i turned the knob on the light. it will strobe until the knob is turned below 10 or so. i would like to see what the timing is set on. to do so id leave the knob at 0. but i cannot get it to strobe. also checked compression. 100 on all 3 cylinders. not sure if thats good or bad. more concerned about why i cant get a good timing reading.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: 1998 Yamaha 40 2 Stroke C40LTRW. will not idle. weak spark.

I have never used new one with adjustment on it, My good old snap-on from the 70s still functions fine.
See about borrowing a different one maybe

During start /warm up the timing is advanced some(about 7BTDC I think), but after warm up it drops back to 7ATDC at idle.
At least it is suppose to, mine was 14 ATDC and I ended up having to replace the CDI
100 sounds a little low, but it could be your gauge
 

benptn

Recruit
Joined
May 26, 2012
Messages
5
Re: 1998 Yamaha 40 2 Stroke C40LTRW. will not idle. weak spark.

Got the timing light working correctly. not sure what i did. maybe i got it clipped on the plug right. Now im trying to set the timing without the motor running. plugs out. cranking the engine. just like this http://www.youtube.com/watch?v=iTJyrf9m_oE . with the retarding screw all the way out. the CDI arrow pointing a little above the 7 degrees ATDC. the timing is at 4 degrees BTDC. the lowest I can get it to go. I assume my CDI is bad? Does this sound like a bad CDI?

Thanks
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: 1998 Yamaha 40 2 Stroke C40LTRW. will not idle. weak spark.

Did you not understand what I wrote about starting timing?
 

benptn

Recruit
Joined
May 26, 2012
Messages
5
Re: 1998 Yamaha 40 2 Stroke C40LTRW. will not idle. weak spark.

i think i understand. while the engine is below operating temperature something tells the CDI to advance the timing? While im cranking the engine its not at operating temperature. I should set the timing on 7 BTDC using my timing light cranking the engine? Ive only set the timing on an idling engine before.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: 1998 Yamaha 40 2 Stroke C40LTRW. will not idle. weak spark.

You should set the wiper pointer to the 7 mark at idle and at the other mark for WOT. This is all part of the manuals steps you need to follow.
Crank the motor up on the hose and let it warm up and the check to see how close it is and adjust if needed.
Do not try setting when just cranking over, even when warm it will advance while starting, it is part of the prime start system
 
Top