1986 Yamaha 40 not firing one cyl

[Tobias]

I have an '86 Yamaha 40ELJ that rarely gets past 2200 rpm under load. There is no water in the fuel and the fuel pump has been changed. Carbs are clean, and pumping the bulb does not help. I noticed that pulling the spark plug cable off of the middle cylinder makes no noticeable difference while idleing up to 2000 rpm. I swapped the top spark plug, cable, and ignition coil with the middle and the dead cylinder stays in the middle. Does this mean my CDI is bad? I have the Seloc manual and plan to check the readings on the CDI once I get a multi-meter. Are there any other possibilities that could be causing the middle cylinder to be useless? thanks.

 

[rodbolt]

Re: 1986 Yamaha 40 not firing one cyl

hello<br /> you need to make a spark tester and check for the system being capeable of at least a 1/2 incc spark. the ign system on that egine is simple at straight fwd. test the pulser coils.#2 cyl is w/b-b. it should have 346 ohms+or- 20%.<br /> remember all the CDI box does is rectify and store the input fronm the stator. if you have no inpiuts from the charge coil and triggers you have no outputs. good inputs and no out puts means bad cdi but make sure you test the ign coils as well.<br /> good luck and keep posting

 

[Tobias]

Re: 1986 Yamaha 40 not firing one cyl

I believe you are right rodbolt, I tested the ohms on the three wires from the pulsar coils, and the one that corresponds to the middle cylinder has a lower reading than the other two. I have ordered a new stator assembly and begun pulling the flywheel. I will update the forum again with my progress.

 

[rodbolt]

Re: 1986 Yamaha 40 not firing one cyl

hello<br /> you really should look into buying a cd-77 peak reading multi-meter. resistance readings are fine but when your buying stators and CDI's then you should base your decisions on voltage outputs.and while the exact voltage output specs for your engine are not published its still a batteryless CDI ign, only so many ways to make, store and trigger these things. so you can test the known good and the unknown should be within 10%. a logical step by step elimination is the best course of action. I hope the stator works for yo.<br /> good luck and keep posting.<br /> PS the pulser coil is located in the timer or trigger assy not the stator. once you open the box no one will take the stator back.

 

[Tobias]

Re: 1986 Yamaha 40 not firing one cyl

Rodbolt, I believe the part that I purchased is called the "stator assembly", but includes the charge coil and pulsar coils. thanks for the help

 

[Tobias]

Re: 1986 Yamaha 40 not firing one cyl

Rodbolt, I believe the part that I purchased is called the "stator assembly", but includes the charge coil and pulsar coils. thanks for the help