Yamaha 225 2 stroke starting and running problems

[Rodscott1]

Hi RodBolt, tried again at the weekend to get the 225 running,. This time I replaced the entire fuel line and a new hand pump, also removed the carbs and checked the reeds - all perfect. Engine still starts then stalls immediately, if i disconnect the yellow lead on the CDI it starts but only runs on the top two cylinders. If I crank the engine it sparks on all plugs. Any ideas? Thanks

[rodbolt17]

have you tested the pulser coils?
have you tested the low speed charge coil?
have you tested the TPS?
have you tested the crank position sensor?
they made that system with 3 pulser coils and two pulser coils.
which do you have?

[Rodscott1]

Hi, I replaced the entire fuel line, removed the carbs and checked the reeds, they are like new and no problem. Same problem, the engine starts then immediately stops. If I disconnect the yellow wire below the cdi unit, the engine starts but only runs on cylinder 1 & 4. Any further advice guys? Thanks.

[Rodscott1]

no I haven't tested them yet, ok I will do that this weekend, thanks for your help. But what does the yellow wire below the CDi unit do? Is it normal to run on only 2 cylinders? Is that the protection mode to get home??

[rodbolt17]

when you unplug the ECU yellow wire it places the system into bypass.
it should spark on 4 cyl if it is a two pulser system or all 6 if it is a 3 pulser.
timing will be fixed idle speed will increase and top speed cannot be reached.

[Rodscott1]

Hi Rodbolt, i checked the pulser coil, the ignition coils, the crank position sensor and the throttle position sensor, all resistances are ok as per the manual. How can i check the CDI?
Any other advice?

Thanks

[Rodscott1]

Hi Rodbolt, i checked the pulser coil, the ignition coils, the crank position sensor and the throttle position sensor, all resistances are ok as per the manual. How can i check the CDI?
Any other advice?