Yamaha v4 only firing on two cylinders

S

senza170

Cadet
Joined
May 25, 2009
Messages
10
Hi everyone,

I have just rebuilt my 1986 140A, started it for the first time and it runs, Idles erratically and seems to be firing only on #3 and #4. When i pull the leads from #1 and #2 there's no change. When I pull the lead from #3 or #4 the engine dies and you can hear the spark being generated within the cap. So it seems there's no spark being generated for #1 or #2, which is what I put to you guys out there...HELP, any ideas/common problems?

I've swapped coils around and tested with a meter...all seems ok and swapping coils made no difference. It seems like a bad connection somewhere or dodgy earth but I cant find it!!

Thanks for any help here people....:confused:
 
R

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Yamaha v4 only firing on two cylinders

use a multimeter set on the ac scale,compare the pulser coil,stator inputs and the ign coil primary voltages.
then fix the fuel system.
 
S

senza170

Cadet
Joined
May 25, 2009
Messages
10
Re: Yamaha v4 only firing on two cylinders

Thanks rodbolt,

Checked those voltages, all good. Then as a safety measure i made up a earth strap between all earth leads on the coils and straight to the main ground on the start motor. This gave me 3 cylinders. That proved the grounding. So then I checked continuity on the exciter wire on the final coil pack from the coil to the C.D.I box and found no connection, replaced the bullet connector at the coil end and success, all 4 cylinders firing, but idling roughly.

Carbs off, darn good clean, carbs on, purring like a v4 2-stroke kitten.

Thanks for pointing me in the right direction Rodbolt :D
 
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