1962 YD3 250 not firing PTO side

[willis78]

Hello,  I have a 1962 YD3 250 that will only fire on PTO side every once in a while.  Compression good, carb clean, point set, timing checked, has good spark with it running on mag side.  Seal behind clutch looks good.  I'm stumped.  Inner crank seal? Any ideas!?
Thanks!
 
Aaron

[Rex]

Don't see why a failing crankseal would allow it to fire "once in a while", so I'd go for electrical swap-overs...plug, capacitor, coil etc before thinking about engine strips.
Neoprene seals rarely seem to fail much these days, in my experience.

[willis78]

Thank for the reply Rex.  It is odd that it will only fire once in a while.  I have it running on mag side and I have put a new plug in PTO cap while its running and spark is great.  I hear every once in a while from some folk that spark can fail "under compression" Maybe that is whats happening here.  Can I just swap the plug wires from side to side? Do the coils fire the same?  They are a pain to get at.  Stamped frame and they are inside.  I have run new wires from the mag to each coil so I know they are not the issue. 

[iansoady]

I don't know the bike but if a 2 stroke twin would expect 180 degree crank therefore firing position will be different side to side so no can't just swap plug leads. You could swap all connections to the coils and then swap plug leads however.

[willis78]

Thanks Ian, 
I didn't think about that...I ran new wires to coils from the mag and left lots of slack for routing so i will swap them out there.   I will keep posted. 

[willis78]

Swapped wires feeding coils...and bang bang!! firing on PTO side!!

[willis78]

Just to clarify the fix to this post.  Yes...it is true spark can fail or weaken under compression.  This was the case here.  PTO side not firing-while running on mag side I left the plug in PTO side and just pulled the cap and put a new plug in the cap-great spark!  But under compression it would not fire.  As said in previous post swapped coils and instantly fired on PTO side.  Faulty coil.  Thanks again to everyone on the site.   

[willis78]

Update!! Had her on the road Sunday!!  So fun!!  Feels good to get this old gal back on the road instead of stuck in a barn where it would have died.  Got shifter box all in good working order, charging system, and lights!  Put a new front tire on, next is the rear.  Only thing im missing is the LH battery cover.  Any one know where i can find one???

[murdo]

Good work getting it on the road. Go enjoy.