VH4D intermittent ignition spark

[AutoScott]

I have a 1975 Melroe Bobcat M700 with a VH4D. I did a complete tune-up to it including: plugs (0.030 gap), wires, cap, rotor, coil, points (0.020) and condensor. I also adjusted valve lash to specs. Rebuilt the carb, replaced head gaskets, and cleaned carbon off the pistons and valves. Got it running and checked the timing marks=dead on. It was running great for about 45 mins then it started choking and back firing out the exhaust. I drained the float bowl and restarted. No change. I nursed it back inside, pulled the plugs (dry and black soot-running too rich) checked compression. Still 75psi for all 4. Installled plugs and ran engine and checked timimg, this time I noticed the strobe would go out intermittently. More so at working RPM than idle. Replace coil w another new one, no change. The only thing I havent changed is the Distributor itself. I checked suppy voltage and grounds. All good. Any Ideas?

 

[jerry]

Try a different condenser, has to be something like that if it runs good intermittently also. Condenser can cause odd problems.

 

[6brnorma]

Try a different condenser, has to be something like that if it runs good intermittently also. Condenser can cause odd problems.

On a side note…..doesn't have anything to do with the spark but 75lbs is way low. 120 is good, 100 is fair, 80 is low. Good thing is they are all 75 but still very low. I got sick and tired of this type of problem many years ago and changed all of my machines to electronic ignitions……never looked back.

 

[AutoScott]

On a side note…..doesn't have anything to do with the spark but 75lbs is way low. 120 is good, 100 is fair, 80 is low. Good thing is they are all 75 but still very low. I got sick and tired of this type of problem many years ago and changed all of my machines to electronic ignitions……never looked back.

I know the compression readings are low. Its a 40 yr old machine. Im planning on doing a rebuild in the near future. Im just wanting to use it for a few seasons first. Where did you get your electronic ignition upgrades from? Bobcat says they dont make one but Im sure there is something out there.

 

[AutoScott]

I know the compression readings are low. Its a 40 yr old machine. Im planning on doing a rebuild in the near future. Im just wanting to use it for a few seasons first. Where did you get your electronic ignition upgrades from? Bobcat says they dont make one but Im sure there is something out there.

Well I finally figured it out. The brand new condenser I bought from the Bobcat dealer was bad. I just happened to still have the old one so I put it on just for the heck of it. Runs great. I still want to upgrade to electronic ignition if anyone knows where I can get it.

 

[flyerdan]

Well I finally figured it out. The brand new condenser I bought from the Bobcat dealer was bad. I just happened to still have the old one so I put it on just for the heck of it. Runs great. I still want to upgrade to electronic ignition if anyone knows where I can get it.

I tried several times to make it clickable like a real forum would allow but wasn't able. Copy and paste this, which hopefully won't be injected with junk code since there is no formatting whatsovever here. Afermarket electronic conversion kits :
http://www.hot-spark.com/1-3AUT4U1.htm

 

[SkidRoe]

I tried several times to make it clickable like a real forum would allow but wasn't able. Copy and paste this, which hopefully won't be injected with junk code since there is no formatting whatsovever here. Afermarket electronic conversion kits :
http://www.hot-spark.com/1-3AUT4U1.htm

Did a quick edit, your link is now hot.
Cheers - SR

 

[AutoScott]

Did a quick edit, your link is now hot.
Cheers - SR

Thanks for the info guys. I have to say, this forum is full of good info! I ran the old girl for over 6 hours full bore on Saturday pushing HUGE piles of packed snow. Ran great, no problems. Really surprised me just how strong this 40 year old machine is! Thanks again!