Weak spark / missing fire?

[Ectobass]

Greetings:

88 VMX pretty much stock except for exhaust and K&N filter. Pulled the carbs out and went through them completely. While they were out, I used DeOxit and dielectric grease on all the connectors. Put everything back together, started it up and it ran at idle although one cylinder (left rear) was popping a bit. I pulled the plug and it was dark. Cleaned the plug and added dielectric grease to all the plugs. Then it would not idle at all; some cylinders seemed to be not firing; would only idle with throttle open.

Removed and cleaned all the plugs, boots, caps. Still the same thing. The cylinders all have spark, but it is white / orange, not the "fat blue" that would be expected.

Would like to get some ideas. Unfortunately I have to head out for the evening, but will be attacking this think first thing in the morning. I have not measured voltage yet. Other suggestions welcome!

Thank you!

 

[[email protected]]

When you cleaned the carbs did you remove the jet blocks from the float bowls and remove the jets from the jet blocks and clean them?

 

[maleko89]

What's the resistance of your plug wire, boots and secondary windings?

 

[bazwell]

Dielectric grease is a NON conductor. If it is on any of the terminals it will be the problem!

"Dielectric grease
Dielectric grease is a nonconductive grease. As such, it does not enhance the flow of electrical current. Thus electrical connectors should not be coated with dielectric grease prior to being mated. Dielectric grease is, however, often applied to electrical connectors, particularly those containing rubber gaskets, as a means of lubricating and sealing rubber portions of the connector.
The widest use of dielectric grease is in high-voltage connections associated with spark plugs. The grease is applied to the rubber boot of the plug wire. This helps the rubber boot slide onto the ceramic insulator of the plug. The grease also acts to seal the rubber boot, while at the same time preventing the rubber from becoming stuck to the ceramic. Generally spark plugs are located in areas of high temperature, and the grease is formulated to withstand the temperature range expected.
Another common use of dielectric grease is on the rubber mating surfaces or gaskets of multi-pin electrical connectors used in automotive and marine engines. The grease again acts as a lubricant and a sealant on the nonconductive mating surfaces of the connector. It is not recommended to be applied to the actual electrical conductive contacts of the connector because it could interfere with the electrical signals passing through the connector." taken from http://en.wikipedia.org/wiki/Silicone_grease#Dielectric_grease


If that's not it, then :ummm: I dunno!

 

[[email protected]]

I like koprshield myself. Its messy, and expensive but prevents corrosion and enhances conductivity. I first heard about it at work. It is specified to be used on all grounding, bonding, and AC electrical connections by many of our clients in the telcom industry.

http://www.epinions.com/review/KOPR...er_Surface_Treatment_epi/content_479258054276

 

[Ectobass]

Thank you for all of the quick responses! Well, as Johnny Carson used to say..."I did not know that."

For today's reading, we will quote from the book of Clymer, Chaper 2, Pg 52. "7. Make sure all electrical terminals within the connector are clean and free of corrosion. Clean them, if necessary, and pack the connectors with dielectric grease." Oops! :bang head:

I did clean the entire jet block on each of the carbs. The Seafoam I used with the gas before actually did a great job except for a few of the pilot jets and the "coasting enricher".

Thanks for the tip on the koprshield. Good stuff is never cheap. I will get the meter out in the morning and see what I can find. Ah yes, the price of an education! :biglaugh:

 

[bazwell]

I didn't know before I read your problem. :rofl_200::rofl_200::rofl_200:
You cleaned the carbs - doesn't affect spark. Not the problem.
You put grease on - 1 cyl misses.
Put more grease on - won't even idle.

Just like getting a fresh set of eyes to look at a problem, suddenly it's clear.

I also found out that dielectric insulators do not affect magnetic fields, which I think is their talent. Every time a spark fires down the lead it creates an electromagnetic field. If you quench the field, you also quench the spark. I think.
So that grease stops water, and doesn't quench the spark. :biglaugh: Now we know!

 

[bazwell]

Well, as Johnny Carson used to say..."I did not know that."

For today's reading, we will quote from the book of Clymer, Chaper 2, Pg 52.

Ha ha ha. :biglaugh:

 

[Ectobass]

Well I am happy to say I figured things out. I had two problems neither of which were electrical.

1) Acutely inflammed anus and strained sphincter due to impacted cranius causing excessive pressure on the optic nerve.

2) The inverted knurled dynamic laminar flow adjustment mechanism was not properly set for optimized operation.

Said differently, I had my head firmly up my butt and completely forgot that I had backed out the idle screw / knob all the way when I had the carbs on the bench.

After I put that back where it belonged and tweaked the air screws a bit it idles and runs like a champ. Oh my! 70 mph comes all too quickly. If it ran like this before I know for a fact my brother would not have sold it! Ha ha ha!

Thank you again for all of the comments and suggestions. Have a wonderful Thanksgiving!

 

[Rollie]

Doh ! Welcome to the forum . You may be entitled to one of our more popular awards................. :rofl_200:

 

[Ectobass]

I still don't understand why it would idle when I first started it up. If it wouldn't idle at all it would have been much easier to figure out.

There is not a lot of room left on my shelf for those awards! They tend to follow me.

 

[bazwell]

Well I am happy to say I figured things out. I had two problems neither of which were electrical.

1) Acutely inflammed anus and strained sphincter due to impacted cranius causing excessive pressure on the optic nerve.

2) The inverted knurled dynamic laminar flow adjustment mechanism was not properly set for optimized operation.

Said differently, I had my head firmly up my butt and completely forgot that I had backed out the idle screw / knob all the way when I had the carbs on the bench.

After I put that back where it belonged and tweaked the air screws a bit it idles and runs like a champ. Oh my! 70 mph comes all too quickly. If it ran like this before I know for a fact my brother would not have sold it! Ha ha ha!

Thank you again for all of the comments and suggestions. Have a wonderful Thanksgiving!

:rofl_200: Nice one dude! :biglaugh: