weak spark on lower cylinder, need coil?

[fishermanms]

I finally purchased a spark tester. We talking about a 74' johnson 6hp. The top cylinder wire produces a strong spark at 1/4" on first weak pull. The lower cylinder will produce no spark on first weak pull and will give a weak to moderate spark after a two or three strong pulls. If the wires are ok, does it sound like a bad coil? Two coils on this motor. I'm already in the process of pulling the flywheel... Thanks for some more of that good advice..Fishermanms

 

[iwombat]

Re: weak spark on lower cylinder, need coil?

Could be bad coil. Have they ever been replaced? Might want to pull the flywheel and visually inspect. Either way you'll want to pull the flywheel and reset/inspect points.

 

[Xcusme]

Re: weak spark on lower cylinder, need coil?

Go ahead and pull the flywheel and have a look at the coils. Replace coils if cracked. Parts are readily available and cheap. If the coils look OK, you might want to check the point gaps for .020 and see if the spark improves. Solid core wires seldom go bad except for worn cracked insulation etc. Replacement plug wire is easy to replace, but be sure it's solid core, not resistance type automotive wire. If all of the parts are original (coils, points, condensers, plug wires), I'd personally replace everything and be set for another 30+ years.

 

[fishermanms]

Re: weak spark on lower cylinder, need coil?

As always thank yall for all the help. I will order two coils this morning...just wanted to check first and see if there is any other accessories i need to order for the coil install like gaskits, seals, etc??? Thank yall....Fishermanms

 

[Chinewalker]

Re: weak spark on lower cylinder, need coil?

By 1974 the coils had gotten much better and rarely crack. My bet is that you simply need to clean and gap the points. If they are heavily pitted, replace the points. Gap them at .020 with the cam rider aligned with the crankshaft keyway...
- Scott

 

[wbeaton]

Re: weak spark on lower cylinder, need coil?

I'm with chinewalker. Clean and gap the points and retest before you pull the flywheel. Do a good job of cleaning and use a little carb cleaner or something on the contacts. Also check for corrosion in the spark boot and at the coil if you still don't get good spark.

 

[Chris1956]

Re: weak spark on lower cylinder, need coil?

Does that motor have condersors? If so, they influence the strength of the spark. The one for the bottom coil could be bad or partially bad.

 

[fishermanms]

Re: weak spark on lower cylinder, need coil?

I have removed the flywheel with a harmonic balancer removal tool. No sweat, and as suggested in another thread, used #8 grade 1/4" bolts. Some good stout arm torque turning the bolt down and the other arm and hand with a mule glove locked to the arm of the tool..it popped right off.
Careful examination with a bright light and a magnifying glass for these old eyes revealed two hair line cracks running from the inside of the top of one coil across and down the side. The other coil has two hair line cracks starting half way down the coil on one side and then intersect toward the bottom and then go seperate ways..... One plug wire with the best spark has a small chunk, about 1/16" long and about 1/32 wide, of insulation missing up close to the bottom of the flywheel. The points do not look pitted or worn but one set of points at the high side of the cam is a tight .020 and the other is .016. The area under the flywheel is very clean and everything there is very clean. There is a little grease at the bottom of the shaft where it disappears into the motor. ... I have points and condenser and I guess I need to order both coils??? and repalce that wire. .... Thanks, Fishermanms

 

[fishermanms]

Re: weak spark on lower cylinder, need coil?

I have removed the flywheel with a harmonic balancer removal tool. No sweat, and as suggested in another thread, used #8 grade 1/4" bolts. Some good stout arm torque turning the bolt down and the other arm and hand with a mule glove locked to the arm of the tool..it popped right off.
Careful examination with a bright light and a magnifying glass for these old eyes revealed two hair line cracks running from the inside of the top of one coil across and down the side. The other coil has two hair line cracks starting half way down the coil on one side and then intersect toward the bottom and then go seperate ways..... One plug wire with the best spark has a small chunk, about 1/16" long and about 1/32 wide, of insulation missing up close to the bottom of the flywheel. The points do not look pitted or worn but one set of points at the high side of the cam is a tight .020 and the other is .016. The area under the flywheel is very clean and everything there is very clean. There is a little grease at the bottom of the shaft where it disappears into the motor. ... I have points and condenser and I guess I need to order both coils??? and replace that wire. .... Thanks, Fishermanms

 

[Xcusme]

Re: weak spark on lower cylinder, need coil?

Yup, order both coils, and re-gap points. Don't use any lubrication on the crankshaft when you replace the flywheel, it's a dry fit. Report back on your progress.