No spark Sears suburban 15 with B&S 15HP

[docrocky]

Tractor started and ran with occasional backfire. Then I decided to power wash because heavy dirt oil grime in front of engine and sides. No spark, afterwards plug and changed to new one etc. Have to remove entire grill and hood to get to the points and condenser in front of engine. Gasket in poor shape and the ring of the condenser exiting it wire cracked and fragmented. OK, obtained new points and condenser and installed with .020 gap. Fired right up. Then I ran it for a few hours cultivating weeds with row cultivator and on the last sweep, the engine dies. Gas ok. Oil ok. Now when I test with spark plug tester, no spark at all. So I went back to the points and condenser (having to remove all the front grill and hood) but find nothing amiss. I can not be sure that I am finding the widest gap before using the .020 . Not sure I am finding the TDC. The pin from the engine moves in and out freely but I can't seem to find the maximum throw so I can comfortably set the correct gap(it seems miniscule...less than a 1/16 throw). I am considering removing the head to see where the TDC of the piston is so that I can set the gap properly at the points or am I going in the wrong direction? I could go to the flywheel and check the ignition coil and magneto, but???? Any other suggestions???

 

[tomplum]

Maybe clean the breakers and reset them at .018". I think these old beasts did better firing a touch early myself. Removing the spark plug will help you find the high spot so that you aren't fighting the compression.

 

[docrocky]

Dear Tomplum: To begin with the breakers are brand new but I did clean them also. The spark plug was removed and the drive shaft was easy to turn. The problem that I can not quite get the answer to is that rotation of the shaft the small plunger coming out of the front of the engine to open the points has ssuch a small throw that I can not determine the "high spot". Because of this I decided to remove the head so that I could see where the pistons TDC was in relation to the points plunger. Am I glad I did this because I had to remove the flywheel cover etc and what I mess I ran into. Good thing I did because the area was packed with mouse junk as well as baked oil and dirt. The Ignition coil insulation wires were eaten and the magnet on the flywheel was covered by rust and packed dirt. I also found the hoses from the gas tank also were in very bad shape.

Now the dilemma: AS the piston moves to assumed TDC with both of the valves closed, the points plunger falls or moves inward about a 1/16 of an inch. This move would then appear to momentarily close the points. Now I am assuming that the points should be continuously closed or in contact maintaining the primary circuit and then only momentarily when the gap or points are opened that the secondary circuit fires and produced spark. I am really confused at this point because what I am seeing is opposite ...I need help and direction....Thank you

 

[tomplum]

The power for the spark builds in coil as the flywheel rotates. Once the coil receives the ground signal from the points, the spark is released. I don't know how far ahead TDC this is meant to fire. It could upward to .100 . If you would remove the wire that feeds the coil from the breaker set, an ohmmeter would tell you that the breakers are making contact.

 

[Ken]

Consider a electronic ignition I use a NOVA 2 eBay cost is around 13 bucks. no need for points or condenser cut the wire and attach wires provided to coil.
Just did this to a Sears Suburban. where the fiber pin going into the cam had been broken off. The engine runs with new live and easy to start with strong spark.
ken

 

[fried1765]

Consider a electronic ignition I use a NOVA 2 eBay cost is around 13 bucks. no need for points or condenser cut the wire and attach wires provided to coil.
Just did this to a Sears Suburban. where the fiber pin going into the cam had been broken off. The engine runs with new live and easy to start with strong spark.
ken

Nova 2 listed on E-Bay suggests that it is not for use on an electric start engine.
Is this true?
Why?

 

[Ken]

Nova 2 listed on E-Bay suggests that it is not for use on an electric start engine.
Is this true?
Why?

I have no idea the elec. starter/generator is driven by belt or newer engines it is a ring gear driven by starter.
maybe the newer type coils have the chip built it in so this is what is mentioned.
I have used this NOVA2 since was green plastic blob since mid '70's B/S Kohler and Sears engines also the Clinton engines. all single cylinder.
ken

 

[fried1765]

I have no idea the elec. starter/generator is driven by belt or newer engines it is a ring gear driven by starter.
maybe the newer type coils have the chip built it in so this is what is mentioned.
I have used this NOVA2 since was green plastic blob since mid '70's B/S Kohler and Sears engines also the Clinton engines. all single cylinder.
ken

Thanks!
That limitation of no use with an electric start machine baffles me.
I have a 15HP 1972 B&S on a 1972 Sears 42" riding mower, and I want to change it to electronic ignition.
It is belt drive starting, so I think I will just ignore that warning.