rScotty
Super Member
- Joined
- Apr 21, 2001
- Messages
- 8,258
- Location
- Rural mountains - Colorado
- Tractor
- Kubota M59, JD530, JD310SG. Restoring Yanmar YM165D
In the case of old - vintage - gasoline ignition parts it's not just throwing money at the problem. I don't like that approach either. But with vintage electrics we aren't really doing that. What we are doing is fixing problems that have become cumulative with age and were simply not anticipated back when the machines were built new.
For example, it was thought that since metallic conduction was forever, so was insulation. But not so.
The type of bakelite used for the ignition insulation on the rotor, distributor cap, and points bushing breaks down over time and allows both low and high voltage leaks. We know that now. It's a known problem due to age. Carbon tracks form conductive paths. On a dark night you may be able to see it happening.
Likewise, the "ignition suppression" spark plug wires and caps were designed to do their job by using conductive carbon fibers instead of copper. Those carbon fiber conductors aren't forever either. They do crack with time and vibration. Even the insulation around the carbon becomes "leaky".
The springs on the auto advance get weaker and bushings wear - so it advances too much at progressively lower and lower RPM ..causing knocking and eventually backfiring. If we ****** the distributor to compensate, it will backfire the other way.
Then there is the phenolic gear problem.... Some of the old Brit motors used a phenolic drive gear on the lower distributor shaft where it meets the cam. I don't know if yours did, but it is worth pulling your distributor out to check that the drive gear is not torn up and the push pin that holds it on is still tight. Doing so gives you a chance to dust off the old timing light not used in 30 years and get reacquainted with what used to be a necessary tune up tool.
I just found my own old timing light the other day in the bottom of a tool drawer I hadn't looked at in years. Make that decades....
rScotty
For example, it was thought that since metallic conduction was forever, so was insulation. But not so.
The type of bakelite used for the ignition insulation on the rotor, distributor cap, and points bushing breaks down over time and allows both low and high voltage leaks. We know that now. It's a known problem due to age. Carbon tracks form conductive paths. On a dark night you may be able to see it happening.
Likewise, the "ignition suppression" spark plug wires and caps were designed to do their job by using conductive carbon fibers instead of copper. Those carbon fiber conductors aren't forever either. They do crack with time and vibration. Even the insulation around the carbon becomes "leaky".
The springs on the auto advance get weaker and bushings wear - so it advances too much at progressively lower and lower RPM ..causing knocking and eventually backfiring. If we ****** the distributor to compensate, it will backfire the other way.
Then there is the phenolic gear problem.... Some of the old Brit motors used a phenolic drive gear on the lower distributor shaft where it meets the cam. I don't know if yours did, but it is worth pulling your distributor out to check that the drive gear is not torn up and the push pin that holds it on is still tight. Doing so gives you a chance to dust off the old timing light not used in 30 years and get reacquainted with what used to be a necessary tune up tool.
I just found my own old timing light the other day in the bottom of a tool drawer I hadn't looked at in years. Make that decades....
rScotty
