Martin 20 won’t run

[jimbrizzolara]

I picked up a 1949 Martin 20 at Tomahawk and went through it prior to testing in a tank. The motor has good spark, 94 lbs. compression, and a clean fuel system. It won’t even "pop" when I try to start it. I removed the float bowl drain plug and gas poured out of it, so the carb is getting gas. The float and inlet valve are functioning properly. What bothers me is that gas-oil mix sprayed directly into the carb throat still does nothing. I removed the poppet valve and it looks perfect, as does the valve seat. Is there something I’m missing that’s peculiar to the poppet valve system? Also, how are these motors synchronized? There’s a rod and a spring with two adjustable stops on the left side of the engine block. This isn’t my first Martin, but this one has me stumped.

[Anonymous]

What spark plug and gap are you using?

[Tom]

The WICO condensers are notorious for doing this. Difficult, but not impossible to find a replacement.

Tom

[jerry-ahrens]

I’ve ran into a lot of Wico condensors that were weak. Does that engine have O-rings on the valve skirts? I have a Martin 45 that had those O-rings, that were hard and dried out. They would leak crankcase pressure very badly when cranking the motor. I got replacements from Russ Larson, and that fixed the problem. That motor wouldn’t even make a ”pop” when trying to start it. Just an idea for you to consider…

[jimbrizzolara]

I’m using a J6-C plug with a .030 gap. It looked to me that there was not an O-ring on the valve, just a metal skirt, and the skirt and valve seat both look great. Does that mean that some Martins didn’t use O-rings on the valves? As far as the condensers, I’ve been checking the spark by putting the plug in the boot and connecting a ground wire to the plug and the motor. I thought that I should check spark with a checker I have that shows the spark while under compression, simulating cylinder compression. I’m thinking you guys are on the right track about checking the condenser. I need to order an impeller from Russ anyway. Maybe I can temporarily use an OMC condenser to try things out. Thank you for the help, and I will let you know how it turns out. I was planning on entering this motor in an upcoming "how slow can you go" contest.

[mercuryman]

Gap plugs to .010 and see what happens.

[jimbrizzolara]

If I gapped the plug to .010 and the motor fired, what would that mean?

[mercuryman]

Weak spark. Have you cleaned the points and checked for 1 ohm or less resistance across the points. Do you have the Outboarder Club Magazine it has a story on troubleshooting ignition systems. A good spark will jump a 3/16 " gap or more in free air, a weak spark will jump .030 " gap in free air but won’t fire under pressure.

[mercuryman]

I have a Martin 40 that ran bad and hard to start. I got it out after your post and today it won’t start and has real good spark. I removed the valves and pulled off a O ring it was hard. When to my O ring box and found a fit. Put it back together and now it runs super good. So O rings can look good but will leak when hard.

[The Boat House]

• This reply was modified 5 years, 5 months ago by The Boat House.
• This reply was modified 3 years, 2 months ago by The Boat House.

[Author]

Posts