HM100 woes

[Scrubcadet10]

working on this 10 horse Tecumish....
Sat for years without starting. got it running. rebuilt carb. (needle and seat), float adjusted properly.
it runs good but has a pretty bad miss about every one to two seconds, plugs aren't fouling, and don't look lean, the burn looks good. The problem doesn't go away if i add choke.
verified good and constant fuel flow to carb( i've tried the original rebuilt carb, and put a known good HM100 Aftermarket carb on it, problem persisted), air filter is new.
Its a little finicky on the start too.
I have constant blue spark in my glow tester and the tester with 1/4" gap. Fuel is my non ethanol. fresh. i've tried 3 different plugs, Champion and NGK. Flywheel key is not sheared in the slightest.
I think my next step will be to check the valve clearance. I'm unsure of the hours on this unit.

 

[Scrubcadet10]

Pulled the breather cover off, checked the valve clearance.
The specs I found online were .008 Intake and .012 exhaust
I found the intake exactly at .008, and I couldn't even fit the .012 into the exhaust, nor the .008.... or a .003" there is 0 zero clearance exhaust side. And yes I made sure I wasn't on the ACR bump.

 

[Scrubcadet10]

Exhaust valve spun super easy in the head and appeared slightly open even, possibly. in the closed position. ground the valve, achieved a tight .012" clearance and stopped at that, lapped the intake and exhaust valve, rechecked clearances. all good.
just waiting on a head gasket.

 

[Scrubcadet10]

Well, the dern thing still has a bad miss. valves are right on spec, flywheel key is good, it has fresh fuel, and is getting plenty of fuel to the carburetor.... does the same with the rebuilt and known good aftermarket carb i pulled off one of my tecumseh 100 engines. 3 different spark plugs, coil regapped... good blue consistent spark.
hmmmm

 

[Hammermechanicman]

If the valve guides are worn that can cause a random miss.

 

[Scrubcadet10]

Valves didn't seem too sloppy in the guides.

Should I hit it with a bigger hammer?

 

[Rivets]

What is the spec number?

 

[Born2Mow]

Check the type of plug. Tecumseh has been out of business for more than a decade. Back then, all mowers ran a non-resistor type sparkplug. These days... due to advances in ignition design... about the only thing you can buy is plugs with built-in resistors. And that will trip you up, plus make it hard to start.

NGK puts an "R" in their plug number when there is a resistor present. Example: BP7ES versus BPR7ES. Not sure about the others.

 

[Hammermechanicman]

Valves didn't seem too sloppy in the guides.

Should I hit it with a bigger hammer?

Works for me.

 

[Scrubcadet10]

What is the spec number?

159402S

Check the type of plug. Tecumseh has been out of business for more than a decade. Back then, all mowers ran a non-resistor type sparkplug. These days... due to advances in ignition design... about the only thing you can buy is plugs with built-in resistors. And that will trip you up, plus make it hard to start.

NGK puts an "R" in their plug number when there is a resistor present. Example: BP7ES versus BPR7ES. Not sure about the others.

The plug in it was a J17LM, but all i had was a J19LM.