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Earthquake digger, M# 9000 with a Tecumseh AV520.

If a two cycle comes in the shop with 100lbs or less, I don't normally mess with them. But this one is bigger. Looks almost like a 4cycle. It takes 24:1 mix. I'm only getting about 87lbs of compression. From what little I can see down in the spark plug hole, I don't see any scarring.
So my question is, is it worth the time and money repairing it with only 87lbs? Or can these still perform good with that much or a little less?

Put a teaspoon of oil into the cylinder and retest compression. If the compression increases the rings are either stuck or worn. At that point you can make a better decision. If no increase in compression I would probably file 13 it.

If you spray a shot of carb cleaner or starting fluid in the carb and pull the rope does it dire and run for a few seconds?

Hammermechanicman said:

If you spray a shot of carb cleaner or starting fluid in the carb and pull the rope does it dire and run for a few seconds?

Click to expand...

No. It does have spark. But it doesn't have the right spark plug either. I'm about to run get the right one and recheck that. I tried it last night, with the plug that came in with it. And didn't get anything. But from what the customer told me, that's the same plug he's been using. An AC R43XLS. From what I've found, it's supposed to be a RJ17LM. Or an NGK BMR2A (or 6A crosses to it too)

tecumseh-33636 is a RJ8C ,
www.partstree.com/tecumseh/33636/RJ8C

Alternatives : https://www.sparkplug-crossreference.com/convert/CHAMP_PN/RJ8C

Rivets said:

Put a teaspoon of oil into the cylinder and retest compression. If the compression increases the rings are either stuck or worn. At that point you can make a better decision. If no increase in compression I would probably file 13 it.

Click to expand...

I put a little (50:1) into the plug hole and retested. I got right on the 100 to 101 mark. Definitely a game changer. So I'm going with what you said, worn or stuck ring. IIRC, once an engine heats up, it'll lose some compression. Bringing ti down to less than 100.

Once it warms up metal expands, which will raise the compression.

Scrubcadet10 said:

tecumseh-33636 is a RJ8C ,
www.partstree.com/tecumseh/33636/RJ8C

Alternatives : https://www.sparkplug-crossreference.com/convert/CHAMP_PN/RJ8C

Click to expand...

Jacks gives a different number. I suppose they both cross.

UPDATE: Upon further inspection, it doesn't seem that either mine nor yours are the same.
Check out the Partstree diagram. listed on the diagram page, #135 as a Champion RJ17LM. When you click on #135 in the parts list, it changes to the RJ8C.
When you got to the cross reference page, the RJ8C doesn't even cross reference to the RJ17LM.
Not sure what Partstree is doing. Listing two different plugs, that according to the cross reference website, don't cross.

Rivets said:

Once it warms up metal expands, which will raise the compression.

Click to expand...

Well, that's good news. Thanks man.

Scrubcadet10 said:

tecumseh-33636 is a RJ8C ,
www.partstree.com/tecumseh/33636/RJ8C

Alternatives : https://www.sparkplug-crossreference.com/convert/CHAMP_PN/RJ8C

Click to expand...

Parts store says this BR4LM crossed over. Put it in, primed it and after about 15 pulls she hit and ran long enough to run the fuel I just primed.
Primed the hell out of it, til it was leaking out the intake. Looks like there's some water in it.
Customer says to proceed with the carb. work.

Thanks for the info guys. I almost let this get by me.

Ordered a new carb for it (amazon ugh), with new plug it fires and runs pretty good. Just have a couple of questions.

This model doesn't come with an air filter. Just a baffle turned open side down. Would it be OK to turn the open side up and put a piece of pre filter type foam down in it? Cut just big enough to fit a little snug? And then adjust carb accordingly?

Also, I ran into something like this one a trimmer once, where the carb was adjusted good. But the head kept spinning. Even with the idle screw out to the point it's irrelevant, the digger still turns. I'm thinking this is a stuck clutch? Or do they all just do that?
I remember when me and my dad first got into the fence business, we'd rent a digger like this, and the digger part always turned. At idle, it would turn slow. But would still turn. Even with pressure on it.

P.S. I also got a rebuild kit coming, just incase this carb didn't work out.

UPDATE: There was a spring broken on the clutch.