If you can, get a bore scope and look down the spark plug hole. I'm going to guess that the rings are messed up. Yes, it can still have good compression, but as soon as it has to produce power the rings don't do anything and you lose compression.

 

Thanks, I’ll get bore scope ordered. What exactly am I looking for? I wouldn’t be able to see the rings would I? Am I looking for cylinder scoring?

 

Any odd wear, vertical scoring/polished bore differences side to side and front to back.

 

Copy, my bore scope should come in the mail today. So hopefully I’ll get a chance to take a look tonight or tomorrow morning

 

All that fuel destroyed bearings. Compleat rebuild.

 

I am worried about that. What does a complete rebuild run?

 

Looking into the cylinder with a bore scope is not terrible idea but unless its seriously scored its going to be hard to tell the difference between normal wear and damage. If the fuel washed down the cylinder there should be massive scoring all around the cylinder and not just focused in a few smaller places. Does the engine crank over ok? If so then I wouldn't be too concerned about the bearings. Hopefully you don't have to go into the engine to that degree, kind of a bitch with the way the engine is designed. If you want to get a better idea of the condition of the engine get a leak down tester and check the health of the engine. If it passes I would focus on the carb. The carb float needle should keep the carb from flooding. If you had a flooded engine the float got stuck open and the overflow didn't operate properly either or it would have ended up on the floor also. You still might have an issue. An overfilled bowl will cause a rich condition. Rough idle when warm, stalling and weak feel. Best thing would be to get a good rebuild kit either OEM parts or Shindy and replace all the parts then put it back to stock settings. Don't mess with All Balls junk or Amazon cheap Chinese parts. I'm not sure how experienced you are but make sure to pay attention to the Pilot Screw, I didn't look it up but if its a fuel screw it's going to have a very small washer and o ring on the bottom of the screw which easily get lost when cleaning and forgotten if your not looking for them.

 

Thank you for the very thoughtful reply. I did buy a cheap Chinese carb kit, however, it was running quite well before the fuel oil condition. I have put all the OEM parts back in the carb with no performance changes. I will definitely have time to try the bore scope in the morning. But it sounds like leak down test is really the more helpful info. I need to get a leak down tester. It won’t be the first time I’ve needed one, so definitely just need to spend the money. Thanks again for the direction.

 

Just a note regarding the leak down test. These small engines often want to rotate when you put air pressure in the cylinder. Make sure you have a friend or a breaker bar in position to keep the engine from moving from TDC. Another thing, a trick to polishing up the float needle seat is to use a q-tip in a drill with brasso polish on it to polish up the seat for a good seal.

 

Had a chance to run the bore scope. I attached some photos. Not what I expected to see. All the cylinder marks seems to be sort of biased, rather than linear like I have seen before. I’d like to hear you all’s thoughts.

also, I noticed that the aftermarket seat in still in the carb, so I am going to pull that out and swap the old one back in and check the float. Meanwhile, unless you all tell me the photos are indicative of a diagnosis, then I’ll run out and get a leak down test kit

 

Hard tell but that kind of looks like the crosshatching which is a good thing that it's still there.

 

So, I have never done a leak down test before, but I bought some otc gauges, moved the piston to TDC on compression stroke. The left gauge showed about 98 psi and the right showed 96. Note: I did try this same excercise on the opposite TDC and it held almost no pressure. So is my assessment that the rings and valves are doing excellent correct?

any suggestions on where to go from here?

 

So, I have never done a leak down test before, but I bought some otc gauges, moved the piston to TDC on compression stroke. The left gauge showed about 98 psi and the right showed 96. Note: I did try this same excercise on the opposite TDC and it held almost no pressure. So is my assessment that the rings and valves are doing excellent correct?

any suggestions on where to go from here?

Looking at the scope pics (nice cross hatching) and the compression numbers, I dont think your problems are from the top end. I think rfoster is correct in assessing the problem may be with the carb. Hopefully terrymoore is wrong and you wont need a motor rebuild.

 

….the test was done on a cold engine if that makes any difference

 

Ok, I’m running out of ideas. Did compression and leak down tests that appear to show no issues in top end. I pulled the carb again, cleaned it will extreme care and reinstalled making sure the choke was in the right spot and all connections are sealed tight. I checked the carb float. I tried a couple different needle positions (currently left in #2 spot). I know the carb is getting fuel. I put in a fresh plug (2nd fresh plug I’ve put in) that seemed to help a little, but I can tell it’s just fouling out again.

I just can’t think of what I’m missing. But it idles just fine, but the second I give it any throttle, it bogs. what am I missing? I assume it

 

Looks pretty good inside there. Most likely not a problem.

So back to the carb, 1991 is when they switched to vacuum operated slide. Not sure about aftermarket carbs.

Two types of carbs were used: CV and VM. VM carbs the throttle cable connects directly to a round slide. CV carb the throttle cable connects to a butterfly valve.

CV = Constant Velocity. The flat slide is operated by vacuum. The spring it has can wear out and the slide will open to quick. Or the slide rubs against its guides and doesn't open correctly. Both cases can cause the motor to idle fine and bog out when throttle applied.

With airbox off or at least where you can look through and see inside the carb, can you see the slide moving when you rev it up?

 

I’ll have to give it a look in the morning. I definitely have the CV style you describe. What is the correct clip position for the needle

also, I got to thinking….does that spring hold the needle down also. I pulled the slide out and held the spring in it, as it would have pressure were it installed. The needle just sorta floats in there, as in, I can push the needle into the slide with no spring resistance. Is that correct, or could I have lost a washer or something?

 

In looking at the parts diagram, it shows a piece above and below the pin and clip. I am pretty sure I have part 7 (below) but am missing part 5 the part that it shows above the clip. It seems it would hold that pin down in place?