Old B&S engine won't start

[judge2b]

:smile: That being a up draft carb. Check for warping between the the two carb halves. Also check for air leaks around the mounting gaskets. Did you install the gasket between the two carb halves correctly? Instead of a comp test, I would do a leak down test.

I don't think there's any warping as I made sure the two halves fit tightly all the way around. Although I did notice that it seemed some fuel may have been wicking out between the two halves via the gasket. Is that possible? Or does that mean it's definitely warped?

Air leaks around the mounting gaskets of what? The carb?

Yes I installed the gasket between the two carb halves correctly.

 

[judge2b]

Wet compression test (twice) holds solidly at 55 psi. Slightly higher than the dry test (51 psi).

 

[Rivets]

Those readings are to low for me, but it does tell me we don't have a ring problem. At this point I'm thinking valves. If you had a cylinder leakdown tester, that would be the next step, but without one you are going to have to remove the head and visually inspect the valve movement.

 

[judge2b]

Those readings are to low for me, but it does tell me we don't have a ring problem. At this point I'm thinking valves. If you had a cylinder leakdown tester, that would be the next step, but without one you are going to have to remove the head and visually inspect the valve movement.

Sounds like a plan. What exactly I am I looking for? Just proper seals on the valves when closed?

 

[Buckshot 1]

I don't think there's any warping as I made sure the two halves fit tightly all the way around. Although I did notice that it seemed some fuel may have been wicking out between the two halves via the gasket. Is that possible? Or does that mean it's definitely warped?

Air leaks around the mounting gaskets of what? The carb?

Yes I installed the gasket between the two carb halves correctly.

:smile: Everyone of those style carbs that I have worked on, there was always warpage in the top half. Therefore on the wicking it could be warped or you need to retighten the screws. Mounting gaskets: carb to intake, intake to block., either one could not be sealing. There are two carb kits for that carb, 291763 pre 81 code date NLA and 394693 after code date 81. Which leads me to think, you may have purchased the wrong carb kit.

 

[judge2b]

:smile: Everyone of those style carbs that I have worked on, there was always warpage in the top half. Therefore on the wicking it could be warped or you need to retighten the screws. Mounting gaskets: carb to intake, intake to block., either one could not be sealing. There are two carb kits for that carb, 291763 pre 81 code date NLA and 394693 after code date 81. Which leads me to think, you may have purchased the wrong carb kit.

I got a carb kit that contained both sets I believe, although I'd have to check.

 

[judge2b]

I got a carb kit that contained both sets I believe, although I'd have to check.

Yep, it contained both, I just used the parts and gaskets that matched the ones I took off.

 

[Rivets]

What you are looking for is: are both the valves opening at the correct time. At the valves fulling closing, we should not be able to twist or move them at all when the piston is half way up on the compression stroke. Are the faces of the valves burnt or have a carbon build up. All this could cause a lose of compression, as well as vacuum on the intake stroke.

 

[judge2b]

What you are looking for is: are both the valves opening at the correct time. At the valves fulling closing, we should not be able to twist or move them at all when the piston is half way up on the compression stroke. Are the faces of the valves burnt or have a carbon build up. All this could cause a lose of compression, as well as vacuum on the intake stroke.

Ok. I opened up the head. The head gasket had absolutely no coating on it so it's possible I was getting low compression by that. There was also a LOT of carbon buildup on the piston and on the intake valve (which would explain why the fuel/air mix isn't getting into the chamber). I'm going to get one of those spring compression tools and take the intake valve out, completely clean the carbon off and reinstall it. I'm also going to put a new head gasket on. The piston appears perfectly aligned parallel to the valve opening and not worn where it seals to the opening, I just need to clean off all the carbon around the valve opening so that it closes all the way.

When the piston is halfway up the compression stroke I cannot move or rotate the valves at all.

Can I get away with not replacing the intake valve since it appears to be the carbon buildup that's the problem, or is it highly likely that the valve is damaged and I just can't see it?

Also, apparently on this model there is no intake valve seal, or it's built in somehow otherwise I would have just replaced that to be sure.

 

[Rivets]

If you pull the valve you are going to check and possibly grind it to get the proper valve clearance. If you replace the valve you will have to do this for sure. Do you know how to do this, if not don't remove the valves, just clean them on the engine and replace the head gasket. Make sure that you don't get any of that carbon between the piston and cylinder walls or you will score the cylinder walls. Don't even think about seat work.