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No compression after overheating

#1

X

xxboulavardxx

So for starters I own a craftsman push mower with a Briggs 190cc engine and never had problems with it for 10 years. Never went low on oil but I probably could’ve been better about changing the air filter and oil. Recently noticed it running sluggish and low power so I decided to switch the carb out. I think I made two mistakes when I did this: 1) I added a gasket (between the carb and intake manifold) that came in the kit, the manual doesn’t show one 2) the carb I put in fit right but had a different valve shape for the air intake. After I put the new one in, it started right up but was surging. Had an excessive amount of power too, was shaking quite a bit from it. I believe something with the carb caused it to run too lean or rich. I mowed for about 5-10 minutes until it started overheating. White smoke came from the exhaust and then it quit. Won’t start up and there’s no compression. I’ve checked the cylinder, gaskets, valves, flywheel, crankshaft, and haven’t seen much that’s broken or damaged. I replaced the valve gasket and the intake manifold is going to be replaced when it gets here (randomly snapped when I was putting it back together). I’m wondering if the problem is deeper and if I’m at a loss with this mower


#2

B

Born2Mow

Remove the air filter and check your engine's compression. You could have dropped a valve seat.

When was the last time you cleaned the clippings from inside the engine cowling ??


#3

X

xxboulavardxx

Born2Mow said:
Remove the air filter and check your engine's compression. You could have dropped a valve seat.

When was the last time you cleaned the clippings from inside the engine cowling ??
Click to expand...

Still no compression. Both valves appear to seat properly. I didn’t see any clippings as I was taking it apart. I wish I could send a picture but the file is too large


#4

Scrubcadet10

Scrubcadet10

xxboulavardxx said:
Still no compression. Both valves appear to seat properly. I didn’t see any clippings as I was taking it apart. I wish I could send a picture but the file is too large
Click to expand...
upload your image to a Image host and then paste the link here on the forum

Postimages — free image hosting / image upload

Provides free image upload and hosting integration for forums. Free picture hosting and photo sharing for websites and blogs.
postimages.org postimages.org


#5

X

xxboulavardxx

Scrubcadet10 said:
upload your image to a Image host and then paste the link here on the forum

Postimages — free image hosting / image upload

Provides free image upload and hosting integration for forums. Free picture hosting and photo sharing for websites and blogs.
postimages.org postimages.org
Click to expand...
Thanks man, here are the images https://postimg.cc/gallery/7DgtmKf


#6

X

xxboulavardxx

I recently put everything back together and noticed that there was suction in the spark plug hole when I put my thumb over it which leads me to believe that there might actually be compression. Maybe my compression gauge is faulty. I’m tempted to cave and see if a mechanic can look at it. I’ve checked everything to my knowledge


#7

7394

7394

xxboulavardxx said:
noticed that there was suction in the spark plug hole when I put my thumb over it which leads me to believe that there might actually be compression
Click to expand...

Should also try & blow yer thumb off the hole on comp stroke..


#8

O

Ocean909

xxboulavardxx said:
I recently put everything back together and noticed that there was suction in the spark plug hole when I put my thumb over it which leads me to believe that there might actually be compression. Maybe my compression gauge is faulty. I’m tempted to cave and see if a mechanic can look at it. I’ve checked everything to my knowledge
Click to expand...
Try dribbling a little gas or a quick shot of carb cleaner in the spark plug hole. If it runs and dies, you know you have compression. Rules out a few other things as well.


#9

M

MParr

xxboulavardxx said:
So for starters I own a craftsman push mower with a Briggs 190cc engine and never had problems with it for 10 years. Never went low on oil but I probably could’ve been better about changing the air filter and oil. Recently noticed it running sluggish and low power so I decided to switch the carb out. I think I made two mistakes when I did this: 1) I added a gasket (between the carb and intake manifold) that came in the kit, the manual doesn’t show one 2) the carb I put in fit right but had a different valve shape for the air intake. After I put the new one in, it started right up but was surging. Had an excessive amount of power too, was shaking quite a bit from it. I believe something with the carb caused it to run too lean or rich. I mowed for about 5-10 minutes until it started overheating. White smoke came from the exhaust and then it quit. Won’t start up and there’s no compression. I’ve checked the cylinder, gaskets, valves, flywheel, crankshaft, and haven’t seen much that’s broken or damaged. I replaced the valve gasket and the intake manifold is going to be replaced when it gets here (randomly snapped when I was putting it back together). I’m wondering if the problem is deeper and if I’m at a loss with this mower
Click to expand...
Verify the problem before throwing parts at it.


#10

StarTech

StarTech

Well if the piston is at TDC then you have a mechanical timing problem. Now without the model and type I don't if this had the plastic camshaft or not. IF it the one I suspect then the cam lobe section has slipped on the camshaft. Now it does depends which TDC you are on too. Normally the exhaust only opens from BDC to TDC on the exhaust stroke. It also opens slight and close right before TDC compression stroke as most of these engine do have automatic compression release to slightly lower cranking compression.

For the compression gauge you do need one for small engines as compression gauges for larger engines are not accurate at low volumes.


#11

X

xxboulavardxx

StarTech said:
Well if the piston is at TDC then you have a mechanical timing problem. Now without the model and type I don't if this had the plastic camshaft or not. IF it the one I suspect then the cam lobe section has slipped on the camshaft. Now it does depends which TDC you are on too. Normally the exhaust only opens from BDC to TDC on the exhaust stroke. It also opens slight and close right before TDC compression stroke as most of these engine do have automatic compression release to slightly lower cranking compression.

For the compression gauge you do need one for small engines as compression gauges for larger engines are not accurate at low volumes.
Click to expand...
Thanks for the pointers, a lot of good info. The compression gauge I have ranges from 0-300
psi. The engine model number is 128T02. I didn’t take a look at the camshaft but I looked up the original part (691449) and I think it’s metal. This is the first time I’ve taken it apart so I’m learning as I go


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