Briggs & Stratton OHV Plastic Engine No Compression

[Montecore]

Trying to figure out why this engine has no compression.....I have spark, fuel and no compression. I have checked the valve lash and everything seems to be correct. So I removed the head and attached pictures to see what the experts out there think? I have before and after carbon removed. Please advise would love to hear your thoughts? I tried attaching photos but they were too large and would not allow me to attach. So I will provide a google photo link to the 8 photos.

Engine Photos

Thank you for your time helping trying to figure this out.

 

[ILENGINE]

From the looks of the intake valve and cylinder walls, there is a high amount of dirt ingestion causing excessive wear The intake valve covered in burnt oil suggest that it is pulling in oil from the breather and burning it. The intake valve seat and valve face are showing wear which could result in the valve not seating properly and therefore not sealing against the seat. The exhaust valve looks to be sitting too high in the seat with uneven valve face to seat contact area, which could indicate either the exhaust valve is bent or the seat isn't sitting flush with the valve.

 

[Tiger Small Engine]

From the looks of the intake valve and cylinder walls, there is a high amount of dirt ingestion causing excessive wear The intake valve covered in burnt oil suggest that it is pulling in oil from the breather and burning it. The intake valve seat and valve face are showing wear which could result in the valve not seating properly and therefore not sealing against the seat. The exhaust valve looks to be sitting too high in the seat with uneven valve face to seat contact area, which could indicate either the exhaust valve is bent or the seat isn't sitting flush with the valve.

Cylinder is scored, valves need to be ground or at least lapped, probably need to replace rings. May be time to chuck it and get another engine.

 

[Auto Doc's]

Not sure why you would call this a "plastic engine". Is that because of all the dress up plastics around the engine?

Sorry, this looks like it would cost more to save than a new one likely cost. This all looks like damage from dust ingestion and overheating, especially the one valve that is indigo blue on the stem near the top.

Are you a hobby DIY repair type?

If so, Parts tree should have everything you need for this engine.

You need to look at the side of the engine for the digital etched digits to figure out the model and type information. The chassis label information usually does not apply to the engine parts.

 

[Montecore]

From the looks of the intake valve and cylinder walls, there is a high amount of dirt ingestion causing excessive wear The intake valve covered in burnt oil suggest that it is pulling in oil from the breather and burning it. The intake valve seat and valve face are showing wear which could result in the valve not seating properly and therefore not sealing against the seat. The exhaust valve looks to be sitting too high in the seat with uneven valve face to seat contact area, which could indicate either the exhaust valve is bent or the seat isn't sitting flush with the valve.

Thank you sir for your excellent description this is why its not worth the time energy or effort to fix the internal issues it really is cost prohibitive especially if you do not have the right tools for the job.

 

[Montecore]

Cylinder is scored, valves need to be ground or at least lapped, probably need to replace rings. May be time to chuck it and get another engine.

Thank you sir this is what I was thinking as well not worth the time, energy and effort to fix when you do not have the parts of correct tools for the job. I agree with you just part out what I can and scrap.

 

[Montecore]

Not sure why you would call this a "plastic engine". Is that because of all the dress up plastics around the engine?

Sorry, this looks like it would cost more to save than a new one likely cost. This all looks like damage from dust ingestion and overheating, especially the one valve that is indigo blue on the stem near the top.

Are you a hobby DIY repair type?

If so, Parts tree should have everything you need for this engine.

You need to look at the side of the engine for the digital etched digits to figure out the model and type information. The chassis label information usually does not apply to the engine parts.

Thanks for the response.....these are known as plastic engines because they have plastic flywheels, camshaft and carburetor. They are not like the late 90's and early 2000 B&S steel built like a tank engine that will last 30 to 40 years! Thank you for the description and interpretation I know it must have gotten hot and one person said 600F!!! WOW!!!! Yes just self taught small engine guy flipping mowers and snowblowers I am not a small engine shop. This is not worth the time, energy and effort because there may be other issues internally that is causing the overheating. Best to part it out and scrap.

 

[grumpyunk]

So far everyone says sayanora to this B&S. OTOH, it does not have the head gasket failure so common to the brand. The valves themself seem to have a lot of meat left on the seating area, and could be ground or lapped to improve compression. Need a picture of the valve seats built into the head for evaluation.
You should look at the installed height of the rocker arm mounting studs. They have been known to pull out of the head over time, sometimes made worse by overheating. If you have not checked, take a look down on the cylinder from above and make sure there's no clippings, etc that will block airflow over the fins, block and head both.
If you have low compression, check that the valves move freely in the valve guides. If sticky, that can make the valves hesitant to seat, causing low compression. They should slide in the guides freely, with no wobble of the valve tulip when the valve is open 1/4". A slight wobble is acceptable.
Not having any more information, I would clean the head gasket surfaces and use a new gasket to re-assemble the cylinder head, and then adjust the valve clearance.
If it does not have compression after cleaning up the valves, squirt some oil through the spark plug hole and re-check compression. If the rings are toast, oil will provide a temporary assist and compression should improve.
From the little I see, the valve seating area is not great, and the valve seats are not shown.
If you actually have no compression, and you have adjusted the valves, and they are not sticking in the guides, all that's left is the ring condition. Most times, rings will fail slowly over time, and will not suddenly cause a no-start. If the compression release built into the cam is stuck(or broken) it may hold the valve off its seat and cause no compression. B&S compression release is known to die and scatter parts throughout the crankcase with no warning and no particular reason(that I know of). That can explain a no-compression problem that came up instantly. Replacing the cam cures the problem in most cases. Bad ring sealing would also tend to cause the engine to feed oil to the carburetor leading to blue smoke when running. If you did not have blue smoke, most times your oil consumption would be low. If you have significant oil useage, rings are more likely.
tom

 

[slomo]

Another opinion

I see a perfect bore (for a mower). Have had many pushers with way worse gouges and piston rocking. Little smoking is fine. Oil is cheap guys.

One tight intake valve guide. Easily reamed out with a simple reamer tool.

Little valve guide and head lapping. New head gasket.

Minimal money and she is back cutting grass. Guy already has it torn down.

 

[ILENGINE]

Another opinion

I see a perfect bore (for a mower). Have had many pushers with way worse gouges and piston rocking. Little smoking is fine. Oil is cheap guys.

One tight intake valve guide. Easily reamed out with a simple reamer tool.

Little valve guide and head lapping. New head gasket.

Minimal money and she is back cutting grass. Guy already has it torn down.

I wouldn't really call those gouges. More like deep scratches, and like you I have seen mowers run with far worse cylinders. I agree fix the valve issue and install new head gasket and see what happens.