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Murray lawn mower, oil in cylinder

rjels's Avatar

Join Date: Nov 2006
Posts: 103

12-26-06, 06:57 PM   #1  
Murray lawn mower, oil in cylinder

I have a 99 Murray riding mower with a Briggs & Stratton I/C engine. I used to have a scrap of paper with the specs, but if you could see my desk you would know why I can't find it. If you need it I can go get it for you. Anyways, they left the machine when I bought my house back in August. Neighbor used it to mow the lawn when it was on the market and he said it was running fine until one day it seemed to lose power. He replaced the plugs but didn't help.

I checked the plugs and replaced them again and left one seems to foul with oil, right away. The engine will run, although rough, with the choke engaged half way. When I took the air filter off the engine seems to come up to full speed, and runs good. But instead of air being sucked in to the carb, it blows out and sends gas up with it, a pool of gas will form on the air filter housing if left running for a while.

I removed the head to the offending cylinder and found some oil sitting in it. The cylinder wall seems fine, no scratches or marring.

I have replaced plugs, fuel, fuel filter and air filter.

I am thinking worn or cracked cylinder ring. Anyone else have any other ideas? I have never taken an engine apart and thought I have all winter to work on it, so it would be a good time to learn.

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cheese's Avatar
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12-27-06, 12:01 AM   #2  
The engine numbers will help. Sounds like a 420000 series briggs. Have you verified spark on both cylinders? Sounds like one cylinder isn't firing, and also maybe the carb has a restriction. Compression on both cylinders?

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thiggy's Avatar

Join Date: May 2002
Posts: 718

12-27-06, 06:59 AM   #3  
If it is spitting back through the carb, I would suspect a burned intake valve/seat. An easy check would be to pop a compression tester on it for a quick test. A little lapping with some valve grinding compound might resolve the problem.

rjels's Avatar

Join Date: Nov 2006
Posts: 103

12-27-06, 04:57 PM   #4  
Thanks for the responses. It is a 1997 Murray Ultra 20 HP Twin 46" riding mower, Model # 46102x6A. The engine is a Briggs & Stratton 20 HP Twin II, I/C Plus, Model # 460777, Type 2277E1.

There is spark at both plugs. I do not have a compression tester, guess that will be my next step. I will get back to you when I get one and have a chance to test, probably this weekend.

Azis's Avatar
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12-27-06, 06:19 PM   #5  
This url will let you get manuals and info for the engine using the model and type #'s

You may also find manuals and parts for the rider here

rjels's Avatar

Join Date: Nov 2006
Posts: 103

03-28-07, 01:00 PM   #6  
Almost time to mow the lawn!!!

Sorry for the long delay, its finally getting warm enough to work out in the garage again. I tested the compression in the right cylinder (the one I thought was bad) is 110, the left is 0. I never opened the head on that one, so to my surprise I found a metal seal/gasket/sleeve (not sure what to call it) around the top valve. I have included a picture, I can get my camera to take a pic if it'll be helpful, only had my camera phone on me.


As you can see, it has ground some metal off around the right and bottom edges of the top of the head around the valve, from being run in this condition. I'm not sure if it has damaged the bottom of the valve, or even bent it.

I was wondering how this sleeve seats in the valve area, just press in or is it fastened somehow. Do you think I might get lucky and just be able to press this back in and start mowing? Or will this be a big rebuild job, I have never completely taken a motor apart.

Thanks for all the help.


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