# Mtd 18/46 w/ b+s twin cylinder 422707 1510 01 running on one cylinder



## CHUCK533 (Sep 18, 2013)

Hello everyone, I am new to this site and look forward to hearing input on my troubling engine. I have recently purchased a MTD 18/46 tractor model#130800H000/D090B1, equipped with a Briggs and Stratton twin cylinder engine model#422707 type 1510 01 code 90031412 . I ran the machine prior to purchasing it and everything seemed fine. I brought it home and put it in the garage and noticed it didn't seem right. So I rebuilt the carb,changed the oil, spark plugs, air cleaner and overall cleaning. I started up the machine and noticed immediately it did not sound right again. There was too much vibration and puffing from the exhaust, also fluid coming from the exhaust flanges.

I decided to do a compression test and had 120PSi from cylinder #2, and 0 from cylinder#1. I pulled off the head and found that the exhaust valve seat was loose and had been run this way for a long time. The aluminum block was worn pretty badly. I purchased fluid weld from silver seal company and used the valve to index the seat evenly in the block. I used the fluid weld sparingly to secure the seat to the block. Since it was worn badly, the valve did not seat properly. I ground the stem until the valve face met the seat. I lapped the valve accordingly. I reassembled the engine with the original head gasket and achieved a compression reading of 100 PSI. I put everything back together and it will only run on one cylinder ,not the recently repaired one. I checked compression again and still have 100PSI. I have great spark to both plugs and have good fuel. I pulled spark plug wire for # 1 cylinder and the motor dies. I am at a loss right now. I have what I would think is enough compression to run the engine, I have good spark, and ample fuel. 

Can anyone help me figure this one out, I am getting very frustrated. Thanks for everyones' help


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## Rattosh51 (Sep 10, 2008)

Did you try swapping the spark plug wires from one side to the other?
Maybe have a weak coil that only shows up when it wants to???
Only thing I can think of doing.


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## Country Boy (Mar 18, 2010)

Did you check the valve to tappet clearance on that exhaust valve you cleaned up? If you ground the seat and valve, then the clearance may be zero or close to it. There should be a gap between the tappet and the valve so it can shut fully. You can grind some off the end of the valve to increase the clearance, but don't take too much off at a time. There should be a clearance of 0.007" and 0.009" between the valve stem and the tappet with the valve springs installed. Its possible that the valve is being held open and letting too much pressure bleed off. 100 PSI is marginal for an engine. Most new ones will give you over 150 PSI per cylinder. A better test to do would be a leakdown test. It pressurizes the cylinder with compressed air and measures the bleed off and corresponding pressure drop. You can listen for where the air is coming out to determine the location of the leak.


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