QuestionQUESTION: Neighbor & I have a Yard Machine 17.5 HP B&S engine 42" riding mower from "Wallyworld"!
The engine has 306 Hours on it and has been regularly and carefully serviced by us over 6 seasons.
The compression is 75 psi, the valves aren't burned, with only a bit of carbon on them and we laped them. There are no scores or scratches in the cylinder wall. There is no "blow by" out the oil filler tube or out the carby.
The muffler is intact.
It has started to "puff & snort" (best description we can come up with!!)once it starts to warm up and it then starts to lose power. Almost sounds like some kind of a blow by leak but no oil anywhere and it does not use oil.
Any suggestions other than a stick of dynamite???
Thank You for any ideas.
Dean
ANSWER: How about 2 sticks of dynamite?...lol 75 psi compression is just way too low. As with most engines the symptoms of low compression does show up more when a engine has warmed up. At the same time 306hrs of use isn't that much either. Only problem is that there is a number of causes of low compression. There's the most basic Bad rings, piston, cylinder wall, valves, valve seats, valves hanging-up not closing all the way, cracked valve, or seat. Blown head gasket, cracked head, cracked block. Then there are a few lesser know causes, there is a compression release for easier starting, this may not be working correctly, and allowing the compression to leak. Kind of hard to check with it being located in the oil sump pan section of the engine and requiring engine removal, and engine to be disassembled. In the same location is the timing gears, which once before I have seen the gears somehow jump out of time. ....This is going to take some investigative work on your side for sure...........Tom
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QUESTION: Sorry, only have 1 stick of dynamite available!
Removed heads, etc. & seems problem MUST be the comp. release. It runs OK sometimes and sometimes it doesn't! Lots of time spent searching for photos or anything that might help us know what we’re looking for when we take the engine apart. NO LUCK!!
We need some hints as to what we might look for that denotes a problem with the comp. release device or any other help / experience you might be able to pass on.
Purchased the small manual for that engine and it really doesn't show us much.
Photos, repair manual pages, where to find them, or whatever - we would sure appreciate, ANY ADVICE!
Gotta get it working, snow is down to < 3 feet deep in the yards, so summer must be JUST AROUND THE CORNER!!!
Thanks
Dean
AnswerBefore you take the engine apart, back off the exhaust vale making it no functional with the adjustment. Then take another compression test. The compression release works in conjunction with the exhaust valve, by backing off the valve adjustment so it's not functioning it will tell you if it's the compression release is sticking or hanging up. It compression comes up then the compression release is working. If it remains low your problem is with in the rings or valve system, or head gasket.........Tom
