I have a 1996 Murray mod 46904x92a. It needed a new starter as the old one died. Wouldn't even turn with direct battery connection. Got a new one off ebay. Freewheels fine with battery power. Installed it and it won't barely spin the engine. I have 90psi compression in both cylinders. It spins great with the plugs out. I can start the engine with either plug in, of course running like crap, but I know I'm not locked up or having no spark. This is all with a 225amp booster/charger. I even put the cables directly to the starter terminal and an engine ground. So my questions: possible bum starter? Is there a compression release on these engines that may not be working? Is 90psi a good compression reading? Lastly, the engine isn't real easy to spin by hand by turning the screen on top of the flywheel. Not real hard, or no rough spots, just that you can feel it up against the compression. Is there a torque spec for resistance? Meaning turning the flywheel with a torque wrench to see if its out of spec. I'm guessing I got a bad replacement starter. Thanks for any help!
18hp Briggs no start
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It would really help if you had posted the model number of the engine. From what you have said, I am going to guess that it is a 42 series engine. Difficulty in cranking is common with that engine. The compression release is in the camshaft grind which holds the Intake Valve open late into the compression stroke relieving some compression at cranking speeds. I have a list of possible causes for hard cranking in these engines if you would like it. Address below, put in proper format and remind me what you want.
90 lbs. of compression is enough to run, note that B&S does not give a compression rating for these engines and the compression release feature makes it difficult to get an accurate reading. A "blow down" test is more accurate.
Walt Conner
90 lbs. of compression is enough to run, note that B&S does not give a compression rating for these engines and the compression release feature makes it difficult to get an accurate reading. A "blow down" test is more accurate.
Walt Conner
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Walt's on board with this one......I was only guessing, but I seem to recall they had a more heavy duty starter for the L-head twins. It is about an inch or so longer in the body, as I recall. If I'm wrong, and that is possible, Walt can straighten me up and I'll pick up some more info for my head chamber.
It is a model 422707. I got it to run today by giving an "assist" by shoving the flywheel screen with my hand as I hit the starter. Ran like a champ then, although I had to do that everytime I tried to start it. I think the new starter has a gear that is taller than the old one. It's getting chewed up on the top of the gear by the bottom of the flywheel when engaged. I think I'll swap the old gear onto the new starter.
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If you end up needing to change the starter pinion gear, I can help with the one held on by the little c clip. I also have a "tool" idea that puts the clip back on easy as pie....................................
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Just in case more info is needed.
422707-1264-01 should be the engine the factory put in.
Welcome to MTF by the way...............
You should be able to download a free Service Manual at - http://www.mymowerparts.com/pdf/Briggs & Stratton Service and Repair
For a few years in the recent past, before gasoline got so darned expensive, I sort of specialized in rebuilding these engines, 40, 42 & 46 series and sold them all over Southern part of the state. As far as I know, the starter on them is the same as most B&S starters except for the end/mounting plate. I often switched them. The difference in length of B&S starters, again as far as I have been able to determine, is because of a difference in mfgs, different commutator/brush assembly methods.
Difficulty in cranking is common with these engines and I offer a list of possible causes above. Well I guess I didn't put the address, address below, put in proper format & remind me what you want.
Walt Conner
wconner5 at verizon dot net
For a few years in the recent past, before gasoline got so darned expensive, I sort of specialized in rebuilding these engines, 40, 42 & 46 series and sold them all over Southern part of the state. As far as I know, the starter on them is the same as most B&S starters except for the end/mounting plate. I often switched them. The difference in length of B&S starters, again as far as I have been able to determine, is because of a difference in mfgs, different commutator/brush assembly methods.
Difficulty in cranking is common with these engines and I offer a list of possible causes above. Well I guess I didn't put the address, address below, put in proper format & remind me what you want.
Walt Conner
wconner5 at verizon dot net
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3,135 Posts
Good info! I just assumed the longer model was a more heavy amped model for the Twins for the torque needed to spin them.
Update. My new starter was junk. I took it apart to find a winding loose and caught up in between the armature and the magnets. I'll get another new one soon. Come spring, I'll go through decarboning the heads and servicing the valves. Thanks for all the help guys. This is a great forum. I'll be sure to keep hanging out here to learn lots more!
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