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dav

17.5 I/C Briggs

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dav
been trying to help out a friend fix his murray with the Briggs 17.5 I/C verticle crank motor. replaced the flywheel key and it started right up. ran for about 20 seconds, backfired, and would do nothing more than an occaisional pop. took off the flywheel to find that the aluminum key had sheared again. put a new key in and it did it all over again. what can make it keep shearing off the flywheel key? for the 20 seconds it runs, it sounds good and strong. btw; what does the I/C stand for? and is there a horizontal crank I/C? thanks for any help and hints.

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3314WV
dav, if i am not mistaken the I/C stood for Industrial / Commercial Grade motor which i think had stronger internals and possibly a lined cylinder bore.....does the motor turn free with no points of contact ?......any unusual noise from inside when it fires up ?

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dav
the motor does not make any clunks or weird noises as it is hand turned. when it does start, it sounds like it will run forever. but that only lasts for about 15 to 20 seconds before it farts once and dies. then it only farts but wont start. the key was replaced with one from the dealer the first time, the second with one from my 'spares' which was the right size. the bolt holding the flywheel on was snugged tight as possible but not torqued. i can lift on the flywheel and get a verticle movement of the crank that i would guess to be , at most, 1/32 of an inch but is probably less. i'm sure that is way out of spec but cant see it causing the keys to shear. what should the flywheel bolt be torqued to?

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ketchk
dont SNUG the bolt tighten it as hard as you can i had the same problem after a few keys i tightened the flywheel as tight as i could and no more problem one thing i had a Briggs 17 and the cam was worn down i doubt if that is your problem but keep it in mimd

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dav
thanks for the replies. i torqued the bolt to 125# and she fired right up...and stayed running. which is the next problem. it stays running. with the key off or even out of the brand new keyswitch, it stays running. told him to lift his butt off the seat until it shuts down, then climb off the mower. not worth the headache of trying to track down a wiring fault. works for him! again, thanks for the hints and tips.

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dav
revisited.... stopped by my friend's to change the valve cover gasket today on his mower. last visit, i had torqued the flywheel bolt to 130 punds. ran it for a while, stopping and starting it. ran great but was pouring oi out of the valve cover gasket. next day it crapped out again. he took the murray to the dealer. they found a sheared key-again!!! and that the valves were out of spec on the gap. regap, new gasket, and it runs fine!! cases like this make me want to turn in my tools!!

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