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Old 07-06-2015, 06:32 PM
joe_mows joe_mows is offline
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Craftsman YT3000 Starting Issues... Again.

Mower is having trouble starting. New spark plug, replaced starter, and tried adjusting valves: flywheel will still only make a partial rotation and then stops. When spark plug is removed, engine will crank fine. Any ideas?

Mower is a Craftsman YT 3000 Model Number 917.28852. Engine is a Briggs and Stratton 21HP Model No. 331877-2371-G5.

Thanks,
Joe
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Old 07-06-2015, 06:57 PM
Uncle Knuckle Uncle Knuckle is offline
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Remove valve cover and confirm that the rocker studs have not backed out and the valve train is operating as it should. If all that is correct you may have a broken automatic compression release mechanism on the cam shaft. Although not very common, it happens from time to time. You can watch the rockers very closely while rotating the flywheel by hand to see if one of the rockers "jumps" just a little bit on the compression stroke. You should see a small amount of extra movement in one of the rockers as the piston comes up on the compression stroke. If you don't then you will probably need to open the engine for inspection of the ACR.
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Old 07-06-2015, 07:54 PM
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BigFish BigFish is offline
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Also, make sure the rotator caps are in place on top of the valve stems, can easily fall off if stud worked loose, pushrod bent or ya removed rocker arm.
The ACR acts on the intake valve, which is the lower valve. As mentioned, should see a little "bump", just before TDC on compression stroke.
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Old 07-06-2015, 08:24 PM
shop22 shop22 is offline
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Adjust valve lash and check all mentioned above. I've seen some acr's on the cams fail but most problems are related to valve lash.
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Old 07-06-2015, 08:51 PM
joe_mows joe_mows is offline
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I was not able to see any movement on the intake valve just before TDC. All valve parts are in tact. Not going to open up motor, rather have somebody more experienced take a look at it. Took battery off (had charged it two weeks ago) and put in on charger just for kicks. It does not seem to be charging. Going to pick up new battery tomorrow, and if the issue is not solved I'll take it to a shop. Thank you all for the suggestions.

-Joe
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Old 07-06-2015, 10:28 PM
suspicionofignorance suspicionofignorance is offline
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Only takes a minute to slide a feeler gauge under the intake rocker...if too loose, CR will not function....005 will do it...If correct...than you'll know that engine has to be opened up....Another trick...use your hands on top screen, spin back [CCW] till hard compression...Then hit key for start..usually the "running start" will help
the cranking go past the compression stroke...I lived with one like this for quite awhile...I would merely preset it [ccw] after each mowing, then easy key start up next time...Was too costly to have the cam replaced for sake of new CR mechanism...
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Old 07-06-2015, 10:43 PM
joe_mows joe_mows is offline
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Quote:
Originally Posted by suspicionofignorance View Post
Only takes a minute to slide a feeler gauge under the intake rocker...if too loose, CR will not function....005 will do it...If correct...than you'll know that engine has to be opened up....Another trick...use your hands on top screen, spin back [CCW] till hard compression...Then hit key for start..usually the "running start" will help
the cranking go past the compression stroke...I lived with one like this for quite awhile...I would merely preset it [ccw] after each mowing, then easy key start up next time...Was too costly to have the cam replaced for sake of new CR mechanism...

Intake valve is adjusted to .004 (recommend between .003 and .005, so I just split the difference). I've tried rotating the flywheel in different orientations before starting, and sometimes it will move 2-3 rotations but then stop. I'll try your CCW trick if I end up picking up a new battery, but I might just let the shop deal with it. Thank you for your insight.

Joe
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Old 07-07-2015, 12:26 PM
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Bill Kapaun Bill Kapaun is offline
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Did you adjust the valves with the piston 1/4" ATDC?

Get the battery load tested before replacing to make sure it's bad.
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Old 07-08-2015, 01:55 PM
joe_mows joe_mows is offline
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Brought it down to the shop this morning. ACR was the culprit. Mechanic said that he has the same issue among most B&S platinum motors. Never buying a Crapsman mower again.
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Old 07-08-2015, 01:59 PM
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BigFish BigFish is offline
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Quote:
Originally Posted by joe_mows View Post
Brought it down to the shop this morning. ACR was the culprit. Mechanic said that he has the same issue among most B&S platinum motors. Never buying a Crapsman mower again.
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It ain't the mower, it's the motor that's bad.
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