How to adjust valve lash

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  #1  
Old 03-25-08, 09:47 AM
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How to adjust valve lash

How do I adjust the valve lash on my Briggs and Stratton
17h riding lawn mower? Model # 42A707.
 
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Old 03-25-08, 04:21 PM
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Remove the valve cover then rotate the engine over by hand until you reach top dead center compression stroke, Then remove the spark plug. Once at TDC insert a small screw driver in the plug hole touching the piston and rotate clockwise past TDC until you see the screw driver move down inside the hole 1/4". Now loosen the jam screw in the center of the adjustment nut and adjust to .005-.007" both intake and exhaust. Hold the adjuster nut with your wrench while tightening the jam screw. It may take a couple times to get it right because when tightening the jam screw it could throw the adjustment out so check after tightening.

Good Luck
 
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Old 03-25-08, 09:12 PM
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31YTech is right for the overhead valve engines, but this one is a flathead twin, which requires valve removal to make adjustments. 31YTech usually covers each topic with such a well thought-out reply that I rarely have anything to add...so I'll jump on this opportunity...ha!

If you think this engine has valve clearance issues, you'll need to remove the valve cover for each side and check clearances between the lifter and valve stem with the engine at TDC on the cylinder being checked. If adjustment is necessary, you'll have to remove the valve from the engine and grind the stem accordingly.

What problems are you having that make you suspect valve issues? These flathead engines don't usually need valve corrections during their useable lifetime.
 
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Old 03-26-08, 04:16 AM
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Originally Posted by cheese View Post
31YTech usually covers each topic with such a well thought-out reply that I rarely have anything to add...so I'll jump on this opportunity...ha!
Well, Guess I had my head up someplace when I looked at the model number.....

The floor is yours....I'll hang my head in shame....
 
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Old 03-27-08, 12:59 AM
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You covered my mess-up several weeks ago and I was just glad to be able to reciprocate the favor, lol! I'm famous for not looking at the model #s.
 
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Old 04-02-08, 11:05 AM
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I am sorry I did not read and reply to all of your posts, I had to go out of town on a job and just got back in and checked . The problem I am having is the engine will not turn over rapidly enough to start, acts like a dead battery, or bad starter, I put a new battery in , removed the starter, disassembled, cleaned , reinstalled, same thing. If I take the plugs out , it will spin the engine fine.
 
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Old 04-02-08, 10:21 PM
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Did you replace the drive end cap on the starter? Usually I find that the bushing has worn enough to allow the armature to push away from the flywheel and rub the field magnets and cause the starter to drag on these engines. It also doesn't hurt to put a dab of white lube on the bushing areas of the armature shaft before reassembly of the starter. Also, don't use a twenty dollar 180 cranking amp battery from the dept store. For this engine, you'll want to get the bigger amp battery...over 300 cranking amps.
 
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Old 04-03-08, 05:52 AM
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valve lash adjustment, or not.

Thanks for the info, no I didn't , I will try your recomendations and see where that goes. I am going back out of town tomorrow, but will post back in a couple weeks to let you know the results. Once again thanks for the info.
 
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