MTD series 690 thru 699 lawn tractor valve adjustment

this is a 42"MTD lawn tractor with a 16.5 hp twin cylinder ,L head series series 420000 Briggs and Stratton
this is a link to the engine:
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I want to adjust the valves but can't figure out how to access the adjustments like on a single cylinder engine where you take the cover off the front of motor and the rockers are right there. on this motor there are 2 small valve covers , when you take them off you can only see the end of the valves.

 

You don't adjust the valves on these, it's not an OHV engine.

 

thanks cheese, you saved me some time there

 

i don't know it still seems like the valves need adjusted. i had a chance to look at the lawnmower again today. and it seems so hard to start. the battery is new. i pulled the starter thinking that was it. put new starter in it figuring that must of been what was the problem since you said you can't adjust the valves.still starts the same. it cranks as if battery is low. it will eventually start but the way it turns over you don't know wether it will or not. i pulled the plugs and turned it over without plugs in. i it turns over like it has a new starter and battery in it. put plugs back in and turns over as if battery is low. sounds like too much compression as if valves need adjusted. anyone have any ideas. this thing is making me crazy.

 

There is no valve adjustment on this. The valves get tighter as the engine gets older, so that would only make the engine start easier, not harder, if it were the valves. These engines need a 300+ cranking amp battery, and the problem I see quite often is that people go buy the cheap $25.00 battery at walmart and put it on and it doesn't work for long.