QuestionQUESTION: Can anyone help me with how to adjust the valves on a Briggs 17.5 hp Model 31C707 Type 0154? This engine came out of a Troybilt lawn tractor. How do you set the overhead valve adjusters?
Am doing work for a friend and found the exhaust valve dropped the seat. A quick trip to the machine shop fixed that now it backfires thru the carb. The valves need adjusting I think. Any help is greatly appreciated.
baron
ANSWER: Rotate the engine by hand to top-dead-center (TDC) on the compression stroke. Continue to rotate the engine 1/4 inch past TDC on the compression stroke. I use a straw to feel when the piston reaches TDC the make a 1/4 inch mark on the straw and continue to rotate the engine until the mark is at the top of the spark plug hole. Finally, set the gap. Intake should be set to .003-.005 and the exhaust .005-.007. You will need to loosen the rocker locker and then ajust the clearance screw.
Let me know if this helps.
Eric
---------- FOLLOW-UP ----------
QUESTION: Thanks for the speedy reply. I'll set the piston 1/4" down, but still unclear on the "rocker locker and clearance screw". Is it one in the same? My rocker arms are held inplace by the capscrew on the end. Can't find any other adjustments. How does the cap screw stay put once adjusted?
Baron
AnswerThe rocker arm adjuster has a hex nut on the outside and a set screw in the center of the hex nut.
You need to loosen the inside screw first, the adjust the clearance with the hex nut. Once the clearance is set, hold the hex nut and tighten the inside rocker ball screw. Rotate the engine several times and re-check the clearance to make sure it is correct.
Eric
