B&S Intek 18.5hp ohv valve adjustment questions

johnpalmer6940June 18, 2014

31P777 SINGLE cylinder motor.
A few questions as I have seen many different "ways" to adjust my valves.
One way is to rotate crank until upper exhaust? valve is fully decompressed and adjust intake valve. Then compress lower intake? valve completely and adjust the exhaust valve.

THEN, I read to turn crank 1/4" past tdc on compression stroke (where neither valve is moving and both are fully closed) and adjust both intake (.004) and exhaust (.006) at the same time without turning the crank any more. This is because my motor has a compression relief valve on the cam.

Now for my questions:
Which is the INTAKE valve on my motor? (I am pretty sure it's the bottom but internet info has also said the top??)
Also read where the intake valve's pushrod is aluminum and exhaust is steel but mine is opposite??) what should each be?
Thank you!!

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The intake valve is the lower of the two, should have the aluminum push rod- set to .003". The exhaust to .005". Before making the adjustment, check the rocker studs at the head (bottom) w/ a 10 mm wrench and make sure they are tight. The adjustment is done cold, 1/4" either past TDC or 1/4" back before once TDC is reached. TDC is where the piston reaches the top once the intake valve closes.

    Bookmark   June 18, 2014 at 11:25PM
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So the intake pushrod is aluminum? Weird. My intake pushrod is steel. Why did they make the 2 different metals?

    Bookmark   June 19, 2014 at 8:30AM
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Need to follow the exhaust port path to know which Is intake and exhaust. If in fact the al. is on the exhaust side then somebody has tampered with it and put it together wrong. IMO same reason the make compression release, so they can make component parts cheaper. With compression release don't take no heavy duty starter system to crank if over. Light weight equate to Cheaper manufacturing costs and design IMO Intake don't get as hot or stress at exhaust so parts can be made cheaper IMO of course.

    Bookmark   June 19, 2014 at 9:17AM
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" 1/4" either past TDC or 1/4" back before once TDC is reached."


Note that when properly installed, ALL B&S Engine use an aluminum push rod on the valve which is utilized for Compression release. In the case of B&S V twin Vanguard engines, the aluminum push rod is on the EXHAUST valve.

18.5 Intek would be on the Intake.

I can send you a Service Manual for your engine IF you like, address below, put in propber format and remind me, engine model number and what you want. I am having commuter trouble so don't be surprised at delayed reply.

Walt Conner
wconner5 at frontier dot com

    Bookmark   June 19, 2014 at 9:56AM
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I think I read somewhere that you should rotate the pushrods around each valve adjustment to avoid uneven wear-is this correct?

    Bookmark   June 19, 2014 at 9:53PM
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Switching the aluminum push rod end for end will prolong its' life IF the engine is one of the older ones which has a fibre guide that the push rod rides on. Newer design does not have this guide so no need there.

Walt Conner

    Bookmark   June 19, 2014 at 10:03PM
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