Intek valve issue

smallengineguy(z5 NH)June 22, 2010

I have an MTD tractor with a Briggs 14hp Intek OHV on it. Customer gripe is hard starting/only runs on choke. OK, carb problem, right? Wrong. It has almost 100 psi compression, but when you crank it you can hear the air in the carb intake getting sucked in, THEN being blown back out some. It seems that the intake valve isn't closing quickly enough before the compression stroke. On the old L-heads, you just grind the valve, but how do you adjust the valve to close quicker on an OHV? Valves are in spec now.

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Weak/broken valve spring.
Sticky Valves due to fuel being stale.
Valves set at snug .003 int and .005 exh, 1/4" drop past TDC.

Could be blown headgasket into the pushrod cavity also, esp is this engine has 4 head bolts?

Flat cam?

    Bookmark   June 23, 2010 at 12:03AM
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smallengineguy(z5 NH)

This engine has the 8 head bolts. Valves aren't sticking, are those the specs adjustment wise?

    Bookmark   June 23, 2010 at 7:50AM
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Something you want to remember here, the Compression Release works on the Intake Valve. The INTAKE Valve is bumped or held slightly open late into the compression Stroke to relieve some compression. How much leak back is normal and how much is excessive is something I can't tell from here.

Walt Conner

    Bookmark   June 23, 2010 at 8:02AM
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smallengineguy(z5 NH)

Yes, good point. I think it's excessive, though, I can hear the air "chuffing" OUT the carb intake, and it'll only run on full choke. Already tried another carb.

    Bookmark   June 25, 2010 at 3:57PM
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Can't say from here if blowing back thru carb is excessive or not but I had one about a month ago that would only run with the choke full on. Turned out it had a pc. missing out of the gasket between the head and intake manifold.

Walt Conner

    Bookmark   June 25, 2010 at 9:49PM
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smallengineguy(z5 NH)

Yeah, gasket is good, I checked it when I swapped carbs. I'm stumped.

    Bookmark   June 26, 2010 at 10:08AM
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