Briggs vtwin intek 20hp running on one cylinder

[davidsh]

Hi Fish,

Unfortunately the feeler gauge I have only goes down to .008 (I think I read somewhere its supposed to be .004 clearance) so was a bit reluctant to go adjusting until I picked up a new one. .008 was very tight on the intake but wouldn't fit in the gap for the exhaust valve - so maybe it is too tight (and intakes too loose).

I guess that's my next step - get a new gauge and make sure they are correctly adjusted?

I did the "screw driver in the spark plug" test too on both sides and the pistons are moving as expected.

 

[Tiger Small Engine]

Hi Fish,

Unfortunately the feeler gauge I have only goes down to .008 (I think I read somewhere its supposed to be .004 clearance) so was a bit reluctant to go adjusting until I picked up a new one. .008 was very tight on the intake but wouldn't fit in the gap for the exhaust valve - so maybe it is too tight (and intakes too loose).

I guess that's my next step - get a new gauge and make sure they are correctly adjusted?

I did the "screw driver in the spark plug" test too on both sides and the pistons are moving as expected.

Your compression readings on cylinders are varying widely. Don’t think adjusting valves will be the fix for that large a difference, however, it is a good first step.

 

[Fish]

The one valve/rocker looks tight {as in not letting the valve fully close}. But unless the jamb nut/adjuster is loose, it would mean that something else is up, like maybe a loose valve seat.
But I may be wrong, as I am not there to really see things.

 

[davidsh]

The one valve/rocker looks tight {as in not letting the valve fully close}. But unless the jamb nut/adjuster is loose, it would mean that something else is up, like maybe a loose valve seat.
But I may be wrong, as I am not there to really see things.

I finally got my hands on a feeler gauge (ordered it and got lost in the post so had to wait for another). Valve clearances on the intakes were very big and the exhaust ones were very tight. Adjusted on both sides and am getting compression readings of 125 on the good side and 75 on the bad side (the cylinder that wasn't firing). That's up from 105 on the good side and 25 on the bad side pre-adjustment. I also replaced and resealed the valve gaskets - (not sure if this makes a difference but the gaskets were in poor condition)

I think that both cylinders are firing now because she's not bogging down when I engage the blade. So thanks very much for all the suggestions and help!

Fish - I guess there's something else at play here as you suggest with the lower reading on the the cylinder that wasn't firing previously. Am I ok to motor on, or should I investigate further for fear of causing damage?

Thanks again
David

 

[Fish]

It is hard to say, it is likely a valve leaking or head gasket. If it were mine, I would run it a bit and see what it does. If it is a bad head gasket, you will likely start burning oil, if the bad spot is at the pushrod chamber.
I never mess with compression gauges with these engines, as the compression release mechanisms mess with the readings normally.

 

[davidsh]

It is hard to say, it is likely a valve leaking or head gasket. If it were mine, I would run it a bit and see what it does. If it is a bad head gasket, you will likely start burning oil, if the bad spot is at the pushrod chamber.
I never mess with compression gauges with these engines, as the compression release mechanisms mess with the readings normally.

Thanks Fish - I'll think I'll go with that and see how I get on. Thanks again everyone for the help

 

[Affordable in Indy]

This sounds like a blown head gasket on the low compression side to me. Pull the head off.