Setting valve clearances...

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- Duane Bozarth
  
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posted
20 years ago

Mon, Dec 8, 2003 6:49 PM

Wisconsin VG4D air-coooled industrial engine.

Replaced jug ass'y/pistons/head owing to blown head gasket resulting in cracked cylinder and burned head.

Question #1--setting valve clearances. Manual gives clearance for exhaust/intake, but my question is how do I know where in the rotation to adjust tappet to give proper clearance? Do I simply adjust exhaust when intake is full open and vice versa or is there a way to know where cam/crank position should be precisely when doing so?

I set the valves as described above and it fired right off and sounded pretty good, but I soon discovered the #1 cylinder isn't firing. Has fuel/spark, but doesn't fire on #1. Any other ideas of what could be causing same? I've reached the limit of my understanding...

PS have 80 psi compression +/- 5 psi or so on the two new cylinders and

70 on the old two. Seems as though #3 is running hotter than #2/4 but I'm thinking that may be in part owing to #1 not hitting as much as anything????

Any suggestions/trouble shooting/possible causes/screwups appreciated...

PPS...Distributor w/electronic points. Found weak wiring between generator and coil +-ive terminal...repaired it and it improved somewhat but still firing only on 3 cylinders. Put new coil wire and plug wire for #1. New rotor/cap.

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- pete selby
  
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posted
20 years ago

Mon, Dec 8, 2003 8:46 PM

When your not familiar with an engine for setting the valve lash, do one cyl at a time. Rotate the engine until intake valve opens as the exhaust is closing (overlap). Rotate the engine one complete turn and set the valves for that hole (both valves closed). Then go on to the next hole. This is a round about way but not a major operation on a V4.

The missfire could be mis-gapped points, bent distributer shaft, carbon tracking in the dist cap, a bad wire, a bad or mis gapped spark plug, a tight valve, air/fuel blockage. Set the valves first and then check again.

P.

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- Duane Bozarth
  
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posted
20 years ago

Tue, Dec 9, 2003 7:16 PM

Pete, Thanks...that confirms what I did--I thought I was ok, just not sure enough to rule it out as a possible screw-up. Turns out were several more problems--first was when checking more closely discovered plug was arcing across to ground instead of across gap. Replaced it, then pulled carb to find why too much fuel--jet orifice was lying in the bottom of the bowl--put it back and marvelous things begin to occur...long story short, it now is running like a top. Need to pull fuel tank and clean it, put a kit in the fuel pump, clean out remaining sediment after cleaning tank, then new oil change/filter, recheck timing, retorque heads and away I go...anyway, thanks for confirming.