241 exhaust valve ???

[Ed Kennell 41,802]

:eusa-think: I pulled the head off the 241 on my C-101 gift horse that I picked up about a year ago. No history from the PO , it came from a friends fathers estate. I have not seen it run. It came minus the carb and starter.

My question is ----- when the piston is approx. 1/3 of the way up on the compression stroke, the exhaust valve opens about 0.010", then closes as the piston reaches the top Is this normal ????? If yes, what is the purpose of venting on the compression stroke ????

The lifter/stem clearance is on the uppe end , 0.020". The valves seem to seat OK. Piston has 0.025" total clearance to bore. What kind of power loss and oil use should I expect if

I don't replace the piston??

Thanks for all input. Ed

[puddlejumper 67]

This is a complete guess, but I think that is the auto compression release, At a given rpm, I forget the number but basically a flyweight disengages and runs at full compresion.

[TT-(Moderator) 1,162]

:handgestures-thumbup: on the ACR (automatic compression release)

Piston has 0.025" total clearance to bore

How / where was this measurement taken? :scratchead:

[Ed Kennell 41,802]

Thanks for the answer ACR I forgot all about this feature.

Terry, the clearance was measured with a feeler guage with the piston @ the top. I can push the piston against one side of the bore and measure the clearance on the opposite side.

[rmaynard 16,291]

The piston to cylinder clearance cannot be measured accurately with a feeler gauge.

[TT-(Moderator) 1,162]

A feeler gauge "test" would work if you'd come up from the bottom - or if the piston was upside-down in the bore.

A piston crown is smaller than the skirt area - to allow for heat expansion. As long as the ring gaps are in spec, it might be fine.

How bad is the ridge (the unworn area above where the rings stop) at the top of the cylinder?

[Ed Kennell 41,802]

Thanks for the input. It sure pays to ask the GURU's. I got it on the taper on the top of the piston. I do see quite a bit of radial movement from the piston though and was thinking , if i put a magnet in top of the piston and mount a dial indicater on the block to the .magnet , Icould measure the total side to side movement. Would that be an indicater of piston/bore clearance? The indicater would be about 1" above the top of the piston.

Gotta go , Mommas callin me-She's ready to go out to dinner. I'll do the test tomorrowww

[TT-(Moderator) 1,162]

The piston's aluminum, so forget the magnet.

What does the bore look like? Is it scratched, smooth & shiny like a mirror, etc.?

Can you see any of the cross-hatch pattern from a previous honing?

Can you feel a ridge at the top of the cylinder?

You can either put it back together, run it, and see if it rattles, smokes, etc. - or tear it down for inspection and/or replacement of the worn parts.

[Ed Kennell 41,802]

Terry, Took some pics of the bore. I'd say it is a mirror finish. No sign of honing crosshatch. There are some barly visible vertical scratches that are probably a result of some carbon dust that I failed to get out even though I vacumned with a high suction small tube on the shop vac. After removing the carbon at the top of the bore, I can feel a small ridge, but when I place a 0.0015" feeler below the ridge , the feeler is higher than the ridge. Therefore IMO the ridge is about 0.0010" high. My mics only go up to 2".

My plan now is to take your advice ---put her together and see how she runs.

Thanks again, Ed

[TT-(Moderator) 1,162]

I see that it's still standard bore, so at least it can be machined in the future.

It's a 50/50 shot as to what you'll have once it's running. You've got nothing to lose but the cost of a head gasket and your time.

I've bought $15 dollar yard sale engines that looked rough but worked like new. Maybe you'll get lucky. :confusion-shrug: