Big P.A.W.
 

I bought this motor on another site. It was advertised only as a "Big PAW". Can anyone help me identify it? I have a 40 and it seems quite a bit bigger than that. Did PAW ever make anything bigger than a 60? Is that what it is? If not, anyone know what it is?

It weighs 1lb 8.5oz as shown. I will try to get more photos later.

Thanks,

Scotty

Nothing stamped in the backplate?

Nope. I couldn't find any markings anywhere. There is actually a nipple in the back plate!

I do not remember PAW making a model diesel engine larger than the .60 engine. So it is very likely a .60 engine then.

The prop washer, spinner, prop mounting bolt and exhaust collector all look non-original.

There was a .60 Mk 1 which was larger and heavier than the current Mk 2.

I agree that the exhaust collector looks like a homemade affair (although well done except for misaligned holes, and it is well-mounted). The spinner is aluminum and is probably after-market. Not so sure about the bolt and the washer - they could be original. I took more photos and will post them below. This weighs 693 grams as shown. According to the PAW website, the MK2 weighs in at 500 grams with silencer. So maybe this is a MK1? Anybody know if the MK1 had a pressure port in the back plate? It's perfectly centered and I suspect is original (see photos). The head outer diameter is ~48mm, the output part of the case is ~25mm. Anybody got a 60 to measure?

Also, note the 3 fins at the top of the head. All the photos I've seen of the PAW 60 only have 2.

The condition of the motor looks good - compression is good. It definitely has been mounted. The tops of the mounting holes are clean, but if you look closely, you can see the bottoms have some elongation wear (which seems a little odd to me).

I see what you mean by 'elongation'. A textbook case of the good old 'lets wiggle the hand drill back and forth' to make the holes in the lugs fit the engine mount holes, rather than the other way round :rolleyes:.

From the look at the R/C Carb it is definitely very old. PAW have fitted the more sophisticated 'varijet' carb for over 20 years now. It will probably work just fine though.

Those oval mounting holes is typical where someone didn't quite drill the holes in the motor mount rails accurately, so the elongated the holes in the engine to fit the holes in the motor mount.

I am guessing that the '60' stamp has been drilled out by the back plate nipple.

OK, I'm convinced this is an older PAW 60. I did find some other pictures online that look like this one (except for the collector ring). I have a few questions:

If this is the MKI, do you suppose the current stock 60 silencer will fit it?

Is the pressure nipple in the backplate original/common?

Is there a special technique or tool for removing the prop bolt (without using vice grips on the washer)?

Thanks!

Big PAW
 

Silencer: Contact the US distributor Eric Clutton, aka "Dr. Diesel". He should be able to advise.

Propeller bolt: It is non original. The prop bolt should come off be using the correct size allen key in the head and turning counter-clockwise. If it is seized and you simply turn the engine over you will need to remove the exhaust collector to put a piece of medium to hard wood (like a sliver from a cut down wooden ruler) into the exhaust across the ports to 'lock' the piston at BDC. Be careful. The cylinder is not pinned in place and will rotate/lift if not secured. Best tried with the cooling jacket replaced and hold down screws set home.

I would use a small piece of a really good hardwood, if you use the exhaust port to lock the piston down. The wood rulers today tend to be made from really crummy low quality wood anymore.

I would use a small piece of a really good hardwood, if you use the exhaust port to lock the piston down. The wood rulers today tend to be made from really crummy low quality wood anymore. Cut or size the piece of wood to just fit through the exhaust port.

But usually if the screw isn't on there too tightly, just unscrewing it against the engine compression works too.

a " jam nut" approach may work also if it does quick and simple use 2 nuts on the crank using 2 wrenchs tighten (jam) the outer one against the inner one then see
if you can back it out and of course the wood sliver in the exhaust as pointed out in the previous posts martin

Thanks for info and suggestions everyone. I guess I should decide if I'm going to be able to replace the silencer before worrying about the bolt. Looks like I'm going to have to remove and replace the head and cylinder twice in any case.

Any thoughts on the back-plate nipple?

A piece of neoprene rubber tubing and a piece of brass tubing with the end crimped and rolled to seal it off.
One could also find a screw that matches the size and threads and cut it off short, put a fiber washer on it and screw it in. You want the screw short enough to not hit the rod or crankpin.
You could also remove the fitting, clean it and fill it in with solder too. Or even JB Weld epoxy for that matter. Then put the fitting back in.

Annother way to restrain the engine is to fill the cylinder with string. It will compress and not damage the engine. We do this to Lycoming engines to allow the reaming of the valve guides without needing to pull the jug.
Ken

I am curious, how do you get the valves out of the way so you can ream the valve guides without pulling the head. Do the valve guides come out?

earlwb,
You remove the spark plugs and set the piston to bdc. Remove the rocker box cover. Through the top spark plug hole feed in all the soft cotton rope that will fit. Rotate the piston against the rope as hard as you can. The rope presses against the valve heads to prevent them from moving. Remove the rocker arms. Use the regular tool to compress the valve springs and remove the valve spring retainers. Remove the rope. Push the valve most of the way into the cylinder bore. Grab the valve with mechanical fingers and remove completely from the valve guide. Ream the guides, clean, lube and then reverse the procedure. This is a standard procedure for Lycoming engines used in helicopters to keep the valves from sticking.
I taught aviation maintenance for a number of years and most students reaction was along the lines of "You are kidding, right?"
Ken

Thanks, interesting. I would normally think that one couldn't do it either.

What is wrong with a good old hydraulic lock with oil and a heat gun on the bolt?

That's a thought. Anybody see anything wrong with this idea? (I'm new to diesels.)

Well it can be very messy.
:p

More so than using a 60 sized diesel on castor strained through a shower head disguised as a muffler?
But honestly here, if you are not sure about an expensive piece of kit and want to get it back in good running order then send it back to PAW or post it to Dave Owen in Oz.

Dave would be my pick and not just because he lives down the road a bit - there are things like do you know the correct way to torque down the head bolts, marking the cylinder orientation BEFORE work starts, checking bearing pre-load on the shaft, accurately drilling out elongated bolt holes to 440 sized stead of that BA bit, getting a better carby and muffler etc.

Much to think about with an engine that costs well over $200.

Yeah, I hear you on the muffler. I'm pretty sure I will eventually swap it out. But if I can get the prop bolt out without disassembling the head, I want to fire it up with that "shower head". I bet it will sound pretty cool...

I'm going to try your hydraulic lock method and report back...