Paw 2.5
 

Has anyone ever tried running a PAW 2.5 with no amil nitrate. I have an R/C version and want to run it on a 1/3-1/3-1/3 mix. What are your thoughts?

Unitrated Fuel
 

Should be fine.

However, to ensure optimum performance why not buy a quart bottle of Amsoil Diesel Cetane Boost and use that instead?

It is a very effective and inexpensive substitute and at 1.5% of the mix a bottle will last a very long time.

sounds good mate. i'll try it

I've done it and does it ever start nice on low compression. Does anyone know if the 1.49 and the 2.49 share the same crank case? My 2.49 seems quite small.

The 1.49 and the 2.49 have different crankcases. The engine capacity may be stamped inside the backplate.

It came in a box from Macclesfield marked 2.49. I had a 1.49 from the 1960's and it seems the same. The 2.49 seems quite anemic with an 8X6. Mabe it was put in a 2.49 box by accident? I can't see Tony making that mistake.

How long is it? From tip of crank to backplate. I can duck down to the shed and measure one of mine if you can give me a distance to compare.

73 mm tip of crank to the backplate. the cooling fins are 23mm across.

That's exactly the measure of my 1.49cc Paw.

The Blue Head 09 is the same length, but the cylinder fins are 25mm.

I can dig out my old 2.49 tomorrow.

What is the secret in getting the backplate unscrewed on my 1.49? I used to use an old 1P coin but this one is on real tight from PAW.

qaz, it is the 1.49. It is 127 grams and the measurements are the same.

I carefully clamp the backplate rim in the 3-jaw chuck of my lathe. Naturally you don't turn it on! It's much easier then to screw off the rest of the engine by holding on to the crankcase/head fins and twist with one hand whilst holding the chuck stationary (via the key) with the other.

Righty tighty, lefty loosy.
It's worked every time.

If no lathe handy, put your coin in a bench vice and position the back plate slot over the coin and turn the engine anti clockwise. If it's stubborn place the engine in an over and heat at 200c for about 10 minutes.

The old coin in the vice trick is another good method to get the backplate off, but can I caution against heating an engine in an oven to 200 degrees C.

That temperature is perilously close to the critical heat treatment temperature of some Aluminium alloys. I'd stick to under 100 degrees C and only as a last resort, and after stripping anything inflammable off the engine. Boiling on the stove in a pot of water would be much safer.

To Controlliner's Q: in Post 10 -

In the USA, at least, there are still a few "hardware stores" (UK equiv: 'ironmongers' ?) which sell small parts loose, I..e., not packaged in always the wrong number of pieces. ( 3 bolts or 12 bolts in shrink-wrap when you need but one... or 4.) In the "fasteners" section you can find bins or drawers of individual iron washers in many diameters and thicknesses. ...and much else. The clerks never seem to mind when I bring, e.g., a PAW to find which iron washer has the best diameter and thickness for correct fit, or which small Phillips head screw driver fits an odd small metric screw...Or which metric or SAE thread comes close to fitting some oddball Pacific Rim or Eastern European thread.(Some come very close!)

The first few times, I made sure to ask the section clerks where I could find things, so they'd know I wasn't trying to sneak something by. By now, they recognize me and let me dig.

I would rather clamp a properly fitting iron washer in a vise, than ANY part of a model engine. My old, old Unimat mini-lathe would probably withstand using the 3-jaw as a clamp, but if it doesn't, a replacement part will be very hard to find...And yes, each PAW engine size will need its own "best fit" washer for the job, possibly excepting their .15 (2.49) and .19 engines...