Currently in the process of transplanting a 12 hp from a Murray into a different chassis.
Everything fits fine (of course it does its the same engine config) bar the drive pulleys. Turns out the pulleys on the incoming engine are different, both in diameter and distance from each other.
After putting the engines next to each other I could see the incoming Murray engine is 3ish cm taller than the old one. I'm hoping this is because of the difference in pulleys and not a longer crankshaft.
Before I go hammer and tong on swapping the old pulleys onto the new crankshaft, I would like to know if the crankshafts are going to be the same length. Otherwise when I do the swap I'll just be confronted with the same issue.
I guess you could but the best method is to use a puller. If you welded a nut you would need to be able to cut it off clean so you can tighten the retaining bolt up. There should also be an allen key grub screw holding the pulley on as well
Those type of pulley can be the hardest to remove. I have in the past had one glowing red! It still wouldn't budge and had to cut it off with an angle grinder. Unfortunately because they are pressed tin there is nothing solid to pull with. A nut on the bottom may well be you're best bet. Personally I have never seen a grub screw on a pressed tin engine pulley.
Weld a nut on the bottom so you have a solid point to apply pressure, then soak in inox or wd, then apply heat..
These pulleys are usually one extreme or the other, I have also had them fall off when undoing the crank bolt. depends on how much moisture got in there.
I'd go with nath here. This 'stack pulley' is a design that will get rust-bound if any moisture at all gets in between the pulley sleeve and the shaft.
Since it's now knackered anyway, I'd have at it with a thin cutting disc on an angle grinder.
First cut a wedge out of each of the pulley sheaves, to allow you access to run a lengthwise cut all the way down the tubular sleeve. Don't worry about marking the shaft; it won't cause significant damage to it.
A bit of prying at the cut edges will loosen things up enough to get it off, with the aid of a bit of CRC, Inox, Penetrene or similar penetrating lube.
Cheers, Gadge
"ODK Mods can explain it to you, but they can't understand it for you..."
"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."
You are actually quite lucky in that you got the engine off. Some of the ZTRs I work on the engine pulleys must be removed before you can even get the engine off. Most times I destroy the pulleys as no one appear to use anti-seize compound.
In my case I have a bearing separator and ACE/OX torch to remove these pulleys. Can't get cutter into the areas. Carefully applying heat I can usually pull the pulleys without even damaging the oil seals. I have; however, destroyed one forcing screw in the last 10 years. I usually use an impact (rattle gun) wrench to do this but it was strange that I stripped the forcing screw with just a hand ratchet instead. Anyways I had the puller bar reworked to fit a larger forcing screw. Of course now I must use adapters for the smaller crankshafts but the donor adapters are extra shaft protectors
The big issue is getting the one off the old motor you want to re-use. I would cut the crankshaft above the top pulley with a grinder or whatever you can get in there, then soak it with penetrene or a 50/50 acetone/atf, leave it for a day or so then see if you can put it in a press to break it free. If you go this way make sure when you put it in the press you support the pulley in close to the shaft and not on the face of the pulley because it will just bend the face of it
