Crankshaft removal tips needed

I have a Magnum XLS .40 2-stroke, with a single-piece crankcase, which was in a crash I had last week. The engine took quite a bit of dirt, which got into the carburetor. Several of the other guys in my club suggested I disassemble the engine and clean the inside with denatured alcohol. I got the carburetor, prop drive washers, head, back cover, piston, and sleeve off, but I can't get the crankshaft out. I'm afraid that if I do it wrong, I will destroy both ball bearings. Any suggestions on how to proceed with this? I would like to use the engine again soon.

Thanks, Harry Sanchez

Reply to
Harry Sanchez
Loading thread data ...


It should push right out the back of the case without a lot of force. The bearings are pressed into the crankcase and the fit is generally pretty tight. Normally takes heating the crankcase and allowing for thermal expansion to ease the grip between the bearing seat and the outer race to get them out. The fit between the inner races of the bearings and crankshaft is normally not that tight and they are assembled/disassembled cold. If the fit is more stubborn than usual, you might push the rear bearing out with the crank, but that's no problem - just saves you a step in disassembly. You are only likely to damage the bearings if you tap the shaft with a hammer to coax it out, so don't do that. Instead, press it out. If you don't have ready access to a shop press, you can do this with a large C-clamp. Use a couple of small blocks of wood to protect the rear of the crankcase and the propshaft threads, and line things up to ensure the pressure is applied axially when you turn the screw. Abel

Reply to
Abel Pranger

Harry, if you wash it out really well, you probably won't have to remove the crank. However, if you must remove the crank, put the engine in a 350 degree oven and bake it for about 30 minutes. Remove the engine from the oven and place a wood block on the end of the propshaft and give it a sharp rap with a hammer. Automatic transmission fluid makes a good reassembly oil.


Reply to
Morris Lee


You're very foolish to take this engine apart. After all, it's only a

40 sized and Chinese at that! At most you'd be out fifty bucks if it was completely destroyed!

Your best course of action is to clean off the outside carefully making sure dirt doesn't get in through the carburetor opening. Even if some dirt does get in and assuming you haven't turned the crank over, you can flush it out with some fuel in a bulb.

You might also take off the back plate and flush out the inside making sure you add some lubricant like 3-in-one oil before you leave. Incidentally, these after run oils are a lot of hokum!

After all of this, try turning over the crank. If it sounds smooth without any grinding like noises, you're good to go. If you do hear any bad noises, you'd be better off sending it back to the manufacturer under warranty. I can tell you that they'd likely send you a new engine to build customer goodwill.


Mr Akimoto

Reply to
Mr Akimoto

Harry. I agree with Abel Pranger , although there was nothing wrong with the other's advice....except Mr Akimoto' certainly aren't foolish to repair an engine. As you can see now that you have already tore it apart , not a lot to it . I'm sure Mr Akimoto was well meaning in his comment , but some peoples pockets are deeper than others. To me , 50 bucks means a lot and it's good to be able to handle your own repairs. Part of the hobby.

And...... after run oil of some sort is a good thing , not a bunch of 'hoakum' as Mr Akimoto put it. I have tore many apart that did NOT have after run oil and it's not pretty if it's been sitting a while. Of course , different fuel contents make a differnce in the rust and corrosion. You probably already know this though.

Hitting the end of the crank with a hammer and block of wood is OK if it's a sharp , light rap as someone else has already said. This will usually do it. If a light tap won't do it , then a clamp and wood blocks as Abel said.

I usually wash my engines in hot soapy water , hit them with the heat gun and immediately dunk everything in Marvel Mystery oil or transmission fluid. All the other reccomendations are fine , I just like soap and hot water because it's handy . it works well , and your hands are all clean when you get done. :-) Can't beat the price either. Of course , if the engine has a lot of build up inside , then obviously you need something more heavy duty.

Don't worry , hot soapy water works well. I always used it to clean the cylinder walls after honing them in a car engine. Used to build racing engines a few years ago and still build one occasionally.

Although I said basically what everyone else did , I just wanted to post to cast a vote for the other suggestions. We are all in agreement. Safety in numbers or something like that :-)

Incidentally , I repair model engines and sell a few parts. Most will be used parts in good condition from other engines I have taken on trade or bought for parts. I do get a few new parts. Something I like to do and supplements my hobby budget. :-)

Ken Day

Reply to
Ken Day

To everyone regarding Ken Day:

This guy rambles on about nothing. Model plane fuel contains a lubricant that'll will protect your engine when you put it away for the day. It's true that model plane fuel is hygroscopic or absorbs moisture, but after run oil doesn't prevent this from occuring any better than any light lubricant such as 3-in-one oil.

The after run oil that the model shops sell or the Marvel Mystery Oil is just over priced "snake" oil to nick the ignorant, like Ken Day, for a couple of extra dollars.

The engine rusting shouldn't be any concern expecially if you fly fairly regulary. However, if you store your engines for long periods of time, it would be wise to put a few drops of oil in the cylinder and turn it over. In fact, Max recommends this. The only problem with adding any lubricant is what effect it will have on any rubber or synthetic gaskets like for example, the one around the carburetor flange.

If you're concerned about engine rust, take off the backplate. If you see any redness inside the engine, then you have a problem. I have several model plane engines in my shop, and I have an old Max my father gave me many years ago. All of them run and are occassionally taken out to the field. I have examined all of them from time-to-time, and I have never seen any rust. Probably Ken Day live down by the swamp in an old shack and has a problem with moisture (and alligators?).


Mr Akimoto

Reply to
Mr Akimoto

Never heard of him...

You got something against this mysterious bloke them?

Won't do much good in the cylinder of your average ABC glow engine... Put it down the carb straight to where the steel bits are - the bearings and crank.

In fact, Max recommends this. The only problem with

Never had a problem with gaskets and after run...

Engine rusting is very much a concern if you fly in the typical British winter... condensation, the water in the fuel, and the products left over from burning model fuel (esp. if it contains nitro) is a recipe for rust in side the engine. Left in a cold garage, or even in a heated house, rust

*will* establish itself within the week...

My advice... run the engine dry at the end of the day, pour a goodly amount of after run oil down the carb and turn the engine over a few times. I've not had rust since I've been doing this.

Many people do live in damp places...

Reply to
Philip Rawson

The majority of the human race lives within a hundred miles of the ocean.

Reply to
Robbie and Laura Reynolds

You do have a burr under your saddle don't you ? Simply because I disagreed with you when you called Harry Sanchez 'foolish' for tearing down his engine and repairing it himself.... and for calling after run oil 'hoakum'. I thought I disagreed very respectfully.

I would write more but the roof just fell in and I gotta go feed the gators.

Having a great time here in the swamps. Wish You were here. :-)

Ken Day

Reply to
Ken Day

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.