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
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.
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
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.
Harry. I agree with Abel Pranger , although there was nothing wrong
with the other's advice....except Mr Akimoto's......you 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. :-)
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
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?).
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.
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
Having a great time here in the swamps. Wish You were here. :-)
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