The aluminum prop driver hub is locked on with a split cone and this one’s really on there. I don’t want to damage or distort it. I guess the best way to remove it would be a with a gear puller, which I don’t have. There is a deep groove in the side of the hub. Any tips that don’t involve prying, banging or special tools?

It’s a new/old RJL K61 I tried to bench-run. I think it hydro-locked, burped then froze. I suspect that the crankshaft is twisted at the weak point-where it’s ported. Crank will turn but it’s very stiff. I want to examine the damage and determine if it’s worth buying parts for -$30 for a new crank, may need bearings, etc.. I’ve had other engines do this but they just spit the prop at me with no damage the engine. If the crank is really this weak, I may not want to sink any money into this unit. Thanks for the help!

Yes W.O.P., to avoid damage to the prop driver, the only safe way that I am aware of is to use a gear puller & a heat gun. Recently I used both those items to remove a VERY tight prop driver on my Saito 65 - worked a treat, the heat gun being necessary in my case.

Attach the gear puller, tighten it up with a small spanner/wrench, apply heat & wait for it to pop off. Sometimes the pop will be a loud bang & that can be a bit disconcerting. My gear puller cost me about $20 & I have now used it at least half a dozen times. It's good value.

As for your other issues, I'll pass on those & let the others answer that one.

You should be able to get an inexpensive battery terminal puller, or small gaer puller from Harbor Freight, or Auto Zone, or a place like that.

The use of heat makes it "pop" off much easier..(more easily? I ain't none too good at grammar)

If you really loaded it w/ fuel, I would think maybe it's the rod...perhaps bent it...I doubt the crank is broken? Unless you can feel grunching metal to broken metal as you try to turn it, I'd say it's prob. the rod.

Thanks for the tips guys. Battery terminal puller is a great idea. I may be able to mooch one. I hope it’s the rod-and the crank is good, but at first glance, everything looks OK from the top and the back of the engine but there’s a bit of of aluminum-colored goo under the carb so I’m thinking crank. Thanks again.

Hi Guys,

Friend of mine demonstrated removing ball-bearings by extreme cooling with liquid nitrogen and without any
instruments, i.e. only by its own weight droped out.

Would that work in this case or it will get even worse, i.e. depending on the
difference of the thermal elongation coefficient of the metals; has anyone
tired that ?

Regards,
Nick

I use the "brute force and ignorance" method of removing prop-drivers from tapered shafts.

This consists of placing the engine on a hard wooden surface (backplate end down) then placing a small block of aluminum atop the threaded end of the crankshaft and giving this a good smack with a hammer.

Okay, you can stop cringing -- it really doesn't hurt anything.

if nothing comes loose after a couple of good blows I put a heat source (usually a propane torch) on the prop-driver (NOT the crankshaft itself) until it just sizzles if you wipe it with a wet finger -- then try again.

If it still won't budge, try a little more heat -- but don't melt it. On a real stubborn driver you can wipe a little plain laundry soap (the yellow bar stuff) on the driver and heat it until that soap just starts to discolor (it'll start turning brown) -- but no hotter!

This method has *never* failed to release a crankshaft/driver and I've never damaged either in the process.

Points to watch:

1. Don't use this method unless your reason for dismantling the engine is to *replace* the bearings -- because it may cause some brinnelling of the balls in some engines.

2. Make sure you hit the aluminum block/crankshaft squarely with your hammer blows -- this is to ensure you don't bend the threaded portion of the shaft (I have never bent one yet).

3. Don't substitute steel for the aluminum block -- its purpose is to protect the crankshaft's threads from being damaged

4. Make certain that the wooden surface you're sitting the motor on allows the rear face of the crankcase to contact evenly. Some motors won't sit flat on a large flat surface because the diameter of the cylinder is too big. In such cases, move the engine to the edge of the table or whatever so the larger diameter bit can overhang, allowing the crankcase rear to sit flat.

Yes, I know this sounds brutal and a great way to wreck your engine but, if you understand what you're doing and take care, you can get even the most stubborn prop driver off this way without any trauma.

The big benefit of this method is that it doesn't leave ugly scars on your prop-driver.

As tested on: Thunder Tiger 46Pro and SuperTiger G90 engines :-)

I used a battery terminal puller to remove the hub from an HP .61 that had been stored unoiled for several years - it works. You'd be surprised how easy it will come off - and you won't have to bang on it either.

Thanks again for the tips-all good suggestions. The goods news is that the disassembly was quick and easy with no special tools. The bad news is that the engine is lunched. It needs a new crank, a new rod and a front bearing at minimum. I think that if the RJL is too weak to withstand a little hydro-lock, this will just happen again and it’s not worth pursuing. However, I did learn some things that may help others. Basically, heat did the job for the removal of all stubborn parts and no special tools or forcing was required. The MECOA web site (source for RJL parts) has some good (but incomplete) instructions. They suggest using a toaster oven to heat the engine (minus any plastic parts) to 300 degrees. I purchased a used toaster oven at a thrift store for $2.00 and it worked to perfection.

After heating, the piston sleeve popped up right up with a partial rotation of the crank. Even if it had not come out that easily, it could have been coaxed out without the use of any tools (other than a finger and a rag) and it’s always better NOT to take the chance of damaging the piston/sleeve with a tool.

The prop driver popped right off by holding two pieces of snug-fitting scraps of 3/16” round steels rod in the groove of the hub and tapping the front of the crank on a wood block. This particular prop driver was very stubborn so the heat method should work for anyone.

The crankshaft came out with very light taps with a brass hammer and could have been unseated just as easily by pressing the front against a wood block.

The rear ball bearing dropped out by tapping the crankcase on a soft wood block. The front bearing came out by using a 5/16” bolt (with a nut threaded on to act as a shoulder) to drive it out the front. Only very light taps with a hammer were required.

So....what broke??? (or was causing the binding, etc.?)

Edit: Forgot to say glad you got it apart!
With a little "persuasion" now and then, they are fairly easy to work on, aye!?

Proptop,
Without the bearings installed, the crank journal seems fine and turns freely in it's bore. With the bearings, it binds so I suspect a twist in the weak, ported area of the crank-or even the case. Can't be seen by eye or crude mearsing devices. The front bearing has way too much play between the races - but I think it's mostly due to being a crappy quality rather than being damaged. However, as it turns out, I have the correct new bearings (all I have to do is pull the seals and flush the grease) and they are much better quality than the originals so I'll try it again. The rod is bent - just barely enough to see by eye and but enough to add much to the binding feel at the crank.
Later

That grease will come out of the bearings anyway when you run the engine and the model airplane fuel gets in the engine.

If you take a seal out of the bearing, it is unlikely you will be able to reinstall the seal back into the bearing so be sure you do not remove the outside of the front bearing.