I was going to tear down the TT .46 I bought new last fall. I broke the engine in before it got cold. Before I ran it I tried to pull it all apart to clean and inspect it before its first run. Everything came apart fine except I couldn't get the connecting rod off the crankpin to pull the piston/rod assy. I asked about it here and the concensus was it should come apart after break-in. Well, I'm pulling it all apart to look it over, clean and oil it and get it ready for spring. Problem: The conrod still won't come off the crank pin. It looks like the conrod should be able to slide another millimeter or so on the wristpin to allow the rod to move far enough away from the crankshaft to come off the crankpin but it will not move that extra little teeny bit. I tried lightly prying on the rod from behind to see if I could get the conrod to slide on the wristpin the rest of the way, but no go. I don't want to wreck it, but if at some point I need to replace a bearing or P/L set, I won't be able to get the darn thing apart.

Also - whats needed to remove the aluminum prop hub off the crank? Is it on a collet or pressed onto the crank? On my engine, it looks like it has a brass/bronze collet but I wanted to ask since I wasn't sure.

You have to remove the liner first. then the rod will come off the crank pin.

Sorry, I forgot to mention that but the liner was out. The liner came out with the head. When I was trying to get it apart, I had everything off of the engine I could get off. Head, sleeve, backplate, and muffler. I left the carb on.

I couldn't get it off brand new and I can't get it off now with almost a quart of fuel through it for break-in. Everything inside looks brand new.

You have to remove the cylinder first to remove the piston and rod.

A prop hub puller tool is needed to removing the prop driver/hub.

This being said taking apart a good running engine is not a good thing.

If You pull the piston out of the cylinder it will need a new break in period and shorten it life.

Pulling the muffler & removing the head & back plate is all I do to inspect an engine or to flush it out if it's new before break in.

An engine that is running good doesn't need any thing but after run oil and a zip lock bag.

The only time I disassemble an engine is when it's had a dirt nap or needs new bearings, P/L or new ring.

So if it's not broke don't fix it, comes to mind.

Jeff

Well, after reading about some people having bearing failures, I wanted to inspect my rear bearing to ensure its in good shape. I can't inspect it very well with the crank in the way. I'll get the hub puller later this week but if the rod won't come off the crankpin, I'm still stuck.

Also - pulling the piston out of the liner will not need a new break-in period. The piston goes back in the same way it came out - Since its going back into its same position, nothing will have changed.

I agree if it aint broke, don't fix it; However - I pull all of my engines apart after break-in. Being that ABC engines are so tight from the factory, I feel better about looking them over before putting them into fulltime r/c service.

I recently purchased a top post battery terminal puller from NAPA Auto Parts for $19.00 and tax and it works wonderful to pull the prop hub off of engines, just a fyi in case you need to buy a puller.
John

You do not need a thrust washer puller or hub puller to change out the bearings in a RC model engine.
Here is how you do it.
http://rcmodelreviews.com/bearings.shtml

if the engine is working fine, and you haven't done something to it to warrant taking it apart to inspect, you really want to leave it alone.
The piston wears into the cylinder and the microscopic grooves in the cylinder and piston match up for a perfect fit. When you pull the cylinder out, you cannot get it back in exactly the same way as before, so now the piston fit is not perfect anymore. So you'll need to break it in again. Sometimes you wind up with a slight performance loss, sometimes no power is lost. it depends.

When it comes to checking bearings for wear, I do it more by feel and sound.
If the crank rotates smoothly and quietly, and there is no radial play in them, then the bearings should be OK.

You can see enough of the R. bearing to tell if it's corroded badly enough to warrant replacment...

I would suggest replacing it anyway though, if it has a metal ball retainer. The older TT R. bearings (w/ the metal retainer ) would sometimes let go at higher r.p.m. so it's pretty much standard procedure to replace it w/ a new bearing w/ a plastic retainer.

Check out this thread for bearing supply sources...
http://www.rcuniverse.com/forum/m_10272775/tm.htm

As far as the rod on the wrist pin...there's probably gum or varnish on the wrist pin preventing the rod from sliding back far enough.

A little carb cleaner, or acetone, brake parts cleaner, penetrating oil, etc. on it and let it soak for a while.
Then some heat...then try gently prying-pulling it back...w/an Allen wrench w/ tape wrapped around it to prevent marring the Alum.

If you're gonna replace the bearings, you won't need a puller for the prop driver...just put the prop nut on the end of the shaft....use a small block of wood as well for added protection of the threads, and give the end of the crank a few taps w/ a hammer to push the crank back and out. Heat the prop driver first.

You don't take an engine apart after break in! You will have to break it in again, do this every year and that is a lot of wear! Ok to take apart before break in but totally unecessary. Just take the back cover off, clean out any swarf and run! Don't take it apart again till you need to over haul it! Other than to take the back off to inspect for dirt and corrosion. A total waste of time.

You don't even need to look at it. Side to side or radial play will tell you if it is worn. Also bad bearings will whine. Even if you inspect it you may confuse castor varnish with rust. The cage can even be rusty but the balls and race be fine. But if you are doing this as a learning experiance, then the cost is cheap education.

Even if the sleeve is pinned it is very unlikely you will get this exactly in place, it may be microscopic but still out of place. Not to mention the risk of breaking or loseing something every time you take it apart. But I recall I took several engine apart for the education when I first started. You will most likely not notice the effect, especially with an ABC or ABN engine. This is more of a problem with ringed engines.

I like being more proactive so that's why I do certain things as a precautionary measure. Perhaps I'll do things a little differently from now on.

As it is, the wristpin is as clean now as it was when it was new. I'll was just going to clean it out and run it, but The rear bearing has a metal retainer. ( this engine was made in the early 90's.) I will need to remove the hub to pull the crank in order to replace the bearing. This engine is getting a Jett stream muffler and it set up to scream. I don't want the bearings to explode. Should I just run it as-is or pull it apart and replace the bearing?

Your crank/rear bearing is not fully seated.Try to heat the engine,then try to seat rear bearing into case fully.Then you will see your connecting rod will slide out easily from crankpin.

I don't think thats the problem. It was like this new, as I've said before. The rod won't slide to the end of the wristpin on the inside of the piston. Its about 1-1.5mm away. If the bearing isn't in fact seated, then it was like this from the factory. The engine ran fine on the break-in stand this past fall.

The million dollar question is what is the most realistic bearing choice? This thing is going to see some RPMs, so I dont want the bearings to fly apart. It might be optimistic, but I'd like to see 16k from it with the Jett pipe, and 15% fuel on a 10x6 APC. This engine will not see constant sustained high rpms being that its going on an airboat, so do I really need to change the bearings? I would like to find out why it wont come apart, but it does run as-is so maybe just leave it..?

I've been running TTpro .40's with 9/6 props for the last few years, they run around 16,500 or a little more on the ground.

I've had rear bearings fail, no warning, no corrosion, no rust - the stamped metal ball retainer cage gives up.

This pretty much makes hamburger out of the piston, sleeve, head, and sometimes the case.

Now ALL of my TTpro .40's get new bearings with plastic ball retainers in the rear bearing, before they ever run. The bearings will probably be replaced at some point before they're worn out, and I haven't seen that make much of a difference in piston/sleeve fit anyway. After they're past their prime for racing, they make good sport engines still!

I think I'm just going to find a way to get this thing apart, replace both bearings since I'm in there and be done with it. Then I know its good to go. I'll look on those bearing links I had seen earlier and get some ordered. I'll probably opt for the highest quality Steel bearings w/ phenolic bearing cages I can find. I'm not putting a full tuned pipe on this engine (yet..?) so I'm not gonna try to crank out every last bit of RPM from it so Ceramics are out I think..

The final concensus on the prop hub is just to tap the thing off with a block of wood on the end of the crank (with nut screws on) or is it worth buying the hub puller?

I don't know about the Jett I'm going to get, but this TT is the only engine I currently own with a pressed-on prop hub. I don't see it being worth it if the block of wood will do the trick.

Yeah...the block of wood trick will work...but heat the alum. prop hub / driver first.

<div style="border-right: medium none; border-top: medium none; overflow: hidden; border-left: medium none; color: #000000; border-bottom: medium none; background-color: transparent; text-align: left; text-decoration: none">Seems like an extra expense to replace bearings on a new engine. Voids the warrenty as well.. Or do you mean when you buy used TT engines?</div>

Its common practice to replace the TT 40 bearings on a new engine if you plan to race them. The rear bearing will not last long at high rpm.

Not sure why anyone would completely break down an engine just after breakin. You can check the rear bearing by pulling off the backplate. Heck, I just found 2 rear bearing problems doing this (different manufacturer). The purpose of breakin is to get everything seated (including bearings), taking it apart messes that up. There is no way you will ever get everything back the way it was.

Most of the engines I've ran have been ABC, and being they are so tight when new, I like to pull the rod out and look it over for cracks or bends. Ive seen it happen too often on Asian made engines - broken or split rods. I just don't have full faith in the quality on most of them. You guys might think I'm crazy for what I do but Ive yet to wear an engine out nor blow it up. It can't be all bad.

I'm gonna replace the bearings and be done with it. This engine was new/never ran when I got it, but it was made in 1997 according to the box.

If this was a Jett or Rossi or other high-end engine, I wouldn't take it apart for any reason.

I use the Stainless 6902's from rc-bearing...$8.99
The front is an R6Z (metal shield ) or you can use an R6-RS (rubber seal )

Nope. New ones. I really don't care if it voids the warranty, I'm not going to run a TTpro 40 in Q500 racing without a rear bearing with a plastic retainer. In 2009, my best engine puked a rear bearing and carved up a piston/sleeve/head combo. Not going to do that again. We had three club members that summer lose good piston/sleeve combos due to stock rear bearings shedding pieces of the retainer cage. None of them were rusty or corroded, they just weren't up to what we were asking of them. 16,500 to 17,000 on the ground with a 9/6, who knows what they unload to in the air.

Bearings are pretty cheap compared to the cost of all those parts. I've been buying stainless from rc-bearings.com and had good luck with them.

I did buy one used TTpro .40 engine once. It's about 500 RPM down from my other three, pretty worn. It's good for practice, but when race day comes, it's staying home.

I always pull the backplate as a minimum before running any engine, new or used. The heads of 2 strokes come off and usually the carb too.

Its cheap insurance to look them over. I've cleaned enough metal shavings out in the past. Not good.

Most of my rc car engines have metal caged bearings, now that I think about it. Those engines turn 33,000rpm+, and the bearings never explode. What's so different with airplane engines?

Can't speak about the car engines, I don't know. I just know that I have first hand experience with .40 rear bearings having ball retainers come apart. Maybe they weren't very good bearings to begin with? I do know that in some of the newer TTpro's they are coming with bearings with plastic ball retainers, and those don't have to be changed.