Simple, these are sport engines with sport bearings. While they are happy turning 13-14k all day, running them at max rpm will cause issues (bearings are usually the first to go). Most people can get a season out of them just adding hi speed bearings. I usually push mine harder and have to replace piston/liner each season.

If you want higher performance, get a hi performance engine, or at least a better quality sport engine.

Hi!
TT .40 SE and .46 are some of the best sport engines there are!
WIB ( C4 ) plastic retainer bearings are available for those who want better performance.

TT's are not a trash engine. If you are not racing I see no need to replace the bearings if it has never run. Just take off the back plate to check if there is no rust. Being new there should not be an issue confusing rust and varnish.

I have never worn an engine out (other than used ones that were half or more to begin with), and only one set of bearings prematurely worn out.  I probably don't fly on one engine as much as others but I have been flying models of one type or another since the 70's. 

But this is a hobby and if you get satisfaction from tearing them apart and putting them back together then it is all part of the enjoyment.

If you don't expect the engine to run 30,000K then there is no need to go to the expense of putting bearings rated for that. So they use bearings good for 15,000 to 20,000K. So if you plan to put on a small prop and rev it to that then you will need the harder and higher tolerance bearings that will do that.

You ever know what you'll find inside an engine when you take off the backplate. I found a small rubber band once in a new engine.

I plan to run the engine fast. Short of a full wave tuned pipe, I want to get the most of what I can out of it. Probably no smaller than a 10/5 prop. I'll get a better engine in the spring.

Quote:

ORIGINAL: 1QwkSport2.5r

...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 wrist-pin to allow the rod to move far enough away from the crankshaft to come off the crank-pin 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.

1QwkSport2.5r,


It must come apart like that, if for no other reason apart from the fact; that this is how it was put together in the first place...

Try turning the crankshaft to bring the piston to BDC; putting a medium,tie-wrap around the con-rod's top part and pulling back on it.
This should make the con-rod's top-end slide over/past an obstruction (most likely congealed castor oil) on the wrist-pin.

This, in turn, will allow the con-rod's bottom-end to be unhooked from the crank-pin...


The only other possibility, is that crankshaft is not fully seated in the rear bearing, or the rear bearings is not fully seated in the crankcase...
But since the prop-driver is still on the crank, this is very unlikely to be the case.

With a 10-5 prop and pipe you are probably looking at about 16K RPM. The stock bearings should last a few years, but obviously not as long as if running at 13-15K where most people run it.

1QwkSport2.5r,

I second what DarZeelon says. You want the crankshaft pin on the bottom center for best leverage to unhook the connecting rod. Slightly turning the crankshaft while gently pulling on the connecting rod should also help.

For good high performance bearings try the Boca http://www.bocabearings.com/bearing-...engines-pro-46
and http://www.bocabearings.com/bearing-...engines-pro-46
The ceramic bearings are lighter and may help acheive higher rpms.

My experience with the ceramic bearings indicate that they are far from being cost effective. They are a downright technological failure.

The standard 52100 steel beaing with a a polmite or phenolic ball retainer is best for the high speed situation like in the second link

I didn't think about using a ziptie on the rod. Though the wristpin is clean and shiny; at least what's visible. I will try that and see what happens. I had the piston at bdc when trying to get it apart. I will try it again.

Jim,


That's what Paul (RC Bearings) offers in nearly all his standard two-stroke sets.

And, BTW, there generally is no difference, in the RPM limit; between bearings with steel cages, and the same bearing sizes with plastic cages.
...And this limit is around twice what most engines are capable of turning...
The advantage of the plastic cage over the steel cage is that if it happens to fragment; the pieces are much less likely to take out the piston/sleeve.


Jeffie,


The problem with Boca, which you so avidly endorse, is that the price they charge for this type of bearing set (which they call 'High Performance'), is as high as what Paul asks for his ceramic hybrid sets.

word to the wise..............TT46s can run under water,,,,,,,,run them use them fly them and dont take them a part,,,unless you break something, flush a eng out with after run oil or wd40 but dont get inti taking them or other nitro apart................oh thats 40 yrs of flyingthats talking

Handyman,


That may have been true with engines in the past... and with modelers from the past...

In current times, people in this forum and elsewhere, are too used to engines with inexpensive, corrosion sensitive bearings; and to fuel that contains too little castor oil, or none at all; and to not running their engines dry at the end of a day's flying...
...And to WD40, which is quite useless as a corrosion inhibitor...

I have an MVVS .49 engine with far more than 100 hours on it, still with its original bearings; but for most of the 'general population', you can just forget all you wrote...

The times certainly have changed. What I don't understand is why these fuel companies don't use more castor oil. There are just so many benefits to using it. When I mix my own fuel, I'm probably going to run all castor oil in my fuel. I just don't see any reason to spend that much more money on the synthetics when castor is all they used to use back in the day.

Times have changed. Years ago, you built your own planes and sometimes radios. Hams built their own stuff. When I first got into computers you had be proficient in BASIC at the minimum. You were a hero if you could program in machine language. It's an across the board thing.

Not all of what we did in the past is good. I wouldn't give up CA or expo. I prefer some synthetic oil with castor.

Well, I did manage to get the piston out, finally. It was extremely tight. What I found was the flashing from the casting of the piston to be in the way. My camera wouldnt take a clear picture that close up, but it seemed that the flashing around the wristpin journal to be the culprit of the rod not moving far enough. (please don't bash me for this...) I took a diamond bit on my dremel and shaved off just the flashing around the wristpin journal and there was quite a bit on the piston skirt where the notches are cut into it so I shaved the flash off. There is no flashing anymore and everything is clean. Now I'll order a set of high-speed non-ceramic bearings and be on my way. When It warms up enough to get outside to run it, I'll do a short re-break-in on it so everything seats again and test out the fuel system I'm going to use on the boat.

This has to be the only engine I've ever had in my hands with tolerances as tight as they are..

1QwkSport2.5r,


This is the RC-Bearings set for yur engine (and many other engines...).

Ask Paul to substitute the double sealed R6-2RS for the R6-ZZ front bearing.
The grease packed bearing lasts longer.


It comes with a polyamide cage rear bearing, which is the essence of a high-performance bearing set.


EDIT: Added info.

Is the front and rear bearing the same size?

Rear is a 6902 (28 x 15 x 7 mm )
Front is an R6 (7/8 x 3/8 x 9/32" )

Thanks for all of your help, guys.. I appreciate it. As far as those bearings go - is one really SAE and one Metric? Aren't both bearings usually metric? I totally believe those to be correct, I just find it a little odd that one's metric and the other isnt.

I'll order those up and pop 'em in. I can use the 300°F oven trick to swap bearings on an aircraft engine, right?

It is common for the rear bearing to be metric and the front to be inch.

I use the heat method myself and have never had a problem.