[Second time around]

ThunderTigre Pro .46 motoro BB--ABC. The motor only has about 6 tanks of fuel thru it. It may have had a lean run or two because the motor turns fine but gets really tight at the top of the stroke. It still will run but the idle is a problem.
Any suggestion on this motor would be helpful please .
Thanks

[cassat]

It doesn't sound damaged to me. I would run a few more tanks on a test stand wide open and hot but use a good fuel with proper oil. Maybe even add a bit of Sig Castor oil and let it seat some more. You don't want it very rich or the sleeve will not expand.

[Gary Maker]

You said its had: " a lean run or two! Believe it or not, just a few seconds of lean run can do serious damage to the piston and sleeve. Take the muffler off and look through the muffler port at the piston....has it discoloured, perhaps a pale or even dark blue colour? If so there could very well be damage.

If you find the piston discoloured then I would dismantle the engine and take out the piston and sleeve for a close inspection with a magnifying glass to see if there are any small lines or groves in the cylinder wall or piston. That would very definitely cause run problems especially on the low end. If thats the case, then you either buy a new piston and sleeve or replace the engine. Hopefully you'll see no problems.

As for the tightness at the top of the stroke, thats normal especially with a new or fairly new engine. The tolorances are very tight in an ABC engine! (no piston ring).

If theres no discolouration, then as has been mentioned, it could just need a bit more breaking in especially if your runing a castor/synth blended fuel. Castor will lube so well that the parts take longer to mate therefore a longer breakin period is required.

I've had a few TT 46 BB Pro engines and I just love them. A real solid relyable running engine with lots of power for most 40 size planes. Hope all is well with your engine. Please let us know how you make out with it!

[Second time around]

I found this information at another sight and thought it to be interesting to all

TT ABN engines need a HOT break-in. DON'T do the rich run routine or you could possibly ruin the engine! Don't run them full lean at first, but definitely past the rich/lean break. Typical break-in for a TT PRO .46 is to run it up with a 10x6 to get the needle set to run lean...this is a short as possible run...let it cool afterwards. Then put a 9x6 on it and take it to 16.5K RPM and hold it there for two minutes...let it cool a LONG time. Then put an 11x5 on it (this engine's favorite prop IMO) and run it through 3-4 eight ounce tanks at full throttle just leaner than the rich/lean break...let it cool well between tanks. After that put it on a plane and go fly it...it will just keep getting better. BTW, all props are APC.

Further, I've owned just about every engine they make except the .07, .61 & 1.20 two-cycle ones. They are inexpensive and do the job quite nicely IMO...particularily if you are a 'sport' flier. Currently I own 2-GP.15's, 2-GP.25's, 2-PRO .36's, 1-GP.42, 10-PRO.46's and 2-FS.91's. No, they aren't all in use...but I'm a packrat.

Thanks for the information guys. I am awaiting delivery on this motor .It was purchased very cheap and delivered as well . Even if it has been leaned out it will be worth the repair. However one might get lucky and find it to be nothing more than minor.
Thanks will let you know when I get it and inspect it.
Ken

[Second time around]

Ok
Received motor in great shape.
Ran today and seemed top end run OK .
idle OK
when stopped and turned engine over by hand it was pretty tight on top end almost squeaky tight .

Piston looks as new so does motor It seemed to run hot though .
Suggestions please Ken

ABC motors need to be brought up to the operating rpm and temperature for the first couple of runs. However it also has to be well lubricated.

Break the engine in this way.

Get say an old 10 x 6 prop cut it down to 8" dia, balance it. Use this prop for break in.

mount the engine Preferably on a test stand with a max of 8 ounce tank.

Start the engine and needle it up to about 17,000rpm. The small prop will allow that engine to come up to that rpm and operating temperature but with a rich needle setting. There should be lots of smoke and a very wet exhaust. let the engine run do not play with the needle, maintain the rpm. When the tank is nearly empty stick your finger over the intake to stop it. Do not let the engine run lean . If an ABC engine is allowed to run cool on it's first runs the piston will wear out very quickly.

Let the engine cool down completely.

Repeat the process two or three times then the engine is ready for use.

Ed S

[Flypaper]

Check for that tight spot as soon as the engine shuts off hot. Tight spot shouldn't be there. As the engine cools off, you should feel it tighten up. I have an old KB 21 DF engine that has many miles on it and is still tight at the top. A sign of a long lasting engine if looked after properly.

I have an old KB 21 DF engine that has many miles on it and is still tight at the top. A sign of a long lasting engine if looked after properly.

How true that is. Convincing people how to achieve that is a task.

Ed S