Picked up a new in box gp42, but no breakin instructions.
I have a pro46, but don't know if uses the same breakin proceedure .

Any info appreciated

If you broke in your 46 and like the way it runs break in the GP just the same. These little engines are pretty much bullet proof anyways.
This was my first engine and had multiple lean runs,a few dirt naps,broken parts,covered in jb weld and no controled break in at all. After all of this, once I learned how to tune it properly and set up a feul tank it ran like a clock,and still had lots of compression. For what it is,this is a powerfull little unit,but don't expect it to put out like the PRO 46.
TT 42 GP Master Airscrew 11 5 11,500 rpm
APC 10 6 12,100 rpm

I have a buddy who has cornered the market on 42GPs, or so it appears. They are very popular in my club.

They are really great little engines. On a light plane with a 10-6 or 11-5, you'll really love the 42. They are 5 ounces lighter than the .46 (12.5 vs. 17.7 with mufflers) so plan ahead. Keep the tail light. They are a good sport engine on something like a 4-Star 40, a World Models Sky Raider Mach II or a Tower Kaos-I have flown all of these. They can also pep up a .25-.28 size fun fly plane.

Most are pretty tight when they are new. Mine was tighter than my Pro .46. You may have to heat up the cylinder with a heat gun to start it the first time. Expect a pretty long break-in-as I said, they are tight.

I would run a castor blend fuel, at least for the first gallon. I like castor fuels for all my ABC type engines. 10% is fine.

I have a Thunder Tiger pro .46 and when i got it new it ran like a top, now i have ran almost a gallon of fuel through it and i cant get it to idle properly. With the glow ignitor on it runs good, as soon as i take it off it quits- changed plug, works better, but when come in for a landing i'm either too fast coming in or dead sticked. Does anyone know what could be my problem?

I've always had problems with my Gp42 that came with my Tiger Trainer. It lastes less than a year. It overheats like crazy, and grime got all over it from somewhere (Yah, i diss it, but i bet it was just me being a newbie). Anywho, i busted the muffler off. Would a TowerHobbies muffler fit it? I just ordered an Uproar, and i kind of want to test out the GP again in it, but cant do that without a muffler!

The Tower muffler for the 40-46 will not fit your Thunder Tiger GP42. That engine's exhaust matches the OS 40 FP and I believe LA series engines. It also matches all the 25 through 39 small case engines that have a helicopter version also. ( OS 28-32 Webra 32-36 Irvine 39 Thunder Tiger 36-39 Etc.) One of the best values for your engine is actually the stock muffler from Thunder Tiger.

Rich,

To break-in your TT GP.42 properly, follow [link=http://www.rcuniverse.com/forum/m_1850473/anchors_1850473/mpage_1/key_tapered%252Dbore%252Cbreak%252Din/anchor/tm.htm#1850473]this thread[/link] closely.

Any other tapered-bore (without a piston ring) engine must be similarly treated, to achieve the best power and reliability and the longest possible service life.

As anyone would know that has visited most R/C sites over the years, I am a Thunder Tiger engine backer...they are ALL that I own in as far as modern engines (I've got a few McCoy Redheads). I've probably helped them sell a LOT of engines with my sharing the positive experiences I have had with their engines.

With that said...

To break in these engines don't baby them, run them hard right out of the box. Use a fuel with at least 20% lube, preferably ALL castor. Nitro should be 10% or less. Fuel for after break-in should be 10-15% nitro, 20% lube (1/2 castor, 1/2 synthetic).

For the GP .42 I would start with an APC 10x4 and an OS #8 plug. Get it on a test bench and fire it up. Get it to running a clean two-cycle run QUICKLY! Tweak the needle leaner unitl it starts to slow down then open it up 3-4 clicks. Run it through a full 8 ounce tank this way...at full throttle. Let it cool and do another 8 ounce tank with the same setting...at full throttle. Let it cool and check the air-bleed screw on the carb before the next run so that it closes off half of the bleed-hole opening, this is a good starting point. Check the idle stop by putting a builder's pin into the throttle rotor opening and adjusting the stop so that the rotor is set to be open the amount of space the pin makes at idle position, this is also a good starting point. Then do another eight ounce tank, this time vary the RPM some to see if it will idle. If the engine needs more full throttle run time it will die when you try to idle it down (still too tight), otherwise it will idle down fairly low. This engine's idle will continue to get better (lower) the more it is run. My GP .42's idle and transition are excellent for an air-bleed carb engine...I had to run the 'H' out of it to get it to idle down...it was real tight! You will have to piddle with the air-bleed screw setting and idle stop setting for a while to get it 'right' until about a gallon of fuel has been through the engine, then you will never have to touch either as it will run flawlessly.

Bottom-line, these engines typically come from the factory with a TIGHT TDC pinch that takes time to run-in. Do not even consider running this engine rich during the first hour of run time or you will lessen its usable life.

Should you have any further questions about TT engines contact ACE Hobbies (the US distributor) http://www.acehobby.com/acehobby/pro...nes/index.html I'd bet they would be able to email you a file containing the manual.

The quitting problem would have been the plug. You've fixed that by installing a new one.

The other problem re the dead sticks etc is a tuning problem. You obviously are having to set the engines idle quite high.

Get an experienced modeller at your club to help you sort it out. You will probably find that both the high speed and mixture needles need adjustment. This is common with engines after initial run in.