TT 50 Engine set up (Help Needed)

[guygate88]

I brought an almost new Raptor 50 a few weeks ago, I was told the engine hadnt been fully run in so I took it very easy for a gallon or so, occasionaly richening it up as it started to lean out.
All was fine for about 10 tanks till one day it just cut on me. I managed to get it down ok but I noticed the engine was very hot.
I stripped it down to check for damage all was well and I reassembled it and it ran fine on a short test flight. As a precaution I booked an hour long set up lesson with a local pro who set it all up for me. It flew great during that hour but as soon as I went out on my own it cut again.
Stripped it again - No visable problems, re-newed the Glo plug, clunk lines, and everything else I could think of and booked another set up lesson. The pro got it running great again during the hour I had with him but as soon as I went out on my own it has started overheating again.

What's going on?

I cant afford another £40.00 session to try and get this engine right, should I just cut my losses & but another one?

The only thing I can think of is that when I first stripped the engine I noticed a slight amount of endfloat between the front bearing and the fan, when I reassembled it I did the fan up to (not tight on) the front bearing and locked it off with the lock nut.
Should I have left a slight gap between the engine and the fan to allow for heat expansion of the engine casing?

Please help, I'm relativly new to this, and although my flying is coming on well, I have no confidence in the heli, and seem to spend all my time fiddling with the engine!

[forjer]

The fan should be tight down on the bearing with no washer in between. I had a problem with mine backing off which was due to not tightening the fan enough, and not letting the thread lock set long enough to cure.

A fan that has backed itself off the bearing can cause excess heat by allowing the clutch to interfere with the housing and load the fan.

As far as the condition of your engine, it's tough to say. I think you need to get to a club and spend the afternoon with other heli guys. Hopefully one of them can help you.

[Helirat]

Sounds like the typical TT mid-range lean issue that plaque's these engines. Try richening the idle mixture up, probably need to go a fair amount. This will make it idle rougher and probably need to add idle trim to get it to idle but may help the mid-range lean issue. Ultimately you will probably want to modify the main needle by putting it in a hand drill and sharpening the end to a finer point. This will allow you to lean out the idle but run a richer mid-range.
You could also replace the carb with an OS carb, or just replace the hole engine with an eaiser to tune OS-50

[guygate88]

Thanks for the input guys. I've tried everything, even took it to see a few local flyers who's advice was "Get a Zimmerman muffler" but I dont want to waste any more money flogging this overheating dead horse!

So it's had new bearings, clunk lines and fuel lines, cleaned the carb, cleaned the muffler, put a point on the main idle screw, tried new fuel & glo plugs. And i've by passed the header tank. The headspeed is 1580 in a hover and its still getting red hot after 5 or 6 minutes hovering.

I've richened it up so much it looks like a crop duster flying over a Queen video! At one point I went another couple of clicks and the needle fell out!

Any last ideas before I take a nice cool running 4 stroke chainsaw to it!

[greg006]

There is a article on the aussie site archeli on how to tune TT50 MOTORS. read fangs post
http://www.archeli.com.au/cobra/showthread.php?t=117282&page=2