Thunder Tigre 50 Tuning

[HeliSat]

Just trying to sort out the mixture screws on the Thunder Tigre 50 engine. The high screw is ok, but how many turns should I have on the low mix screw? The engine has only done approx 1hr work and runs fine in my raptor during flight but it refuses to idle for too long. Symtoms include spluttering, and bogging down initially when spooling up. It seems too rich on the low screw but leaning this screw didnt have much effect. After 3 more turns in on the low screw the engine would idle ok but was too lean at higher rpm, even when richening the high screw.

Any help would be appreciated.

[StillTryin]

I would suggest you do the low speed needle mod first - basically it involves putting a 2mm length taper with approx 1mm of overall diameter reduction. It's well documented on RunRyder. This increases the size of the "sweet spot" or decreases the sensitivity if you like of the low speed needle.
I did it by removing the low speed needle, chucking it in a small drill and, with the drill running, touching it against a running belt sander at a very small angle. Easy as ...
Remember that on TT engines, the low speed needle manages the mixture to approx 2/3 throttle opening.
What you describe sounds like a good starting point to begin a slow leaning of the low needle and simultaneous richening of the high speed one - it's a balance of the 2 needles you are after. It's best to "sneak up" on the final settings or you will end up chasing your tail.
These engines seem to need a fair run-in period and do run hotter that some, such as the OS 50 hyper. Don't be put off, they are tunable and perform well with good economy albeit with less outright power than a hyper.
Hope this helps.

[HeliSat]

Thanks for that ... Ill see how it goes. I might put the LSN in the lathe and use a dremel. I am assuming that your overall result is to have a longer taper along the needle.

[StillTryin]

Hi Helisat
The low speed needle has no taper ex factory - that's why the sweet spot is so narrow. Don't overdo it :)

[HeliSat]

Ok, before I go do something that I regret. Let me doublecheck, I will be grinding a taper 2mm long and at the thinest part it will be 1mm narrower?

[StillTryin]

Yep that's about it. Here's a photo.
http://runryder.com/helicopter/gallery/6213/TT50LOWMF-.jpg

[HeliSat]

Excellent ... I checked out his whole gallery. I will try that this week.

I should be able to set up my lathe with the dremel as my grinding (cutting) tool. This way I will get a perfect taper.

Thanks for the info.

[Snowman]

I am about to buy a TT 50 for my heli and was wondering about this mod and if it applies to the current model TT 50?
If it does, is everybody happy with the result?
Cheers in advance.