Has anyone seen or tried the new TT .75? Several years ago we ran the TT .91 and found it to be a very reliable engine.

Thanks,

Cajuncharley

im trying to tune one right now, what a pig

Tell us more...

The TT91FS can be fussy to tune -- throwing props at the blink of an eye -- but it *is* a real powerhose and they settle down a lot once they're properly broken in.

What's the 75 doing?

Ive got it running sweet now, the factort settings were FAR too lean, especialy for running in. It idles great, transitions from idle to full noise with no hesitation, bad thing about it is I have it in a 46 sized Seagull Ultimate, and its just not anywhere near enough power for it. So out it came and A TT 61Pro was shoe horned into it...the 61 is actualy larger in diamentions than the 75 4c.

So now im left with wondering what I can put it into. I have a room full of aircraft, but none that would be suitable.

Where did you buy it and how much did you pay?

You must like flying bricks because a TT Pro .61 is way too overpowered and way too heavy for that plane. It also should be more powerfull than a .75 four stroke.

Yeah, im used to flying bricks, I own a lot of them...and the ST61pro wasnt too much engine for that Ultimate by any means. its dimentions arent much smaller than the 120AX powered ultimate I fly as well.

Yeah, im used to flying bricks, I own a lot of them...and the ST61pro wasnt too much engine for that Ultimate by any means. its dimentions arent much smaller than the 120AX powered ultimate I fly as well


That would be TT61pro

I have run about 3 tanks of 15% Omega (with 3 ounces of castor added), and the engine seems to be just fine. One unusual feature of this engine is that the cam gear (heli cut gear) is held in place not by ball bearings, but rather by what appear to be bronze bushings. According to the parts manual, both the .54 and the .91 do have ball bearings on the cam gear. I wonder how it will hold up over time, and why bushings only on the .75? All my Saito 4 strokes have bushings on the cam gear and it does not seem to be a problem. It will be interesting to see how it plays out over time. I wish Bill Robison were still here to address this situation. Another question is how does the cam gear get lubrication? The breather nipple is located in the backplate, and after run oil can't reach the cam gear (I think).
Cajuncharley

What prop are you using to break the engine in? Have you tached it?

I used an 11 X 10 prop as it was the only prop with a 1/4" hole that I had. My tach has gone bananas, so I am not certain about the rpms.

Fourstrokes sound horrible until you get them dialed in. Vibrating, kicking, bucking, crying, whining and you thought you bought a piece of junk. ONce you get it done, like shoving a pacifier in a baby's mouth.

I was just checking out the specs on this motor and it would appear to be awesome! 17oz for a .75 four-stroke definitely gets the nod so far. Please keep us posted on the tach numbers.

Ive given up on mine....should have stayed with electric or 2 stroke

Don't give up too soon -- remember that TT 4-strokes take a *lot* of running in.

But, if you're going to throw it in the bin, toss it over the Tasman to me :-)

Ill keep that in mind mate, I mostly fly aerobatic electrics mostly and a ST45 ST51 TT61 or an OS120AX 2-stroke. So im not used to 4-strokes at all, in the ultimate I had it in it just didnt perform, and im not so sure how it handled being inverted, very smokey in the low end, and impossible to adjust, smokier than any of my 2strokes. Ive got probably 20 differnt aircraft id like to try it in, but i just cant get it tuned properly. I even went out and bought a Panic fun fly to chuck it in, half way through building it i decided to get out the ST51. So now its just sitting there, waiting to be tuned.

4-strokes tend to smoke more than 2-strokes, partly because they have higher combustion temperatures and partly because the combustion is more complete.

I suspect that your fuel tank may be too high for an inverted 4-stroke which is why it runs rough at idle.

You've also got to remember that prop-selection can be mighty important and if the 75 is anything like the 91 you should be aiming for about 10,000 RPMs or maybe a little more on the ground. The TT 4-strokes like to rev a little more than OS or Saito.

But most of all -- it'll need a couple of hours running (at least) before it starts to settle down.

Oh, what am I saying...

It's rubbish -- send it to me and i'll make sure it's disposed of safely and in an environmentally friendly way (so you don't get into trouble)
:-)

LMFAO, good on ya. its not so much that its running rough at idle, it transitions well, dont get me wrong, but SMOKEY, at idle and mid range it smokes like a tyre fire....waaay too much smoke. maybe youre right about what you said about the fuel tank.... ill chuck it in an Expo3D and see how we go.

Dont worry mate, ill keep the disposal thing in mind

I finally got to run my ThunderTiger .75 on my Sig Kadet, Sr. today for its first flight. It ran very well. It ran for about 15 minutes at about 65-75% throttle, and shows great promise. It seems to have at least as much power as the Saito .72, but it is a little too soon to tell. This was the 4th tank of fuel run through the engine. I'll keep you updated...
Cajuncharley

If the combustion is more complete it should smoke less not more. My four strokes smoke as much or less than my two strokes, but then I don't use a plug that is too hot or mixtures that are too rich. IMO most four strokes smoke more than they should because the user is using a plug that is too hot for the prop and nitro percentage in use.

so what props would you fellas run on a 75 ?

Look at all the money and hassle you save on a smoke system. Lots of guys would dye for a free smoke system.

haha yeah, but the money pouring out of the exhaust from idle to mid 3/4 range sort of cancels out the smoke machine savings

The prop I ran on the .75 yesterday was an APC 11 X 8. I finally got a tach that works, and I will check the rpms this afternoon. I also plan to run an APC 11 X 7. As mentioned before, the engine ran well with the 11 X 8 on its first flight (4th tank of fuel-15% nitro).
Cajuncharley

It may be that the prop is too small. I'm running an APC 11X7 on a TT 54 four stroke... perfect combo. I realize you're still breaking it in but I'm thinking a 12X6 or 8 might be a better choice.