angelsddy

I bought a thunder tiger 91 4 stroke and it has not been run what is the break in period and what is the best fuel 10-15%? It also seems that a 11/6 prop is to be used during break in? How many tanks of fuel ect. for break in? Thanks

bbbair

Every engine is different...didn't this one come with instructions? []

As a general rule of thumb;
10% nitro for a 4 stroke engine should be fine.
I am a firm beleiver in a high Caster oil content and a long break in period with the engine running very rich for the first two tanks and then slowly leaning it out over a gallon of fuel. [8D]

However; when all else fails... read the instructions.

Don41

This address should get you the manual. If not I can email it to you.

http://www.acehobby.com/ace/PDF/Engine/F_91s.pdf

angelsddy

It is a new engine and came with no manual, thanks for the Ace Hobby website for the down load.

alan0899

G'day Mate,
An 11x6 is way too small, try a minimum 14x6, you don't want to over rev a 4 stroke, especially during break in. They suggest a 11x10 for break in, & up to a 16x6 for scale.

Sport_Pilot

I have had two of these engines and they are very good an powerfull. First they don't seem to take to large props as well as many and it likes nitro. Like Saito break in is long. I wouldn't even attempt to run it at idle till you run about three tanks full through it. Follow there proceedure for an extremely rich mixture for the first tank, so rich it will not run without the igniter, then run another tank just lean enough that you can remove the glow igniter. After that lean it out a bit each tank or so till it can hold a steady peak plus about 300 RPM, then you can try for a smooth idle. Don't expect full power till you have run a couple of gallons of fuel through it. But it will have plenty of power before you finish a gallon of fuel. You can use cheaper 5% nitro for break in, but till it has run a few gallons through it it will be difficult to run with 5% fuel as the idle mixture will be tricky. I would start with 15% nitro and a Fox Miricle plug.

Oh, and speaking of plugs, use the cheapest plug you can find for break in. With nitro below 15% the OS F plug or Hobby People Thunderbolt works best, above 20% and the K&B 4C works best. With Since you won't mess with idling for a while you won't need a four stroke plug. It will likely foul the plug before finishing the break in. Other than the above their procedure works, even the 11-10 prop is a good choice, for break in.

It seems to have the most power with a 14-6 and 13-8 prop. Likes RPM, it has withstood 11,000 RPM on the ground with no problem. For this reason it doesn't seem to like large props as well as other .91 four strokes. If this is an earlier model with the large carb, use the choke, the carb is too large and will not draw fuel well, the choke adaptor has a smaller bore and also works as a velocity stack.

The only quality control issues is that TT doesn't do a good job of tightening up the bolts, so get some allen wrench's and tighten up the bolts. And while you are doing that take off the single bolt that holds the rocker cradle down buy some red Lock Tite put a drop or two on that bolt and tighten down properly. When that one comes loose vibration tends to wear off the head of the bolt and snap it off, which will ruin your day.

It is heavy so best to use it on a model that needs some nose weight. This may seem like a lot of idiosyncrasies, and it is, but powerfull engines often do. Follow the above and it will be a very good engine, but I am afraid it is not a good starter engine.

angelsddy

I would have to say Sport Pilot answered all my questions thank you all and good flying.