Hello... first post here. Looks like a great venue for all R/C issues.

I'm in the process of SLOOOOOOWLY breaking in my TT .91 F/S. I've read a few posts regarding this engine and the proper method of break-in. I'm trying to follow these guidelines, but I'm beginning to get a bit anxious and I need some verification that things are normal.

I'm using Sig Four Stroke fuel, 20% oil, half syn/half castor. I have an OS-F plug installed. I've only run about a third of a gallon, if that, through the motor. I'm using a 13x7 prop for now, but plan on switching to a 14x6 when I go flying (Hog-Bipe). Currently, I'm running rich, rich and richer. Constant smoke coming from the exhaust and glow driver required to keep her going. I can get about a 10 minute run out of it before it gets pretty hot, then shut it down for an hour or so before trying again. It always seems to run best on the first run, then is hesitant to keep running on subsequent runs. Not sure if that is because of the heat buildup or what. I've read that after a tankful or two you can start leaning out just a hair, but everytime I try it gets real balky. Doesn't want to start, or just revs quickly then dies. I can't even approach reliable idle at this stage, and if I try turning the low-end needle in a half turn in order to shed the glow driver, I get nowhere.

So, my questions are these- for those of you with experience with this engine, is my condition typical? One would think that after a third of a gallon of fuel the thing would at least be able to run a few minutes without a glow driver on. I love the sound and feel of this engine... it appears to have a gob of power. I've been looking forward to flying this bipe since last fall when I started building it, and I'm getting anxious to get this motor somewhere near functional/reliable. Is my glowplug not hot enough? Should I be happy just running rich for a few more tanks and then try to lean a bit? I'm using after-run oil religiously following every run session, prior to sitting her back on the bench.

Any and all specific feedback would be appreciated. Thanks.

Sounds like your fuel may be old. Could you try some of it in a 40 size two stroke and see how it performs?

Jim

Hallo!

All engines ,foustrokes as well as twostrokes can and will run without glowpower...even under run-in conditions
Have you tried to adjust the highspeed needle so that the engine run whitout glowpower?
Hot!? Every engine should get hot..othervise it will not function!
But when you say hot....what do you mean by that?
Do not use to much nitro! Most engines are not constructed to work well on more than 15% nitro. I recommend 10% for your engine!
20% castor oil is good! But syntetics are better!
We use 15% in Europe!! Motul "Micro" is the name. You could get it in any Bike shop, its a French manufacturer of racing oil for the Motorcycle market. But they also make a very good oil for us "Glow engine users"!
Thats the Motul "Micro" oil!

Regards!
JanK
Sweden

I've owned several of these puppies and they are a very good engine. The last one I broke in only needed about 2 tanks on the ground before she was ready to fly (400 rpm shy of max lean on the high end) with a decent idle.

some words of advice: ALL TT .91s will need all of their bolts retightened (yes even those under the valve covers, these are the most important because when they get loose they can cause valve train damage, happened to me once) after first couple of ground runs.

Fuel: 15% Coolpower is all I over used. I wouldn't use the castor based fuel for more than first couple runs. Any similar fuel will work fine. Use nothing less than an OSF or Enya 3 plug, don't skimp on the plug.

Prop: 14x6 APC, nothing more nothing less. This engine will spin this prop at about 10,500 rpm on the ground at max lean and I usually richen her up to 10,100 rpm with a tach before take off.
Alternate prop that works well is an APC 13x8 for speed, but the 14x6 seemed to be best all around in my opinion.

If your engine is cowled, it may be overheating. If it isn't cowled, and you are running rich, you probably aren't overheating it.

Try adjusting the low and top ends. I like my low end slightly rich and my top end about 400 rpm shy of max lean rpm. You should use a tach for a 4 stroke-enough said.

Good luck, you'll be impressed with this engine, it'll out run an OS .91 anyday.

Homebrewer's advise is good - you should follow it. I have two TT .91's that run with the best of them.

Two things from my experience:

1. Be sure you tighten all of the engine screws as Homebrewer says then check (and adjust) the valves. They are probably going to need it. I did mine (screws and valves) after 1/2 hour on the bench. I then re-checked (and adjusted) the valves after I had flown the engine for two hours. I now only check my valves each year (January) when I replace the glow-plug. I fly year-round here.

2. Make sure you have installed the choke plate on the carb - it is part of the venturi and if you don't install it your engine will never run correctly.

My experience -

Dan