I am breaking in a tt 46 pro engine, and I am wondering how long it takes to get a reliable low end adjustment. I have run 1 tank of fuel through it, and was tinkering with the low end near the end of the tank, but could not get a smooth transition. Should I just try to run 2-3 tanks of fuel before I worry about the low end?

I am using 15% fuel (I have some 10% if I should switch to that) os#8 plug, 11x5 MA prop, and a tower muffler replacing the stock one. It is on a super sportster.

Thanks,

ron

I do a fairly hot break-in and then run at least three - 8oz tanks through it while spinning an APC 11x5 slightly leaner than the rich/lean break point at full throttle...the whole tank. After that, a smooth idle and transition are obtainable, though things will get even better after a whole gallon+ is through it.

Your engine is not dialed in right. Fuels,props and plugs wont' do much until you do.

You sound like you know the basics of tuning and engine.

So lets see where you are. Run it up for a minute or so to get it warmed up.

1. While the engine is at an idle, disconnect the fuel line fro the nipple on the carb. if the engine rpm increases before the engine quits your low end is to rich-close the needle a tad. It the engine rpm just goes down and quits, your to lean-open it up a bit. Now this maybe 1/16-1/8 turn.

You may want to intentionally put it to lean and to rich to see reactions you get. I like to go for a slight increase.

On the high end needle. Give it a pinch test. Most go for a quick increase n rpm. I go for no change. This stuff is in fine print in all engine manuals but most are not aware of it. It works very well

Racine2000,
If you are in a hurry, set the high end a little richer than max rpm, you'll hear the drop in rpm, and run the heck out of it. Soon, (after several tanks), you'll be able to set a decent idle.

If you want to do it right, check out the article titled, "Break-in: the secret to longevity and reliability" in the November issue of Model Airplane News.

It is inadvisable to run a new engine at max rpm or leaner yet for any period of time.

If you treat your TT right it will be happy and you'll get happier the more you use it. (I have beat the BLEEP out of one for four years and I still love it!) (It WAS treated well in the beginning.)

Jeff

Thanks for the advice!

I have no problems adjusting the high end needle, it's the low end that seems to give me trouble.


From what I have heard before, when going from idle to full throttle if the engine cuts out it is too lean, and if it gurgles it is too rich. Sometimes it can be difficult to differentiate the two if it is a quick gurgle.

I like the idea of removing the fuel line when at idle, as it seems it would be easy to tell whether or not it speeds up. Do I need to actually remove the tubing, or can I pinch it like on a high speed test?

I have a ST .51 that was giving me all kinds of problems. I was messing around with it forever, and kept getting dead sticks after it seemed fine in the pits. It wound up being a broken low speed needle. Very frustrating, but at least I figured it out eventually.

I had an OS .60fp and a tower .46 and both transitioned well.

I have heard good things about the tt .46 and decided to give it a shot...

Thanks Again!

Ron

A pinch of the tubing will work if you don't wnat to remove it.
Needle nose plyers sometimes help keep the fingers away from the two spinning knife blades.

For low end needle adjustment this is what I use:
Warm up the engine and bring it to 1/3 throttle or just a little above idle.. Pinch the fuel line and hold. If the engine rpm's increase, it's too rich. If the engine quits right away, it's too lean. If it does nothing, it's really close. Now you need to tune it in the air... Run 'er up into the sky and idle it around a bit. Now gag it! If she quits, you'll need to richen it up and if it gurgles, lean it out.... Just make sure you're high enough to land 'er safely if she dead sticks.