OK, Just trying to find out what might be my problem with this Engine. I have a 3W 150 TOC engine in a SD 40% YAK. It has baffles in front and rear of the engine for cooling. Problem. when running at full throttle on level flight for about 2 to 3 minutes the engine will automatically shut down like you throttled back to 1/4 throttle, if you move the throttle up and down between 1 quarter an full the engine does not change but If you move the throttle stick all the way back to idle then back up again it will run at full power again for another few minutes and do it again. If I run at 3/4 or 1/2 throttle for 2 to 3 minutes then try to go to Full power same thing happens, need to bring the engine back to Idle then it will respond

Here is what I have checked so far.

Engine has cooling baffles. Checked engine temp and got readings of 160 to 173.
Carb has been completley cleaned out so no debris in the Carb.
Tank has Large tubing and no kinks so fuel is not an issue.
Needles (H end ) is bout 5 turns out just to make sure engine is reach, Low end is about 2 1/4 out. If we turn the H end in to 2 .5 turns it goes lean. ?
prop size is 32x10

You are way rich...

The factory settings for the engine (which is almost always rich) is H 1 1/4 and L 1 1/2. Thats for the regular 150.. I am pretty sure the TOC uses the same carb and just gets matching ports + enlarged etc... even so 2.5 turns out from where it goes "lean" is a huge jump.


You should open your manual and set everything to factory.

Go to full throttle with a tac and lean (1/16 of a turn at a time) it till the rpm goes down... find the peak rpm setting.. then back it off using small turns again until you gain back 200 rpm.

Adjust your L needle lean (same way) until you find where it doesnt transition anymore.. now it's lean.. back it out till your transition comes back.

Double check your H needle again.


SOunds to me like you are loading up the engine by having it way too rich... you will probably see smoke coming out the exhuast when this happens... your temperates also reflect very low numbers.

Probably looks more like rain coming out of the exhaust....

haha... true enough

I had a 3W do that awhile ago.
The ignition was getting hot and petering out []

3W ignitions don't like heat...

3W currently (all new style ignitions) recommends that you mount the ignition with an 1/8" gap behind it and not on foam... just an fyi.

Thanks guys, I was wondering about the ignition getting hot an possible quitting on me, Currently it is mounted on foam. I will try putting it on stands to get some air running under it, As for the "rain cominfg out the of the exhaust" This was done once to ensure the engine was not running lean, Like I said before if you tried to lean it out it quits. I know the standard settings are around 2 1/4 out for both High n Low for a good starting point.

Well I would double check your manual 2 1/4 is more than almost every other engine out there recommends. As I stated before I am pretty sure it uses the same carb as the normal 150 and just has porting work done.

Needless to say I am pretty sure that "2 1/4" you are quoting should be 1 1/4" for the H needle. You should give Bobby a call at Catcus and confirm this if you dont have a manual.. 2 1/4 doesnt sound right at all.

Regardless of that issue... ALL factory settings are rich. This is done so they can run anywhere without hurting the engine. You always lean the carb from teh factory settings not richen it...


The only way this is feasible is that you have so much dirt in your carb that it's plugged.

76Phantom: The first thing you need to do is go to the 3W web site, it is in Germany, and they have an English translation. Look up your motor to find out what the exact needle settings are. I was suprised when I looked up mine, which is a 3W 150 TOC QS TS with a Tillitson carberator. The factory settings are 3/4 of a turn on the high end and 1 and 3/4 on the low end--that is not a misprint. You will also find that the needles have a very coarse thread and a little bit does a lot. Hope this helps.

Big Bob