3w 157 issues

[postie999]

Okay, so I recently purchased a 3w yak powered by a 3w 157 w/ stock muffs spinning a 32x10. I sent the motor to Aircraft International because some of the prop bolts were sheared off and stuck in the hub, so the hub was replaced. Got it back and the engine wouldn't fire. Sent it back to AI and got it back with a new crankcase, new ignition sensor, carb, and gaskets. Gerhard said that the engine ran 6000rpm on the bench. Next time at the field, engine fires and I fly it, but I noticed a severe lack of power. I landed and tach the motor at 4650rpm. I fiddled with the high end needle and got the rpm's up to 4900-5000. Today, my dad and I tried a different ignition module...no change. I tried a different carb...lost 300rpm. Switch back to the original carb. I fiddle with the needles again, and got max. I've been told that with this motor and a 32x10 I should be at 5700-5900 rpm.

I'm stumped. Any ideas?

Thanks

[GmanBill]

Check the seal on the base of the read box and the carb base gasket to make sure you are not sucking air. It could be sucking the gasket or even sucking air at the cylinder base gasket. If you were close I would look at it for you.

[Flyinhigh]

I would agree with the Gman - sounds like the kind of performance you would get after one of the cylinder base gaskets have been sucked into a transfer port. Not a tough fix if you can confirm this is the problem - look at the head base all around with a flashlight - if you can see a gap with no gasket showinig, you probably have a sucked-in gasket. Just pull the head a little with the piston at TDC (about 1 inch to get to the gasket) coat the case and head or both sides of the gasket with Permatex #2 gasket sealer, and replace the head with bolts torqued. Run the engine for e couple minutes to get up to operating temp, and retorque the bolts (about 1/4 turn) and the problem shouldn't persist.

[atique]

Btw Postie whats wid your number of posts?

[Radioactive]

Agree, one of the two, either gasket, or carb block air leak...

[Plane Wrappers]

How about a timeing issue????
I understand when a new hub is installed, they have to align TDC and drill and install the magnets in the hub. It may be off a little.

[GmanBill]

If you sent it to AI and they replaced the hub you know they had to set the timing and run it there, I have never know him not to test run one after he repairs it. I don't think he tacks them, just makes sure they run, your timing is probably at 26 deg or more which is OK, they check that when they put on the new front hub so it should not be the timing. Check your gaskets first then if that is not the problem we can go for other things.

[tkilwein]

I have a 3w150ts and with a 32x10 msc-menz it swings 6400-6800 with the needle settings I have.

[buttface]

Postie999 ,I think it has something to do with the 4 billion some posts you have made......Thats crazzy!

[backroadrider69]

The most probable cause is that the timing is retarded. On both of my 3W200's I advanced the timing and immediately found a huge improvement in performance.

One of my engines went back to AI for a new case and prop hub and never had much power until I advanced the timing. I advanced it 1/8" and have run 10 gallons of fuel thru it with no problems (3W200iCSTS, KS 1090's, 3.3m Yak 55, 3W 32/14).

If you mark the hub and then move the sensor to the right (opposite prop rotation) 1/16" to 1/8", you will probably find a big improvement in throttle response and rpm.

As long as you don't overload the engine with too much prop or run it too lean it should be fine. If you hear anything that sounds like marbles crushing (detonation), then move the timing back the other way a little.

Hope this helps.

Butch

[rcdart]

Make sure your sensor is not plugged in backwards, I have heard of this causing this issue before.

[Plane Wrappers]

	Quote: Originally Posted by backroadrider69
	The most probable cause is that the timing is retarded.

Hey Butch,...your timing has always been a little off,...but I would not go far as to say retarded! LOL

[postie999]

Well, after a nasty dead stick landing last week my 3w yak is down for a few months. I talked to a bunch of people and I can't troubleshoot this out so I am sending the engine to Ralph Cunningham so he can look at it. I'll let everyone know what up after I get it back. Thanks for the help guys.

[BOSSIER_ROB]

	Quote: Originally Posted by rcdart
	Make sure your sensor is not plugged in backwards, I have heard of this causing this issue before.

GUILTY!!! I did this with a brand new DA. Makes a big difference! I knew for sure it was plugged in right, until I checked it again. 1000 rpm difference.

[Flyinhigh]

I can vouch for Ralph from personal experience - he is 'someone' who has earned the title of 'Guru' if anyone has. He will get your engine straight.