rexbirk

Need some help from some of the 3W Experts out there. It is a 55I US version competition edition. Have had it for 5 years or so. Maybe has 30 or 40 flights. Since new it seems to load up on takeoff and go rich inverted. I have tried leaning the low end and different top end settings. At my last outing I leaned the idle more and it seemed good on the next flight. I was happy untill flight two after the adjustments. This flight the engine seems to lose power at about 20% throttle. Idle is still good and top end is good. Throttle response is good until I fly at 20% throttle for a short time. Seems like when I lean the low end out to prevent the loading up and richness when inverted it seems the low end becomes too lean. I can't get a consistent run.

Very frustrating. I'm starting to wonder if Ihave an ignition issue? Thinking of trying an Rcexcel 3W Ignition.

Ideas?

Turk1

My guess, your transition zone from low speed fuel feed to main jet feed is problematic. Seems you are happy with idle adjustment then open HSN very slightly to help delivering a little more fuel from main jet during mentioned transition zone.

Ih82crash

3w engines are famous for leaking air. Take the carb and the reed valve off and seal the gaskets with permatex. I had a similar problem with my 106 and after it was sealed it became very reliable. I do not believe that you have an ignition problem. My experience with ignitions is that they either work or they do not.

rexbirk

That makes a lot of sense. I will richen the high end first. If that does not work I will try sealing the carb.

rexbirk

I have always wondered what the two magnet ignition accomplishes?

DaddySam

My Feedback: (9)

If you choose to seal the carb block use anaerobic gasket sealer. Permatex makes it.

rexbirk

Saw an old post here about a 3w like mine from years ago (mine is 4 or 5 years old even though it only as 4 gallons thru it) that showed some frayed reeds. I heard somewhere that some 3W engines got out without a cage to stop the reeds from being damaged from opening to far and making contact inside the engine.

Anyone have any ideas?

Would my engine idle and run with damaged reeds?

rexbirk

Talked to Gerhard at Aircraft Aviation last week about my problem. He felt it is due to airflow over the carb inlet causing a vacuum. The carb keeps putting out the fuel it is supposed to but does not get enough air so it goes rich. He explained how to make a scoop to put over the inlet to force air into the carb. He was very helpful and spent a lot of time explaining it to me. The reason it goes rich when inverted or in knife edge is turbulence from the different aircraft angle. My rich takeoff runs are from the increased airflow over the carb as speed picks up.

Unfortunately I don't have room in the cowl of my Yak for a scoop. I'm going out this morning and am going to tape off more of the opening on my Yak55 to see if that will make a difference. I already have the top half of the cowl closed off with a carbon fiber plate. I'm going to tape off both sides even with the cylinder and see what happens. If it works I will build some permanent pieces to close it off.

Love those round cowls but they sure do let in a lot of air!

Ih82crash

interesting.... make sure to keep us updated!

rexbirk

First off, I'm saddened by the crash at the Dayton Airshow. My thoughts and prayers go out to the families of those killed. I can only hope that when my time comes I go out doing something I love!

I think I'm on the right track with my 3W 55ius. I went out this morning with my plane and a roll of duct tape. I put tape over the rest of the opening only leaving the cylinder exposed. After a few adjustments I got what I have never gotten before. A full power takeoff!!. I made a few more adjustments and dramatically reduced the richening when inverted and in knife edge.

While I was at the field some of the imac guys showed up with their huge multi cylinder planes. I helped one carry his stuff from the parking lot. I happened to get his cowl since it was a new plane and he was setting up the engine. I looked inside and saw that he used some foam workshop flooring to make baffles. He used small pieces like ribs to support it. He told me the advantage to using this is that if it touches a hot engine part it just melts away and custom fits itself so to speak.

I am hopeful that with some baffling and some careful adjustments I will have a great running engine that will outlast me!

I could smack myself in the head and make that Homer Simpson noise for not calling Gerhart 5 years ago!

I truly think I have my issue fixed!

You guys out there with Yaks remember that you may need to close off some of that huge cowl if you have any strange performance or overheating issues.

I am hopeful that with some baffling and some careful adjustments I will have a great performing engine. Sad it took 5 years for me to figure it out!

WhiteRook

My Feedback: (38)

i have a 3w70 and the rear carb is a real pain. you need a really longed nosed plane to put it in. and than theres , getting to the needles and choke .

rexbirk

I have two rear carb engines. Both PTE36. Luckily the carb stays outside the firewall and adjustments are not that bad. I run a pushrod forward to just inside the cowl for choke.

The good thing about the rear carb engines is that the carb is away from most air currents.

rexbirk

I have success with my 55i us version!!!
After cutting off more of the large Yak Cowl Intake and adding some baffling to keep air currents away from the carb I had three flawless flights. The engine ran strong and well. I'm a happy camper now.

Thanks to Gearhart at Aircraft International for pointing me in the correct direction. It was airflow over the carb intake after all. I did not have room for a scoop inside my cowl as he suggested but I was able to use foam flooring material to fence off the carb, so to speak from air currents.

As I made mixture adjustments on each flight today it ran better and better.

krayzc-RCU

My Feedback: (31)

u r da man!