COLE

My os 61wc has developed a couple of unusuall habits.

In a hover, the engine seems/sounds to have a "miss". The engine produces a smooth idle and top end but when hovering the engine goes (don't laugh) taaaaaaatotaaaaaatataaaatotaa etc. If I give just a smidge more power/collective it dissappears. It sure plays fits with my gyro.

I'm sure its a needle thing. One other piece of info that I'd bet is related, After landing/cutting the throttle following a bit of FFF, the engine pauses for a few secs at a really fast idle before slowing and settling into a smooth slow idle.

Which one do I need to turn which way?

Thanks
Michael

Furyflyer2

My Feedback: (117)

Richen your low end , set the mid needle to about 3/4 open to closed.

heliguy

My Feedback: (3)

Michael, You symptoms are of a lean mid range needle. The mid range needle is the one opposite the fuel input. Try opening it up about a 1/4 to 1/2 turn. This needle is not as sensative as the high end needle and will usually wind up about 3/4 to 1 1/2 turn open.

The high idle before slowing down is a sign of a hot engine (too lean). The mid range needle only affects the mixture setting from about the throttle 1/4 to 3/4 open range.

For what it's worth - Al
http://www.rchelibase.com

Furyflyer2

My Feedback: (117)

Interestingly the mid range needle only affects throttle transition not hover mixture. The low end needle play's a big part of the hover mixture, you could actually close the mid needle all to together and it would not affect the mid range hover mixture. If this engine is in a Fury the low end needs to be a little richer because of the lack of adequate cooling.

Straight from Curtis-

http://www.curtisyoungblood.com/faqs...=Muscle%20Pipe


2.) Carb mixture wrong - With the OS 61 you want the low end out about 1 turn, the mid range 0.25 turn or closed completely and the high end 1.5 - 1.75 turns open.

heliguy

My Feedback: (3)

Furyflier2, I must disagree with your statement that the mid range needle on the 60b carb does not affect hover. Although the idle can be set overly rich to compensate for a lean mid range (you had to do that on the OS 32 as it had no mid range adjustment), the 60b carb mid range gives you a way to adjust this. The mid range needle feeds a cats-eye boost port cut in the barrel of the carb which provides maximum boost at about 50% carb opening, your hover point.

The following is a previous post I made concerning 60b carb adjustment:

First lets understand the function of the mid range needle. The mid range needle only adds fuel above 1/4 throttle up to about 3/4 throttle. It also is a tapering supply which means it start adding slowly, peaking the amount of fuel added at 1/2 throttle, and tapers off to 0 above 3/4 throttle.

The OS 60b carb has by design a slightly lean mid range. This allows the use of the mid range needle to fine tune your engines mid range performance. It is only a mid-range boost and does not directly affect the idle and the wide open throttle settings.

To start with the mid range needle should be closed. Set your engines idle so that when you pinch the hose you get about 3 seconds operation before it starts to rev up.

Now you need to fly the heli at “full power” and adjust the top end needle/pitch to get maximum performance while still having a good smoke trail.

When you return to hover you will find that you engine is now slightly lean at mid-range. Without adjusting the high speed or idle needle, adjust you mid-range for proper hover performance.

I have found that on 30% fuel using a Hatori type muffler that the mid range will wind up between 3/4 and 1 1/2 turns open.

For what it’s worth—Al
http://www.rchelibase.com

Furyflyer2

My Feedback: (117)

On both my OS 61 WC and my OS 70 the low speed needles is the only needle I adjust for idle/mid range . When I was running the OS61 WC the mid needle was closed. I believe that the instructions say to adjust the mid range needle for produce a smooth transition from hover to full thro?

Like Curtis said you could close it , so it can't have that much affect on hover mixture. I spoke to Cutris and he instructed me to ignore the mid needle all together, just adjust the carb like a 2 needle carb. So in my case I found that to be the case , so all I did was richen the low speed needle, and it cured the problem described. I guess all i'm saying it that in Cole's situation I suspect a low end needled adjustment not the mid range. I could be completely wrong . The settings on my OS61WC on a Muscle pipe with 30% WC , low needle 1 turn , mid closed to 2 clicks open , high 1 1/2- 1 3/4 turns open.

The settings on my OS70 on a 90 size Muffler with 30% WC , low needle 25-30 deg , mid closed to 2 clicks open , high 1 1/2- 1 3/4 turns open.

COLE

Thanks guys for the suggestions. I will give them a try. The engine is in an Ergo with a Hatori muffler. Stock fuel plumbing setup (no header or uniflow).

What a great site.
Michael