Goosarama

Gentlemen,
Have just completed a YAK 54 with a cowling. The cowling is mounted with four screws. With a 2 stroke engine I am sure that fine tuning of the .25 engine is often (if not always) neccessary before flying. Unless I drill holes in the cowling the low speed and high speed adjustment screws cannot be accessed. How is this problem usually solved? I know I see many models with cowlings that are not drilled. Is it neccessary to invert the engine? What if that is impossible? Thanks in advance for your valuable advice. I'd really be lost without this resource.

What goes up must come down - if it can solve the reentry problem!

MinnFlyer

My Feedback: (4)

It's rare that you should have to adjust the low end once the engine is broken in and properly tuned.

If you find that you DO have to adjust it often, Drill a hole - You'll never see it once you taxi away

w8ye

My Feedback: (16)

Get the airplane flying well and the engine tuned with the cowling off.

Then you will need holes for the needle valves and glow plug if any are covered by the cowling

Upright or sideways engines run great. Inverted engines sometimes cause trouble for people.

I've seen several planes with the engines mounted sideways or upright when the designer intended for the engines to be inverted.

Whichever way you mount the engine, the tank should be as centered on the needle valve as you can get it.

Missileman

I have never seen a cowled glow engine plane that did not have holes drilled to access at least the high speed needle and most of them also have extensions on the needle valve to extend outside the cowl.

bigtim

My Feedback: (13)

small bent wire sticking through hole in cowl for needle valve,like minnflyer posted the low end almost never needs touching and really doesn't need a hole in the cowl.
the holes I have to access needle valve, and the other side for fuel filler,the front has a air inlet and a exit for the pipe is all you really need.
I also have a sullivan remote glow location but its on the side of the fuse of this particular plane.

w8ye

My Feedback: (16)

As Tim says, you need a wire extension on the high speed needle. The vibration of a running engine make it impossible to keep a screw driver in the screw.

If the glow plug is not exposed, you will need some sort of remote glow plug connector

horace315

My Feedback: (15)

i would still make a hole for the low end.i have several os fp 40's that i havent ever had to touch the low end screws.but you know something if i put them in a cowled type airplane sure enough they would need to be adjusted.it isnt hard and isnt noticable.

Goosarama

You guys have been a great help. How does one put this wire extension on the needle valve? Solder it to the needle?

TexasAirBoss

My Feedback: (22)

There is generally a small set screw in the needle valve handle. You can generally place a small allen wrench or a piece of wire in there hole and tighten the set screw down.

w8ye

My Feedback: (16)

The very outside end of most needle valves have a hole for a wire extension. As said above, there is a set screw on the side of the high speed needle knob that you use to retain a wire into this hole. I use push rod wire left over from assembling the plane.

opjose

Holes and/or extensions for the needles are a must.

A problem with tuning the engine with the cowling off, is that it may behave a bit differently with the cowling in place.

With temperature changes, etc. you almost always have to adjust the high end at the least and give a slight tweak to the low end.

One problem with cowled engines is that it is difficult to perform a pinch test.

I use these guys from Airborne-models.com ( World Models ).



They are unobtrusive and come in various colors.

You can detach one end to fill the tank w/o pushing fuel into the carb, and when in place, you can pinch the line for the pinch tests.

danny31292

I agree with just drilling a hole and having a wire attached for the high speed. Just forget the low end. You can always take the cowl off to ajust it anyway.