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Hello all,
I'd like to ask how important is it to make holes in the cowl for carb adjustments. I hate to make additional holes if I don't need to, it's a O.S. .55 engine. Do you have to frequently adjust fuel mixture or is it very infrequent? I'm thinking if I adjust the engine and then put the cowl back on I'm done for the season or is the adjustment on a regular basis.
Thanks for your input,
Pat

Scar

My Feedback: (3)

I didn't put a hole in my Cub cowl. The Saito 100 required about 3 low end adjustments the first 4 times I flew it.

So, I lined up with the low end screw, put a hole in the cowl, adjusted it about twice more, and haven't touched it since.

In general, your OS .55 will require some adjustment during the first few hours of operation. It may not need much adjustment after that. I still prefer to have the capability.

Just my 2¢ worth,
Dave Olson

CK1

My Feedback: (60)

I don't usually make holes for adjustment until I know I need them . Some engines run differently when cowled and require adjustment with the cowl on, some don't.
Try it first and make holes later if need be. Only you can decide if removing the cowl every time you need to adjust the engine is practical for you.

tailskid

My Feedback: (34)

PDF, what plane are you using?

flyinwalenda

My Feedback: (5)

Depends how well you want the engine to perform. What climate you fly in .
Many check and adjust the high side every time they fly to get max rpm and make sure it's not running lean.  If you fly in changing temp conditions you have to adjust  and readjust the high side.
As the engine wears in (or out) the low side will need adjustment too  Some just run them stuttering rich on the low side but if they end up lean then the engine dies on throttle-up.
I say take the time and make the tiny holes and add the extension wire for the high needle for adjustments outside the cowl.

PDF

Hi Tailskid, I'm flying the Phoenix .46 size Extra 300S

Warbird40

My Feedback: (24)

90% of the adjustments needed will be on the HS needle due to different temps. Once your LS is set and engine is broken in, you probably wont have to touch it as long as you use the same nitro fuel/glow plug combo.

flyinwalenda

My Feedback: (5)

True. Forgot about that. When I changed my 4-strokes over from pink fuel to the green synthetic ,the low side on all of the engines had to be adjusted. Persoinally I'd rather see a small hole in the cowl to make the adjustments rather than disassemble , remove the cowl, reassemble,tune the carb, disassemble, install the cowl, reassemble, fly and hope it's OK in the air !

Granpooba

My Feedback: (5)

Drill the freakin hole !

PDF

All right, I guess i'm going for the hole.
Thanks for everyone's input
Pat

iflircaircraft

There is an alternative. cut your cowl in half lengthwise. Put a strip of plastic on the seam (on the underside) and screw the halves together along the seam. Then when you need to adjust the needle you only need to remove half the cowl (no need to remove prop,spinner,etc).
Or go electric.

Tom

opjose

What do you normally do?

Put foam or something to retain the cowl shape while you make the cut?

How do you make the actual cut? A bandsaw?

Thanks.

markhamregular

I have never seen anyone in my field with a cowl without a small hole for the high needle and another for the small needle.
You will need to adjust no matter how good a job you do in the beginning.
I make mines very small. It takes some time to find the right place to drill.
Use a dremmel. Make sure you take all the precautions. Use gloves, mask and goggle.
Even a very small amount of powedered fiberglass is made of glass and will mess up your lungs or your eyes.

hugger-4641

My Feedback: (6)

I usually melt a hole in the cowl with an old solder iron that has a wornout tip. Doesn't shred the fiberglass that way and makes just the right sized hole to insert a screwdriver, just be carefull not to breathe the fumes while melting the hole.

Charlie P.

Ido for all my glow engines. My gassers usually can be reached without a hole as the carb is partially outside the cowl. I have one scale (Ultimate) that Ican't easily get to the idle screws . . . but Ihaven't found that a hinderance as it runs fine as is.