Hi dont understand what's going on with engine

[Highlander1]

Hi I have been flying 2 trainers for past 5/6 years on and off without a hitch.

The one with the OS46 was most reliable until recently when it kept cutting out. I stripped out the tank pressure tested it and checked the fuel was getting thourgh etc etc.

It has always been put away carefully so no one could have touched the mixture setting.

In desperation last sunday I wound the needle right out ( 2 and 1/2 turns )more than normal and it ran and flew perfectly.

It's been running perfect for years until it decided weekend before to keep cutting out.

I don't understand why it suddenly needed so much of a re adjustment all of a sudden.

[rcminiman]

Hi,
It could be an air leak at the carb. If air was drawing in past the O ring or similar, it would cause the engine to run too lean, and require more fuel.
Ive been out on right cold days that have required a bit of adjustment, but nothing like 2.5 turns!
Nobody has tampered with the needle, and screwed it right in? 2.5 turns out sounds like the ideal from fully closed on an OS40 series.

Are you a real Highlander???? If so, where do you fly?

Barry

[Highlander1]

Yes I am A Highlander www.brydens-craiglea.co.uk has my details. I fly at Arisaig and Fort William sometimes at a place called kinlochmoidart.

Hoping to get into float planes so I can fly from the loch opposite my house.

No one could have tampered with the needle valve I just dont understand unless like you say the carb itself is leaking cos the tanks air tight.

Cheers John

[Highlander1]

Ps I am heading for Ulapool for a couple of days tommorrow on my bike. not cycling.

[pentaxman]

Highlander

Could your model have been stored for a while.

I could be that the castor oil goo has closed up the valve bore or you have some dirt in there. I would strip the valve out and give the valve and the bore a good clean.