Countersunk Screw

Hi Roger,

"....take my small butane torch and heat all around the outside housing the screw is in."

Bit concerned about the naked flame residual fuel/fumes

Just wondering - 

Would a heat gun be as good? Would it heat too large an area? 

Why don't you heat the screw directly? Heat & cool a few times?

😈

Take the carb off. Put it in a vice with a cushion on the edges. I've done this several times. A heat gun heats up an entire area. The butane torch heats up only a specific area and quicker. The heat on the carb body edge around the screw will help expand the metal and help loosen any corrosion.

Further exploration:

It appears that countersunk A4 (316 SS), M5 x 0.8 x 12mm, screws are generally available - ie from non aviation suppliers.

Further they are available in  A4 screws with Allen Key drive heads. I understand that Allen Key drives are more robust, able to take more torque than a Philips head.

Most screws on a Rotax have Allen key heads - the carby being one of the few locations that doesn't.

Is there any good reason not to replace the Philips Head with Allen Key heads?

Should the screws be replaced with a smear of stainless anti seize?😈

Couldn't wait for an answer to the above,

Purchased X 4, SS 316 grade, Allen Key head;

Countersunk M5 x 0.8 x 12mm

Cap screws M5 x 0.8 x 20 mm

Total cost $1Au

Same thing from reputable aircraft parts supplier would have set me back about $45 + delivery.

Will replace all 4 Philips head screws, with above & have spares left over.Will also include a dab of SS anti seize😈

Report:

Removed carburettor, as advised.

Turned out the Flange Strap screw was also "frozen'. Ended up cutting it off - I have a spare.

Took carby back home to workshop. With plenty of padding placed in vice.

Used a liberal quantity of  Loctite Freeze & Release,  befog attempting to remove the countersunk screw.

Used a round /pointed drift at an angle & a small hammer (light taps) - only took a few taps to get movement.

Replaced with SS Countersunk M5 x .8 x.15mm & a smear of SS anti -seize/anti gall.

In the interest of consistency and improved "drive" ,I will be replacing as many Philips head screws with Allen key heads as I possibly can.

I will also be using anti seize on all SS to aluminium & SS to SS fittings.

Is Duralac (yellow) the best anti seize for use on a Rotax engine.?

About once per month, I have been in the habit of conducting a 500ft beach run. The beach is about 20 minutes flight from my inland base. The salty air may be the cause of my (galvanic) problems. I think I will stop this fun practise.😈