Weber DCOE 40 - removing throttle butterfly screws

[DamianB]

Posting here some lessons learned after struggling to remove the screws securing the throttle butterfly valves on my Weber DCOE 40s. I am giving the carbs a thorough service including an ultrasonic wash, so needed to strip them down to bare bodies.

The problem is that the 2 countersunk screws securing each butterfly are peened to prevent them shaking free and being sucked into a cylinder. A sensible precaution but it makes removing them a PITA.

There are some helpful videos on YouTube, but sharing my approach here in case helpful

1. You need to hold the carbs very securely so that you apply consistent torque and load on the delicate screws. The YT videos recommended securing the carb in a wide face woodworking vice. I don't have one so instead used a piece of wood and drilled holes to match the studs normally used to secure the airbox to the carb. It worked, especially when the wooden board was secured to my bench with a G-clamp.

2. It can also be a struggle to remove the small roll-pin securing the accelerator pump to the butterfly/throttle shaft. I found that at 2mm drill-bit was the perfect size to drift it out.

3. The YT videos recommend using a metal file to file away the peened end of each screw. I tried that but it was both slow and v.hard to avoid damaging any other parts of the shaft or carb internal body.

I found it much faster, and easier to be delicate using a Dremel with a small rotary stone,

4. In a couple of cases, even after removing the peened ends, and liberal use of penetrating oil, the screw refused to budge and I was close to destroying the screw heads, so put the Dremel into service again, carefully drilling out the centre of screws from the threaded end. I slowly increased bit size up to 2.3m max. Whether it was the vibration or relief, I cannot be sure, but the last stubborn screws came out without destroying the heads, which would have probably resulted in me needing to cut the shafts out. Ouch $$. Of course I'll still need to replace all 8 countersunk screws, but WebCon have them in stock

5. Another tip. It helped to secure the throttle shaft so that it wouldn't turn when grinding or drilling. I used a heavy adjustable spanner on the flats of the throttle shaft. Worked well.

[2cams70]

Looks like you are on the right track there. Note I found it easier to use a carbide burr than an aluminium oxide stone for grinding down the peened end of the screws. You need a steady hand though because they cut faster. Suggest you check Eurocarb for torx headed countersunk replacement screws. They are better than original pattern (but in steel) supplied by the likes of Webcon. There’s a better method too than twisting out those shaft end caps. What you see suggested on the internet is not correct and not the method in the factory Weber manual. Make sure you mark everything so parts go back in their original locations.

[DamianB]

Many thanks for you suggestions 2cams70.

-I tried using a carbide burr but found that it juddered and 'bit', risking taking a chunk out of the precious casting, so switched to the v.fine stone which worked better for me. Perhaps too coarse a burr or too slow rpm, or just rubbish skills.

-Screws. Thanks. I'll have a look at Eurocarb. Torx sounds a good alternative. What do you recommend for securing the countersunk screws. More peening, or Loctite? If Loctite, which grade?

-End caps. Not sure which method you are recommending against. I used a soft hammer on the end of the shaft and gently drifted the caps and bearings out together. I am planning on replacing the bearings by sealed units. Does that sound right to you?

-Marking. Yes. I made liberal use of the ever-handy centre-punch.

[2cams70]

Eurocarb P/N 6416 are the screws to use. I prefer to peen as original rather than loctite. Whilst peening you can use a large diameter brass rod placed inside the barrel and resting on something solid to support the shaft whilst doing so - otherwise you'll bend the shaft. A small Roberts drive bit has the same square shaped end as the original Weber tool used to peen the screws. The screws are drilled at the end and the tool splays the material of the screws outward to create the locking effect. Inspect how they were peened originally and you'll see how it was done at the factory.

You are removing the caps the right way by the way. Tap them out from the inside. It's not necessary to twist them out by inserting something into the two holes on the side of them (this is what most of the information out there tells you to do) Reuse them if you can. Originals are better quality brass whereas replacements are steel.

Note carbide burrs need to be run at high speed otherwise they can judder if the speed is too low. Sounds like you still achieved what you needed to do however with the aluminium oxide burr.