Hitchcocks Forum

While I have my head off (again) I was planning on some cleaning up and tidying up of the ports (500 AVL) and never done this before!

I have a good Makita battery drill (don't have a Dremel) and was looking for any recommendations for end tools that would best do the job, guess a wheel to open up the diameter and a flexible mop for cleaning and polishing, any recommendations chaps?

I use a mains drill, with a bull-nose 12mm O/D tungsten carbide burr for the bigger chunks and a selection of coarse flap wheels for less drastic removal, rough finishing, then you can move onto the finer/polishing stuff. If you can get them with extended stems, so much the better.

The exhaust ports on all the Electra-X cylinder heads I've had are really rough and need some TLC, but you can have some fun with the inlet too.





Since the head is already off, you could also think about converting to the old-style Bullet decompressor valve, with some not very complicated machining. I can't remember if you've said whether yours still has the electric start or not

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Thanks, I do have some burs somewhere from about 30 years ago when I last used them as an Aluminium welder!

Good idea on the decompressor while doing it, will have to find a local (Suffolk) machine shop, can anyone recommend anyone?

There’s a thought - does the decompressor valve have a seat insert, or does it seat directly in the aluminium head? I never noticed when I dismantled it and gave it a quick regrind a few years ago.

Possibly doesn’t have, it shouldn’t get exposed to exhaust gases.

The valve assembly just screws into the head, it has a 14x1.25mm thread - same as a 14mm spark plug (this is why twin-plugging a traditional Bullet head is a fairly easy option). The valve itself just sits in the valve body.

Fitting one to an Electra-X head is a bit of work, you have to remove at least part of the fins between the rocker box parts of the head casting. I use a hacksaw fitted with a tungsten carbide rod-saw blade which let me cut at 90° in a confined space, and tidied up with the carbide burr and a finger sander. I find it easier to remove them completely, but someone with a decent milling machine can just remove only what's needed. After that, drill through the combustion chamber up to the tapping size for the 14mm thread (12.5mm or 1/2"). I also counter-bore the hole from the top to get the valve head sitting more flush with the surface of the combustion chamber, not completely possible with the chamber shape as the hole is drilled vertical. You probably could have it drilled on an angle to sort this, but then you might not have clearance to get a box spanner on the valve

Getting the pilot hole in the right place is important, centre 7mm from the flat edge of the combustion chamber, you don't want the finished hole too close to the valve seats. I also try and tidy up the tapped hole where it has some exposed threads on one side.

The only real machine-shoppy bit of kit I have is the pillar drill. Good hunting!



















This was my first attempt, which works very well.



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All modifications are at you own risk, of course.

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Adrian wrote: ↑

Wed Oct 06, 2021 11:40 am

All modifications are at you own risk, of course.

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Haha, of course!!

Many thanks for the step by step phots, very helpful, job added to list while engine is down again!

If you or whoever you get to do the job has put the hole in the right place, you should be able to use a 1/2" x7/16" Whitworth tubular box spanner to fit the valve, you can use this to screw-in the valve with the cable fitted, just slide the cable through the tube of the spanner. Replacing the lower washer on the valve with a plain copper M14 crush washer is a good idea.

You can either use a classic British bike valve lefter lever on the handlebars to operate it, however the original valve lifter plastic lever in the Electra-X left hand switch cluster should do the job, rather more easily than with the original thingy in the tappet cover. Or fit something like this.



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Starting to work on my head (found a box of carbide burs I had forgotten about, reckon from at least 30 years ago!) Looking at the exhaust port it is very off centre (discussed on another post i think) so first job will be cleaning this out and making concentric, meaning it will be no wider than it's narrowest point, this looks ok using the copper ring in the picture.

Just as a sense check the copper ring (looks to be a crush type) is part number 582638/A that according to our hosts website can be used in place of the flat grey washer type of gasket 510804, I have a couple of them in original packaging, are they an improvement over the flat type or would I be better with the flat type?

This will be fitted with one of our hosts open downpipes.

Yep, par for the course.



Have fun. This was work in progress, it's all cleaned up now.



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