Author Topic: Newbie - Decompression starting query  (Read 143 times)

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Sigreen

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on: June 27, 2020, 11:55:45 am
Hello everyone. News to the forum, new to RE & could really use some help! I've picked up a 2006 electra 500 with a 535 upgrade. Now this issue is that I can't find anything that looks remotely like a decompression valve. The lever on the hand control is disconnected & I can't see anywhere in the head where it would go. There are fins on the head between where I was expecting the valve to seat. And on the front of the head opposite to the exhaust there is a threaded hole. Compression is really good, strong spark etc. But there is no way I can kick this over easily to start manually & the electric start has no chance, can't turn the engine over. Any suggestions would be really appreciated. Cheers Si


Adrian II

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Reply #1 on: June 27, 2020, 01:58:28 pm
You won't find it there, the 500 Electra uses the AVL "lean burn" engine with quite a few design changes. From the factory it would have had an exhaust valve lifter mechanism located in the finned tappet cover, it would have had a cable-operated lever pushing against a flanged collar on the exhaust tappet. The cable was supposed to be operated by a rather feeble plastic lever in the left-hand side handlebar switch cluster.

As supplied it never worked well, many owners junked the whole set-up and just fitted a plain tappet cover, others managed to get it to work better by using a vintage-style metal valve-lifter lever on the handlebars, which seemed better able to cope with the effort needed to fit the exhaust valve off its seat against the force of the valve spring.

What you could also do if the original valve lifter parts are missing is remove the head and modify it to take the older Bullet's decompressor valve, there's some machining needed, but I managed this a few years ago and other owners have successfully done the same since then.







A.
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Sigreen

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Reply #2 on: June 27, 2020, 02:11:58 pm
Hi. Bang on description of what I have here. So it's either reinstate the original problematic one or head off & machine it to take the decompression vavle. I've got a very good machine shop close by, so that's what I'll do. Thanks very much A. Any problems & I'll post it. Thanks again.


Adrian II

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Reply #3 on: June 27, 2020, 03:01:07 pm
If you're adding the decompressor valve it uses a 14x1.25mm thread, which is the same thread as on a 14mm spark plug.

The job involves either completely or partly removing the three center fins and filing/milling the top flush with the rest of the casting, drilling and tapping the 14mm thread, have a good look at the pictures, and in case this is not obvious from the picture, you can also counter-bore the top of the new hole out to 7/8" or 22mm diameter just deep enough for the decomp valve head's outer face to sit flush with the combustion chamber roof. Don't over-do the counterbore as the valve only has the same length of thread as a short-reach spark plug, and you don't want the valve actually to stick out into the combustion chamber too far or you start to run into clearance issues.

I don't know where you are, I'm in the UK and found it easy enough to get a set of 14x1.25mm taps (though your machine shop should have those already) as well as a decomp valve, cable and handlebar lever.

If your l/f switch gear still has the plastic lever for the valve lifter, you can probably re-use it as the spring on the decompressor valve is nowhere near as strong as the exhaust valve spring.



https://www.pricepartmotorcycles.co.uk/ourshop/prod_2585410-141207.html



https://www.pricepartmotorcycles.co.uk/ourshop/prod_2657122-83011.html

By the way, you will need a long series M12 socket to remove the cylinder head nuts, as the cylinder studs are too long for you to use a regular socket. I never did find out why the factory didn't just use studs with a shorter threaded section on top.

I hope this helps.

A.


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Sigreen

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Reply #4 on: June 27, 2020, 05:50:11 pm
I've stripped the head off & everything you've said again ties right in. The machining, tapping etc is all clear. I've already ordered the assembley. I'm in the UK too, so all this gear & services are easy to sort. Thanks again A, much appreciated. I feel much more coffin I can sort this now.


tooseevee

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Reply #5 on: June 28, 2020, 02:59:32 am
You won't find it there, the 500 Electra uses the AVL "lean burn" engine with quite a few design changes. From the factory it would have had an exhaust valve lifter mechanism located in the finned tappet cover, it would have had a cable-operated lever pushing against a flanged collar on the exhaust tappet. The cable was supposed to be operated by a rather feeble plastic lever in the left-hand side handlebar switch cluster.

As supplied it never worked well, many owners junked the whole set-up and just fitted a plain tappet cover, others managed to get it to work better by using a vintage-style metal valve-lifter lever on the handlebars, which seemed better able to cope with the effort needed to fit the exhaust valve off its seat against the force of the valve spring.

A.

        Well, again I'm a little late to the fair. Didn't read this until Sunday night at almost 9:30.

         The decomp on the AVL doesn't work "exactly" as you described, A.

          You aren't "lifting the exhaust valve against valve spring pressure" when you pull on that insufferable plastic lever. You can pull on it all you want and you're not going to lift that valve off its seat.

            What happens is the engine has to be turning over as you pull on the lever. Pulling on the handlebar lever lifts the lever on the tappet cover which then rotates a cam that then jams against the collar on the pushrod and prevents the pushrod from coming back down AFTER it's been lifted by the rotation of the engine. It essentially holds the valve open AFTER it's been opened by the rotation of the engine. 

           The lever, in itself, is not lifting the pushrod.

            Matters not, however, as Sigreen is installing the much more sensible system.

             I did away with the whole mechanism on mine quite a while ago; lever, cable and tappet cover.
'08 Black AVL Classic.ACEhead 9.8:1/manifold/canister. TM32/Open short bottle/hot tube removed. Pertronix Coil. Fed mandates removed. Gr.TCI. Bobber seat. Battery in right side case. Decomp&all doodads removed. '30s Lucas taillight/7" visored headlight. Much blackout & wire/electrical upgrades


heloego

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Reply #6 on: June 28, 2020, 03:02:31 pm
Hi, and welcome to the dark side! ;)
There's a veritable wealth of info here just about any time you need it.
Looks like my next project will be a proper decomp.  :)
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'06 Electra X AVL w/32mm Mikuni and Gold Star system.


Adrian II

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Reply #7 on: June 28, 2020, 05:50:48 pm
Dark side indeed!  ;D

If you've been reading up on the Electra-X, it amounts to what could have been RE India's best bike EVER at the time but was let down in a small number of key areas. Do a search on here and on Hitchcocks' forum, plenty said about it, but the good news is that any big problems are fixable, even on an engine which hasn't been built for eleven years. Ongoing interchangeability of 500 EFI Bullet pistons and conrod/big end assemblies is good news.

That said, some of them have just kept chugging on. The really good ones have produced fiercely loyal owners. Tuning isn't quite so straightforward on these as with the classic Bullets if that's your thing, though the 535 kit ought to make it pull the stock 18T gearbox sprocket more convincingly.

The decomp mod will certainly take the strain off the sprag clutch, for stopping the bike as well as for starting, and make kick-starting a lot easier too.

Which end of the country are you, assuming you're not in the middle somewhere?

A.
Grumpy Brit still seeking 500 AVL Bullet perfection! Will let you know if I get anywhere near...


Sigreen

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Reply #8 on: June 29, 2020, 01:06:51 pm
Thanks for the responses Adrian, Tooseevee & Heloego, really great info & very much appreciated. I'm in Warrington, North West for what it's worth. I think I'll cut my RE teeth on this bike & see how it goes. In fairness I'm keen on it already & I'll see it through(to whatever end). I like the look & feel of it & not daunted by the work. Once I hit the road I'll see how it goes. I ride a CVO Electraglide but want something quirky to play about on & educate my 12 year old lad with, who's just getting interested in bikes. Looks like this might just be quirky enough! And a completely different animal. I'll post some info & images on the valve work, so you can say even a novice can work it out! Lol Cheers all


Adrian II

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Reply #9 on: June 29, 2020, 06:57:56 pm
Quote
Looks like this might just be quirky enough!

You won't be disappointed.  ;D

A.
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heloego

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Reply #10 on: June 30, 2020, 02:33:22 am
Quote:

"You won't be disappointed.  ;D"

   Do tell. Do tell.  ;D
'18 Bonneville T-100, Blue/White
'12 C5 Classic
'06 Electra X AVL w/32mm Mikuni and Gold Star system.