Author Topic: Removing The Whole Decompressor Mechanism  (Read 5757 times)

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tooseevee

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on: October 20, 2017, 06:55:38 pm
            I'm thinking of removing the whole decompressor mechanism from my 2008 AVL. One less cable and needless busy-ness on the side of a beautiful engine.

            The only thing I have ever used it for is to kill the engine with no kick back. I've experimented quite a bit since switching to Champion plug and have gotten zero kick backs when shutting it down with the key. And the AVL decompressor is virtually useless for anything else anyway.

           I've had a set of the deeper shouldered pushrod adjusters on hand since about 2011 and I think I'll put them in and do away with everything to do with the decompressor from the lever on the switchset to the lever and pushrod collar at the other end. The only glitch might be getting the aftermarket adjusters to fit in without raising the head. If that's the case I'll just leave the stock ones in. It's not worth breaking the head loose.

           I'll fill the hole in the cover with J-B Weld, sand and prep and paint it satin black.

            Comments?
« Last Edit: October 20, 2017, 06:59:02 pm by tooseevee »
RI USA '08 Black AVL Classic.9.8:1 ACEhead/manifold/canister. TM32/Open 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.


Superchuck

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Reply #1 on: October 20, 2017, 07:02:02 pm
Sounds fun!

I removed my decomp cable a few years back, but left the decomp nub on the tappet cover panel.  I always use the key, and I don't think I've had any issues.  I agree... less is more.

I also installed the 'performance pushrod adjusters' last year.  I had to remove the rocker covers, and there was a good amount of finagling to get it all seated properly  (and that circlip is a pain!) but no head removal was necessary.  I remember it was more frustrating than I expected it to be...

I say go for it and good luck! 

However, I am by no means an expert.  Hoping to hear you're not dissuaded when the real gearheads chime in.

Chuck


tooseevee

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Reply #2 on: October 20, 2017, 09:41:34 pm
Sounds fun!

I also installed the 'performance pushrod adjusters' last year.  I had to remove the rocker covers, and there was a good amount of finagling to get it all seated properly  (and that circlip is a pain!) but no head removal was necessary.  I remember it was more frustrating than I expected it to be...

I say go for it and good luck! 

However, I am by no means an expert.  Hoping to hear you're not dissuaded when the real gearheads chime in.

Chuck

            So from this I assume that the adjusters would not go into place at the lifter end and that you had to lever the valves open a bit to slip the push rods into place under the rockers?

            I should have done this when I got the head back from Ace in 2014. Duh  :-[ :-[
RI USA '08 Black AVL Classic.9.8:1 ACEhead/manifold/canister. TM32/Open 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.


Arizoni

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Reply #3 on: October 20, 2017, 11:10:18 pm
Maybe, as you say, killing the engine with the key or kill switch instead of the decompressor like many recommend is safe.

Maybe doing this won't kill the sprag clutch. 

Then again, maybe you guys have just been lucky.

Envision this scene:

The engine is running and suddenly the ignition is turned off.

The crankshaft has enough energy to shove the piston up on a compression stroke and gains some of it back as the  piston decends from TDC on the now, unpowered power stroke.
This action, coupled with the energy remaining in the crankshaft runs the piston up thru the exhaust cycle and down thru the intake cycle.

The valves close and the remaining energy in the crankshaft attempts to drive the piston up against the compressing gasses.  It barely has enough energy to start the next compression stroke when it runs out of power and things come to a stop with no further movement.
Success.  The engine suffers no damage.

Now, on another shut down everything goes the same except this time, during the final attempt to compress the gasses, the crankshaft has quite a bit more energy.

Why?  No one knows.  Maybe an angel pissed in your helmet.

Anyway, with this extra energy, the crankshaft drives the piston almost to TDC before coming to a stop.
The compressed 100+ psi  gasses now trapped in the cylinder promptly shoves the piston back down, driving the crankshaft rotation backwards.

The sprag clutch, which has been sitting idly by while this happens senses the crankshaft moving in the wrong direction and suddenly locks up on the crank.

The energy of the compressed gasses and the newly found energy of the now, backwards rotating crankshaft is suddenly transmitted thru the sprag clutch to the starter drive gears which try to accelerate the starter armature.
The stationary inertia of the armature, coupled with the gear ratio of its drive gears gives the armature a large advantage in its effort to stay motionless.

Suddenly, the brittle hard teeth of the sprag clutch must absorb this large amount of energy.

Maybe they break.  Maybe they just begin to fracture.
In any case, the sprags life is materially shortened.
If they didn't fail, they are one step closer to the time they will.

This is the kind of "kick back" that happens.
There is no real outward signs of it except for maybe a "clunk" sound.  Maybe no sound at all.

I guess, you does what you does and takes your chances.
« Last Edit: October 20, 2017, 11:12:25 pm by Arizoni »
Jim
2011 G5 Deluxe
1999 Miata 10th Anniversary


Superchuck

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Reply #4 on: October 20, 2017, 11:40:57 pm
That sounds like it's a real risk... 

Especially for tooseevee, I seem to remember you use the electric start every time when starting cold.

I removed my solenoid, but haven't yet removed the sprag.  Kick it every time. I have not noticed sprag teeth in the primary though, but as you say maybe I've just been lucky thus far.

As to the other question, I had to remove the rockers altogether in order to slide the pushrods in from the top (remove banjo bolts, slide them out, pull rockers up and out.)  I think getting them back in perfectly was the hardest part.

If you can squeeze it in by applying pressure to the valve that would probably save you some time. Like I said, i am really just a dangerous novice... This bike is the extent of my mechanical experience and I've learned by doing the entire time.

I can't thank this forum and the great  knowledgeable people on here enough.

Cheers!
Chuck


Adrian II

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Reply #5 on: October 21, 2017, 01:14:46 am
It took me 17000 miles to kill my Electra-X's sprag clutch.

Some of that was caused by engine backfires which produced some truly appalling clang/crunch noises, but the poor old sprag kept going. However stopping the engine with the kill switch would usually have the engine bouncing back on compression putting just that little extra bit of strain on the sprags every day until...

My valve lifter tappet cover was an early casualty, apart from the fact that the valve lifter was pretty useless, the casting cracked around the valve lifter spindle and leaked a surprising amount of oil. Replacing it with a plain cover solved that problem, but the demise the sprag clutch was going to catch up with me eventually.

I would have a word with Ace about what decompressor valve options are for your re-worked cylinder head, C.I. Bullet or (e.g.) chainsaw, because I don't think you want your sprag clutch to go south.

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


tooseevee

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Reply #6 on: October 21, 2017, 12:38:14 pm
That sounds like it's a real risk... 

Especially for tooseevee, I seem to remember you use the electric start every time when starting cold.

Cheers!
Chuck

          If you think back, you will recall my "20 (or more) days of cold kick starts in a row after a simple switch of spark plug brand" thread? This after years of experimenting and learning from this problem. I haven't heard the hated sprag noise since the change of plug.

          And I get zero kick backs of any kind now (starting OR shutting down). No, I can't explain it  :) :)
RI USA '08 Black AVL Classic.9.8:1 ACEhead/manifold/canister. TM32/Open 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.


tooseevee

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Reply #7 on: October 21, 2017, 01:08:37 pm
Maybe, as you say, killing the engine with the key or kill switch instead of the decompressor like many recommend is safe.

Maybe doing this won't kill the sprag clutch. 

Then again, maybe you guys have just been lucky.

Envision this scene:

The engine is running and suddenly the ignition is turned off.

The crankshaft has enough energy to shove the piston up on a compression stroke and gains some of it back as the  piston decends from TDC on the now, unpowered power stroke.
This action, coupled with the energy remaining in the crankshaft runs the piston up thru the exhaust cycle and down thru the intake cycle.

The valves close and the remaining energy in the crankshaft attempts to drive the piston up against the compressing gasses.  It barely has enough energy to start the next compression stroke when it runs out of power and things come to a stop with no further movement.
Success.  The engine suffers no damage.

Now, on another shut down everything goes the same except this time, during the final attempt to compress the gasses, the crankshaft has quite a bit more energy.

Why?  No one knows.  Maybe an angel pissed in your helmet.

Anyway, with this extra energy, the crankshaft drives the piston almost to TDC before coming to a stop.
The compressed 100+ psi  gasses now trapped in the cylinder promptly shoves the piston back down, driving the crankshaft rotation backwards.

The sprag clutch, which has been sitting idly by while this happens senses the crankshaft moving in the wrong direction and suddenly locks up on the crank.

The energy of the compressed gasses and the newly found energy of the now, backwards rotating crankshaft is suddenly transmitted thru the sprag clutch to the starter drive gears which try to accelerate the starter armature.
The stationary inertia of the armature, coupled with the gear ratio of its drive gears gives the armature a large advantage in its effort to stay motionless.

Suddenly, the brittle hard teeth of the sprag clutch must absorb this large amount of energy.

Maybe they break.  Maybe they just begin to fracture.
In any case, the sprags life is materially shortened.
If they didn't fail, they are one step closer to the time they will.

This is the kind of "kick back" that happens.
There is no real outward signs of it except for maybe a "clunk" sound.  Maybe no sound at all.

I guess, you does what you does and takes your chances.

             Yup, I realize all that and, believe me, I think about it a lot (which is why I still haven't done it and I really respect your input over the years. I've lived with this beast since 2014 when I got the head back (Thanks again, Ace) and every day after tweaking the carb yet again I would pray for a clean cold start and again get no joy and maybe the hated sprag Klank again.

          I can't explain it, but the simple change to a Champion plug has changed this engine just as much as the miraculous Ace head work and the TM-32 did. You'll recall months ago when I spoke about the 20 or more cold kick starts I got after the plug change. The Champion also shows a much more perfect color compared to the NGK.

          I have almost always (a good 90 out of a hundred) used the decomp to kill the
engine from day one. Since the plug change, I also noticed a change when shutting the engine down with the key. So I experimented for quite a while.

            The engine just stops now (with the key). It simply stops moving immediately, no sign of even thinking about kicking back. It was eerie at first.

            That's what set me to thinking about removing that whole mess from the right side of the engine.

            I am extremely happy with this engine now. I get immediate flawless electric starts now. The button never hesitates now or seems to not be making contact since I added the Bosch relay and I get cold kick starts in at the most three kicks and that was IMPOSSIBLE no matter what I tried since 2014 until the plug change.

             Thanks for all you guys input. I still may not do it, but it's hard to get it it out of your head once it's there.

              And I've never used the kill switch to shut down. Just would never enter my mind. I see on Youtube that the Indians use them to blow fire out their exhaust. Good luck with that.     

             
RI USA '08 Black AVL Classic.9.8:1 ACEhead/manifold/canister. TM32/Open 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.


DanB

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Reply #8 on: October 22, 2017, 03:33:16 pm
Hey 2CV.

Just as an FYI,  I removed my decomposition several years back to make room for the s cams. I just kill the engine with the key.

I've had no real issues with it. With the Acer avl fireball head, I think i get a lot better shut downs. Never heard the sprague spin at shut down.

I also seem to recall BW said you can get the pushrods with the better adjusters in by lifting the rockers a little with a pry bar. No need to pull the head.  Something I want to do as well.

Good luck with whatever you decide!
Suppose I were an idiot, and suppose I were a member of Congress; but I repeat myself. ... Mark Twain
2006 AVL Electra


tooseevee

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Reply #9 on: October 22, 2017, 06:11:26 pm
Hey 2CV.

Just as an FYI,  I removed my decomposition several years back to make room for the s cams. I just kill the engine with the key.

I've had no real issues with it. With the Acer avl fireball head, I think i get a lot better shut downs. Never heard the sprague spin at shut down.

I also seem to recall BW said you can get the pushrods with the better adjusters in by lifting the rockers a little with a pry bar. No need to pull the head.  Something I want to do as well.

Good luck with whatever you decide!

                 Oh, thanks. I knew I remembered someone saying that years ago and I (of course) forgot who it was. Sorry, B.W..   :-[ :-[

                  I think I'm gonna do it. I just want to do anything I can get away with (without disassembling the whole bike) to clean up any busy-ness I can. 

                   I can't believe that finally, after an incredible amount of tweaking and sometimes horrendous frustration and, yes, real anger, since 2014, I now almost totally trust this damn black bitch to start when and where I want it to start, kick OR electric, cold or hot, and with zero sprag Klanking or nebulous starter button contact.

                   Now if I can just keep myself from pulling the wheels off (and a lot of other lower parts of the bike) to have them all powder coated I'll be all set  :) :) :)
RI USA '08 Black AVL Classic.9.8:1 ACEhead/manifold/canister. TM32/Open 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.


tooseevee

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Reply #10 on: October 22, 2017, 08:05:34 pm
        Here's a weekend special I ran across while grazing the verdant meadows of eBay:

https://www.ebay.com/itm/NEW-ROYAL-ENFIELD-CHARCOAL-CHROME-EMBOSSED-TAPPET-COVER-CAD-/253210918731?hash=item3af48bff4b:g:VFwAAOSwux5YNsPZ&vxp=mtr

          Do you suppose they've noticed by now ?  :) :) :)
RI USA '08 Black AVL Classic.9.8:1 ACEhead/manifold/canister. TM32/Open 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.


DanB

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Reply #11 on: October 22, 2017, 10:38:28 pm
Quote
    Do you suppose they've noticed by now ? 

Hahahaha
Suppose I were an idiot, and suppose I were a member of Congress; but I repeat myself. ... Mark Twain
2006 AVL Electra


Adrian II

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Reply #12 on: October 23, 2017, 01:53:06 pm
These have been around for a while now. Someone was suggesting that deliberately spelling the name incorrectly was a ruse by pattern part suppliers to avoid being sued by RE India Ltd. Or somebody just got wrong...

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


tooseevee

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Reply #13 on: November 12, 2017, 07:51:50 pm
       Well, good or bad, right or wrong, all the decompresssor mechanism is gone except for the collar that holds the exhaust push rod open. I adjusted the valves and left it on.

       I'm hurting more & more doing this kind of work and I'm doing the last of the combined lawn mowing/leaf blowing  and will soon be blowing leaves so I'll leave removing the collar and installing the hooded adjusters for early spring. I blow the leaves every few days now otherwise the piles get so huge I can't move them to the back (I'm surrounded by huge old trees). I'll be getting the snow blower up into the garage next to the bike soon also (and the snow tires) so have to leave the bike alone now and pick what I do carefully.

       The only thing I had to do to the cover was make the gasket surface flat with sand paper on a flat surface. It's a very well finished little piece.
RI USA '08 Black AVL Classic.9.8:1 ACEhead/manifold/canister. TM32/Open 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.