Double Dog Dare on Compression releases

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Hobot

Hobot

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I bet a set of uninstalled RGM alloy yokes no one can come up with effective compression release in a Combat 750 CHO head. Double Dog Dare!

Here's Harley 10mm set that wouldn't fit. Maybe chainsaw but would it be enough to matter for 10.5 static CR 920? Cam calculator says only 7.5 dynamic but don't believe it.
Double Dog Dare on Compression releases
 
Why run the risk of ruining a head, why not modify the exhaust valve rocker covers or fabricate new ones so they have a lever to push the exhaust valve down.
 
Do you really want to push the exhaust valve down and risk contacting the piston?

If the bike can't be kickstarted normally, you've got a problem that needs fixing!
 
Pushing the exhaust valve down is the way it is usually done on most of the big singles (350 and 500) and is used to stop the engine as well as to get it just past compression when starting. Scared me the first time too! It doesn't lift it very much at all. The Matchlesses have a shaft with a flat cut in it. In normal operation the flat faces the rocker arm and when the lever is pulled the shaft rotates the flat away so it pushes down on the valve.

I guess I just don't see a need for a compression release on a Commando either.
 
I want release that allows starting with it open and it auto closes on first combustion.
My chain saw does this with poppet valve. My diesel genset haS valve lift to spin up and drop to start or lift to shut off. Don't think a valve lift will work on Peel if can't start with valve lifted, but still open to idea if it works to get head start kick over TDC. I may have to spend for 9 CR pistons in the end, ugh or give up defeated.
 
There's a difference between a Combat and a "HoBat".
Click to expand...

Yes - my P!! 750-11.5 CR would break bones if not a karate death kick done right.
My two 10 CR Combat were ordinary pleasant compared. I could almost kick them as much as Swoohdave. 750 cc = ~45 cid like old Harleys. Actually when tuned good a hand start was not too hard on first swing though on either of em.
Calculators imply the 2S cam over lap should lower kicking PSI but the actually PSI measuring shows 190-200 PSI, but must relieve CR some as 2S cam don't detonate on Combat as easy as standard cam installed.

HoBat-Ms Peel is 920 cc = ~55+ cid with 10.5 CR. About 1/5-20% bigger piston to punch. I'm skinny 155 lb this year. I plan on longer kick lever custom or off the shelf but still wish for compression release. I bet there'd be a good market if a nice kit was developed. I know when I'm tired or injured and pulling on my big
6+ cid chainsaw and it jerks in up to my face, I've forgot to press the release first. Saw will run with release held open spitting combustion gases, so may not take much a hole in the head to vent to relieve kicker power.
Heck can ya imagine the loss of vendor revenue on electric start devices if effective releases installed?

I don't guess taking release bore out at the gasket seam would be a good idea : (
 
One of my other bikes has 11.3:1 in a 500 single with a left hand kickstart and is still easy to start (Husaberg FC501), the decompressor (well one of the two) is clever. The back of the exhuast lobe on the cam has a half round hole that goes about 2/3rds of the way across the face of the lobe, there is a pin that sits in this hole with a counter weight and a spring, the pin has a kind of flat ground on on one side which roughly matches the shape of the cam lobe. At low speed the spring holds the pin so the round face protudes from the cam lobe, momentarily lifting the exhaust valve off its seat, then the engine speed increases the counter weight swings out, rotating the pin so it is flush with the cam, this also helps prevent low speed cough and stall that a big short stroke single is prone to doing. All that said though the Berg is still easier to start by pushing to just past TDC (exhaust rocker/kickstart decompressor) and giving a smooth kick through.

You could get real high tech and come up with a hydraulic lifter/follower that had a magnetic rheological fluid in it so you could flick a switch and it would hold the exhaust valve open... or possibly a spring loaded follower that did the same and then the forces form the higher valve train acceleration due to increased speed would completly compress the spring. Neither of these will work as well as the above system though, the pin in the cam will have maybe 0.5mm lift for a very short duration. Holding the exhaust rocker down would be the easy way of doing it.
 
Thanks for the uplifting reports and insights on clever bodges.
Racer Canaga could not find way to fit vent-poppet type releases and he's the best there is on clever machining. I take youf lead and industry to focus on EXHT valve.
I'll save the ferrofluid for my active suspension but I'll have a potent energy source of 100 PSI air pressure to power some intrusion or direct valve contact, hm.
Could dial in gap to allow decent kicking yet running to allow time to seal up before stalls. Hm. Maybe ram a wedge over the rocker then spring pulls it back. Solenoids are big ugly warts to me. Air on a tiny piston in a tube could be more steam punk compact. If dead battery and air leaked down could pump up by hand or compressor for safer foot starting, hm.

Hm, could I use air pressure direct to turn to start? hm.
 
I just took a look at my head to see if there is room for the KTM LC4 style and have to say that it wont fit. They would have to be mounted in the covers and I don`t see that working either. You can see where the cable would attach to the lever to push the rocker down on the valves in the lower right of this picture I found on ADVR.
Double Dog Dare on Compression releases
 
Nope Will I can't tell where cable-lever would go from photo, but if it don't apply to Norton then what's it matter to me. The new concept I'm not sure of is exht lift that can still run with instead of just spin up to drop valve to run or lift to shut down.
I'm not current on head geometry though have two exposed heads in shed. Maybe a cam with lever sticking out rocker cover. I hope to suck vacuum in Peel so might just suck air in the lever shaft bore instead of blowing oil out, ha in my dreams but then this is my dream machine. Maybe I can just kick off like normal healthy people.
I've not read much comments of street 920 owners kicking issues but have from racers who likely run hottest over lap cams on hi CR, similar to Peel.
I know what Trixie will be like once back to factory intact, but Peel is always a mystery to lead me on deeper.
 
Compression releases are really only needed on bikes belonging to geriatrics or on high compression singles. A colleague at British Aircraft Corp had a 500cc Velocette, and it was impossible to kick that thing over without the compression release.

I never found that the Commando (or its immediate ancestors) needed a compression release system, but I was a lot younger then! I'm not sure I could kick-start one now (at 69).
 
A colleague at British Aircraft Corp had a 500cc Velocette, and it was impossible to kick that thing over without the compression release.
Click to expand...

Ugh Frank, a 920 has two 460 cc pistons to kick over. I think I can handle it when refreshed, if a one-two kick relief, but when tired or stuck in traffic on in wet-muddy places, has me pensive. Plus saving the kicker mechanism too.
Keep thinking of ways to relieve starting strain.
 
Since one of the cylinders is on compression and the other on exhaust, and the CR is probably a good bit lower than the 10.5 on friend's Velocette, maybe the new Norton wouldn't be too bad for a young chap. I'm staggered that it doesn't have electric start for us old farts (sorry - more mature riders), particularly in view of the vastly increased power in modern starters.

My 315cc Honda mower can be started reliably by four NiCd D-cells, and has for 12 years on trhe same set of batteries! Never had to use the charger - the engine-driven generator keeps the batteries charged. If Honda can do that on an $800 mower, why can't Norton provide a reliable electric start on a $30,000 motorcycle. The Gold Wing, BMWs and even the current Triumphs all have good electric starters.
 
Hehe Frank enjoy your attitude. If I ever ask a question on forum 99.9% of time it will be about Ms Peel and have no application to others. Peel has Jim's light 10.5 pistons kit fit to 750 Combat head, so yes really 10.5 or more to start with using .020" gasket so fudge room with thicker gaskets.

Peel only needs this brute engine to wipe some sneers off elite sports biker and doubting Thomas's on various lists. Then beyond that by 3 more levels just to please me. Ken Canga said it became 50/50 to kick start before a race when he moved up to 920 racers. I tease tee not that the most elite digital controlled fat tyre corner cripples are my target flashy bait fish I want to out sprint as well as out turn. If I can't pretty easy start it any condition if won't be so good as daily commuter-explorer which is Peel's main planned use. So punch to whip up on pure race bikes while wearing road legal equipment and luggage rack and bags and crash bars. Torque via displacement and combustion pressure is only way a Norton twin will stand a change after the apexes load reliefs.
Can't give up much compression or drag only cam will not allow slow trials tame riding in mud and leaves or Gravel slopes.

Deep in my bones I'd like to just sorta step hard on kicker to get instant running at low steady idle. I learned not to reveal Norton SNORTs too soon from P!! daze or they just idle back and creep away at first turn off, time and time again.

Simplest way I conceive is a screw through rocker covers to turn in and out to hold valve just off seat then un screw and leave the scene.

You just have no idea the high of leaving very angry moderns miles behind in minutes time and time again. The reactions I get after we stop ranges from high fives jumping in saddle joy to spit in my face heat ray death vision. Peel got left behind 4x's in her testing contests but only thrice I couldn't catch right back up.
One by BMW RS1200 that I just couldn't face the fear of entering tight blinds I'd had surprises at, two, by 990 Ducati Monster with little girl on it after Peel lost 3rd gear teeth and stuck in 4th, 3rd when phase 3 lo>hi side turn sloshed 4 gallon of fuel slower than air borne front tire jerk and threw us across lane, an '04 Triumph Triple got the jump on me while I avoided going off the edge riding out a controllable tank slapper. A damper would have crashed us by first resisted fork jerk on touch down. So it follows I want some ease to start anew. This last event was the only upset I ever got on Peel in handling extremes. Still ain't figured a solution to the 2/3's full tank mass yet. Or bunch other stuff : (
 
hobot said:
Hehe Frank enjoy your attitude. If I ever ask a question on forum 99.9% of time it will be about Ms Peel and have no application to others. Peel has Jim's light 10.5 pistons kit fit to 750 Combat head, so yes really 10.5 or more to start with using .020" gasket so fudge room with thicker gaskets.

Peel only needs this brute engine to wipe some sneers off elite sports biker and doubting Thomas's on various lists. Then beyond that by 3 more levels just to please me. Ken Canga said it became 50/50 to kick start before a race when he moved up to 920 racers. I tease tee not that the most elite digital controlled fat tyre corner cripples are my target flashy bait fish I want to out sprint as well as out turn. If I can't pretty easy start it any condition if won't be so good as daily commuter-explorer which is Peel's main planned use. So punch to whip up on pure race bikes while wearing road legal equipment and luggage rack and bags and crash bars. Torque via displacement and combustion pressure is only way a Norton twin will stand a change after the apexes load reliefs.
Can't give up much compression or drag only cam will not allow slow trials tame riding in mud and leaves or Gravel slopes.

Deep in my bones I'd like to just sorta step hard on kicker to get instant running at low steady idle. I learned not to reveal Norton SNORTs too soon from P!! daze or they just idle back and creep away at first turn off, time and time again.

Simplest way I conceive is a screw through rocker covers to turn in and out to hold valve just off seat then un screw and leave the scene.

You just have no idea the high of leaving very angry moderns miles behind in minutes time and time again. The reactions I get after we stop ranges from high fives jumping in saddle joy to spit in my face heat ray death vision. Peel got left behind 4x's in her testing contests but only thrice I couldn't catch right back up.
One by BMW RS1200 that I just couldn't face the fear of entering tight blinds I'd had surprises at, two, by 990 Ducati Monster with little girl on it after Peel lost 3rd gear teeth and stuck in 4th, 3rd when phase 3 lo>hi side turn sloshed 4 gallon of fuel slower than air borne front tire jerk and threw us across lane, an '04 Triumph Triple got the jump on me while I avoided going off the edge riding out a controllable tank slapper. A damper would have crashed us by first resisted fork jerk on touch down. So it follows I want some ease to start anew. This last event was the only upset I ever got on Peel in handling extremes. Still ain't figured a solution to the 2/3's full tank mass yet. Or bunch other stuff : (
Click to expand...

The picturethat Will put up is going to be the simplest way of doing it, if you look at the bottom right of the pick by the date there is a pin that goes behind the exhaust rocker, its probably abot 6-8mm dia (1/4-5/16) that has a flat cut in it which will be to about the centre line of the pin. The hole in the rocker box is positioned so that when th flat is down the pin doesnt touch the rocker, when rotated the round side will just hold the valve open a little bit. On the out side of the head there is a spring that retains the pin with the plat down, the end of the pin has a folded piece of steel peened onto it with a hole for a cable, which you could just run back to the left side of your handle bar and have a small lever above or below the clutch.
 
hobot, Click the picture for a better view of what we're talking about.
 
Ok Cheesy and Will - pointing out what to look for resolved the construction. Kwel.
Hm, will look at a head to see if I can conceive how to implement this in Peel.
A warm glow simmering at possibility to ease effort to kick er over. Would just use local lever not extra cables thank you.
 
I had look at shaft with a cut out method to press exhaust rocker down a tad.
Looks like its possible to do. Rocker arms stand above the cover gasket surface ~1/4" where the tallest part of rocker ach is. So shaft would have to cross rocker boxes about .8" below the top cover stud. Actuating lever would go rotate along side of head, lifting up sticking forward to press on valve then flopped forward to lay down almost vertical tucked in close to head for a tiddy device.
No oil passage on valve side of rocker so some metal could be removed if needed.

Main issue I ponder is if the two small studs and ridgidity of the rocker covers could take the spring force to hold valve open slightly and still seal or not break.
Space for shaft must be made, either just drilled through cover or by a half nip out of head and cover. Don't know how to seal shaft ports. Advice accepted.

Wonder if valve gap can be diddled to both lower kick force yet still start and run long enough to lower releases in time. May be able to kick engine over with the long duration over lapped cam, but don't think it'll be much help going by the starting efforts of racers with similar aggressive cams and CR.
Would have to start with too much gap to run then file and try file and try file and try till either works as hoped or becomes too hard to kick and start, ugh.
 
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