Compression Ratio - how low can you go?

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I had an early Boyer and had some nasty kicks when the battery was low. I fitted a Pazon Altair which they claim will function down to, I think, 3 volts. I don't know if the coils will throw a spark at that low voltage but I do know the Pazon starts and runs much better than the old Boyer ever did. Mine is a MK3 with a Dyno Dave starter and 3 phase alternator so I'm mostly pushing the button but it kicks easy.

I agree that women tend to have great leg strength and not so much upper body. I think if you have one properly set up and she gets the proper technique down, you will have a great riding companion.

I would limit the total advance to no more than 28 degrees so it starts somewhat retarded.

When I was a kid the girl across the street had a scrawny boyfriend who showed up on a Gold Star. We always liked to watch him get it started!
 
Comnoz and hobot have video of hand thrust starting but its not something to make a habit of on lightly built jockey like me. Cams with more over lap lower the low rpm CR for starting. Found out you can't find a place for a chain saw type plunger release. Someday there will be a Commando exhaust valve lifter.
 
Most important question: does SHE want an old, kick start Commando or do YOU want her to have an old kick-start commando? ;)

Frankly, if she wants a Commando, after I got her the necessary psychological evaluation, I'd either either buy her a MKIII or, as suggested earlier, install an electric start in an older one. That way if she wants to demonstrate to the "guys" that she can kickstart, she can. But she doesn't HAVE to deal with it. I'd bet money that the first time she stalls the kick-start-only bike in traffic, it'll be the last time she rides it. Women tend to have more sense with such matters than we do… :)
 
mike996 said:
Most important question: does SHE want an old, kick start Commando or do YOU want her to have an old kick-start commando? ;)
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That's the real issue, I think. For most women, an old kick-start Commando is too "mechanical". A few of us have The Sickness but we're a rare breed it seems.

As for body size, shape, configuration - doesn't really matter. It's all in the technique. That said, there's this big "gravity enhanced" fellow in our club who comes to mind. He's probably somewhere north of 270 lbs these days and he's tall too. He just jabs at the kickstarter like it was a little Triumph or something. I have to throw my entire body weight into it. But one good kick is all it takes! :D
 
elefantrider said:
Is there much of a difference in terms of kickstart effort, Atlas 7.5:1 compression pistons vs Commando 9:1?
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Atlas 7.5 CR vs Atlas 10.5 CR......I never perceived any difference. Maybe the technique (and there is one) rules.

Slick
 
If you want to make it easier to kick then sleeve it down to a 600.

Of course timing is all important. Jim
 
I have been reading this thread looking for any tidbit of kickstarting info I might use to improve my style. Then I remembered that I first learned to kick start an ES2 500 single at age 12. Compared to that, my 850 Commando is like starting a Honda 90. I have no problem kickstarting my 12 to one 490Maico, which is also much harder to kick over than the Norton, but this project bike is something else.
Truth is, no amount of technique will help with my problem, that is trying to roll over 1360ccs at 10.5 to one with very large squish bands cast into the heads .
If it goes in one, good, if not, the leg starts to tire from exertion, a little of the muscle strength needed is lost and you go nowhere, can't get thru compression without the decompressor, in other words, can't start it.

It might be time to fit an electric starter!

Glen
 
worntorn said:
I have been reading this thread looking for any tidbit of kickstarting info I might use to improve my style. Then I remembered that I first learned to kick start an ES2 500 single at age 12. Compared to that, my 850 Commando is like starting a Honda 90. I have no problem kickstarting my 12 to one 490Maico, which is also much harder to kick over than the Norton, but this project bike is something else.
Truth is, no amount of technique will help with my problem, that is trying to roll over 1360ccs at 10.5 to one with very large squish bands cast into the heads .
If it goes in one, good, if not, the leg starts to tire from exertion, a little of the muscle strength needed is lost and you go nowhere, can't get thru compression without the decompressor, in other words, can't start it.

It might be time to fit an electric starter!

Glen
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When Godet built my 1330 @ 10:1, he refused my request to supply it without electric start. I came to understand why!!
 
I've seen a few women's and men's Cdo with welded up longer re-chromed or painted kick levers. The sparkplug type compression releases make for Harleys' went out of flavor after blowing out regularly taking plug threads with it. At some point must face it, the Commando is a "real man's or woman's" motorcycle that takes some success in business life with luxury time to spare, adequate muscular joint force application and sense of self worth that is hard to beat down dealing with a such simply complex craft.

Compression Ratio - how low can you go?
 
After seeing how unreliable the Godet Estart was on the 1330s at the IOM 2007, I would say having a kick start as well is still a good idea. I have started mine 30 or 40 times now with the kicker , but every now and then it just gets too much.... Godet has a better starter now, actually it is a Harley starter with a proper Bendix rather than a sprag, perhaps your bike had this type, Eddie?

On the low compression Commando idea, the Maico uses a compression release that is situated part way up the bore. When the lever is pulled, it releases compression until the rings pass by it on compression stroke, from there on up compression occurs normally. This reduces the effective CR from 12 to one down to about 9 to one, which is plenty to start the bike, but makes kicking it over much easier. Sometimes I think it starts a little quicker on full compression, so I don't always use the release, but if the leg is tired then the compression release is the way to go. Is this similar to the Sunbeam, John?

Glen
 
comnoz said:
If you want to make it easier to kick then sleeve it down to a 600.

Of course timing is all important. Jim
Click to expand...
600 or 650 cc seems like a good idea. You'd need to notch the bottom of the cylinders to clear the conrods, but that's fine. If you could get 6:1 pistons made, it should be easy to kick (about 58% of the effort or less). You'd lose 30% power or more, but that might not be a problem.
There's no need to make any change to the camshaft.

Briggs and Stratton use a slow closing intake cam to reduce compression at cranking speed. The intake valve is held slightly open (but not much) until late on the compression stroke. It's enough to bleed off compression at cranking speed, but at higher rpm the leakage is negligible.
 
I weigh 130lbs and am a short guy as well and have hand no issues kick starting anything that has come my way. I literally have zero issues kicking over an 850 or 750 commando, or a high comp single due to weight, and I'm not particularly muscular either... If the bike is poorly maintained, then it can be a bear but there's a quick solution for that! :wink:

The only time a bike has made it's weight and difficulty to start more apparent than it should have was an enfield interceptor, where the center stand is a bear to lift he bike onto, and the kickstarter is rather poorly geared. Bikes that are too tall are an entire other issue. If you're a shorter person and can't solidly support the weight of a bike with two feet (minimum the balls of your feet on the ground), you will have a tough time balancing it when kicking on the bike. I prefer to avoid situations like that because you can't always predict when a bike may die in traffic, and getting off the bike is not always an option.
 
Godet has a better starter now, actually it is a Harley starter with a proper Bendix rather than a sprag,
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Wartorn Better ShutTFup on this Harley part mention, as it got a well known Nortoneer in Oregon recently kicked off and locked out from even viewing forum as a lurker for pointing out identical 961 starters. I had comnoz and Canaga both thoroughly investigate plunger type compression releases I supplied to fit anywhere in bore or head chamber to find it not possible in our Commandos. To save me some trial-error time it would be helpful if anyone can report the range of amounts of exht valve lift used in various cycles to big marine engines. That way could make adjustable releases for the starter's state of vigor or mood of sex gender at the time.

location of crossed off list of possibles for nice 10 mm Haley releases
Compression Ratio - how low can you go?
 
worntorn said:
After seeing how unreliable the Godet Estart was on the 1330s at the IOM 2007, I would say it having a kick start as well is still a good idea. I have started mine 30 or 40 times now with the kicker , but every now and then it just gets too much.... Godet has a better starter now, actually it is a Harley starter with a proper Bendix rather than a sprag, perhaps your bike had this type, Eddie?

On the low compression Commando idea, the Maico uses a compression release that is situated part way up the bore. When the lever is pulled, it releases compression until the rings pass by it on compression stroke, from there on up compression occurs normally. This reduces the effective CR from 12 to one down to about 9 to one, which is plenty to start the bike, but makes kicking it over much easier. Sometimes I think it starts a little quicker on full compression, so I don't always use the release, but if the leg is tired then the compression release is the way to go. Is this similar to the Sunbeam, John?

Glen
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I believe it did Glen, it span the motor very fast and was 100% reliable.
 
Glenn,
The RTV as a electric start and with a heavy duty {RSV 1000 gel battery] starts easy.


worntorn said:
I have been reading this thread looking for any tidbit of kickstarting info I might use to improve my style. Then I remembered that I first learned to kick start an ES2 500 single at age 12. Compared to that, my 850 Commando is like starting a Honda 90. I have no problem kickstarting my 12 to one 490Maico, which is also much harder to kick over than the Norton, but this project bike is something else.
Truth is, no amount of technique will help with my problem, that is trying to roll over 1360ccs at 10.5 to one with very large squish bands cast into the heads .
If it goes in one, good, if not, the leg starts to tire from exertion, a little of the muscle strength needed is lost and you go nowhere, can't get thru compression without the decompressor, in other words, can't start it.

It might be time to fit an electric starter!

Glen
Click to expand...
 
In my kick over technique, I first slowly rotate the engine to get the kick lever full down. Then I slowly ratchet the engine up (with short arcs of the kick lever) on one cylinder's compression stroke until stiff resistance is met. At this point, I can only guess where the piston is relative to TDC, but it is definitely not at full compression. Then, a brief pause during which compression leaks off thru the ring gaps, and I bring the kick lever to nearly full up stroke (I want 90 degrees between lever and my nearly extended leg), then pushing down by straightening the right leg and also shifting the body weight from the left to fully on the right. It is usually a one kick deal. I reason the pause acts like a compression release and accounts for no perceived difference with higher CR. Why not simply extend the pause time? I may give that a try when the Atlas bits all come back together.

Slick
 
I'm surprised no one's mentioned this:

Google "linda's norton you tube", Linda can't be much over 120lb, makes kick starting a Norton look like child's play.
 
Steve, as was pointed out to me recently in my quest to fit some sort of compression reducing gizmo to the head, there is no need for a full 10 mm hole all the way thru. From the combustion chamber going out to join the 10 mm hole with bottom, one can drill just a tiny hole, perhaps 1/8" or so for communication to the 10 mm decompressor, the bottom of which might sit perhaps 3/8" or so above the surface of the CC, depending of metal thickness available.
This allows for more siting options.
All depends on the type of decompressor though. If poppet style, then the poppet needs room to move down.
Glen
 
Jeez, I hope this thread doesn't cause my wife to have me remove the Estart on her 2012 BMW and see if a kickstart can be retrofitted!

HaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHaHa !!!!!!!!!!!!! LOL :) :) :)
 
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