why not fire two at a time???
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why not fire two at a time???
I was wondering why hypo motorcycles fire two cylanders at a time and has any detroit motors ever tryed this..there must be some advantage if the japs do it..and what about roller bearings on the crank. works very well in bikes..why not hi performace cars...bill 
"Mifflin Clay"
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From: Mifflin, PA
I THINK that of the two cylinders fired, one is on the compression stroke, and one is on the exhaust stroke, where the ignition spark does nothing. It's a way to cut down on duplicate components in the ignition system; I could be mistaken .... I was once!
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I believe alchymist is correct. At least that is the way bikes I have seen were done. It is often done on coil pack engines. One coil fires two cylinders, don't know why it works and just doesn't fire the easiest gap to jump only.
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From: Las Vegas
Originally Posted by hotrodfordpickup
I was wondering why hypo motorcycles fire two cylanders at a time and has any detroit motors ever tryed this..there must be some advantage if the japs do it..and what about roller bearings on the crank. works very well in bikes..why not hi performace cars...bill
You won't find any modern inline 4 cylinder bikes with roller bearings anymore.....makes for a much weaker crank.
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From: Groton, MA
In the early 60s my friends older brother used to race on short tracks. His car sounded different from the others so I asked him about it and he told me that he had a "crossfire setup" in his engine so two cylinders fired at the same time. He said it gave him much more low end torque and it was done by changing the cam and ignition. I don't know if it was BS or not, but he won a bunch of races and it would accelerate out of the corner like it was shot out of a cannon. It also blew up after about a year of running like that.
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From: Marion, VA
Originally Posted by hotrodfordpickup
I was wondering why hypo motorcycles fire two cylanders at a time and has any detroit motors ever tryed this..there must be some advantage if the japs do it..and what about roller bearings on the crank. works very well in bikes..why not hi performace cars...bill
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From: savannah,ga
harley engines are still built with roller bearings
also just recently that all the harleys went to single fire ign. systems
in the late 90s almost all were still dual fire, even with electronic ign.
the roller bearing setup is a good system BUT the clearances are
very hard to set up and get it right
when set up right it will last very well
also remember this is a long stroke, high torque, low rpm engine
also just recently that all the harleys went to single fire ign. systems
in the late 90s almost all were still dual fire, even with electronic ign.
the roller bearing setup is a good system BUT the clearances are
very hard to set up and get it right
when set up right it will last very well
also remember this is a long stroke, high torque, low rpm engine
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From: Connecticut
Ford's DIS/EDIS ignitions are "waste spark" designs, as well. One coil fires two cylinders at a time. The cylinder firing on it's exhaust stroke contributes nothing to power.
Summary of Ford DIS/EDIS "Waste Spark" Ignition Systems
Summary of Ford DIS/EDIS "Waste Spark" Ignition Systems
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From: Marion, VA
Originally Posted by loudfords
How in the heck would you get roller bearings onto the middle journals of a crankshaft???? 2 piece housings? That would be a recipe for disaster....
"Mifflin Clay"
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From: Mifflin, PA
Originally Posted by osbornk
Most of the roller bearing crankshafts were single or twin cylinder engines with only one rod journal. Most of them were 2 piece cranks that were pressed together. I have seen a few with a one piece crank that used a rod cap like an insert bearing engine but reinstalling the roller bearings was a real challenge (with thick grease).
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LOudfords take a look at NTN corp..they make precison roller bearings for auto cranks..as far as bikes go rollor bearings are the way to go..my low slow hog is set up like that but so is my KZ..and 10.000 rpm is no problem..it seems to me that a new mustang set up the same way with its over head cams..would be a giant killer..on bikes the cranks are pressed togather.but if you nitro it than you can weld the crank and have it reballanced take care...bill