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Post subject: Rebuilding the crank, but turning one side 180 degrees?
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Billy  One-handed Stoppie! Joined: 12 Oct 2007 Total posts: 2199 Location: Sweden arise! |
Heh, just theoreticly, would it be any good? So the pistons are in the same position?
It's hard to explain but you know, the crank are made so when one piston is down, the other is up. But i mean so both of the pistons are up at the same time..
Guess you get it. 
With this, you could put a motocross ignition on and split the ignition cable in two. Would it work or would it require more powa? I have no idea about the actual electronics, i just know how to set it up. 
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Posted: Sat Jun 21, 2008 9:14 pm
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| weaver Joined: 06 Aug 2003 Total posts: 6066 |
Think this has been done before, sure I read it on here somewhere.
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Posted: Sat Jun 21, 2008 9:23 pm
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cb250g5 Mmm, Fully Synthetic! Joined: 03 Dec 2005 Total posts: 1144 |
Billy, I don't know about LC's, but YPVSs spark both plugs at the same time, so a 360 degree crank wouldn't need any changes to the ignition system.
Have you considered the vibration issues? Ride an old british 360 degree parallel twin, see what it's like.
Why not give it a go, here is an idea to get you started.
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Posted: Sat Jun 21, 2008 9:27 pm
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BillyOne-handed Stoppie! Joined: 12 Oct 2007 Total posts: 2199 Location: Sweden arise! |
| weaver wrote: |
| Think this has been done before, sure I read it on here somewhere. |
Aye, it must have been done by some wacko! Not so easy to search up though, i guess.
| cb250g5 wrote: |
Billy, I don't know about LC's, but YPVSs spark both plugs at the same time, so a 360 degree crank wouldn't need any changes to the ignition system.
Have you considered the vibration issues? Ride an old british 360 degree parallel twin, see what it's like.
Why not give it a go, here is an idea to get you started. |
Oh really? Would be nice, no need to change the ignition then. 
I have thought about vibrations and honestly don't know what would happen. But i can't imagine it would be much difference from a single cylinder one.
The good thing about having the crank like this is that both sides then have equal pressure.
In a normal/stock crank, you have the compression on one side, forcing the crank backwards, and on the other side, it is pressing the crank forward. Dunno if it actually is like that when it all spins a bit though. But theoreticly. Hmm, it doesn't really make sense when i think about it. Heh...
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Posted: Sat Jun 21, 2008 9:40 pm
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| Numbskull Joined: 26 Nov 2005 Total posts: 609 Location: Lower Arkansas, USA |
I built an RD350 (air cooled) like that years ago. It was going to be in a dirt
bike, but ended up in my 73 RD. It vibrates a little too much, but could probably
balance crank/piston assem. to be smoother.
The "power band" is more like a 360 Enduro without the low-end grunt.
I think some people used 360 degree cranks in late 60's - early 70's short track racing.
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Last edited by Numbskull on Sun Jun 22, 2008 10:29 pm; edited 1 time in total
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Posted: Sun Jun 22, 2008 12:28 am
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Bare All-gear Wheelie! Joined: 28 Jan 2006 Total posts: 1909 Location: Vancouver Canada |
Has been done often in the past Even earned a name : "Tiwngle"
Google it might turn up something ?
But as was mentioned (if memory serves) more low end grunt, more vibration and reduced top end power.. Worked OK but neither Ideal nor a fabulous configuration.
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Posted: Sun Jun 22, 2008 1:52 am
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Disqmaster Powerband Master Joined: 31 Aug 2006 Total posts: 857 Location: North East U.K. |
The Twingle was actually made by Puch and only had One Combustion Chamber
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Posted: Sun Jun 22, 2008 8:43 am
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BillyOne-handed Stoppie! Joined: 12 Oct 2007 Total posts: 2199 Location: Sweden arise! |
Allright, sounds like it's no good then.
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Posted: Sun Jun 22, 2008 12:41 pm
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rz500performance Sunday Rider Joined: 29 Sep 2007 Total posts: 47 Location: chesterfield, Michigan USA |
Billy, it is called a twingle, if you just rotate the webs it is unridable (done that) it vibrates so bad you cant hold the handle bars, we did it in 87 to a banshee it instantly broke the radiator mounts from vibration, we cut the crank up and got it ridable, you could sit at a stop on pavement and do 3rd gear holeshots it was amazing! wanting it perfect we sent it to Falicon in Fl. and they ruined it had no idea what to do so it got put on the shelf, 2008 rolls around and a friend of mine works for a Co. here in Detroit that builds NHRA pro stock motors 1700 hp at 12000 rpm! what does he do? crankshafts, I tell him what we tried to do and he says his machine will actually machine the crank and balance it so it will turn 10,000 rpm's and be perfect he told me it is almost done, when it is I will put it on a dyno and see what it says
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Posted: Sun Jun 22, 2008 7:07 pm
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TrigOne-handed Stoppie! Joined: 04 Aug 2003 Total posts: 2430 Location: On Cloud 9 |
Rotax 256's (tandem twin)are like this, just need to get the balance factor of the cranks right.
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Posted: Sun Jun 22, 2008 7:51 pm
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bryanbengalAll-gear Wheelie! Joined: 03 Oct 2006 Total posts: 1994 Location: Eastwood, Essex |
sorry, did this post start as a wind up and end up sensible.
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Posted: Sun Jun 22, 2008 10:34 pm
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BillyOne-handed Stoppie! Joined: 12 Oct 2007 Total posts: 2199 Location: Sweden arise! |
| bryanbengal wrote: |
| sorry, did this post start as a wind up and end up sensible. |
Heh, i know it's crazy but i'ts no wind up. I will probably not do it because of the vibrations.
Strange that it is that much difference, i assumed the vibes would be the same as stock but apparantly not. 
rz500performance, will you post a pic of the crank when you get it? Would be very interesting.
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Posted: Sun Jun 22, 2008 11:38 pm
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