Two stroke V twin ? - xBhp.com : The Global Indian Biking Community

rennjie · 11-02-2009, 08:29 PM

We all know it is near impossible to have a V-twin 2 stroke without separate crank chambers/ forced induction/ split crank pins. Usual crankcase induction will not work with common pin.

Now here's what i came across over the net, a 100cc V2-2T made from 50cc Suzuki K50 single. Externally it doesn't appear to feature any serious crankcase mods to include separate chamber or offset pins by looking at the cylinder alignment.

I could find no further info on this. What are the possibilities to configure one such?
welcome all experts, lets discuss..

Videos here:

YouTube - Moped Suzuki K50 V-twin

YouTube - Moped Suzuki K50 V twin

ken cool · 11-02-2009, 09:30 PM

Discussion Approved

gsferrari · 11-04-2009, 02:14 PM

Cannot work without split crank-case as far as I have heard/learnt. Why don't you PM Rajkumar11 for his inputs?

velociraptor13 · 11-04-2009, 04:29 PM

Quote:

Originally Posted by gsferrari

Cannot work without split crank-case as far as I have heard/learnt. Why don't you PM Rajkumar11 for his inputs?

Or joel,he is one of those DiY guys.

desideep · 11-05-2009, 10:28 AM

i would not be able to say much. would wait for Venu's (Enginehacker) input on this one. i am sure after the sucess of his Fiero Vtwin he would want to help on this one aswell

Old Fox · 11-05-2009, 12:26 PM

Off-hand this could posibly have some sort of a disc-valve arrangement (the kind seen in the KB100) though a common crankcase would create issues with the intake as the 'pumping' efficiency of the crank-case would suffer. Conjecture all the way actually.

The disc-valve impression is re-enforced seeing the placement of the carb and the 'throttle butterflies' inside the intake horn are downright funny. So is its 'reverse diffuser' design. One doesn't increase the flow velocity of intake air. The target is to reduce it so as to increase local air pressure around the intake.

The low 'transfer' efficiency (if the crankpins are off-set by 90 deg to make it a true v-twin) I guess would make it an engine thats difficult to run at idle or low rpm's. No wonder the idling seems to have been set pretty high as seen in the video. And I also feel that an engine can live with such design inefficiency only for small displacements. Go higher and the fatal flaws get pronounced in effect exponentially.

PS: Devilsh conjecture this: maybe the second cylinder is a dummy!!

gsferrari · 11-05-2009, 03:21 PM

Quote:

Originally Posted by Old Fox

PS: Devilsh conjecture this: maybe the second cylinder is a dummy!!

Just evil

Joel · 11-05-2009, 04:04 PM

Such a v-twin 2-stroke sharing the same crankcase will never make enough power to justify the effort put. The 2nd cylinder could very well be considered a dummy, if the intention was only to make a working 2-stroke v-twin and not a performing one.

Rajkumar11 · 11-05-2009, 04:07 PM

Yes, this is a single crank pin and single crank chamber design. It has a very poor efficiency compared to a seperate crank case chamber design. This effort seems more of an academic one rather than one of function. Also this design would only last on small displacement engines and that too only with a narrow angle V. The cylinder seem to be splayed by about 60 degrees.

rennjie · 11-05-2009, 11:23 PM

Thnx all

for sharing views.

It appeared something much interesting as i didn't know any such trials done even for demo sake. Couldn't locate any similar over the 'net too. Separate cases or forced induction is preferred allover.

I learn that though possible to run such configuration it is not worth the effort in terms of output. I might sound stupid but lets pls consider this as a topic of academic interest. hope we can discuss possibly a few options (if any) which may improvise the setup to keep it atleast good as original single. And I would like to try deriving engine character from these.

Big Q: Would this second cyl possibly become parasitic load?

I presume that lower case pumping is suffered mostly by front cylinder taking that engine spins clockwise viewed from RH / carb side. it gets less gas. Can this be countered by a tighter combustion chamber?
And yes the angle seems 60 deg from pic.

11-02-2009, 09:30 PM	#2 (permalink)
ken cool Been Around Join Date: Sep 2005 Location: New Delhi Posts: 4,649	Discussion Approved __________________ The Wheel was a great invention; Two Wheels with a Motor in between was even better! BMW Motorrad Days 2011 Xbhp's Indo-French Kashmir-Ladakh Tour

11-04-2009, 02:14 PM	#3 (permalink)
gsferrari Poser Killer Join Date: Sep 2008 Location: Bangalore, India Posts: 683	Cannot work without split crank-case as far as I have heard/learnt. Why don't you PM Rajkumar11 for his inputs? __________________ Kriss : 15.06.1981 - 11.10.2009 You will not be forgotten...RIP

11-05-2009, 10:28 AM	#5 (permalink)
desideep Oh FCUK!! Join Date: Jun 2004 Location: PB03,DL Posts: 754	i would not be able to say much. would wait for Venu's (Enginehacker) input on this one. i am sure after the sucess of his Fiero Vtwin he would want to help on this one aswell __________________ 1993 YAMAHA RX100 \| 1977 RE Bullet 350 STD \| 2008 HH CBZ \| 1997 LML NVSpl \| 2009 Suncross Proceed www.desideep.blogspot.com

11-05-2009, 12:26 PM	#6 (permalink)
Old Fox Senior Member Join Date: Oct 2007 Location: Noida Posts: 649	Off-hand this could posibly have some sort of a disc-valve arrangement (the kind seen in the KB100) though a common crankcase would create issues with the intake as the 'pumping' efficiency of the crank-case would suffer. Conjecture all the way actually. The disc-valve impression is re-enforced seeing the placement of the carb and the 'throttle butterflies' inside the intake horn are downright funny. So is its 'reverse diffuser' design. One doesn't increase the flow velocity of intake air. The target is to reduce it so as to increase local air pressure around the intake. The low 'transfer' efficiency (if the crankpins are off-set by 90 deg to make it a true v-twin) I guess would make it an engine thats difficult to run at idle or low rpm's. No wonder the idling seems to have been set pretty high as seen in the video. And I also feel that an engine can live with such design inefficiency only for small displacements. Go higher and the fatal flaws get pronounced in effect exponentially. PS: Devilsh conjecture this: maybe the second cylinder is a dummy!! __________________ I don't let my motorcycles interfere with my motorcycling... Join xBhp On

11-05-2009, 04:04 PM	#8 (permalink)
Joel Race Concepts Join Date: Jun 2004 Location: Bangalore Posts: 1,759	Such a v-twin 2-stroke sharing the same crankcase will never make enough power to justify the effort put. The 2nd cylinder could very well be considered a dummy, if the intention was only to make a working 2-stroke v-twin and not a performing one. __________________ joel@raceconcepts.in

11-05-2009, 04:07 PM	#9 (permalink)
Rajkumar11 Junior Member Join Date: Sep 2008 Location: Chennai Posts: 25	Yes, this is a single crank pin and single crank chamber design. It has a very poor efficiency compared to a seperate crank case chamber design. This effort seems more of an academic one rather than one of function. Also this design would only last on small displacement engines and that too only with a narrow angle V. The cylinder seem to be splayed by about 60 degrees.

11-05-2009, 11:23 PM	#10 (permalink)
rennjie Junior Member Join Date: May 2005 Location: off line Posts: 7	Thnx all for sharing views. It appeared something much interesting as i didn't know any such trials done even for demo sake. Couldn't locate any similar over the 'net too. Separate cases or forced induction is preferred allover. I learn that though possible to run such configuration it is not worth the effort in terms of output. I might sound stupid but lets pls consider this as a topic of academic interest. hope we can discuss possibly a few options (if any) which may improvise the setup to keep it atleast good as original single. And I would like to try deriving engine character from these. Big Q: Would this second cyl possibly become parasitic load? I presume that lower case pumping is suffered mostly by front cylinder taking that engine spins clockwise viewed from RH / carb side. it gets less gas. Can this be countered by a tighter combustion chamber? And yes the angle seems 60 deg from pic. __________________ Last edited by rennjie; 11-05-2009 at 11:25 PM.

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