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May 19th 2017, 09:56 AM   #1
 HalcyonSon's Avatar
  Apr 2016

Two-Stroke News and Qs

Found an interesting article on Asphalt and Rubber while surfing at work. I get that two-strokes are supposed to be lighter, quicker, and simpler than four-strokes. I can even understand part of why - fewer moving parts and more power strokes. And the benefits of Fuel Injection are obvious. But why the hell has it ever been considered a good idea to have crankcase scavenging? I've heard of far too many old bikes ending up rotting in a barn with burned out pistons and siezed cranks from bad oil injectors or off mixtures. Why is it so difficult to separate the lubrication and intake tracts? Why not just use a simple throttle-body injection and a sealed crankcase? It should be even easier than a four-stroke, because you don't have to worry about cams or valves in the head. Any heat from vales low in the cylinder should be easy to manage by running oil or water channels around the cylinder walls.

I understand how reed valves work, and the advantages of using the downward piston movement to compress the intake charge... Still baffled how these things still seem so backward after a century's work. Seems like a simple valve run directly or geared off the crank would solve so many issues with burning oil and environmental regulations.

Here Is KTM’s Fuel Injected Two-Stroke Motorcycle
KTM FI Two-Stroke Info: The Scoop on TPI (Transfer Port Injection) - Dirt Bike Test

Edited by HalcyonSon on May 19th 2017 at 10:02 AM
May 19th 2017, 01:10 PM   #2
 holypiston's Avatar
  Jan 2016
  Vancouver, WA

This looks like a good answer:

The intake and exhaust ports being located directly on the cylinder pretty much explain why it is a problem. The piston also has to be much longer also as it acts as a seal/pump/port opening-closing mechanism. Would be nice to have short pistons in a two stroke, but then you'd need a mechanical valve of some kind. I've seen a horizontally opposed (old beamer style) two stroke that has been developed in recent years...but more complex. Cylinder has no ports if i remember correctly.

I'd love to see someone solve this problem. Sounds like removing the ports from the cylinder might be part of the solution, but it will be more four stroke like and probably sound like one two.

Just bring back the noise, oceans are being polluted every day and billiions of pounds of other crap much more by other sources. Might as well enjoy the ride to hell-la-la-la. I hear of too much methane., well build machinery that burns it right? All that baby/people shi* can be made into fuel. kind of makes sense to me...not sure what to do about carbon dioxide, except stop shipping toothpicks to china and everywhere else. See trees cut down all the time up towards cogar now. Gonna be apartments and condos in 20 years or so, my guess.

A guy on on the RZ/RD forum spent a lot of time adapting a fuel injection system off (competent mechanic) and R6 to an RZ and ultimately gave it up, if I remember correctly. Bimota? tried it too and failed. I t hink the RZ ran good at steady engine speeds, but the increasing use of throttle and different riding conditions, not to mention carbon possibly blocking the sensors was proabably a part of it.

I think if you look at snowmobile tech, they've really cleaned up dirty two strokes, more complicated, but use much less injector oil and ultimately burn cleaner. Wonder if they'd be clean enough for street use?

jSome BIG company is gonna have to take a chance and spend millions on developing the tech. then the smaller companies can buy the technology as they won't need to do the expensive development work...or so I've gleaned from what I have read.
May 19th 2017, 01:59 PM   #3
 HalcyonSon's Avatar
  Apr 2016

I've read about plenty of attempts to do away with mixed or oil injectors, but they all seem insanely complex. Rotating sleeves, opposed pistons, etc, etc. Also read about "power valves" changing the size of the exhaust port or opening / closing a resonator off the exhaust. If a "power valve" partially blocking the exhaust port can be successful, why not one that completely closes the ports? IIRC old (WWI) rotary aircraft engines had something like that, so why was it never adapted to motorcycles? Of course, they were notorious for spewing castor oil everywhere...
May 21st 2017, 08:06 AM   #4
 Wrench's Avatar
  Jan 2016
  West Richland, WA

In a nutshell:

You either keep the simplicity of the design, or you don't.

2-strokes need the upper and lower rod ends lubed, and the port design/crankcase porting is what allows the 2-stroke to make great power. It would be very difficult to separate these two.
May 21st 2017, 02:36 PM   #5
 Parilla125's Avatar
  Jan 2016

The snowmobile and outboard folks have been working on cleaning them up for some time and they are cleaner than the 4 stroke's when you bring the oil changes the 4 stroke needs. I read the new electronic controlled FI ones at idle are at a 500/1 oil ratio. No smoke and no 'stutter' any more. Not 'pipey' either. Pull from the bottom up.
My father in law wanted to sell two stock two stroke 600cc FI snowmobiles (100 hp!) that had been sitting for two years. One took two pulls and the other took seven pulls to start. Both are battery less systems. Awesome.
It will take a 'major' manufacturer taking the leap to put a two stroke back on the street. They have to be convinced there is a market or they will not do it. KTM has done well with the off road two stroke stuff. They may be the ones that do it first.
I have been looking at the new smaller outboards and while they are getting lighter in the small four strokes, you still have to be careful how you lay them (oil leaks out) and they are still heavier for the same HP. The two strokes (older) still have a wider useful RPM range as well.
I would really like to buy a 'new' street two stroke before I keel over, but it may not happen...
May 21st 2017, 05:25 PM   #6
 TOPDECK's Avatar
  Jul 2016
  Mill Creek, WA

  2016 ZX-6R 636, 2017 Husqvarna 701 Supermoto
The elephant in the room?
May 23rd 2017, 02:59 PM   #7
 Sentinel's Avatar
  Jun 2016
  Poor Tortured

  2013 Kawasaki Ninja 1000 Harlequin
vw diesel?

but seriously, please god make ktm give us a 2-stroke v-twin 900cc Hyper Duke that weighs 340 lbs wet.

Edited by Sentinel on May 23rd 2017 at 03:01 PM
May 24th 2017, 08:20 AM   #8
 PeteN95's Avatar
  Jan 2016
  Muklilteo, WA

  Suzuki DL1000, Honda XR650R, KTM 250 XC-W
Originally Posted by Sentinel
vw diesel?

but seriously, please god make ktm give us a 2-stroke v-twin 900cc Hyper Duke that weighs 340 lbs wet.
How about just a 600cc Duke (2 x 300XC)?!

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