The Kneeslider

Doers Builders and Positive People

DIY 1000cc V-Twin 2 Stroke Project

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DIY 1000cc two stroke project from two CR500 top ends
DIY 1000cc two stroke project from two CR500 top ends

Gotta love two strokes, fewer parts and lots of power. Of course some guys always get the itch, they look at a single and think, nice engine, but why didn't they make it a twin? Then the really rare fellow says, hmm, ... ya know, that's not a bad idea.

Milling aluminum for the clutch cover
Milling aluminum for the clutch cover

This project, currently under way in a long build thread over on the PBmag forum, is still in progress, but the photos here will give you an idea of what he's doing. Started way back in November of 2009, he's had a few starts and stops, but it looks like he's under way again and making headway.

Checking progress and dimensions
Checking progress and dimensions

The engine will be a 1000cc V-Twin using the top ends from two Honda CR500s. The bottom end isn't cast like Aniket's Musket, instead, he's using blocks of aluminum, a rather substantial milling machine, careful design and lots of patient work.

Trial fit and dimension check
Trial fit and dimension check

We'll check back to see how it goes, but I thought you might like to see this one as it comes together. The work so far is very impressive.

Thanks for the tip, Eoin!

Link: PB Mag forum

Checking progress
Checking progress

Comments

    • Clever and clever. No need to create the wheel twice, right. These guys make it around the RS fame,and probably know a thing or two about the history. – And for everyone who likes the old two stroke GP bike (RGV250,RS250,RG500,RD400-500) knows that this is a copy of how the old 2 stroke V engine these engines and teams had. Exhaust out in the bottom, second around.

  3. It appears he is running 2 cranks linked together, I wonder why he wouldn’t go that little extra step and either source or have made, a crank that can accommodate 2 rods on its journal? He is already going to great trouble and expense to hog out a billet, seems he has the capability to put both rods on the same crank/journal. Am I missing some sort of mechanical trickery that he is achieving, maybe even fire via crank phasing or counter rotating cranks?

    • Two-strokes use the crankcase for the intake and compression strokes, so if both cylinders were connected to the same crankcase but with a 90 degree angle between them, the induction would be much less efficient. I think it would’ve made more sense to have the cranks right next to each other on one shaft rather than have two crankshafts geared together.

      If you wanted two cylinders to share the same crankcase, you would need to have them in a boxer configuration — the only problem being that they would both fire at the same time, so it wouldn’t be very smooth. Lots of small aircraft, like drones or ultralights, have two-stroke boxers like this.

      • It’s actually easy run arbitrary phasing with a 2-stroke if the crank has a divider between each piston rod. Just search Google for pictures of a BRP V6 crank.

        • Yes they can, most outboard engines have multiple cylinders and only one crank, but rods can’t share the same pin, there must be a divider on the crankcase.

    • When Aprilia went 250GP racing, they started with a tandem twin (2 crank) Rotax disc valve 2-stroke and cobbled it into a twin crank V-twin. It’s been pointed out that many 2-stroke racing engines have used multiple cranks. One advantage is that it reduces rotational inertia. I remember reading that there was an issue with the single crank NSR500 of the crank inertia making the bike pitch up or down (more) when it accelerated or decelerated rapidly. Twin cranks also made it easier for Yamaha to introduce Big Bang on the YZR500, they could just clock the cranks relative to each other to get the power pulses closer together.

    • Thats why a Puch Twingle is really a split single. I believe that the other comments are correct. Its almost mandatory to do it this way if you want off set firing. I would love to know if you could make a 2 stroke v-twin with a Harley styled firing order. I wonder what that might sound like?

  4. It appears to me as if it’s got two whole engines(with two crankshafts) connected in a common crankcase to a common gearbox. .
    Very interesting. It reminds me of the old days when some inventors attached two whole engines together with a common gear drive to a clutch and drive line.

    His work looks very nice!

  5. I’m always flabbergasted when I see build like this — someone has an idea and sets out to make it a reality. Love the milling work — lots of CNC programming there, but the good thing is that once it’s done he can run off as many as he wants. I’ve seen this sort of thing done to build parts for helicopters; not enough volume to justify making dies for injection molding, just clamp a billet onto the table and program the machine. Keep the chips and sell them for scrap. Works great.

    I’m also curious about the crank. Looks like two cranks geared together; that might be easiest and use stock cranks. I also like the exhaust mockup — clever. The finished product should make impressive power. Can’t wait to hear it run!

    • Actually, there is zero CNC going on here.
      He is doing it all manually, hand wound, and even has to compensate for temperature on the readouts when working in the winter.

  6. Hi everyone,

    I really admire work like this. For those of you that are old like me, Walter Roehrich built the original Roehr RV500 about 10 years ago with fundimentally the same design. The bike weighed a whopping 325 lbs in street trim. If I remember correctly it made about 112 hp at the wheel.

    It was priced at around $ 12-14 thousand and he sold a whopping none of them. That bike evolved into a Folan/Highland powered 1000 cc bike. Again tons of interest, but no sales.

    Enter the V-Rod engine and you have the basis of the Roehr 1250SC. That bike sold fairly well, especially at $ 44,000+ a copy, then the economy crashed…..

    This looks like a terrific street bike!

    Mark L.

  8. I’m studying two stroke, cross-head bearings, crank compression (sort of), turbo, inter-cooled, compressed, direct injected, powervalved, common plenumed, hydraulic valved (no camshaft), long stroke, diesel engines. On boats. Of 1,820 litres per cylinder…
    But there is a lot of tech that could be lifted and used on motorbike engines (the most obvious being the camshaft less valve and the direct injection) like this.

  9. That is some truly sexy machine work, I can’t wait to see it finished!

    I had two Cr500s back in the day, an 85 and a 94 and enjoyed riding neither of them, but I sure did feel super human once I stepped off of them alive and in one piece.

    Since I’ve switched to sport bikes, then to street fighters, then to dual sports I really feel myself yearning for another bike that really scares the daylights out of me…I think this could be one such bike!

  10. I’ve often thought of a V4 two stroke made of four CR500 cylinders. I just don’t have the skills or the time to learn them. I reckon that you would over 200 HP at the rear wheel with a very low weight maybe 190kgs. You would have to add all the modern traction control, Launch control etc or otherwise it would probably be unrideable. Still I can dream. This project just makes me think it is quite feasible.

  11. That’s some impressive milling! I wonder how the intake is going to be, the 2 reeds are really close together! 2 strokes really benefit of independent throttles, i just can’t see the space for them, and the rear exhaut chamber? the rear shock can’t be on the stock position.

  13. So how will the cranks be clocked? You could set them however you want – firing 180 degrees apart which should sound like any parallel twin two stroke – or 45 degrees apart to sound like a Harley on angel dust – or zero degrees apart for a big thump, though that would defeat the purpose of dual crankcases.

    In theory you could change it any time you want to fit your mood

  14. this is mother freakin awesome. i have always wanted to build a bike with a rotax tandem or triple 2-stroke. this guy took it to the next level and i really love him for it. one of these days- i will cram a 700cc snowmobile engine into a norton featherbed and have it be my dayly driver. oh if only i was rich- such annoying things i would build!!!!

  15. Hello All,
    Chris Howe is the nutter making the motor and is my old mate in England, he is a time-served toolmaker..
    He does not use cnc it all done on an old mill in his garage.
    It was designed using software and his years of engineering experience and his knowledge of road racing.. Something we both dabbled in I as a sidecar passenger/racer in the 90s and he a yamaha 250 stroke racer..brands hatch snetterton thruxton etc.
    I just skyped with him that is how I found out about this article.
    I still ride bikes in Miami where I now live dr650se kz650 1978 .
    Ian.

  16. This is one hell of a project!

    Thanks for posting up the link, definitely interested to watch it progress from here. This is exactly the type of project that makes me sign up to a forum, just so I can subscribe to the topic…

    I really hope he gets it running and finishes the bike. Just because I want to see who will be brave enough to twist the throttle to the stop!

  18. I would like to see a Rotax 800R E-TEK in a bike. Out of the box they make 164 bhp no kidding with very low emissions and class leading fuel consumption that knocks spots off competing 4 strokes. They are however designed to lug at constant throttle so might hunt at low throttle. But some dyno tuning should sort it. Snags? loads but well worth a go for someone with money (lots) and time (even more lots).

    Has anyone got a spare BMW boxer 1200 with a blown up engine.

  20. Double CR500, very nice ! I’ve also seen a side by side CR500 twin. I’ve built my own 500 square 4 from 4 x rotax 125 kart engine barrels, GSXR1000 gearbox, clutch and water pump. I only have a manual Bridgeport type mill so I had to do it the hard way. Any one interested I can send pic’s

    • Send the pics to Paul! We have to see your four square. It sounds great, a testament to your fortitude.

  21. How much would it cost to buy also I not a bike god like u but I would have also looked at the airplane ulralight engines they have some high horse power and Niger 2 strocks 2 forgive the spelling I have ADHD