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Help settle and argument turn a 4 stroke into a 2 stroke

Discussion in 'Modifications and Projects' started by crutch, Jan 8, 2007.

  1. Yes, i always wanted a 1000cc 2 stroke bike

  2. No, Techincly not possible

    0 vote(s)
  3. Yes but way more trouble than its worth

  1. Me and my mechanicly challanged mate where woundering what would be needed to convert a 4 stoke into a 2 stroke on a single cylinder engine.

    Obvously change the ignition timmings.

    Remove most of the top end,

    make a new top end crank shaft which would open the exhust valves twice as much or remove it all together

    beef up the cooling system as it would run alot hotter.

    I would be worried about clutch/bottom end bending and warping under the increased stress/heat

    Anything else we forget
  2. Yep can be done

    Need supercharger to blow fuel air mixture in

    Just buy one of them Orbital engines and couple it up to a gearbox and your away
  3. evein if you make the camshaft open twice per cycle hows the burnt gases gonna get out while its compressing the next lot of air/fuel...

    other than recasting a whole new block with different ports and head its not possible in my opinion. you could mount a two stroke motor into a traditional 4 stroke bike but thats not the question is it?
  4. A rotary engine those things are weird, arnt they making scooters with them in it now. Anyways read an article of a prototype ford using a 1.2L 2 stroke rotary engine in it

    Intresting But im talking about converting a existing engine

    ok gota check how eatxcty a supercharger works (just blows in high presure air into the expansion chamber from memory)

    well u can just remove it all together or maybe file it down so its semi open all the time. make the shaft so the valve is open most of the time.
  5. Step 1

    Take barrel mark out for exhaust port machine fins off and weld plate for exhaust port mill pocket / exhaust out deburr

    Step 2

    Pin piston rings in place need gapless oil control ring though

    Step 3

    Remove exhaust cams or get real smart and incorporate head to four valve induction need to re configure cam so as all valves open and shut in one to one crank phasing

    Step 4

    Get small Toyota supercharger Configure supercharger with big plenum chamber and reed valves to stop blow back and run off engine i.e. belts and pulleys off alternator extension

    Step 5 give it the full throttle


    Would not need expansion chamber, as valves and positive inlet pressure would scavenge engine. Would even be able to control wasted inlet gas to give big fat burns out of exhaust at idle :shock:

    Ignition systems as long as it’s a wasted spark type CDI they fire every rotation anyway need to mod so as TDC fire anyway and junk advance

    Because its supercharged can use four stroke bottom end plain bearings and oil pump and no need to use cylinder pumping to draw in inlet charge no need to run 20 to 1 premix maybe able to get away with 100 to 1 only needed to lube rings

    Go for it
    :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :LOL:
  6. wow thanks brucey.
    I understand all of that except the terminology in step one "mill pocket / exhaust out deburr "
    r u saying move the exhust port.

    Any ideas on how to mod the CDI. would it be as simple as to add an extra charge coil and hall sensor into the alternator at the oppisite position of the exhisting one

    gapless oil control ring. this is just a wrinkled type wring that goes under the lower main ring?

    BTW im excited, when i finish on my current project(s) i think i might tear the daliem apart and stock up on two stroke oil
  7. why would you want to?
  8. Because we are men with garages

    :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :LOL:

    And like to play with our tools

    :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :LOL:
  9. Well Here we GO

    Suck Squeeze Bang Blow to be achieved in one rotation of the crankshaft needs some aid the simplest way is to machine the exhaust port directly into the base of the cylinder wall

    Chose your bore stoke combo say for this example a simple 54 x 54 125cc engine

    That’s why two strokes are more square they tend to use the longer stroke to promote the cylinder pumping effect to give more internal pressure (supercharging) in the transfer stages boost ports etc to get the charge in at the right time in this case you will need to get that from else where as I suggested a small supercharger running external to the engine will accomplish this task.

    The exhaust port in this case may be located Port floor 54 mm down from top of the cylinder and the port roof located at say 34mm down from the top I would not bridge it and the port width would be approx 22 to 24 mm with nice radius in the corners say R4

    The inlet would normally be in the range of 44mm Port Floor and say 24 Port Roof and width any where between 22 mm and 26 mm wide with a bridge but in this case / discussion its not needed as we are using the existing head inlet valves and maybe exhaust vales to get the mixture in

    Compression ratio would need to drop as the most compression you will want will be about 6 to 1 as you will get a diesel effect running 12 to 1 that most bikes currently run

    Any CDI system that used a mechanical advance / retard system can be used you just junk the mechanism and run the CDI fixed on the end of the crankshaft or for that matter fixed on the cam also because that’s running one to one now anyway. Remember it needs to fire at TDC no advance / retard or get real flash boyer bransdon set up

    For the valve components I would be looking at say a cbrrrrrrrr 250 as you springs etc would be needed to run to 10,000 rpm and remember that the cam is now one to one.


    Look at GMC truck engines Diesel two strokes the old big bangers where all the hot rodders got their GMC superchargers from that’s right they all originally come off trucks good reference material in the design

    The High-Performance Two-Stroke Engine by john Dixon

    That’s it for now I have to do some work

    :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :LOL: :cool:
  10. That GMC/Detroit diesel design goes back to the 1920's too! They have a reputation for excellent throttle response and horrendous fuel consumption.
    I believe 2 stroke engines with conventional exhaust valves are called uniflow or similar engines.
    This project is entirely doable, but realistically, will cost a bomb.
    Rotary engines in bikes is not a new idea either........

    Regards, Andrew.
  11. Sorry Typhoon to correct you but uniflow engines are steam engines

    Designed in the early 1890s to 1900s, which is the ultimate reciprocating steam engine for high speed needed for the early days of electric generation pioneered by the westing house corporation of America. They had holes for exhaust in the block as per two stokes.

    These units often run rotary valves or indeed poppet valves in the head and used steam temps in the region of 200 to 300 degrees from your steam tables is around 300 to 400 psi when pushed they could get up around 600 deg c 800 psi but that was there limit as the valve faces would be cut away in short order. speeds achieved consistantly i believe around the 3000 rpm mark

    I n flash steam times it was indeed possible to get it up around 900 to 1000 degrees but at this pressure and temp no lubrication was possible and so it went on until a gentleman by the name of parsons used the expansive quantities of steam as it cooled to develop the turbine whooo whooo rpms in the region of 20, 000 to 30,000 and so it goes on

    Go the steam punk in all of us :LOL: :LOL: :LOL: :LOL: :LOL: :LOL:

    Nothing more primevil then stoking a fire is there boys
  12. specifically - Toyota SC-12 of an MR2, I think there is an SC-14/16 aswell. Just check which one because I'm pretty sure there's a big difference with the power outputs, I had one on my datsun once.

    on the mr2
    3 PSI at 1000 RPM in 5th gear
    6 PSI at 2000 RPM
    7 PSI at 3000 RPM
    8 PSI at 4000 RPM
    8 PSI at 5000 RPM
    8.25 PSI at 6000 RPM

  13. Yah, the Jap/USA 1987-1989 MR2 and Corolla got the smaller SC-12 (1.2 litre swept volume), while one of the older 3 litre V6 engines got the bigger SC-14 (1.4 litre swept volume).

    SC-14's not too much physically bigger, and won't need to turn as fast to generate the same boost as the SC-12, which means cooler intake temperatures and a stronger performance in the higher rev range.

    I'm not sure of the longevity of using either, however. Both the SC-12 and SC-14 are designed to run as "clutched" superchargers - that is, they are only spinning when the driver wants to accelerate. The rest of the time they are automagically disconnected from the drive belt by a clutch attached to the SC unit.

    The seals on the supercharger lobes have been known to wear out within 10,000km if they're hard-wired to be "always on".

    I digress. :)
  14. Thanks for that guys on the supercharger info

    I reckon the 1.2 size geared down to run at say 50% would be ideal of a motor of 500 cc would be kind to the seals that way too

    Whoo hoooo this topic is getting some great feed back

    PS any body know where to get one of the little suckers cheap as in blown up no cost ?????? i have the need to play :wink: :wink: :wink:
  15. Pfnar - two stroke?

    Any REAL man would convert his motorcycle to Pulse Jet power:

    So, wether on a go-kart or on a motorcycle . . . a Pulse Jet is sure to kick a**e! :?