Motor RPMs, tack???

Discussion in 'General Questions' started by JVROOM, Oct 13, 2012.


    JVROOM Member

    Curious, I get the message that over 4500 to 5000 RPM will toast the Chinese motorbike engine. Any guess on what this equals to speed? 26 inch wheel 44 tooth drive sprocket. Found some two cycle tacks online, but past experience, has been one should you use them, there, waste of money.

    I can tell, pretty closely engine speed of vehicle's V8, but I don't have any experience with the Chinese motors. Any thoughts, thank you for your replies. Sincerely, John :detective:

  2. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    over 4500 to 5000 RPM will toast the Chinese motorbike engine????
    BS, they rev to 7,000 rpm stock and race motors go to 10,000 rpm

    Download gearratio.exe from:

    to calculate your speed at any rpm.

    I like the TTO tachs.
    Only $24 from
  3. jaguar

    jaguar Well-Known Member

    If you mod for higher rpm or higher compression then you need to replace the crappy chinese wrist pin bearing but other than that the normal 5500rpm is of no threat to these engines.
  4. Fabian

    Fabian Well-Known Member

    7,000 rpm and expecting dependable long term reliability - - - now that is a lot of BS - - - sounds like someone is pushing hot air around the tent again.

    The extensive modifications employed in race motors going to 10,000 rpm are not transferable nor is it relevant to good reliability and usable power delivery for everyday motorized transport.

    Keeping these engines alive for the long haul and as road speed varies is best served by operating in their maximum torque zone; around 4,000 rpm as a stock standard engine. You can only get that through a shift kit.

    The 4,000 rpm torque figure is even more enhanced further down the rpm scale with a Rock Solid Engines reed valve intake. A Walbro carburettor is a handy replacement option to the standard NT carburettor as well as the Jaguar CDI with mult adjustable ignition curves.

    From my experience with 40,000 kilometers and 2 1/2 years on my motorized bicycle, i can say that a single speed system isn't the best option. I quickly discovered that after the first 30 seconds of riding and hit the internet looking for a usable drive system - which was found in the SickBikeParts shift kit.

    7,000 rpm and expecting 300+ miles of good reliability - where is the mute button, because only a politician would have the nerve to say something like that.
  5. jaguar

    jaguar Well-Known Member

    Depends on whether or not you've replaced the wrist pin bearing and balanced the engine (usually by lightening the wrist pin and installing a Jaguar CDI). I did those to mine and was revving to 7500rpm on a daily basis for over a year. No problemo. Without those changes there is too much vibration which wrecks havoc on bearings and bolts.
  6. Fabian

    Fabian Well-Known Member

    With some engine modifications as you've described - disassembling the engine and balancing and changing of internal components and reassembly, it may be possible to operate the engine at 7,000+ rpm, but on a completely standard engine, 7,000 rpm on a daily basis is nothing but a pipe dream.

    Most people do not have the tools or knowledge or the confidence to do a strip down and internally modify the engine, then correctly reassemble it.
    The greater majority of people run their engine in standard configuration with maybe a few external add-on accessories, like a Rock Solid Engines reed valve intake and your own Jaguar CDI.
  7. jaguar

    jaguar Well-Known Member

    You make it sound like the wrist pin is down in the crankcase. The wrist pin is the shaft that runs horizontally thru the piston. To get to it just take the head and cylinder off, remoce the pin clip, and push with a small allan wrench from the opposite side for it to slide out. Then buy a 9/32" carbide drill bit, take them to a machine shop, and have them drill out the wrist pin hole bigger to lighten it up. Twalla, pipe dream come true! no more engine vibration. If the owner doesn't have the tools to do this then they have no business owning a 2 stroke. (Tools needed: 10mm socket ratchet wrench, 10mm open end wrench, needle nosed pliars)