Grubee 4g belt drive

Discussion in '4-Stroke Engines' started by abikerider, May 20, 2009.

  1. abikerider

    abikerider Member

    Hi, I'm shopping for the best 4 stroke tranny and found that the Grubee site has more info and pictures of the 4g belt drive here See Whats Coming.htm It looks like it uses a timing belt drive belt and centrifigal clutch which would be a sweet setup. I talked to the guy at and he said it probably won't be available till the fall. Anyone here have any more definitive information about when these will be available?

  2. azbill

    azbill Active Member

    he would probably have the info before anyone else
    Josh has been his biggest guy for quite a while
  3. Silvaire

    Silvaire Member

    This does indeed look like a sweet setup, and I've been waiting to see it too.

    As usual, the devil is in the details, and in this case I am suspcious of the size and configuration of the components used. Looking at the picture of the open belt and pulleys (on the right, midway down the page), there appear to be few very belt teeth in full contact with the engine pulley teeth. This condition occurs when there is a large differance in the size of the pulleys when there is a short distance between them, and can cause early belt failure. Based on this condition and the size of the belt, I'd be concerned about short belt life and the need for very critical belt tension ajustment.

    Just my $.02...
    Last edited: May 20, 2009
  4. ocscully

    ocscully Member

    The folks at bicycle-engines are the US distributor for Grubee so when they say the Fall you can be pretty sure it will be the Fall. They seem to get just one shipment of kits from China each year. Their latest shipment of 4-stroke kits arrived in late Sept. early Oct. 2008 I believe. You might be able to find one thru a European distributor or maybe the dealer in Australia might have them sooner. The video at the link you provided seems to indicate that MBB Imports in Australia already has them?

    Last edited: May 20, 2009
  5. fetor56

    fetor56 Guest

    "Available with or without engager".....good that finally we have the choice.
    Provided it's PERFECTED & working flawlessly i'de also be interested in the price....i was keen on another tranny but at AU$500(delivered) it's out of my reach.
  6. fetor56

    fetor56 Guest

    Phoned George from MBB & he'll be getting them in approx 3 mths.....price AU$150-200.
  7. abikerider

    abikerider Member

    Good observation. It looks like only about 1/4 of the pulley teeth are in contact with the belt. Does anybody know what forces such a belt can normally handle? The Honda engine puts out a maximum torque of 2 ft-lbs and the small pulley looks to be about 2 inches or .16 ft so the the engine is only pulling with 2ft-lbs /.16ft = 12.5 lbs of force on the belt which doesn't seem like much to me. Of course you have to consider that it might experience higher forces when the clutch first engages or if the engine or rear wheels stops suddenly. If the clutch engages smoothly I would think the belt could easily handle it but thats just my engineering intuition. Those Gates belts that drive the rear wheels of Harley Davidsons handle waaaay more force than that but of course are wider and are premium quality. Just my 2 cents.
  8. Silvaire

    Silvaire Member

    I should probably wait until this unit is on the market and in use, and has shown its reliability (or lack thereof) before critiquing it.

    However, I do have some experience with toothed drive belt systems and am a big fan of them. They have an excellent record for many reasons. If you look at the most common use of this type of drive system - the timing drive on most every small auto engine - you will see that they are always designed with a large number of teeth in contact with any driving or driven pulley. They typically use two (and sometimes more) idler pulleys to wrap the belt more fully around the toothed pulleys.

    The soon-to-be-released Grubee unit could do the same if those designing and marketing it chose to add an idler pulley near the engine pulley on the slack side.
  9. duivendyk

    duivendyk Guest

    These cogged belts are quite durable,in your car thay are good for 75 k miles driving the camshaft,hardly a nice steady load !.I'm not worried at all about the potential durability however substandard component quality,more than inherent design flaws have plagued some Chinese products.The dimensional stability of these belts has proven to be excellent too.I think this is a very welcome development.
  10. HoughMade

    HoughMade Guest

    When it is on the market and I have heard some reports, I may go for this...but I'll take my chances and run it without the cover.
  11. Danny3xd

    Danny3xd Member

    That's pretty exciting. Looking forward to hearing more on them.
  12. cspaur13

    cspaur13 Member

    dose any1 have some info on the push tailer they have on the same link at the bottem of the page. looks pretty cool. liking the belt drive. hope it works as well as it looks,
  13. jared8783

    jared8783 Member

    I just looked at it and it looks interesting. I have just one question, and it may sound stupid but I'm a newb so give me some slack. Why would you want the belt drive vs the gear box? What is the difference? Pros and cons of each.
  14. ocscully

    ocscully Member

    The reduction gearboxes offered with the various 4-stroke kits have been the source of many problem for the users of thse engines. The chinese 2-stroke motors have a primary reduction of 4.2:1 built into them. The 4-stroke motors have no built in reduction hence the gearbox. The Gearboxes have had problems with the noise level and their reliability. A belt drive primary reduction wether v-belt or metric timing belt offers a pretty much silent primary drivetrain. Also belts require no lubrication.

  15. duivendyk

    duivendyk Guest

    A high speed chain running in the open air is subject to wear, needs to be protected from dirt and needs to be lubricated.Belts are less vulnerable,run silently but take up more room sideways and can stretch,so a belt tensioner may be needed or means provided to adjust the belt tension.A chain running in an oil bath lasts almost indefinitely,a quality belt has a long but more limited life.In open air the belt probably wins out.
  16. Silvaire

    Silvaire Member

    Timing Belt Drive:
    1. Quiet
    2. Needs no lubrication
    3. Needs minimal adjustment
    4. Long life when properly designed
    1. Greater initial cost than roller chain components
    1. Difficult to source components (difficult for R&D)

    Roller Chain Drive:
    1. Noisy
    2. Needs more frequent adjustment than timing belt
    3. Needs frequent lubrication and cleaning (or rapid wear will result)
    4. Shorter life than timing belt in typical use
    1. Low initial cost and easy sourcing
    2. Easy to change ratios and center to center distance (great for experimenting)

    V Belt Drive:
    1. Any slippage leads to rapid wear
    2. Cannot tolerate accidental lubrication
    3. Greater power loss than either timing belt or roller chain
    1. Good for constant load applications, or when slight slippage at high torque might be beneficial (such as air compressors, automobile engine driven accessories or table saws)
    2. Low cost, easily sourced components
    3. Easy to change ratios

    1. Very long life (when properly designed and constantly lubricated)
    2. Quiet (but only if the gears are of high quality, properly clearanced, and are of helical cut design)
    1. Very considerable cost and effort to source and engineer
    2. Require precise machining and alignment and must be rigidly mounted in relation to other gears
    3. Difficult to modify the geartrain once it's designed and manufactured

    Last edited: May 27, 2009
  17. glacknoid

    glacknoid Member

    4g T-belt

    About a week ago I was told they would be shipped at the end of May and would take about a month to get here. 50 to USA and 50 to Australia. That's for the transmision that works with the motor you see it featured on the web page with. The honda adapted drive system won't have a sample to test for 90 more days or so. So ya, probably late fall for a honda trani. Also the honda one won't have the same bearings on the clutch bell and shaft, so I'm told it may have a bushing, don't know why. The HS motor has the clutch built in to the motor houseing. Look at the parts page for the 4g and you will see the difference in clutch bell design. Honda will have the new 3 pole clutch just like the HS. Other than the clutch bell design, I think the rest will be the same. Have to wait and see. The video on youtube shows the torque it has with the 5 to 1 ratio and that may be with the 11 tooth. Put the 10 tooth on and hold on to your hat. Apparently Don designed it so a spanner wrench could be used to tighten the belt to go without a third belt tensioning wheel. I do see what you mean about the small area of contact with the front gear, a loose belt would maybe slip easy on that. Hopefully the belt is quality enough to not stretch too much. Hopefully it will be available alone without a kit, for everyone with a finished bike who just want's to upgrade the drive system.

    I agree with Houghmade. I would take off the cover and go with the exposed look, much cooler.
    Last edited: May 30, 2009
  18. Danny3xd

    Danny3xd Member

    Awesome Glack. Thanks for the update.

    Any one have a direct link to the youtube vid?
    Last edited: May 30, 2009
  19. glacknoid

    glacknoid Member


    Don't forget there will be a wet clutch available for the stage 3 soon. I think Jeremy from BD is suppose to be testing them with different oils to see how they work. He may have some feedback on if a significant amount of oil will help with sound or wear reduction. Although like Jeremy said, packed with enough greese dampens the sound some but we'll see if an oil bath at the point of where the gears mesh will reduce the sound even more or not.

    Then with a 10 tooth non freewheel and a SBP shift kit and you'll be in good shape.

    It's hard to decide what to do at points where there are so many new developements waiting to emerge. You don't want to invest more into one thing then replace it with another. I'm anxious to see all the new products available to the motorized bicycle enthusiast, and summer is short here in MN. At least I have my finished 4stroke stage 3 to tide me over.
    Last edited: May 30, 2009
  20. wildwestrider

    wildwestrider Member

    running without the cover

    I had the same thought........What kind of open cover would they have done on an early 1900s bike.......maybe just a perimiter band to keep loose clothing or your leg from rubbing up against the edge........a good project for you Hough-made.