Will this work

Discussion in '4-Stroke Engines' started by dougsr.874, Jun 21, 2012.

  1. dougsr.874

    dougsr.874 Active Member

    I just acquired a HS engine with the tapered output shaft....including the attacthed clutch....along with an unattached 4G gearbox....the gearbox seems to fit the engine but I'm need to know for sure before investing more into it.....I'm concerned because the bicycle-engines.com website show the 4G using the 5/8 tapered shaft engine...

  2. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    There are 2 models of the Grubee 4G gearbox.

    One fits the HS engine with the tapered shaft / built in clutch.

    The other fits the HS or Honda engine with the 5/8" straight shaft and this
    is the type that bicycle-engines.com sells now.

    If you have the correct gearbox there is no problem.
    Post a pic if you still have doubts.

    bicycle-engines.com used to sell the the engine, gearbox combo that you have.
  3. BigBlue

    BigBlue Active Member

    Here's a link from Grubee that shows the difference in the 4G kits:

    http://www.grubeeinc.com/USA/4G/4G V frame Instructions.htm

    Kit#1 for the centrifugal clutch with tapered shaft
    Kit#2 for 5/8" keyed straight shaft

    Just looked at the Bicycle-engines.com website and the kits are 5/8" keyed straight shaft. I don't see any kits with a 5/8" tapered shaft.

    Good Luck,

    AKA: BigBlue
    Last edited: Jun 21, 2012
  4. Barry

    Barry Member

    Hey Chris,
    I just bought an HS 142/taper shaft engine for a Hoot type gearbox. The gearbox came with a clutch that does fit the engine output shaft but, the HS output shaft does not have any provision for a key (no slot). What's the trick to get this clutch glued onto to shaft?
    PS: did you get the Qmatic OK?
  5. darwin

    darwin Well-Known Member

    Tapered shafts have a compressed fit when the tapered attachment is tightened onto the shaft. Tighter = more compression.
  6. BigBlue

    BigBlue Active Member

    Hi Barry,

    got the Q-matic - thanks.

    I am not sure which engine with the tapered shaft you've bought. There is an engine with a 1/2" tapered shaft that should of come with the clutch attached. There is no slot for a key. The bolt on the end of the shaft holds the clutch onto the shaft. Is this the one:


    AKA: BigBlue
  7. Barry

    Barry Member

    Yes, the pic is the one I'm working on. I bought a bare engine, transfered all the components from my straight shaft 5/8" over to the new engine and installed the clutch that came with the gearbox. This clutch has a slot for a key and the taper shaft does not have a slot. I went ahead and tapped the clutch on to the shaft and used a large washer and bolt to seat it. I lit her off and all seemed well but, on the first road test the clutch started to engage at about the right RPM but, you could tell that it was slipping badly. I got up to a whopping 10 MPH. At this point I don't know if the clutch is just spinning on the shaft or that the clutch itself is not fully engaging.
    Whaddaya think?
  8. Josh Moon

    Josh Moon Member

    you may have ruined your shaft by doing that
  9. BigBlue

    BigBlue Active Member

    What components did you transfer over? The clutch should have a taper to it to match the shaft. The clutch shouldn't have a straight shaft. Make sure your not using a 5/8" straight shaft clutch on a tapered shaft.

  10. Barry

    Barry Member

    Thanks! I'm stuck with XMas light installation duties tonight but, will pull it apart again to insure the the clutch has a taper to it..
    Thanks again