My 4 Stroke Shifter...

Discussion in 'Photos & Bicycle Builds' started by tridim, Nov 5, 2015.

  1. tridim

    tridim New Member

    I think I can finally call it finished! Woohoo! It uses a SBP jackshaft and has a full lighting, turn signal, brake light system running on a 12v LiPO. The big breakthrough was swapping my rear FW hub for a beefy Freehub and cassette, no more bent axles! It maxes out at about 36mph and can climb any hill with ease. So much fun!

    I plan on lacing in a front drum brake this winter, though the clinchers work very well as-is.




    Left to right: Gear shifter, light switch, turn signals, horn, headlight, volt meter, speedometer, brakes, kill switch, throttle.

    Running light, turn signals and brake lights attached to the electronics "bag". There is a 12v LiPO battery in there, relays, fuses and wiring harness and alarm switch and relay.

  2. The_Aleman

    The_Aleman Active Member

    That's pretty cool. Haven't seen a Grubee Stage III in awhile. Well, an intact one anyway. I have several pieces of a pair of Stage IIIs in my bike box.

    They're notorious for grenading randomly. Use a fine oil and don't be too abrupt with it in lower gears. I also recommend using KMC HL710L chain on jackshaft input and output.

    You'll get the best chain tension with HL710L regardless of length and it will last quite a long time. I've put thousands of miles on this chain with my shifter 4G over the years.
    1 set should do inner and outer jackshaft. link:

    Looks like a fun ride! Hope you have a Wednesday-built Stage III.
  3. tridim

    tridim New Member

    Thanks for the advice. The Stage 3 is holding up nicely so far... About 500 miles. I have it packed with goopy white lithium. I do hate the stupid fake clutch thing on the final gear.

    I wasn't aware there was another gearbox option available for the SBP jackshaft. ???
  4. The_Aleman

    The_Aleman Active Member

    Well Stage III is the easiest way to get a 4-stroke shifter with GXH50 or it's HS clone, but Honda-style 4G will also work. These are for keyed shaft engines.

    I first did this back in 2010, very tight fit, but it was pretty much plug and play. I've changed several gear ratios since:

    4G SBP  11T-18T.jpg

    The new 7G also uses GXH50 or clone version of it, it's output sprocket may or may not be in the right place. I haven't tried one, but would like to.

    A Grubee Stage III has only a 3.7:1 reduction, so it's not quite pedal-friendly in stock SBP shifter-config. I bet you can't help the engine much over 3600 RPM, and it lugs helping you. :D

    I changed my jackshaft output ratios so that my engine redline and pedal redlines were about matched. Maximum engine torque comes at same time as maximum pedal torque.

    Took a lot of outer crank sprocket! 9T to 76T (#35), 44T inner to 15T (415H) on rear wheel. 69.09:1 engine to pedal reduction, 14.5 pedal revs per 1000 engine.

    I've used Sturmey X-RD3 and X-RD5 rear hubs, 3- and 5-speeds with 70MM brake. Not enough brake so I run V-brakes on each wheel as well.

    4G SBP  9T-76T.jpg

    Anyway, if what you got works great, run the heck out of it til it doesn't! Your ride looks good, I'd double-check that front fender mount tho. Make sure it's shakeproof.

    Fenders can be dangerous. Still trying to get mine done right, too :D
    Last edited: Nov 6, 2015
  5. tridim

    tridim New Member

    Actually the fenders were the last thing I did before taking pics and posting the final product. I'm very happy with the rear fender mount I came up with (and the slight chop that makes the ugly rear mount unnecessary) the mount is made from a bent gas tank bracket. The front is still a little iffy, though it doesn't shake enough to worry about binding.

    As for the gearing, I figure that'll change as time goes on, but I'm really not there yet. Still enjoying riding it as-is, and really don't have any issues with pedal assist, though I tend to only pedal in low gears. I usually cruise in 5th gear on my cassette at around 30-35mph. 2nd or 3rd around corners depending on grade.

    It seems perfect for a urban commuter, but it's the only motorized bike I've ever ridden, so I guess I really don't know.

    Again, thanks for the advice and data. I'm sure it'll come in handy later. :)
  6. tridim

    tridim New Member

    BTW, I have a 4G for the tapered shaft engine... It didn't work, but I might try it again.

    Do you happen to know who sells the 5/8" shaft 4G alone, without all the other kit stuff I don't need? Thanks.
  7. Timbone

    Timbone Active Member

    Top Shelf!