Shifter Bike Freewheel Skipping?

Discussion in 'Motorized Bicycle General Discussion' started by cannonball2, Jul 15, 2011.

  1. cannonball2

    cannonball2 Active Member

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    I have searched this and other people have experienced this. The posts were old and I never saw a definative answer, anybody figure it out? While riding momentarily the engine will rev as if it disengages for a second or less and only a couple of skips. Doesnt do it all the time. My chains are well spaced on the front chain rings and show no signs of contact, and there is not enough slack any where in the drive for the chains to skip a tooth. The bike shifts perfectly up and down through the gears. Its not jumping gears because the engine speed never changes when the skipping ceases(nor does road speed). Im beginng to suspect the rear freewheel maybe. Any thoughts?
     
  2. tim turbo

    tim turbo Member

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    I have not noticed that problem, but with the shift kit, with the free wheel you have a very noticeable lag in the drive when you shift and or let off the throttle, and go back to power, it is kind of agreavating! Sorry (Just saying).
     
  3. cannonball2

    cannonball2 Active Member

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    For sure, I noticed that right off. I have eliminated most of that by getting the slack out of the primary chains, used a idler on the jackshaft to chainwheel side. That really helped make a much smoother shifting bike. I would have to say it works about as perfectly as a shifter bike can, except for this ocasional skipping. Guess I will replace the rear freewheel to find out.
     
  4. leezy_1

    leezy_1 New Member

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    i had this problem, as you shift down the gears the bicycle chain hits the other chain on the small cog on the jackshaft, so what i did was to put three washers on each of the five alan bolts in-between the outer ring and the inner ring on the crank and it works perfect now. :)
    i found that as i geared down the gap got closer to the chain, so spacing the rings helped alot.
     
    #4 leezy_1, Jul 17, 2011
    Last edited: Jul 17, 2011
  5. cannonball2

    cannonball2 Active Member

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    Thanks for the reply, but I dont think thats the issue. This happens while riding in a given gear, just riding a long. The bike shifts perfectly, and never jumps to a different gear underway. The primary chains have at least 1/2" of clearence even in top gear, I have watched them while riding, and they run smoothly. Its like if you were riding a motorcycle under power and pulled the clutch in for a second. The engine revs then grabs again. The rear freewheel is my suspect, and its new, maybe its defective.
     
  6. leezy_1

    leezy_1 New Member

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    Well hope you get it sorted,mine used to change gear on its own, slip gears ect, did my head for awhile then i noticed that the chains where touching and one was knocking the other out of line so causing slipping and jumping,it was fine in first second and third gear, but as i moved down thats when it started, if i just peddled the bike as normal it seemed fine, so after awhile a spaced them out and all good again, i thought it could of been the cassette worn out or stretched cable, but it was chain clash..
    anyway good luck sorry i couldn't help.
     
  7. GearNut

    GearNut Active Member

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    If it turns out not to be the rear wheel freewheel, check the engine sprocket.
    The nut may have come loose letting the sprocket slip on the shaft. Of course if this is the case, you would need a new woodruff key too as that would have to shear to allow this.
    Yes, a slightly loose sprocket can slip a little randomly and not free spin. It all depends on how loose/ tight the assembly is.

    Edit: The small pinion gear as well as the clutch can also have these issues where they attach to their respective shafts.
     
  8. cannonball2

    cannonball2 Active Member

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    This one is using the Grubee G4 with the HS 4stroke. I have been all through the Grubee unit every thing is in order there, the belt is tight and not slipping, all keys are good, and the problematic Grubee freewheel has been welded. Cant imagine the rear freewheel is bad but cant think of anything else. Only one way to find out.
     
  9. MotoMagz

    MotoMagz Active Member

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    This has happend to me also.While I was testing the 4 stroke shift kit for SBP my engine would rev up for a second and then back to normal.I talked to Jim at SBP and his was doing the same.I know it doesn't solve the problem...but your not alone.If it was constant I would look further into it but I believe it is just in the motor and not really a problem.
     
  10. cannonball2

    cannonball2 Active Member

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    Thanks for that info! It happens infrequently enough not to be a big issue, its just annoying. Plus when it(whatever it is) grabs again it gives the drive train a pretty good jerk. Thanks for posting this, was just about to buy another freewheel. If its in the Grubee end of things I cant imagine what. This unit was run quite a few miles on a single speed bike with none of this happening, it has only shown up when converted to a shifter.
     
  11. Ghost0

    Ghost0 New Member

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    What you are experiencing is pretty normal with the Shift Kit and Grubee combination. There is just so much "slack" in the system that when you back off on the throttle to shift it creates a little slack in the drive train then when you reapply the throttle all that slack has to be taken back up again before it starts to drive again. This gives the sensation of some free revving of the engine and then catching cause a jerking sensation. The two bits of advice I can give is keep all your chains tight so there is less slack and don't get out of the throttle as much between shifts so there is less "slack" to take back up before it starts to drive again. Also I don't know if you are running the freewheel on the gear box output sprocket but that makes it a lot worse.
     
  12. donutguy

    donutguy New Member

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    A couple years ago....I had a freewheel slip on one of my regular (non-motorized) bikes.

    It was doing exactly the same thing....I would be pedaling and it would slip and the pedals would advance about 45 degrees (out of a full 360 degree pedal stroke)

    The problem turned out to be old congealed grease in the freehub body as it was catching and not releasing the internal sprags from time to time.
     
  13. NEAT TIMES

    NEAT TIMES New Member

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    When slowing down for a stop sign or whatever, I seem to need a bit of throttle to keep the chains turning enabling shifting. When coasting my chains stop because of the centrifical engine clutch.

    Ben, I know this is not your cause of trouble.

    Ron _______________________ .duh._____________ cvlt1
     
  14. cannonball2

    cannonball2 Active Member

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    GhostO, Thanks for the explaination. This skip is under throttle load, riding down the road. It has nothing to do with shifting. It is a momentary free reving of the engine. I just completely dismantled the entite G4 unit, absolutely nothing slipping in there. I did machine me a new shaft from a piece of 5/8 jackshaft. The original one was mis-machined and had horrible run out, the bike surged at high speeds. The new one runs true and I replaced the sprocket with one like is used in the shift kit. Should be smoother now.

    Donutguy: Im really thinking freewheel now, going to pull a rear wheel off one of my other bikes to see.

    NT to down shift I just blip the throttle and shift down. If I am coming to a stop. I just down shift all the way to first while moving pretty fast, with the auto clutch you get about zero engine braking, so there is not much point in shifting down through each gear. I shift twice on the downshift to 3rd, then 1st. I can do this at cruise speed.
     
  15. shaolin

    shaolin New Member

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    I have experienced this myself and baffled what was going on. I did have the 2 stroke kit but I think its the same principle. If not then sorry and good luck finding the problem;) I did check my rear wheel hub and it was functioning fine. It was a little scary cuz going through a corner while leaning, it would disengage,engine revving no load,and id have to stand the bike up again from falling. I did what some of the people sad and just ride it and youd get used to it. But in a couple days of riding, my heavy duty oneway,freewheel(Blue), fell apart while riding and all the cute little bearings fell out :0. I examined what was left of the oneway and inspected it when I walked the bike home. What Ive found was the teeth that the oneway was supposed to engage were wore out and forming a groove in the middle of it. so its kinda like a worn sprocket with the chain just spinning. Also inspect the wings ,thats what I call them, that spring open to engage the teeth. Make sure they open out without binding and are well lubricated.Check the sbp web site to properly dissassemble the oneway and inspect and service the onewasy frequently. Harder you ride the more frequent you should service this. Hope this helps.
     
    #15 shaolin, Jul 18, 2011
    Last edited: Jul 18, 2011
  16. cannonball2

    cannonball2 Active Member

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    Thanks for the reply. Got the G4 unit back together with the 5/8 true running jackshaft and sprocket. What difference that made! The original Grubee shaft was turned slightly of center. Couple that with a sprocket that wasnt on center and the was a bunch of chain whip/oscillation. Smooth and much quieter now. I have been over the entire bike and the only thing I found was the teeth on the inner chain ring look like they could have been over run. I have the small 24t sprocket to get the ratios I wanted. Only has around 12t in the chain. Im thinking I will remove some chain links to increase the derailuer tension, its pretty weak now. I believe I read some where in the forum about doing this. I cant believe it would over run and not throw the chain, but the longer I live Im beginning to beileve anything is possible!
     
  17. NEAT TIMES

    NEAT TIMES New Member

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    Cannonball2

    Are you still running the cogs and cogged belt on the primary belt? Did you purchase a different 100 tooth driven cog, where?? Can you post a part #/maker of the belt and cog pitch? Thanks

    Ron
     
  18. cannonball2

    cannonball2 Active Member

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    NT, the pulleys and belt are original. Its the 80/20 pulley set up with the 505belt.
     
  19. cannonball2

    cannonball2 Active Member

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    First thanks to every one that replied and offered all kinds of good advice. I systematically went over the bike checking out areas pointed out. I believe it was the small chain wheel being over run. I shortened the chain 8 links, til the derailuer was at about 45 degrees forward, has very good spring tension in that position. I have since riden the bike extensively with not a single skip. Never gone that far before, so Im thinking(hopeing) that was the issue. It also shifts somewhat better with the added tension. So, if you are building a shifter with a small front ring, shorten the chain.
     
  20. donutguy

    donutguy New Member

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    I never thought of that! Back when I rode mostly human powered bicycles.....I wore out the front chainrings on one of my mountain bikes and the chain would skip a few spaces on the chainring.

    Here's an article that you can use to make sure your chainrings aren't worn out.

    BlueWheel - Bicycle Mechanix - ChainCare

    Increasing the tension on the chain will fix this short term if in fact the chainrings are worn out...if the chainrings *aren't* worn out....you've fixed your problem :)
     

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