Chain Tensioner Moving chain tensioner back

Discussion in 'Transmission / Drivetrain' started by gearhead222, Mar 9, 2010.

  1. gearhead222

    gearhead222 Member

    Dear Fellow Members-Have a Grubbee 48cc 2 stroke on my Wally World Cranebrook cruiser and discovered that the idler wheel is almost at the top of it's adjustment track. Are there any specs or rules regarding moving the idler wheel assembly further back to obtain more idler wheel adjustment travel? I'd rather do that then remove a link. Also, how sloppy can the chain adjustments be? My owners manual says 1/4-1/2 inch play with the rear wheel rotated forward . I have been measuring from the top of the chain about halfway between the drive and rear sprockets. Can I go up to 3/4" chain play before readjusting? Will eventually install a spring loaded idler but appreciate any info, advice or tips concerning this fixed idler adjustment. Thanx!:)-Gearhead
     

  2. Hey Gearhead

    I would think that 3/4" play would be too much. Generally I accept about 1/2" at the most. I know you said that you don't want to remove chain links but I'm gonna got out on a limb and say that if you have a cruiser with ability to adjust the back tire I would highly recommend getting rid that stupid tensioner that is going to break anyway.Chain brake tools are like $8. Dude, your bike will ride soooo much smoother and you don't have to worry about the tensioner falling into the spokes. If anything, move the tensioner over to the pedal chain side. Again, I would not accept more than 1/2" play in any chain or belt for that matter.

    Scotty
     
  3. gearhead222

    gearhead222 Member

    Beam me up Scotty, as I'm not completely catching your drift. I have a chain breaking tool, but my rear wheel mount will NOT allow for much adjustment-gotta have either a static or spring loaded chain tensioner. Anybody else?-Gearhead
     
  4. Dilly Bar Rob

    Dilly Bar Rob Member

    You should get rid of some of that slack. I also think that 3/4 is a bit too loose. I know tolerances tend to be a bit loose on these things, but lets not get too sloppy:)

    If you want to get a spring loaded tensioner in the future and don't want to fiddle with the chain in the mean time then go ahead and move your current tensioner back a little, wont hurt anything as long as you ensure that it cant spin into the spokes. I say tack weld it (if the frame is steel) but that may be a bit too radical for some.

    I understand your ordeal with not being able to adjust the rear wheel far enough, I wanted to go tensioner-less on my folder bike but then I would have to muck around with half links on both chains to get the tension right (or at least close...).

    I was lazy last time my tensioner got to the point that it was "out of range" so to say, my (short-er term) solution was to cut 2 "rings" the width of the tensioner wheel out of an old bicycle tube (I believe that it was meant for a 1.75 tire, could be wrong) and slipped them on the tensioner wheel, that took out a bit more slack as it added to the tensioner wheel diameter. A pleasant side effect of doing this was that the chain seemed to ride quieter afterwards as it was riding on rubber and not hard plastic. After maybe 100km the rubber is showing minimal signs of wear, when one of the layers peels of I will pull out the old tube again and cut another ring ;-)
     
    Last edited: Mar 9, 2010
  5. gearhead222

    gearhead222 Member

    Dear Sir-Thanx for the quick reply! I actually HAVE a spring loaded tensioner, but after 100 miles or so my original idler is holding up. I will wait until it breaks on me. Did you just cut some rubber rings out of an inner tube and slip them over the idler wheel? I'm guessing that elastic tension kept them in place? BTW, how tight is too tight? How do you measure your chain slack-from top to top of the chain midway between both sprockets with the bike in gear and the rear wheel rotated to induce maximum slack in the chain? Thanx again:)-Gearhead
     
  6. happycheapskate

    happycheapskate Active Member

    "Waiting until it breaks" is a scary idea!!!!!!! If the chain derails or the idler pulley/arm goes into the spokes, the wheel will erupt, and you will be stranded at the least, and wounded gravely at the worst.

    I am running my bike without the tensioner. I suggest using a half link and finding a length that is closest to optimal without the tensioner. If the chain is snug and is tight enough it can't slip over the tooth of the motor cog, just run it.
     
  7. Dilly Bar Rob

    Dilly Bar Rob Member

    Yes, that is exactly what I did with the inner tube. I thought about gluing it on, but since the tensioner was greasy and I didn't feel like cleaning it at the time I figured I would just slip the rings on and see what happens. I wasn't sure how good the rubber would hold up as the tube is fairly thin, but far so good, this was never ment to be a permanent solution anyway... One ring by itself was almost too loose, but the second ring over top of it snugged things down just perfect. I think I would go a max. of maybe 3 layers, anything more would probably bring the chain too close to the point that it could ride off the tensioner.

    Er, how tight? I dunno, have never measured anything. Like cheapskate says the chain should be tight enough that it cant slip off of the sprocket if you were to rotate the wheel and push on the chain sideways (would equal a worst case scenario like riding over bumps with the chain frapping around). Most setups will have the rear sprocket at least a hair off center so that the chain goes tight/loose a bit as you turn the wheel. Turn the wheel so the chain is at its tightest, adjust so you have maybe 1/4" slack. Turn the wheel so the chain is at its loosest, and make sure that it is still not too loose at that point (like not over 1/2" of slack). If it does get too loose....redo the rear sprocket so it's centered better and repeat. Start the bike (starting puts great stress on the slack side where the tensioner is), putt around, stop, recheck everything.
     
  8. ibdennyak

    ibdennyak Guest

    I was lazy last time my tensioner got to the point that it was "out of range" so to say, my (short-er term) solution was to cut 2 "rings" the width of the tensioner wheel out of an old bicycle tube (I believe that it was meant for a 1.75 tire, could be wrong) and slipped them on the tensioner wheel, that took out a bit more slack as it added to the tensioner wheel diameter. A pleasant side effect of doing this was that the chain seemed to ride quieter afterwards as it was riding on rubber and not hard plastic. After maybe 100km the rubber is showing minimal signs of wear, when one of the layers peels of I will pull out the old tube again and cut another ring ;-)[/QUOTE]

    Now that's genius at work. Perfect fine adjustment solution, and quiets the chain besides. I love little inspirations like that.
     
  9. gearhead222

    gearhead222 Member

    Dear Fellow Members-Thanx again for the detailed replies! When I said "waiting until it breaks", I should have said " waiting until it wears out", as I am very anal about bike maintenance. I really like the tube idea! Believe it or not, my front and rear sprockets are VERY close in alignment, definitely MUCH closer than the recommended .5 cm!-Gearhead
     
  10. happycheapskate

    happycheapskate Active Member

    I have the same type of motor kit (48cc Grubee Skyhawk 2st).

    Another option if you have this type of dropout http://www.machinehead-software.co.uk/bike/chain_length/vertdropout.jpg
    [​IMG]

    is to flat the axles with a grinder (ONLY if you have solid axles with hex nuts, do not alter quick release axles) where they meet the back of the dropout.

    Don't get carried away (just one surface on each side of the hub will do) but Sheldon Brown did this successfully in a blog about single speed conversions.

    You can also file 1/32 to 1/16 off the back of the dropout if necessary (cannot be undone! :) ) Be sure to use knurled washers under the wheel nuts now to avoid the wheel moving.

    Another fix is to try a different driver gear (on engine, like a 9 instead of 10) or a different wheel cog (like 39 instead of 44)
     
  11. gearhead222

    gearhead222 Member

    Thanx bro' for the mod suggestion, but I will eventually go to the spring loaded tensioner, which I already bought:)-Gearhead
     
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