So whats the difference

Discussion in 'Frame Mounted Engines' started by Dakman, Jul 2, 2011.

  1. Dakman

    Dakman New Member

    Between bikes having the chain tensioner and those without, is the tensioner not actually vital.

  2. Big Red

    Big Red Active Member


    Hey Dakman, Welcome.
    I'm sure others will chime in, So take this as only MY opininion. And my short answer is, it depends on how good YOU are.
    Now, The long answer. MOST of the time it's very difficult to get the rear sprocket PERFECT. The tensioner allows you to make minut ajustments to the chain. I prefer to leave the chain a little loose (ya noticed I said a LITTLE) rather than too tight, And the tensioner helps with that and also with chain strech. A new chain will strech some.( not a lot, just some.)
    Now, back to my short answer. If you feel you can get the engine to rear sprocket alingnement PERFECT. AND the sprocket centered PERFECTLY on the hub, Then I say give it a shot. Harley, Honda and Yamaha make all their bikes this way. I've also found that on a lot of bikes the chain won't clear the frame without a tensioner. Check out your clearence issues and if it works, It works.
    Thanks, Big Red.
  3. srdavo

    srdavo Active Member nailed it, Big Red!!

    Chains can be made the correct length... removing links; adding ½ links; shimming the engine forward; etc.

    Frame clearance is another story. It doesn't take long for a moving chain to start wearing through the frame. (I've seen gets

    Overall, the chain tensioner is not a bad thing. As long as it is installed so it can't move. (unexpectedly)

    A lot of great modifications can be found on this site.
  4. Dakman

    Dakman New Member

    Thanks guys
  5. Stan4d

    Stan4d New Member

    Something that is often left unsaid.....there is no reason other than clearance to keep the tensioner on the motor side. If you DO NOT have a coaster brake, and you have clearance, you can move it to tension the pedal side where it is unlikely that your leg power will force it to move. (this is a way to keep from using 1/2 links or shimming the motor)
  6. Big Red

    Big Red Active Member

    Chinese "STUFF"

    Hey srdavo, Lets see if we agree on other issues concerning the rear sprocket setup.
    (1) Most of the Chinese sprockets are NOT centered very well, So getting the sprocket hole centered to your hub does not insure that the thing is PERFECTLY centered. You really have to make sure the TEETH on the sprocket run true to the wheel. A lot of times the hole is not cut exactly center in the sprocket and sometimes the sprocket itself is not perfectly ROUND. All I'm saying that getting the sprocket on just right can sometimes be a challange.
    (2) If, as in 99% of the sprocket setups, the thing is NOT perfect, your gonna get some chain slap on the bottom side of the chain as it returns to the rear sprocket. This is caused by the slight back and forth motion of the cheap Chinese sprocket specs. It doesn't take much of this to jump a chain off. Installing a tensioner keeps the "chain slap" foward of the tensioner and allows better "roll on" to the sprocket. stan4d is right but you gotta add a big IF. IF the sprocket is PERFECTLY round and centered by that guy in China that takes a quick look at it and says "Good Enough" (RIGHT).
    (3) Sprocket setup is, in my opinion, is the most critical part of the build, AND the most difficult. Part of that "setup" is keeping the wheel centered in the frame. I've found that whenever possible it's best to let the rear axle rest all the way back into the frame. Most have decent bikes and that alignment is usually closer than you can get it trying to adjust it by eyeballing it somewhere in the axle slot. Also, If not set all the way back, hitting a good bump in the road could knock it out of alignment. It's just a more "firm" setup.
    (4) Again, stan4d is right. Theres no reason you can't use a roller on the peddle chain side of your bike. I do it all the time. I usually just use a old derailer set on my bikes that have a coasterbrake or BMX style freewheel setup. JUST enough extra chain to let it work and the wheel to set back into the frame. It lets the peddle go back a little further before engageing the brake so a SOLID roller would be better, but I dont EVER depend on the coaster brake anyway. They don't work well at 25 or 30mph. They either don't stop you at all or just plain LOCK UP. I ALWAYS install a better braking system on my bikes. So the coaster brake is just a backup brake, just in case, if you know what I mean. And if you DON'T have a coaster brake setup then you most likely have a derailer setup on the bike anyway, and dont have to worry about peddle chain tension at all. The derailer tensions the chain perfectly for your bike. So again, whenever possible, let the axle set all the way back into the slot for a firmer setup. On the bikes that DO have a BMX style freewheel, Adding a few links and a roller to the peddle chain will allow the wheel to be set wherever it's best for the build and best for the motor chain and sprocket alignment.
    So srdavo, Did I miss anything? I'm sure I did as I'm perhaps not the sharpest tack in the box. Let me know what you think.
    Big Red.