Chain Tensioner luck with no tensioner?
- Thread starter 2strokepoke
- Start date
BoltsMissing
Active Member
From actual experience, I have a spring chain tensioner on one bike frame, but does not work well on another frame.
There are points to consider, mainly geometry and swivel, having a bolt with a washer defeats the purpose even when you get the geometry right.
What geometry?
The downward push on the chain when you let out the clutch, the swivel needs to bottom out, sort of like a pendulum, when it's rock bottom and the engine fires, it retains the tension.
It's not the spring tension that holds the compression, it's the correct angle of the swivel action at that maxed out point, at TDC.
Dream ride when it's right.
That pic. shows the right idea for home made, it's all in tweaking the geometry through trial and error.
I would use a better quality chain because the china chain stretches over time and messes up, confuses things, "false positive" and all that when trying to fine tune the angle.
What you have there is right though, except have some sort of adjustment for the spring tension. If it's too tight ya lose power, too lose it falls off.
The swivel part, not cheap, but a flat needle roller thrust "washer type" bearing kit, ( for those of us who don't have a lathe ).
It comes in 3 parts, the flat needle roller bearing and the 2 bearing washers for either side.
Initially it will constantly need adjustment till the bearing "beds in", as close to as zero tolerance as possible. Too lose and it swivels side to side, too tight and it won't work freely enough.
I used a wire ( coat hanger) to lengthen or shorten the spring tension between the fixed part, but above the brake with a special rubber lined wall mounting clip electricians use around small diameter tubes.
It's worth effort when it's all done though.
Warning: Once you have ridden a MB with a corrected spring tensioner on a china engine, it's addictive.
There are points to consider, mainly geometry and swivel, having a bolt with a washer defeats the purpose even when you get the geometry right.
What geometry?
The downward push on the chain when you let out the clutch, the swivel needs to bottom out, sort of like a pendulum, when it's rock bottom and the engine fires, it retains the tension.
It's not the spring tension that holds the compression, it's the correct angle of the swivel action at that maxed out point, at TDC.
Dream ride when it's right.
That pic. shows the right idea for home made, it's all in tweaking the geometry through trial and error.
I would use a better quality chain because the china chain stretches over time and messes up, confuses things, "false positive" and all that when trying to fine tune the angle.
What you have there is right though, except have some sort of adjustment for the spring tension. If it's too tight ya lose power, too lose it falls off.
The swivel part, not cheap, but a flat needle roller thrust "washer type" bearing kit, ( for those of us who don't have a lathe ).
It comes in 3 parts, the flat needle roller bearing and the 2 bearing washers for either side.
Initially it will constantly need adjustment till the bearing "beds in", as close to as zero tolerance as possible. Too lose and it swivels side to side, too tight and it won't work freely enough.
I used a wire ( coat hanger) to lengthen or shorten the spring tension between the fixed part, but above the brake with a special rubber lined wall mounting clip electricians use around small diameter tubes.
It's worth effort when it's all done though.
Warning: Once you have ridden a MB with a corrected spring tensioner on a china engine, it's addictive.
Last edited:
happycheapskate
Active Member
My experience was that with no tensioner, the bike vibrated like crazy! Running a smaller cog (36 tooth) seemed to help, but maybe just because it is truer (milled out to fit on hub) I've heard that running the fat heavy chain helps because you can run it looser and it won't derail. I didn't like the stock chain. I use a neoprene roller that acts as a vibration dampener. The chain is snug but not overly tight. See my pics or pm if you need help. It mounts on the happytime case.
What kind of BMX fits a happytime, or do you have another kind of engine?
What kind of BMX fits a happytime, or do you have another kind of engine?
