diy 5$ engine mounted chain tensioner

mark20

Active Member
Joined
Sep 26, 2018
Messages
303
hi everyone! hope you all are having a great friday!
i made a engine mounted chain tensioner that goes on the outside case unlike a traditional one.
heres how to do it. (please note, this will not work with all bike engines etc. please do this at your own risk)
tool and materials
1.drill with pilot bit, 5/64 bit and a 7/64 bit
2. grinder
3. longer bolt ( if found one laying in my garage so i used that)
4. 1/8 steel, and 1/16th steel (i used the 1/16 for my cover because my clearances are tight. i would recommend using 1/8th steel if you have enough clearance)
5. spring (i used a old governor spring, but i recommend you spend the 2$ on a spring)
6. the old chain tensoner that came with your engine.
7. ratchet with 14mm socket and a adjustable wrench.
20190111_140057.jpg

so first thing you need to do is cut the 1/16 steel into a rectangle (3 and 1/4in by 2 and 7/8in) then you drill the 2 holes in the plate to match the top 2 screws on the clutch plate with the 5/64 drill bit. then replace the top left bolt with the extended bolt
BE CAREFUL ON THIS STEP.
drill a 7/64 hole where you want the swing arm to go. (i would move it up to avoid it hitting the crank arm)
cut a 45 in the lower part so you can gain access to the lower left bolt. (optional, but i did it anyway)
20190111_135615.jpg

20190111_135635.jpg

next we make the swing arm , cut a 4in piece of 1/8th steel, then drill 2 holes with the 7/64 drill bit, one on the edge of the steel, the other about 1/4in away from the edge.
then you grind it down until it swings freely. ( you can see what it is supposed to look like)
20190111_114408.jpg
20190111_135708.jpg

after that you need to put the swing arm bolt facing outward, YOU PUT THE WASHERS IN THIS ORDER
bolt head, washer, plate, washer,
then adjust the swing arm so it had no play, but swings freely, then interlock both bolts.
then add your pulley on the other side like you would normally.
drill 3 small holes with the pilot bit in the swing arm for the spring. then drill a small hole in the airfilter of your bike (you can mount the spring on the engine, but this was easier for me). and
BAM! you have a engine mounted chain tensioner
(you may also need to bend the plate so the swing arm is aligned with the chain, i had to do that)
other pictures
20190111_135722.jpg
 

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RAT RYDER 101

Active Member
Joined
Jul 12, 2017
Messages
174
hi everyone! hope you all are having a great friday!
i made a engine mounted chain tensioner that goes on the outside case unlike a traditional one.
heres how to do it. (please note, this will not work with all bike engines etc. please do this at your own risk)
tool and materials
1.drill with pilot bit, 5/64 bit and a 7/64 bit
2. grinder
3. longer bolt ( if found one laying in my garage so i used that)
4. 1/8 steel, and 1/16th steel (i used the 1/16 for my cover because my clearances are tight. i would recommend using 1/8th steel if you have enough clearance)
5. spring (i used a old governor spring, but i recommend you spend the 2$ on a spring)
6. the old chain tensoner that came with your engine.
7. ratchet with 14mm socket and a adjustable wrench.
View attachment 85480
so first thing you need to do is cut the 1/16 steel into a rectangle (3 and 1/4in by 2 and 7/8in) then you drill the 2 holes in the plate to match the top 2 screws on the clutch plate with the 5/64 drill bit. then replace the top left bolt with the extended bolt
BE CAREFUL ON THIS STEP.
drill a 7/64 hole where you want the swing arm to go. (i would move it up to avoid it hitting the crank arm)
cut a 45 in the lower part so you can gain access to the lower left bolt. (optional, but i did it anyway)
View attachment 85481
View attachment 85482
next we make the swing arm , cut a 4in piece of 1/8th steel, then drill 2 holes with the 7/64 drill bit, one on the edge of the steel, the other about 1/4in away from the edge.
then you grind it down until it swings freely. ( you can see what it is supposed to look like)View attachment 85485View attachment 85484
after that you need to put the swing arm bolt facing outward, YOU PUT THE WASHERS IN THIS ORDER
bolt head, washer, plate, washer,
then adjust the swing arm so it had no play, but swings freely, then interlock both bolts.
then add your pulley on the other side like you would normally.
drill 3 small holes with the pilot bit in the swing arm for the spring. then drill a small hole in the airfilter of your bike (you can mount the spring on the engine, but this was easier for me). and
BAM! you have a engine mounted chain tensioner
(you may also need to bend the plate so the swing arm is aligned with the chain, i had to do that)
other picturesView attachment 85486
NICE...The only thing I would do is move the pivot point an inch 1/2 lower on the mounting plate. That would give you enough room to lift the bottom chain which steers the chain better to the rear sprocket . If not , you take the chance of the chain walking off the sprocket if you get any chain bounce...(carry on)
 

RAT RYDER 101

Active Member
Joined
Jul 12, 2017
Messages
174
This shows the bottom chain tensioner and an arch in combination . Yours probably works fine.
 
Last edited:

mark20

Active Member
Joined
Sep 26, 2018
Messages
303
NICE...The only thing I would do is move the pivot point an inch 1/2 lower on the mounting plate. That would give you enough room to lift the bottom chain which steers the chain better to the rear sprocket . If not , you take the chance of the chain walking off the sprocket if you get any chain bounce...(carry on)
Thanks! Also, you could just do it like this,
But my crank arms are in the way (old mountain bike, if it was a beach cruiser I would do that. I actually had move it up so it wouldn't hit the cranks
 

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RAT RYDER 101

Active Member
Joined
Jul 12, 2017
Messages
174
Thanks! Also, you could just do it like this,
But my crank arms are in the way (old mountain bike, if it was a beach cruiser I would do that. I actually had move it up so it wouldn't hit the cranks
You could use the same flat taper screws they use on the hub adapter sprockets . Any hardware would have them.
 

RAT RYDER 101

Active Member
Joined
Jul 12, 2017
Messages
174
You want as many teeth as you can on the drive gear to grab that chain, to pull the tensioner down opens that space up .
 
Last edited:

mark20

Active Member
Joined
Sep 26, 2018
Messages
303
You want as many drive gear teeth as you can on the drive gear, to pull the tensioner down opens that space up .
good point, but ill keep you updated on how this goes reiblily wise (im getting ready to jb weld and re taping my exhaust right now because the bolts snapped off, probably made in china lol\)
 
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