750 cc Chain Tensioner

[andrecht]

I need one of you boffins co suggest the ideal chain tensioner setup.
I am constantly replacing engine mounting bolts, bent by the amount of torque going down to my drive sprocket.
Especially when changing up in gears.

Currently using a static tensioner, to take up the slack in the chain, and to prevent the chain from catching on the sprocket guard.

Would a spring loaded tensioner be the answer?

 

[OzFab]

It would seem you have multiple problems; are you using high tensile bolts for the mounts? Can you post some pics of you mounts?

Now, the tensioner IMO is at the wrong angle for this type of tensioner &, yes, it should be spring loaded, whichever design you use...

There are two basic designs, the swing type which you have, which work best when mounted in line with the chain or the telescopic type, which should be mounted at 90° to the chain

 

[andrecht]

Sorry or the late reply,
The engine mountings are two 1/2" s/s shafts bolted directly to the buggy frame.
The front mounts i had to support due to the frame twisting. I have left some flex in the supports, to take up some movement.

When you say the tensioner is in the wrong position, please elaborate....

 

[OzFab]

Well, I can't explain why you keep bending stainless steel mounting rods, I can't even suggest an alternative...

As for the tensioner, as I explained,

There are two basic designs, the swing type which you have, which work best when mounted in line with the chain or the telescopic type, which should be mounted at 90° to the chain

Your tensioner is somewhere between the two, it's currently at around 30° to the chain, which is not ideal. IIWM, I'd replace it with a telescopic type, mounted at 90° to the chain

 

[exenos]

That stainless rod wouldn't happen to be threaded all the way like threaded rod would it?

 

[OzFab]

Oh yeah, I didn't think of that; that will turn 3/8" rod into 1/4" rod...

 

[andrecht]

Thanks for the advice.
The mount bolts are 1/2" shank, only threaded at the ends.
I intend to fabricate additional mounting brackets towards the rear of engine, just to play it safe.

I was hoping to get an indication of the amount of tension suggested for the chain tensioner.

 

[fowler]

proper chain tension
u should be able to side the chain side to side on the sprocket
but not pull it away from the sprocket

but....

if u are snapping 1/2 inch bolts then firstly u are using crap bolts

get some 1/2in grade 8 steel bolts
i can guarantee u they will hold 2 1/2 ton of force

the front mount need support
u not want any flex
flex equates to cracks

there must be another mount somwhere
as u have discovered, if u only suport it in two places front and back then theres nothing to stop it twisting side to side
this wasn't a problem the bike engineers had?

there should be anoughter mount in the form of a another long bolt
or two threaded holes

either in the case at the back
or in the head

what bike was it in originally?
Kawasaki?

 

[andrecht]

Suzuki GS750 (82')

There is another 1/2" hole lower down on the block that i will use as additional mount.

 

[fowler]

At yes that'll do it