This item, often called the "Outrigger Bracket" can cause much power loss.
The bracket usually does not clamp up square with the gearbox mainshaft.
First operation, set primary chain tension by slackening gear box retaining bolts on underside of gearbox undertray casting.
2) pull gearbox to rear with adjuster till slack in primary chain at tightest point is 10mm.
3) Push gearbopx forward with adjuster till slack in primary chain at tightest point is 15mm.
4) Tighten gearbox holding bolts.
5) Check slack has not changed.
6) Fit final drive sprocket to main shaft without fitting securing nuts.
7) check freedom to rotate with gearbox in neutral.
8) Tighten securing nuts.
9) Check to be sure sprocket still rotates freely. If there is stiffnes, this is caused by misalignment with the gearbox bronze output bush and this problem will cause loss of power and wear in the gearbox bronze bush. This problem is commen when using a simple ball bearing in this outrigger bracket. It can be cured by fitting a self aligning bearing number ULS11 also known as NLJ 1 1/8 .
10) When sprocket is fixed with nuts and is still free to rotate, remove front nut and washer and file up a piece of aluminium that will just fit between the bolt and the front edge of the slot in the bracket.
11) Fit the packing piece you have made and fit a larger washer to retain this and tighten front nut fixing. The reason for this is that the pull of the rear chain will move the outrigger bracket rearwards during acceleration in low gears and the nuts will hold it in this position. In this position, it produces great pressure on the gearbox bronze output bush causing wear and power absorbing drag. The aluminium packer prevents the outrigger bracket from being pulled backwards and retains the bracket in correct alignment. If you want to prove you have got it correct, slip the rear chain off after a run and check the free rotation of the final drive sprocket.
I have known this misalignment to be so severe that it causes seizures in the bronze bush. Although I used aluminium packers for many years for racing, I have now modified the undertray a little to fit a snail cam to do this job. This information is presented in a basic manner, as I do not have time at present to process photographs. Better to put the basic information and be helpful, than to not do so, because of lack of time for nicities.