hey guys , i have a 74 shovel with 1" western bars on it , i have had it for 12 years and all that time the bars keep slowly slipping down towards the tanks  , i have tried new risers and clamps tightened the crap out of them , the bars have a knurl on them but nothing seems to stop them slipping down , has any body had the same problem and found a fix , the only thing i havent done is drill a hole through the bar clamp and fit up a pin , any help would be great , thanks

Go for the drill and pin, they won't move then.Just make sure they are where you want them before drilling.

The mounting screws on the risers aren't bottoming out are they? That may not allow the clamp to exert its full pressure on the bars

mate you can also try this - go to your local bearing shop and ask for some speed shim (I think thats what its called ) - its the same stuff they use on shafts that are a bit worn to take up the gap between the bearing and the shaft it comes in sheets which you can cut with sissors and wrap around your handle bars - and hold in place with a dab of super glue and then tighten it down - I've done this before and it does work

ride safe

The drill and pin method mentioned is good however if you want to move the positioning later its not so good. Using a centre punch as chopaweezer has suggested around the contact area on the top clamps works really well and should stop them moving, I take it you have chrome risers and chrome clamps with stainless bars? its even worse if thats the case with apes, hit the front brakes hard and you find your face buried in the headlight....

Either pin it or get a set of Burleigh Bars with fixed risers.

thanks boys for the suggestions will give it a try on the weekend , Dave P face plant into the headlight , that made me laugh , not quite that bad

Good idea steamer.

I've heard of the bicycle inner tube as kiwidave mentioned and also heard that you can cut some strips from a beer can, wrap around the bars and tighten down. This works too i've been told.

Go for the burleigh bars.