Daves Bitza #2...

[Prof]

Here's our second part of the build and it has been some time since #1. So a quick recap. Dave has been picking out and paying for bits in The Chopper Shed for about a year. It's now at a point where we can start putting it together. It will be a drawn out project as he puts in a regular small payment each fortnight...

Here on its wheels...

Frame is BSA that at some time in its history had a Harley rigid rear end grafted in. Hard to tell how well it was done due to moulding, but I will add in a couple of gussets were the bottom tubes meet just to be safe...


Rear wheel is disc braked shovel or sportster. Front guard is a new ribbed guard, Rear guard is a swap meet find as is the saddle...


Front end is 90's Low rider. We had to make up a couple of bushes to allow us to use the HD bearings (See Daves Bitza #1). Front wheel is pre 78 shovel. Need to get a rotor and caliper yet...


Ribbed after market tank is also new...


Motor is an XS500 I have had here for quite a few years. Has good compression and gears all change, so we hope it will be good. We do need a set of carbies for it. Any one got some for sale?...


Got in a bit more work on it yesterday... mounting the tank. Existing tank mounting hole is too far forwards. So a new hole is in order...


Cleaning away some moulding and reveals another hole that will do...


A rule down the centre line shows it is off centre...


Enlarge and centre it with a die grinder...


Machine up a threaded bung. Top of bung and the hole are chamfered for welding. Weld will fill groove and then be able to ground back level...


Curved tab needs flattening and a slight downwards bend... done on anvil...


Centre line for drilling marked with odd leg caliper. You can also use normal calipers or verniers...


Ground off bung area. Thread is M8. Note that there is an 6mm lead to reduce the likely hood of cross threading. I do it on all tank bungs. Arrow points to another old hole that I welded in. Common occurrence in these old frames especially around the neck area. This one is within gussetted area so just welded. Other holes in this frame with have solid bungs welded in to keep up strength.


Rear tank mount done. It will be rubber mounted later...


Next step will be front mount done the same way and then the rear guard so we can set up the sprung saddle...

[Prof]

Dave wants the seat and guard mounted. This means centring the rear wheel first. Normally this is done with the motor mounted in the chopper so we can check how well the countershaft and rear sprockets will line up.

Dave needs to cut off some brackets first, so because the motor should be centred and it has an obvious centre line, we measure up from centre to outside of sprocket. The XS sprocket is quite tight so we just run a ruler across its flat and measure up. Some sprockets don't pull up tight and you can easily make a mistake as a mil at the sprocket will end up much more at the back of the motor and throw your measurements way out of wack...


Next the wheel hub is measured up to see how far off centre the sprocket will be. Harley rear hub stubs differ in distance on the hub; 26mm on the sprocket side and 20 on the disc rotor side. As it turns out, with the wheel centred, the two sprockets will be within a couple of mm which is quite satisfactory...


Now to check squareness of the hardtail. This is something you should always check with a second hand frame whether it has a hardtail or the original swing arm. It is not uncommon for stock frames to be bent and some added hard tails can be way out. So let's check.

Frame is levelled...


Are axle plates square? Check like this. In our case they are spot on. The wheel is vertical not twisted to one side as is not uncommon on old frames...


Now to align wheel. Most accurate way is a string line down centre of frame...


The rear tank mount hole is centred and this shows with the string on the wheel it is 6mm to right of centre which the wheel must be 10-12mm to right of centre...


Check axle plate distances on each side of wheel and suggests 6mm to right...


Another check using straight edge down centre to touch wheel. Agrees. Wheel is 10-12mm off centre. Top frame rails are evenly spaced from centre too which is a pleasant bonus...


Do a final check across lower rails. Arrows show measured centre marks. A straight edge across here suggests wheel is 6-8mm to right...


So we will move the wheel 10mm to left and that should put it very close to centre... will certainly ride well this close.

Why write up this exercise? A lot of chopper jocks pick up frames and parts to make up their chopper or even get a roller to rebuild. If you want a good riding chopper, following the above proceedure can save you considerable grief later on in the build or when you get it on the road.

Tomorrow, plan is to machine up left axle spacer then do a temporary right one (will have a caliper mount later) so I can get the guard set up and then mount the seat.