Another XS650 frame

[Mathius]

Hi all. I'm having a debate on Chopperweb... yes it's a debate now. I asked a question and as usual, instead of giving me what I need, everyone goes out of there way to tell you a better way to do it, or why you shouldn't do it.... anyways, I need some help..

I have a '78 XS650, and I'm off this weekend to pickup my second, an '82. The 78 is torn down to the frame and motor, and I wanted to do some frame mods. I'm not really interested in building or buying a jig. It would cost more money and take more time and push the project back. I had hoped to get the bike done over the winter monthes, and a move, and another project have already pushed it back to where I haven't even started it.

I want to stretch my backbone and give it more curve, and go from a double downtube to a single. I'm not going to modify the existing tubes, I'm going to remove them and add new ones. I had planned on using 1 1/4" DOM.

To get the front end where I want it, I'm gonna assemble the front end, use some straps or something to compress the front forks, set the frame (bottom) on some 4x4's or something for ride height (I'm thinking 6"?) and then see where the downtube and backbone need to go.

My question is how can I be certain that my neck goes on straight?

I can easily set the rake I need with an angle finder. I am concerned that the neck will be off to the left or right. I thought perhaps if I drew a straight line on my work surface (or taped one off) and centered the frame on that line, that I could either find the centerline of the front axle and drop a plumb bob, or just use a laser level on the neck itself, and compare that to the centerline on my work table to get my neck centered up.

Does this sound like it will work effectively?

I'm being straight forward and honest. I don't want to use a jig for money and time concerns. But even if I had a jig, I would still want to know how to measure these things out. It doesn't make sense to me all these people who buy a jig and slap these things in and expect it to come out straight.

What happens when your jig is off? Shouldn't you measure everything anyways? A jig is supposed to hold your parts in place while you weld, or mock your parts. I actually heard one guy on chopperweb use a phrase something like, "use the jig as your ruler". I have welding experience, including cerifications in the big three (TIG, MIG, Arc). Measuring and fitment is more important than almost anything you can do with any type of fabrication. In fact, I don't care if you're the best welder in the world, if your parts don't fit properly, 80% of the time or more your welds aren't going to come out like they should or could.

Mathius

[steve.murphy]

Mathius
If you block the frame level, could you hold the front end as described (with steering neck still attached) and use a spirit level on the side of the steering neck to ensure it is perpendicular to the ground.
Or how about removing the front wheel, making two identical triangular plates that are drilled for a neat fit on the axle that have the same distance as the axle centerline to ground as your front wheel. (Of course that means the fork tubes are required to be straight and aligned properly). If the traingular plates were parallel with the frame tubes it would be straight too.

Good Luck, Steve

[captainkirk]

Latch the frame down so it can't move, make two inserts for the steering head that have small holes in the middle make sure they are centered in the steering head and either tape them fast or glue them in with something like hot melt glue so they can't move. Get one of the small lasers used to play with cats or any such laser affix it to the ceiling so that it shines through the holes in the steering head and the spot lands on the floor mark the location of the spot on the floor. Go ahead and hack off whatever you want and weld in whatever you want as long as you don't move the frame or the laser or the spot you can locate the head back in the same exact location regardless of the mods. If you wish to rake it more merely draw a strait line from the spot to the frame and as long as the laser dot passes thought he holes in the head and hits the line your strait....or at least as strait as it came from the factory.

Disclaimer: All advise likely worth what you paid for it....some worth less...no way to tell.
Kirk

[Tin Head]

Mathius,

I too kind of believe a properly built jig is the way to go, but I didn't use one when I built a new HD chopper frame back in the late 70's. I used a shaft to imitate the rear axel and leveled that. Each plate (motor and transmission) that went on was then checked against that same level point. The neck was more tricky, but was basically set plumb to the axel shaft. After welding, all points were verified back to the axel shaft level. I used a steel wire for the center line stretched between two holes in the weld table. Perpendicular was done on the table with a framing square to square the axel to the center line. Kind of crude, but poor people have poor ways.

In your case, why couldn't you use one of the laser levels that do level and plumb at the same time. Set it up along the center line of your frame, using the original neck. Level it to the shaft through the rear axel mounts. Milling a narrow line along the center of the shaft would let you better position the frame to level using the laser. Fab something to allow you to position it in the exact same spot while you proceed to work on the frame. Once you get to positioning the new neck, use the same kind of shaft (with a milled line)through the neck and position it to the laser plumb center line. Size both shafts for a nice snug slip fit to their respective locations before using them. Of course, the longer the shafts (to a point), the more accuracy you would get. Hope this makes sense to you!

Bob

[jlrussell4]

Hi Mathius,

Bob just told you the way I was told to check frame alignment years ago. I was told to make a tee square to fit in the axle slots in the swing arm. Another long straight shaft machined to fit in the steering head. I was instructed to sight from the rear verticle shaft to the front verticle shaft to insure the steering head was in alignment. The availability of cheap lasers would be much better than sighting with ones eye.

[nos1123]

My main concern is how are you planning to hold the neck in the backbone and down tubes while welding. You can definatley figure a way to set it in centered but you need something rigid to hold it from pulling or moving while welding it.

[Boogiemanz1]

The cheapest I've ever gotten by was a piece of 6" channel iron. Square your frame up on it and tack it down . Level the channel and the axles as you go to get as close as possible. Find the centerline by removing the front end and dropping a plumbob through the neck and insure it isn't hanging up in anything, mark that spot. Now hunt up some bearings or drill out some washers that will fit securely in the neck and hold a piece of tubing that will reach forward and down to the channel. Turn this and make sure you have an absolute center then mark the channel again.


Scribe a line through the two marks all the way down the channel. This should be your center line. Pumbob the backbone and make sure you have it all centered. Your frame rails should be parallel to this line generally. Once you have everything square and in line you can modify your butt off and as long as the neck plumbobs to the line and the tube in the neck hits the line it will be straight. Rake and trail are a different matter.........john