how to check frame straightness

[v-twinwalker]

hey everyone, have a 1987 gsxr1100 that id like to check the frame before id decide to build it. 

 

whether it'd have to be a roller or not id like to know how to check it to be straight, it did have a motor in it at one point but it was taken out, came out easy i would say, it has been a while but i don't remember struggling to loosen any bolts or remove them.

[Gixer1460]

Tape measure and straight steel bars can check everything - helps if swingarm is fitted. Chalk line on a good flat floor, centre frame over it so headstock and SA centred and square, drop plumb line from headstock bearing / shaft to line, measure from headstock to SA mounts and axle blocks, fitted forks would help show any headstock twist.

[wraith]

The way I do it 

1. Put a spirit level on the swingarm pivot bolt/spindle and block the frame up so it's level.

2. Get a plum line (or degree finder if you have one) on the head stock and check the line is running straight from the head stock to the ground.

[TonyGee]

or !!!!  put the wheels in and measure the distance from the swingarm pivot to the wheel spindle centres on both sides (this puts the wheel straight),  then do a wheel alignment with a long straight edge.  

[Builder45]

Just went through a somewhat similar situation. I used a Dewalt 3 axis laser level (which I happened to already own) which worked perfect for determining if my front and rear wheel was aligned on my drag bike. Not the best picture, but this was my set up (green laser line). Got very consistent results.

 

Edited December 22, 2024 by Builder45

[Tony Nitrous]

I had a brand new Mk-1 B12 that was 1 full mark out on the chain adjusters on a Motoliner jig. The guy doing it said it wasn’t at all unusual. 

[TLRS]

Another way could be to angle the frame so that the headstock is dead level. Then check if the swingarm axle is level too. If it ain't, it's twisted. Or poorly manufactured as Tony points out.

This method doesn't rule out every possibility but it's fairly easy if you have an angle finder.

[TonyGee]

1 hour ago, Tony Nitrous said:

I had a brand new Mk-1 B12 that was 1 full mark out on the chain adjusters on a Motoliner jig. The guy doing it said it wasn’t at all unusual. 

I was told by one of the top tech's at Suzuki that they seen some headstocks out by 3 degree's !!!!!!!   that was on older bikes though, not so much on the GSXR's onwards.   

just to add, i never use the marks on the swinger till ive measured the swinger spindle to wheel spindle, then check the marks. 

Edited December 22, 2024 by TonyGee