How to check for frame damage?

[madmax-im]

So apart from''just ride it and see" How do i check the frame to be straight and all angles are correct? I know something is bent but specifically where..not yet determined...how much do i need to strip off the frame to check it completely?

[DiverRay]

Long ago there was a paper on checking frames. Now I'd have to go from memory.
1. measure from the front of the steering stem to each upper shock mount.
2. measure from the steering stem to the rear most frame on each side at top.
3. measure from each upper shock mount to the swing arm bearing.
4. measure from bottom frame to the top frame just in front of swingarm mount.
5. measure across the frame in a few places between rear seat mount and tank mount.
This is just a partial, but as you may figure all the measurements MUST be the same, side to side, etc. It only takes 2mm to affect the bike.

[TomB]

I have straightened XS1100 frames, I made a simple jig but the human eye is very accurate when comparing tubes lining up with each other, seeing 1 degree out.

For frame twist, forks not lining up with frame, stand in front of the bike and check frame tubes to forks. Hopefully these photos will work (PB! )
Here you can see the head twist compared to a length of stud iron sat in the swing arm mounts.


The frame tubes all merge at one point on the head allowing it to twist easily.


The next problem is bend from head on collision, this isn't so critical if its only a slight bend and the wheels still line up, however I have seen frames so bad the bike looks very hump backed, which of course causes steering geometry problems resulting in quicker less steady steering.
Good ways of checking this are the obvious wheel base length, and a very simple check, can you get the front cam cover screw out? or does it foul the front upper cross tube, because the frame is shorter and the engine is further forward compared to the steering head.

Bent rear frame tubes can be easily straightened, as can engine cradles.

The Yamaha XS1100 frames are pretty crudely welded up, I found some welds not having any depth penetration what-so-ever, when grinding the weld back it simply fell off leaving an unmarked frame tube. And some of the tubes welded in were out of square.

Tom

[madmax-im]

Thanks for the info guys...

[TomB]

Sorry about the photos, they worked in Preview

[fredintoon]

So apart from''just ride it and see" How do i check the frame to be straight and all angles are correct? I know something is bent but specifically where..not yet determined...how much do i need to strip off the frame to check it completely?

Hi madmax,
the more parts that are removed from the frame the more thoroughly it can be inspected.
Along with all the other excellent posted frame measurement hints and tips, look for cracks in the paint that sometimes show up when frame tubes get bent.
BTW how do you know it's bent? Bike new to you and rides funny or did you hit something?
I've a vague memory of a list member who accidentally restored his bike's proper steering trail by fitting 6" over-length fork tubes to an XS11 that had been (unknown to him) PO-crashed into something that steepened the bike's steering head angle.

[TopCatGr58]

Hey Fred,

T'was Me that bent his frame/steering neck (with a too close cage encounter) unbeknownst to me for 20 years, and it reduced the trail to ~2.5inches, but I didn't "FIX" it by putting the 4" longer fork tubes on it, just wanted a little more of a chopper affect while replacing the bent ones, and the longer tubes just helped the trail be a little longer, but still no where near the OEM 6", and the steering was rather quick/light.

T.C.

[fredintoon]

Hey Fred,
T'was Me that bent his frame/steering neck (with a too close cage encounter) unbeknownst to me for 20 years, and it reduced the trail to ~2.5inches, but I didn't "FIX" it by putting the 4" longer fork tubes on it, just wanted a little more of a chopper affect while replacing the bent ones, and the longer tubes just helped the trail be a little longer, but still no where near the OEM 6", and the steering was rather quick/light.
T.C.

Hi TC,
OK then, can we agree that when you changed the bike's stance you also inadvertently made an improvement to it's steering?