Twisted swingarm, bent frame or both?

[Troyskie]

G'day fellas,
At our recent shed day Alf noticed my rear wheel was not sitting square and centre.
I did the obvious and checked the axel centring adjustment thingies for the chain & they were nicely equal.
My next thought was the subframe must be bent, something I'm familiar with  .

I've removed the swingarm to see if it is bent or twisted.

During disassembly I noticed the following:
I'm pretty certain the swingarm has never been removed.
The LH footpeg mount has one noticeably bent bolt (bottom most one of the two that mount the engine frame to rear of the main frame).
The bolt holding the right hand side upper suspension linkage was really really jammed. The bolt was pretty corroded when if finally removed it. I buggered two drifts getting it out, and ended up using a lump hammer on the drift.
There was some gouging on the chain side, ugly, but not too bad.

After disassembly I noted the swingarm does not sit flat on the floor. The chain side seems to have more of a curve than the brake side.

I'll try and get some piccies up for you too see.

My questions are two..
First, is using a square with the swingarm flat a legitimate way to check for twist?
Second, how can I check the frame?

Troyskie

[Sparky84]

G'day Troy,

On that same bolt I used a hammer with the right amount of whack but didn't budge it, then I moved to the lumpy with a bit of a whack, still no budge, so then I get it a real WHACK and it started moving.
Nylon bushes and rust held it in. No gouging done (lumpy with a bigger head so I didn't miss) and no drifts were damaged.
What are you putting back in?

Not sure about the square to check but how does it look when you place it across the top of both sides?
Are you sure your bikes sitting perpendicular to concrete (that's not always flat either)?

[Troyskie]

G'day Al,

I know the bike isn't sitting square (bent centre stand), which is why I've pulled the swingarm out to see.

Since the post, I've had tea and a bit of time to think. BINGO!

I was too focused on what was in front of me. I Just compared it to the three other bikes beside it!

They are all laser straight compared to the one on the floor.

I'm still wondering if the frame is bent. Any ideas?

[Troyskie]

Whoops, just read the rest of your message (too excited that I'd discovered the swingarm is bent, and twisted  )

I'm going to put in another one that Diesel has (sorry Diesel. I really need it now. I know it's you rolling parts bike  but you can have this one to keep it rolling  ).

I could also get funky and go for a JMC Isle-O-Man arm. Or copy Joolz and do the Thunder Ace. But then I'd need to do the front forks, brakes, cams, carbies, wheels, and get a flash paint job!
Hmmm, I might just be in the wrong section and need to start again in Project Writeups.....

[Pat Conlon]

Motorcycle frame straightening 101: Some things are best left to professionals.

They have the specialized equipment and expertise to get the factory tolerances down to the millimeter.
Years ago I visited a shop in SoCal and it was most impressive.

When Frank bought Klavdy's bike (which Klav had low sided) he had the frame professionally straightened.
I remember Frank remarking how surprised he was with the frame being so far out of factory spec.
Twisted swing arms are easy, change them out. Take the aluminum swingers down to the recycler, get some cash.

Re: Swap frames: I don't know about Australia, but here in Calif, the DMV registration and insurance identification must match the VIN# on the frame.

Cheers!

[Troyskie]

Thanks Pat.
I'm not sure where to even look about getting the frame checked professionally around me.
So there are no suggestions on some measurements to see if the frame is bent? Not that I would even think about straightening it.

I've checked it fairly carefully and can't find any cracks or obvious issues. I might even do the old flouroscein?UV light trick to see if there are any cracks not evident.

I agree with the swingarm, off to the recycle centre with it.

[Flynt]

I went to a place called "Frameman" in Sacramento CA...  he had a thriving business repairing bent Hardleys.  He straightened everything...  frame, swingarm, headset (had to be replaced due to sheer damage you couldn't see without special optics), handlebars...  maybe just look for something like that around you.  He was able to put everything back to dead on Yamaha spec...

Frank

[Shorty]

Thanks Frank
    I tore everything down and found the handlebar broke

[Troyskie]

Thanks Frank.

I did do a search and found a mob a few hours north of me who seem to specialise in fixing bent bikes.

Troyskie

[racerrad8]

If you have it stripped down, drop some plumb-bob strings down at the steering head and the sides of the frame.

Get one of the two of the above mentioned square with the string. The check the other.

For example, if you get the frame itself square to the string and then you check the steering head and the measurement are off then the head stock is bent/twisted.

As long as you establish something to be plumb/square to the plumb-bob strings, then ever other point you measure should be square with in.

Randy - RPM

[Troyskie]

Thanks Randy,

I've not completely stripped it down, just removed the swingarm so far.

I do have a project bike with a straight swingarm so I'll pop it out and see from there.

Also I did come across a few 'check how straight' articles on the web using your method above. Interestingly quite a few said a couple of mm out is 'within tollerance'. The worst offenders seemed to be Ducati of all bikes  .

Troyskie

[FJmonkey]

The worst offenders seemed to be Ducati of all bikes  .
Troyskie

From what I have seen, the higher end Ducati bikes are closer to race ready than street. So a minor issue for a bike built for hamfists like us will bend/twist the lighter constructions.

[Troyskie]

Replacement swingarm arrived.

I compared them side by side and did a few measures with straight edges.

The old one is absolutely buggered.

It was hard to get a pic of the twist in the arm, but all the bushes were knackered, it had never seen grease since new. The shafts were deeply scored and rubbed hard on any moving surface.

In the pic below the buggered one is on the right. It has both a significant twist on the RH arm and the LH arm is bent slightly up by about 4mm.

Putting in a swingarm is pretty straight forward, but remember the chain on the shock early