1977 KZ1000 Restomod

So, I was going over the frame today and I noticed that I had filed a bit too much off one of the seat tubes (in the red oval below). I think I may have gotten a bit too heavy handed when repeatedly trying to get the tail bracket lined up (had to remove it with the dremel a few times and filed the tacks back down each time). I measured it today and it looks like I've taken about 1.0-1.2 mm off the wall thickness (2.5mm walls on those tubes). It's just on the right hand side of the tube - top to bottom the tube is close enough to an inch thick. The thinner area just goes past the brace for the shock mount.

Do I need to take the tail bracket off and build it up again, or am I worrying about nothing?

 
 

Hi Callum, I’m not an engineer but with the additional bracing that is fitted already I would have thought the amount of heat that would be generated from trying to build up the area highlighted would do more harm than good (only my opinion)

With a brace underneath and one nearly beside the area and a bracket above it i also think you will be fine, unless you intend to have your knee on the ground track racing? in that case there might be factory welds that might give up on you first, plan b would to be to cap off the area with a square piece that will fit on top of the tube and into the bracket.

Thanks guys, that was what I was hoping to hear. My knee is rarely in danger of any sort of contact with tarmac

@kzstreetfighter71: I was thinking of something like that. Just some square tubing cut down so it runs inside the bracket as in the sketch below. Is that what you meant?

 

Exactly and probably not even that long, if you drill a hole in the centre of the plate for a fill weld as well in the part that might be the weakest. What kind of welder are you using? mig?  i would use no more than 6mm mig wire on jobs like this.

Only tig and stick and pretty much only use tig. I would probably be just tacking this up and taking it to the local guy that did the bracing on the front end (MOT). I assume you mean that the top of the square profile should be flush with the top of the tubing so it can "spot" welded at the weakest part. 
My main concern is the thin side wall collapsing where the extra bracing is. But if the top was reinforced that would mean bending the tube with the shock mount in it - don't think I'll manage that

It might be a wee bit over the top but to get that feeling of "its done right" when you are riding. The plate you make, if you drill a 8mm hole in the center as my drawn by a monkey illustration shows, then fill the hole with weld and then file smooth you will get a complete reinforced area.

Calum, I had fun fitting those exact same type of mount on my frame too, I only removed mine once but, I only ever tacked them on, so no need for excessive filing. I ended up bolting them to the tailpiece, positioning everything meticulously, and retacking them on, then removed everything and refitted it all again , just to make sure it was all correct, then I welded them on. Its not as easy as it looks, is it ?    Also, when I removed the side stand mount, {why do Kawasaki's lay over so far on their side stands ?}, to get it off without screwing it up too much, I unintentionally ground a groove into the lower frame rail, I just filled it with weld and reshaped it, its all good now..

@750 R1: yeah, I thought I had them first go and then I noticed that the mounts weren't symmetrical (although the actual mounting points were). Just couldn't let it go and had to make a new one!

@kzstreetfighter: sweet, thanks. I'll get onto that this week. Do you have any idea on the effect of heat cycles on the frame tubes? Assuming there is basically no chance of it becoming brittle and the only thing to watch out for is warping.

I would keep an eye on left over frame parts that need to be welded.



As for your seat bracket, bronce soldering is an option.

My god that braze welding is beautiful, i braze weld on a regular but nothing as ornate or complex. "to the best of my knowledge" Kawasaki did not heat treat the frame but welding is a form of heat treat, as long as the weld is allowed to air cool it will become strong, as long as the weld is good ts the steel around the weld that will be the week point.

wrote:

I would keep an eye on left over frame parts that need to be welded.

 

Thanks. The inside part of the shock mount has been welded. There was a piece of tubing between the shock mounts for alignment that has since been cut off, but I haven't shortened the mounts yet. 
The front part is the stock welding. The back side of the join has been welded up, but the original welding was never pretty...

That brazing looks amazing!