Frame Bracing - at what point?

A bunch of recent posts on frame bracing have popped by in the past week or two. Just curious as I haven't really seen any discussion of what point frame bracing becomes desireable/necessary.

So I'm going to be getting my 900 made into a 1075, but a fairly tame one. I haven't seen any cracks yet, but I will be looking the frame over pretty good. When should I start worrying about bracing? I have the frame stripped right now so if I should do it, this is the time to know about it I guess.

As always, I'm relying on the opinions of those much more experienced than me - just trying to do things as best I can.

Thanks for the help!

Well the bikes were designed to hold the weight they have stock with the power they have stock, and stock bikes make around 70bHp +/-. Your 1075 kit has a LOT of potential, if you add carbs, head work, cams, and a good pipe that bike will benefit from superior suspension and some good bracing. If you're going to be a drag-racer, then not so much, but if you like the corners then you should consider bracing the neck, the spine, and the rear of the frame. There has been a lot of info posted, but if you need more, just "axe".

-KR

PS> Plummen has a very interesting frame bracing project going on right now...

the kz series frames are pretty stout even in stock form compared to the z1 frames which tend to have the structural integrity of a limp noodle when any kind of power is put to them.id say with a mild motor your 76 frame should be safe,the swingarm and brakes could use an upgrade though even just adding a kz1000 swingarm and rear disc makes a world of differance on these old bikes

Thanks, BadKaw and Plummen. How much of a difference is there between the Kz900 and Kz1000 swing arms?

trust me guy's any time you increase the horsepower of a motorcycle by 30 to 50% or more even if your dragracing it is a very good idea to at least do some frame bracing. and some swing arm bracing as well, the more power you make the more chance of frame flex can occur when your getting on the throttle hard, even on the street. as far as strength goes the two swing arms are very similar. one of the reasons some people go to different swingarms is for the difference in flex some do it for looks and some doit to gain extra wheelbase but most do it for the strength.

If handling is what youre after, you are probably on the wrong bike. I have one 73 Z1 with a crack and one without. I raced a new 73 every weekend for 2 years with no cracks so Id guess wheelies are the cause of them. Back then going 12.19 with just a pipe was pretty quick

DoubleDub wrote:

Thanks, BadKaw and Plummen. How much of a difference is there between the Kz900 and Kz1000 swing arms?

Hmmmm...well "double dumb-ass" on me, but I don't know of any difference (besides the obvious drum-brake-drama) in the 'Z' series, and I'd be stunned and amazed if a 'J' swingarm wouldn't just be a damn-near bolt on, but I'm not the guy to "axe" about that 'stock-for-stock' swappin' stuff...I like heavy modifications, like late-model suspension on 'Z' and 'J/GPz' bikes. So, I won't be much help in answering that one.

I'd bet Jeff Saunders (Z1 Enterprises) could help with that angle...or heck, about half the rest of the guys on this forum might know about stock-for-stock swapping stuff.
Good luck man!

-KR

yeah the brake upgrade is the biggest plus,double needle bearings versus bushings in some 900 arms is a big plus also.im not sure if theres any noticable differance in wall thickness of the tubing

Thanks - that's what I was looking for!

If I remember correctly one of the improvements when they went from the 900 to 1000 was that the wallthickness of the frame was increased by 0.5 mm.

could be,ive never researched it that far.