The KZ750 twin Super Vintage Racebike

T

tobiism

Been Around the Block
Well, I made it to the vintage CCS races in Phx this weekend, and it was a blast. I saw so many cool bikes, that it cinched my decision to turn my KZ into a track only racer. I threw it up on the table, cut off the rear subframe in anticipation of the monoshock. Threw on some 3-spoke 17" rims with Michelin Pilot Powers, 110/70 17 and 150/60 17.
Forks will be fully adjustable ZX6, and haven't gotten a rear shock yet. The swingarm will run an overhead brace. I'm not sure what brakes I'm going to run yet. The frame will get some minor bracing, to help cope with the extra grip from the radials.
Weight was down to 400 with the heavy steel rims, and stock brakes and shocks. I'm super stoked to see how much the weight drops with these mods.
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WOW! That looks and sounds cool!

I see a single carb manifold with a big HSR carb (or the like), undertail exhaust, very cool hand made seat pan, high pipe, etc.

I love it!

Looks like you are the machining master!
 
Man, that's looking good.

I wouldn't even paint the sucker... just clean up the motor and rims and run it like that. I think that would look sweet, especially with the modern running gear.
 
Madmaxx said:
WOW! That looks and sounds cool!

I see a single carb manifold with a big HSR carb (or the like), undertail exhaust, very cool hand made seat pan, high pipe, etc.

I love it!

Looks like you are the machining master!
Click to expand...

Thanks man! I haven't actually had to machine anything yet, but that'll change when I try to figure out the wheel spacers! Now I just need to find someone with a lathe!
 
tobiism said:
I'm not sure yet, haven't gotten that far.
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Wicked ride!! That's going to be one cool racer!! ;D ;D

If you do need an offset countershaft sprocket and you want to run a 530 chain, give these folk a shout!

http://www.pmfronline.com/

I got a 5/8" offset for my KZ1000 a few weeks ago. They had it in my hands 4 days after I spoke to them on the phone!

I'm running a 180 tire, so you might be o'k with the 150.

Keep us up to date with the pics! :D
 
Drewski said:
Wicked ride!! That's going to be one cool racer!! ;D ;D

If you do need an offset countershaft sprocket and you want to run a 530 chain, give these folk a shout!

http://www.pmfronline.com/

I got a 5/8" offset for my KZ1000 a few weeks ago. They had it in my hands 4 days after I spoke to them on the phone!

I'm running a 180 tire, so you might be o'k with the 150.

Keep us up to date with the pics! :D
Click to expand...

That's killer delivery... it took me a couple months for mine.
 
Druro said:
That's killer delivery... it took me a couple months for mine.
Click to expand...


Ya, AFAM has great stuff if you're willing to wait for it! My source told me it's always a long wait for AFAM.
 
Drewski said:
Wicked ride!! That's going to be one cool racer!! ;D ;D

If you do need an offset countershaft sprocket and you want to run a 530 chain, give these folk a shout!

http://www.pmfronline.com/

I got a 5/8" offset for my KZ1000 a few weeks ago. They had it in my hands 4 days after I spoke to them on the phone!

I'm running a 180 tire, so you might be o'k with the 150.

Keep us up to date with the pics! :D
Click to expand...

I'll definitely keep it up to date, thanks for the info!
 
I'm in a similar project right now with my GS750, and I love the look of the steel tube original swingarm, but how do you plan on mounting the shock?
 
I'll be building a tubular aluminum brace that will bolt to the swingarm in six locations. The bottom of the shock will mount to the top of that brace, and the top of the shock will attach to a rectangular crossmember at the top of the frame, just forward of the seat.
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Drewski said:
Ya, AFAM has great stuff if you're willing to wait for it! My source told me it's always a long wait for AFAM.
Click to expand...

I believe i was that source ;D
 
This is personal opinion, so take it for what it's worth...

If you use a bolt on aluminum frame, you're going to have to drill through the swing arm and weld in bungs. This is a wild ass guess, but those bungs, combined with the aluminum frame and requisite bolts will weigh a fair amount. If you weld on the 6061 or 7000 series aluminum, it will also have to be reheat-treated--requiring a significant jig to stand the process. If it isn't heat treated, it will quickly become a wet noodle. In some cases, this is OK, but I (again personally) would hesitate to take that risk on a monoshock swing arm.

Instead, consider using 7/8" or even 1" 18ga 1020 DOM for the main structure. For the supports, you could go with an even lesser OD tube. I like DOM because it welds easy to the native mild steel swing arm. In the end, I bet the welded steel swing arm will weigh slightly less and be significanlt stronger than a bolt-on aluminum frame.

Just an opinion.

--Chris
 
chrisf said:
This is personal opinion, so take it for what it's worth...

If you use a bolt on aluminum frame, you're going to have to drill through the swing arm and weld in bungs. This is a wild ass guess, but those bungs, combined with the aluminum frame and requisite bolts will weigh a fair amount. If you weld on the 6061 or 7000 series aluminum, it will also have to be reheat-treated--requiring a significant jig to stand the process. If it isn't heat treated, it will quickly become a wet noodle. In some cases, this is OK, but I (again personally) would hesitate to take that risk on a monoshock swing arm.

Instead, consider using 7/8" or even 1" 18ga 1020 DOM for the main structure. For the supports, you could go with an even lesser OD tube. I like DOM because it welds easy to the native mild steel swing arm. In the end, I bet the welded steel swing arm will weigh slightly less and be significanlt stronger than a bolt-on aluminum frame.

Just an opinion.

--Chris
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Hi Chris, thanks for your input, it is appreciated. I was going to talk this over with a friend of my mine who is a race car builder to get his opinion on the situation as he is going to be the one doing the finish welding.
 
Thats a good idea. It is important to consider where to put the smaller diameter supports. They basically need to be placed right at the bending moment of the top structure. It seems like overkill to take this much time analyzing the swing arm, but the springs on monoshocks have a HUGE spring rate, which translates to huge load transfers.The nice thing is that the monoshock is likely a double-adjustable damper.

--Chris
 
chrisf said:
Thats a good idea. It is important to consider where to put the smaller diameter supports. They basically need to be placed right at the bending moment of the top structure. It seems like overkill to take this much time analyzing the swing arm, but the springs on monoshocks have a HUGE spring rate, which translates to huge load transfers.The nice thing is that the monoshock is likely a double-adjustable damper.

--Chris
Click to expand...

Yeah, I'm not going to run anything on this bike without being sure that its not going to fail and dump me on my ass. If I go down due to rider skill, thats one thing, but NOT because of my fab work.
I'm definitely getting a fully adjustable shock.
 
Well I got started on my braced swingarm. The shock I'm going to use I scored on Ebay for $7! Its a brand new take off from an 05 R1. This is a fun project so far.
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More progress on the racebike. I recently purchased a new benchtop mini-lathe and have been having a blast making parts. I was able to make the axle adapters/spacers to mount the 17" front rim in the original KZ forks. I finished the front 4-piston caliper adapters. Finally got the shock mounted where it seems to have the right geometry, that was a bitch. The R-6 rear caliper is finished, just have to weld the brake stay mount onto the swingarm and that is done. Next on the list to make is a fork brace. Thats gonna be a tough one.
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