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Mid 70's streetbike suspension

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Thought I'd try to pick the brains in this forum.

I own a 75 Z1 900 basically all stock, finished restoring it last August. The suspension on this bike is horrible, alot of people perform suspension swaps from newer bikes (ZX, GSX-R), but I'd like to try to improve the stock components. I saw Race Tech make a Cartridge Emulator, I'd just like to see what other options (if any) I have. Maybe even swap internals from another fork?

Main problems with the suspension are the forks are too soft and dive under braking. You get a nice jolt on small, high speed stuff like an old expansion gap in the road. The rear shocks are sealed and basically just keep the ass end of the bike up. There's no dampening what-so-ever for the shocks. I know for the shocks I will probobly have to replace those.

High speed cornering, 45+mph, the bike weaves. I also had an experience once on a straight away doing approx 85mph, the bike weaved side to side like the ass end wanted to go faster than the front. Not a harsh weave, just a gentile swerve but large enough to let off the gas. The steering bearings and swingarm bearings are new/perfect condition with no play. Wheels are straight and tires are new. So I'm hoping that upgrading these parts will make the bike more rideable without sacrificing the original look of the bike. :smirk:

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Oh man...I can tell you a lot about your series of Z1/KZ bikes. I'm hardly the premier expert on these bikes, but I did have several models from '73-'79. The biggest handling problem with these bikes was the frame. It was a freakin' noodle. While the shocks and fork were horrible in light of real suspension damping, the frame was always the lousy foundation. You have to stiffen that frame if you want any type of handling improvement...at least if you're going to push the bike a bit.

I ended up getting the specs from Kawasaki on how to brace the frame with homemade stiffening tubes in key spots that was part of their superbike racing program...back in the day when they actually raced theses bikes. I stripped the frame and cut and shaped numerous stiffening tubes and had a friend weld them into the key points. I then found a motor mount plate kit used for superbike racing that had super thick mounting plates and larger mounting bolts that required drilling to install. I then found a Dresda box-section swingarm with tapered bearings. After all that the frame was at least decent for aggressive street riding with the tires now being somewhat marginal back in the day.

On the fork, I used an aftermarket brace and a modded damper rod kit from some exotic outfit back in the day that I can't even remember who it was. I had Works Performance make me a set of shocks for the bike. Ultimately I spent a lot of time and money to try and make a purse out of a sow's ear, but it was fun and very rewarding. Nowdays when you look at what you can buy right off the floor, it almost makes me cry...LOL!

Still, I think the spindly chassis will always be your weak link here, and in fact I think installing higher quality, beefy suspension will only aggravate this issue. You can improve the ride, but this bike will always weave and wiggle without serious frame stiffening.

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Thanks. I know about the "noodle" chassis, haha, but except for 1/2 dozen parts this bike is all original. I just can't modify it to the point of no return. I used to have a ZX6R and know there's no comparison. Just looking to improve the rideability, and to some point- safety of the bike. The bike is definately not in balance suspension wise with the engine performance.

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The biggest handling problem with these bikes was the frame. It was a freakin' noodle. While the shocks and fork were horrible in light of real suspension damping, the frame was always the lousy foundation.
Kawasaki in particular, and Japanese road bikes of that period in general, had that problem in spades back then. At least the Z1 was a big, smooth 4 stroke.

I built a pair of complete frames for a guy who was road racing an H1 and H2 (500 and 750cc 2T triples) with aftermarket suspensions based on the full double backbone and cradle concept of the Norton Featherbed and Rickman designs, similar to modern twin spar frames. He was one of my happiest customers ever.

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Kawasaki in particular, and Japanese road bikes of that period in general, had that problem in spades back then. At least the Z1 was a big, smooth 4 stroke.

I built a pair of complete frames for a guy who was road racing an H1 and H2 (500 and 750cc 2T triples) with aftermarket suspensions based on the full double backbone and cradle concept of the Norton Featherbed and Rickman designs, similar to modern twin spar frames. He was one of my happiest customers ever.

LOL!...wouldn't you know that I also had a '72 and later a '74 H2 during that era. I never went to any great lengths to improve handling on the H2's like I did with the Z1 series. The motor in the H2 was fun, but it was a beast. The Z1/KZ engines were also beasts, but they were also smooth and mellow. That was a fun era to be a motorcyclist despite the lousy handling...LOL! I remember a couple of articles in Cycle during that period where Z1 motors were installed in trick, aftermarket frames. Yes, I lusted in my heart...LOL!

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