Limited by the Frame?

[loudnlow7484]

This question is more or less directed at those that have done serious suspension upgrades, and really use them......

At what point does the frame become the limiting factor on a katana? What I mean is, I guess, how stiff is a katana frame as compared to a modern aluminum SS bike? I know you can fit a set of inverted forks, and you can mount sticky tires, and you can upgrade the rear shock..... but after all that, is frame flex an issue? Can you notice it under really extreme cornering?

[The CyberPoet]

I'm not sure if you're approaching the question correctly.

The limit in the frame isn't so much the steel box around the engine (which is a fairly well proven design used in many generations of bikes and which does flex quite appropriately), but the long wheelbase of the bike as a whole and the steering geometry are the limiting frame-based factors on fast-handling once you've sorted the tires & suspension.

The Kat is a very long wheel-based bike with a non-radical steering head angle. This gives it good road-manners in the "real world" (esp. typical county highway routes), where it will decrease induced oscillations (i.e. - if you induce headshake, the headshake reduces each repetition rather than wanting to amplify) and gives it a tendency to require less input to maintain a fairly straight course even over bad road surfaces. BUT the penalty for a long wheelbase and the steering angle is that it simply can not inscribe the same circle as an SS bike that's 1/3rd shorter in wheelbase length -- and which has to use a steering damper to compensate for a much less stable (but more flickable) steering angle.

On the track at super-high-speeds, this kind of thing is a major limiting factor, especially coming into hard switch-back turns and chicanes, and is part of the reason that this kind/size of frame isn't used by any of the SS bikes any more (because they are track-targeted).

Back in the real world, most street riders' issues with cornering have nothing to do with the frame as a whole, but have to do with forward-rearward weight shifting getting on and coming off the brakes, and how fast the bike resettles to "stable", plus the same basic effect as the rider shifts his weight around to maximize the center-of-gravity potential in turns. The stock suspension on the Kat is designed for a pleasant, almost leisurely ride in that sense, sucking up road imperfections very readily, but resulting in a lot of pitching (and some yawing) as braking/acceleration/body-shifting occurs. The right suspension upgrades for better handling will remove that tendency to pitch and minimize the return-to-stability time.

Having run the Ohlins suspension all around, I know how the upgrades can make a radical difference in return-to-stability time and massively reduced brake dive (I get about 1 - 1.25" dive at the point where the rear tire wants to lift off, rather than traveling halfway or more through the stock forks' range, with what seems like only a single movement back to stability instead of an oscillation series to get there). That fast snap-back to stability means I can be hard on the brakes much later into a turn and shifting my body at the same time without being concerned about inducing instability oscillations during the actual turn itself -- I pick my line and can put myself into position where other Kat riders are already off the brakes and dedicated to their line waiting for their suspensions to settle.

But the heavy bike (100 lb. penalty) and lazier-than-SS steering means I need to put in more physical effort to get to my line (esp. on a fast reverse chicane), and the long wheelbase means that I can't do a tight 90 degree sweeper knee-down at 90 mph that a modern GSXR or CBR can with their shorter wheelbases (I'll be 70 to 75 through the tight apex to their 85 or 90 through the same apex). Given my age and riding temperament, that's fine by me...
As the curves straighten out and get wider though (think Cherohala Skyway instead of the Dragon), the added stability of the upgraded suspension eliminates any handling benefits compared to the majority of the SS bikes, and their only superiority is the potential ground clearance at full lean and their power/weight differences as a whole.

Hope that helps...

PS - IMHO, don't swap forks -- change fork springs.

Cheers,
=-= The CyberPoet

[loudnlow7484]

Thank you, truly, for that very detailed answer. A couple of notes.....

I'm not planning to swap forks. I like the idea, although I don't know if I would notice any less flex in the forks. But being fully adjustable would be nice. I really just plan on a spring upgrade, and hope I can sort the front end out.

After I'm done with this never-ending project.... I will likely start another one. The idea had crossed my mind that maybe I would focus on handling in the next one, as opposed to outright power. So obviously starting with a 600 would be a must, for it's shorter wheelbase. But I was unsure whether or not the frame would need to be braced up if it was riding on some pretty stiff hardware. I'm aware of the steering head angle issues, but I'm also aware of issues with too steep a steering angle (search "tankslapper" on youtube... ). So, if you were going to try to make the ultimate-handling Katana, what would you suggest? Would you try cutting and rewelding the steering head to sharpen it up? Or would that be too difficult to get straight, or compromise the strength of the frame? Remember, this is all hypothetical, I'm a s***ty welder, so I won't be trying it myself anyway.

It's just a thought, and I'd like your input, as well as the input of all the well-versed bike-building folk we've got on here.

As sort of a side note....... did you ever hear anything more about the stock for that Australian company?
Speaking of investing, I had a thought........ we've got a lot of really bright people on here, from many different industries, from all over the country, and all over the world. It seems to me that if the intelligent people from Katriders worked together, we could probably come up with a pretty successful fund if we wanted to. It would take a f**k ton of organizing... probably more than it's worth. But it's an idea that's been floating around in my head for a while. I don't know if maybe we have some real Series 7er on here somewhere, because I'm certainly no expert on this (I'm studying for the series 7 and 63, but it's still pretty confusing at this point).

Wow, did I just jack my OWN thread?

[The CyberPoet]

Thank you, truly, for that very detailed answer. A couple of notes.....

I'm not planning to swap forks. I like the idea, although I don't know if I would notice any less flex in the forks. But being fully adjustable would be nice. I really just plan on a spring upgrade, and hope I can sort the front end out.

I haven't had any fork-flex issues that I've noticed, and I push pretty damn hard. But I do Always have good fork hardware installed (e.g. - the bike I just got is slated to go in for a fork R&R with Ohlins springs, new OEM internals and new tubes -- new tubes because the old ones have some minor rust pitting at the very top of the stroke I'm not willing to live with).

After I'm done with this never-ending project.... I will likely start another one. The idea had crossed my mind that maybe I would focus on handling in the next one, as opposed to outright power. So obviously starting with a 600 would be a must, for it's shorter wheelbase. But I was unsure whether or not the frame would need to be braced up if it was riding on some pretty stiff hardware.

The frame's need for bracing is dictated primarily by the amount of power being put down (pushing forward/up into the frame under acceleration); with the stock or near-stock power levels, no frame mods are needed, at least on the 98+ model frames.
For a Bandit 1200 engine on the other hand, the real problem would be putting the power to the ground, and for that, a wider/stronger swingarm and wider wheel would be appropriate to permit you to put more rubber to the road.

Personally, I wouldn't even begin to consider a serious frame-mod on a 90+ Kat (the early 81-87 models is a different story). If you're building a bike for handling, either start with a different frame & engine combo (something inherently engineered for a shorter wheelbase), or fab up your own trellis design copying the best the big-boys offer (use Aprilia, Ducati, etc. as a rough guide as to where to trellis in general).

I'm aware of the steering head angle issues, but I'm also aware of issues with too steep a steering angle (search "tankslapper" on youtube... ). So, if you were going to try to make the ultimate-handling Katana, what would you suggest? Would you try cutting and rewelding the steering head to sharpen it up? Or would that be too difficult to get straight, or compromise the strength of the frame? Remember, this is all hypothetical, I'm a s***ty welder, so I won't be trying it myself anyway.

1. I wouldn't alter the steering angle via cutting/welding; if I want that much of a change, I'm going to start with a different bike.
2. Raise the rear an inch or inch-and-a-half (dogbones) without raising the front. This will effectively speed-up the handling by altering the effective angle of the steering. I do sell the appropriate dogbones for this (custom OEM batch from Suzuki).
3. Get the best tires you can for the purpose, since tires make the biggest difference to handling of any upgrade. If you can run the tires hot and keep them that way (i.e. - your riding is specifically knee-down canyon carving all the time), get some Metzeler M3's or Pirelli Diablo Corsa's, otherwise stick to the Z6's or the Stradas -- running road-legal virtual race-tires does you no good until you can keep them in their idealized operating temp range.
4. Rear shock by Ohlin or Hagon with full adjustability; front fork spring upgrade by Ohlin or RaceTech. I'm not convinced the cartridge emulators are worth all that much, but the spring-changes make a huge difference.
5. Brake upgrades - HH pads, teflon-covered-by-SS lines, high temp brake fluids.

Now if you really want to go above-and-beyond, look at ways of specifically reducing the rotational momentum of the wheels -- very lightweight forged aluminum or preferably magnesium wheels specifically would be my specific recommendation (as verses to carbon fiber which doesn't tend to fare to well in the real-world over time).

As sort of a side note....... did you ever hear anything more about the stock for that Australian company?

Got the broker's name & phone number:
Contact our broker Pritchard & Partners Pty
Ltd on +61 2 4920 2877 for more information.

Wow, did I just jack my OWN thread?

Yes, you did.

Cheers,
=-= The CyberPoet

[ericej2344]

How much for the dogbones. Found nothing on Ebay.