V-Max Speed Wobble (ran it up to 115mph and...)

[Fire-medic]

Shuriken, take a look at a couple of KZ1000's from yesterday in my friend's shop.

Let's see if you're familiar with the basic model in green, shown here. As you can see, it has some extensive modifications. This is the customer's wife's bike. His is similar and has more chrome. Do you know the model this is based-upon?



During the work done by the shop, rebuilding the front forks: bushings, fork seals, fork oil, and rebuilding of the front brake calipers. That should help combat weeble-wobbles, eh?



Here is another customer's KZ1000, set-up as a street-trolling dragstrip terror. The bike is L-O-W! Note the sidewinder exhaust, definitely not made to corner aggressively!







The black bike in the back is a KZ1000-based dragster, which has turned well-below 7 seconds, and once held a world record for awhile, until another competitor at the same meet beat its time. A very-proficient female used to ride it, and showed the guys 'how it's done.' The story for one meet in FL, she made one pass, and the e.t. and speed were good, but well-above what it was capable of ('lower' being better). The pit crew changed the setup of the lock-up clutch, and sent her back out. She carried the front wheel aloft to the lights, and when she returned to the pits, there accumulated a crowd of admirers to see the bike and her. She told the bike owner and the pit crew, "next time you make changes like that, I'd appreciate knowing it before I stage and make the next pass!"
Same bike another diminutive (male) rider. This is not the quickest, fastest pass.


What do you suppose that cloud of vapor is, coming from the front of the bike, before it launches?

 

[Shuriken]

Shuriken, take a look at a couple of KZ1000's from yesterday in my friend's shop.

Let's see if you're familiar with the basic model in green, shown here. As you can see, it has some extensive modifications. This is the customer's wife's bike. His is similar and has more chrome. Do you know the model this is based-upon?

I'm definitely not an expert. Is that based upon the Z1-R?

 

[Fire-medic]

Yes

 

[Shuriken]

Have the 298mm rotors installed and a brace. Made a different choice regarding calipers so still waiting on parts so I can get those installed. This weekend is gonna be super busy for other stuff so it may not be until next weekend now before I can ride test. Trying also to carefully address a couple of small nicks on the larger fork tubes as well with a bit of epoxy so that has slowed me down, too.

The larger rotors are nice!

 

[Fire-medic]

Don't be surprised when your new nicked tubes chew-up your new seals in short order despite the patch attempt.

A couple sources for new replacement fork tubes:

• Forking by Frank, I've used them and am satisfied with the product
• Race Tech who has two different types, the titanium nitride forks being the better one
• OEM, of course, but when you see the price, you will be looking at the other two choices

 

[Shuriken]

Don't be surprised when your new nicked tubes chew-up your new seals in short order despite the patch attempt.

A couple sources for new replacement fork tubes:

• Forking by Frank, I've used them and am satisfied with the product
• Race Tech who has two different types, the titanium nitride forks being the better one
• OEM, of course, but when you see the price, you will be looking at the other two choices

Thanks. Yeah, so far, the epoxy repairs aren't working out the way I'd like but this is partially an experiment anyway. I'll see what Forking by Frank says.

 

[Fire-medic]

No way to economically repair nicks in the chrome. Labor is too-costly to make an effective repair. The chrome would need to be removed, the scratch/gouge re-worked to a smooth surface and re-plated.

Buy new.

 

[Shuriken]

I've seen various fork repair suggestions for filling small nicks / dings / pits in forks, including Super Glue, JB Weld, Marine-Tex, and solder. My first attempt some days ago involved first cleaning with brake cleaner, then dabbing (too much) JB Weld on, waiting until fully dry, and then attempting to sand down. This didn't work well for several obvious reasons. So I ditched that idea and used a razor blade to remove the epoxy to start over, but then that gave me a new idea....

I cleaned again like before, and this time, dabbed only tiny amounts into the affected areas using a small pick. I then used the razor blade as a scraper tool on the forks just after dabbing on the wet epoxy. Since the razor blade perfectly conforms to the fork tube profile, one can scrape wet epoxy off of the chrome surface; when the blade crosses over a valley, the epoxy gets deposited into the low spot, sort of like filling a pothole with asphalt. What remains is essentially a very thin (if any) film over the valleys and imperfections and sanding is reduced to simple polishing. In this fashion, one can easily scrape away the excess wet epoxy while leaving what remains in only the pits and dinged areas.

I should be able to polish later this evening and that should suffice as a temporary solution to allow for some ride testing of the larger forks. Hopefully the front brakes will be ready by then so I can ride test and report on Sunday.

 

[Shuriken]

93 forks are nice. And of course I love the various options for brakes, and that the crossover tube is gone.

The ride feels more secure to 75 but this did not cure the weave/wobble. It feels like the forks don't flex as much, which is great...a slight improvement. Braking gets an improvement vs the 85. Wobble/weave improved maybe 5% if any.

Ride testing was performed in an OEM condition with max air psi in the forks.

Observed static sag measurements for under 200lb rider:

0psi
3-13/16" sag leaving 5-3/4" travel

13psi
2" sag leaving 7-9/16" travel

20psi
1-1/2" sag leaving 8-1/8" travel

See the pic. 0psi in the forks means a cracked fender and doesn't seem to reduce the weave. Max psi gives plenty of travel and doesn't seem to reduce the weave, either.

As with other areas, I'm happy to have the newer front end for a variety of reasons, even though it did not cancel the weave.

 

[Shuriken]

New ME888 front tire didn't do much to fix the high speed weave but it is slightly better when crossing grooves, changing lanes, etc. It is just a tad more settled at high speed because it doesn't have the center groove. The bike is rideable-enough to 75 and is very pleasant below 65. It feels like 90-95 is the onset of the weave.

You can really notice the difference with the side view in terms of the tire designs. You can see why the Shinko is more performant in the turns just by looking at this comparison.

Now I will put the ME888 on the rear as well and test (one thing at a time). The Metzeler tires are orders of magnitude stiffer and heavier, including the sidewalls, for better or worse.

 

[Woody]

Shuriken, take a look at a couple of KZ1000's from yesterday in my friend's shop.

Let's see if you're familiar with the basic model in green, shown here. As you can see, it has some extensive modifications. This is the customer's wife's bike. His is similar and has more chrome. Do you know the model this is based-upon?

View attachment 95166

During the work done by the shop, rebuilding the front forks: bushings, fork seals, fork oil, and rebuilding of the front brake calipers. That should help combat weeble-wobbles, eh?

View attachment 95167

Here is another customer's KZ1000, set-up as a street-trolling dragstrip terror. The bike is L-O-W! Note the sidewinder exhaust, definitely not made to corner aggressively!

View attachment 95171

View attachment 95172

View attachment 95173

The black bike in the back is a KZ1000-based dragster, which has turned well-below 7 seconds, and once held a world record for awhile, until another competitor at the same meet beat its time. A very-proficient female used to ride it, and showed the guys 'how it's done.' The story for one meet in FL, she made one pass, and the e.t. and speed were good, but well-above what it was capable of ('lower' being better). The pit crew changed the setup of the lock-up clutch, and sent her back out. She carried the front wheel aloft to the lights, and when she returned to the pits, there accumulated a crowd of admirers to see the bike and her. She told the bike owner and the pit crew, "next time you make changes like that, I'd appreciate knowing it before I stage and make the next pass!"
Same bike another diminutive (male) rider. This is not the quickest, fastest pass.


What do you suppose that cloud of vapor is, coming from the front of the bike, before it launches?

Purging the nitros oxide.

 

[Fire-medic]

Yep.

 

[Shuriken]

Mounted an ME888 on the rear and have re-balanced both wheels. See pics for tire differences. It will be nice to move away from center grooves on the Shinkos... I just don't like them, but they sure corner and stick..

So the ME888 tires feel much more solid to me and are way better when crossing centerlines, road crests, and paint lines so far. They are heavier and have stiffer sidewalls and to me, just feel more appropriate for the weight of this bike.

And... there was a slight but noticeable improvement at speed today, which I expected. Some short jaunts to 95 were improved.

The Shinkos hook up and corner but aren't for me.

 

[Geoff Lewie]

A simple swap of the stock front springs to Progressive,problem solved.

Well to all VMAX owners. I have had 3 gen1 Maxes. I found the answer with my 2004 Max I bought new and amazed noone reported it in any club meet or writeup. GET RID OF THE 15 INCH REAR TIRE. The 15 inch tire was until recently only availble in a "RUBBER BIAS PLY TIRE". To go over 100MPH and not suffer the suicide warp you need a "RADIAL TIRE".

I sent my 2004 Max's rear wheel to Sandy Kofman(sp) and he machined a 17" rim on my hub. It was a beautiful wheel. I bought a set of Z rated Metzlers and hd them miunted and balanced. My Max was a richous 160 mpg beast, burying the speedometer without a single wobble!!!

I had a friend at the time (Moved from there) who did the same thing and he had bought progressive shocks too. Both our Max's were modified. His was more so and he was pushing to get in the 200 HP club. Mine was about 175 horses and a wheelie machine.

My present Max is the 25th Aniversity Model and has the15" wheel with a new 15" Shinko radial tire which I have tested up to 130. Short of finding someone to modify the wheel, Sandy retired, and spending a grand+ this tire is a quick fix.. and since I own other Bikes Making the MAX go 160mph is not a priority now. Been there done that and the tire size is the answer...

A simple swap of the stock front springs to Progressive,problem solved.

 

[Shuriken]

Well to all VMAX owners. I have had 3 gen1 Maxes. I found the answer with my 2004 Max I bought new and amazed noone reported it in any club meet or writeup. GET RID OF THE 15 INCH REAR TIRE. The 15 inch tire was until recently only availble in a "RUBBER BIAS PLY TIRE". To go over 100MPH and not suffer the suicide warp you need a "RADIAL TIRE".

Been there done that and the tire size is the answer...

Thanks for your response and for offering some renewed hope!

I'm not finished testing and your comment does indeed make me wonder... it would be awesome to be able to do a swap and test...

 

[Fire-medic]

Well to all VMAX owners. I have had 3 gen1 Maxes. I found the answer with my 2004 Max I bought new and amazed noone reported it in any club meet or writeup. GET RID OF THE 15 INCH REAR TIRE. The 15 inch tire was until recently only availble in a "RUBBER BIAS PLY TIRE". To go over 100MPH and not suffer the suicide warp you need a "RADIAL TIRE".

Post #251 of this thread mentions using radial tires.

I don't know of any radial tire for motorcycles which is a high-number profile such as our bikes have for a bias-ply tire, from the factory. Ours is a 90-series, bias ply. That means it's a much-taller tire than any radial motorcycle tire. 'Taller' means more top-end, assuming the bike has the HP to overcome aero drag. A significantly shorter rear tire, like a sportbike with a 50-series aspect ratio, is going to be a inch-plus shorter even with a larger wheel diameter, such as a 17" wheel.

On stock bikes, for purpose of comparison, a VMax running the OEM 15" 150/90 tire, is going to be capable of something in the region of the oft-quoted 149 mph top end, given optimal conditions and the space to get there. Of course, the weight of the rider and the aero profile means someone 130 lbs and 5'5" tall, able to 'get under the paint' will be turning a top-end more than someone 240 lbs. and 6' 3" who presents much-more aero drag.

Back to tire size, a much-shorter tire like a 17" sportbike tire will act as a final-drive gearing change. You'll have better acceleration, but your top end will be less. You will hit redline sooner, and at a slower speed. You can use one of the online charts to calculate just how-much shorter your 17" wheel/tire is.

Most of us aren't aiming for 149 mph on the street. I have repeatedly mentioned that in my opinion, the #1 best change you can make to a Gen. 1 is to switch to radial tires. The best way is to have wheels giving you the proper bead width and height for your proposed usage.

The fact is, on an otherwise stock bike that while a 17" rear tire with a lower-number tire aspect ratio will provide you with more speed in a shorter amount of time, an otherwise stock OEM Gen.1 will surpass it on top-end, given enough room to reach terminal velocity.




In the above comparison the 17" wheel/tire combo will be at maximum velocity of just-under 142 mph if you use the factory spec of 149 mph usually claimed, where the top end is lessened by -4.9%. Remember, otherwise stock bikes besides the rim/tire difference.

An interesting idea is to use an 18" wheel, then the difference in wheel/tire height is only 1%, or 0.27" (call the difference a blonde-hair). You might lose slightly on acceleration to the 17" wheel/tire bike, but your top end is nearly the same as OEM.

Another consideration is the sidewall height for cornering, the radial tire will have a shorter, stiffer sidewall, so it will provide a more-secure feeling on the curves. Assume that the tires are set to recommended psi for the tire, the bike, and the usage.

As I don't use my top-end, I'm happy to trade-off a few mph off the top end for better handling in the curves, and the 'gearing change' that a lesser-number tire aspect ratio provides for marginally-better acceleration.

I am not an engineer. I like to ride my bike where a few things can make changes in its operation which give me better handling and affect other parameters which I find personally rewarding for my bike use. Someone else's priorities may be much-different from mine.

 

[MaxMidnight]

The size of the tyre, a.k.a. rolling radius is only one part of the gearing which will influence potential top speed and/ or acceleration.
You also need to consider the ratio's within the gearbox and final drive regardless of it being chain or shaft.
Other factors will be the power output of the engine, the all up weight of the vehicle and amount of drag generated.

Whilst the discerning rider may notice some difference between OE wheel/ tyre combo's and 17" equivalent I suspect most of us won't (I didn't but that may be a reflection on me...). As the 17" combos are usually lighter than OE you should (might?) notice better acceleration and braking as there is less mass to spin up and stop. You may also notice better suspension control and steering for the same reason.

The biggest benefit though (depending on the choice of wheel) is that they will look so much better which in itself is worth an extra 20 m.p.h. on top speed and lean angle approaching those of Moto GP bikes (in your head).

 

[Shuriken]

So I just did 30 miles of short circuit riding back and forth to try to get a good seat of the pants feel on the new tires. The ME888 tires are better for the open road riding that I like to do. However, 95 is the current limit.

That's ok for now, as 75 is now more comfortable. But this old 85 engine runs real nice and it sure would be nice to get it more confident at the ton....

Anyway, I swapped back to old OEM shocks, tried different damping numbers and even set them non-uniformly, tried different riding positions, grip strength, etc. Think of it as a dozen rides over the same circuit. I even tried reaching 95 in 4th gear vs 5th to test vibration at different RPM. Gear selection made no difference.

Pushing forward on the bars settles down the front end enough to push through to 100 or more, and while that remains constant, it's not a viable solution, it's just a clue.

So thinking more about what it feels like riding 2-up, yes, the suspension is loaded more and the sag is a little different. But how this translates to "feel" is most noticeable at the handlebars and front end. It feels planted, heavier, and does not continue to oscillate given quicker steering inputs. In short, it feels solid and safe!

But...here's what I found today that surprised me. I had a passenger sit on the bike with me with the idea that I would measure sag with a 2-up load on just OEM forks, springs, and rear suspension. What I observed was that the front fork sag remained about the same and only the rear sag changed. I did not expect this; I expected both front and rear to sag about the same.

So I did the zip tie trick on the rear OEM shocks. With me sitting on the bike, I have approximately 1" of rear suspension sag. With a passenger, it's approximately 1.5-1.75". With me alone and the front forks at about 20psi, I have about 1.5" of front suspension sag. With a passenger, it remains approximately 1.5-1.75".

So now it's time to interpret how this translates to a more solid feel on the front end and at speed. I'm open to ideas about this, but it seems that the passenger weight is centered more over the rear axle than even center or front. Thus, the steering geometry may be changing enough, along with a little added weight on the steering head, that the high speed instability vanishes.

Keep in mind the speed tests I did in which I slid backwards to the rear seat while riding and found some improvement. Others have reported the same.

At least at the moment, extra weight on the rear is the stabilizer of the whole thing.

Again... the front suspension didn't sag significantly with the weight, so I'm open to ideas, such as going from 13" rear suspension to maybe 11 or 12.

Progressive rears damp really well. The lighter springs are comfortable for me, but aren't suitable for 2 up riding. The standard springs work great for 2 up riding but hurt my back riding solo. Neither the OEM shocks nor the 412s cancel out the weave on their own, regardless of settings, so the benefits of the 412s get offset by their high cost and the compromise of having to swap them for 1 or 2 up riding. At the moment, I've removed them and have been riding on the OEM shocks.

I also was able to notice some differences among OEM settings. I guess I'm too light to have noticed before but with a passenger and I on the bike, if I set both rears to position 4 and bounce them, I cannot hear the distinct rebound vacuum sound. If I set them to 3 and below and repeat the test, I hear the rebound damping. Maybe someone can clarify... is this damping rate? So a 4 means more/slower damping and 1 means less/faster damping?

It may just be either drop the rear end or add more weight. Nothing else has shown as much noticeable difference.

At this point, I have an awesome, unique bike. Super powerful, upgraded brakes, new tires and balanced wheels, new bearings and lube everywhere, and 43mm front forks. It's safe to 75mph and perfectly usable for casual riding. It's been a fun process, and who doesn't love garage time?

 

[MaxMidnight]

By dropping the rear of the bike you will be increasing the steering head rake angle which increases the trail thus getting more castor effect.
The greater the rake angle the more stable the bike will feel but will require more rider input to steer the bike.
The principle behind this is explained at the bottom of this article.

I assume that the forks are mounted with the top of the stanchions level with the top of the yokes?

 

[Shuriken]

By dropping the rear of the bike you will be increasing the steering head rake angle which increases the trail thus getting more castor effect.
The greater the rake angle the more stable the bike will feel but will require more rider input to steer the bike.
The principle behind this is explained at the bottom of this article.

I assume that the forks are mounted with the top of the stanchions level with the top of the yokes?

Thanks, that's a great explanation.

Yes, on these 43mm forks, I've mounted them level.

I also forgot to mention (because I forgot the OEM shocks even had a preload setting, and because I haven't touched it in ages) that my testing of the OEM shocks has been performed with them at preload setting 1.