Noticed something interesting.

[Savage]

When I would get on (heavy throttle) my 200 and kick out the back tire it would kick out and keep going out. When I get on my 450 and kick out the back tire it doesn't stay out very long. It's like the bike wants to "right" itself. Am I crazy or what's the deal with the larger engine? Just curious...

[will_kc]

The Gyroscopic effect of the engine's rotational mass (crankshaft, flywheel, etc.) against the slide angle of the bike causes the motorcycle to correct itself. The slide angle of the rear tire moving near of the point of support (front tire) places torque on the gyroscope, which of course resists the torque. IMHO ...

[Savage]

Sounds good to me. It felt like a gyro effect bringing me back up.

[safiri]

When I would get on (heavy throttle) my 200 and kick out the back tire it would kick out and keep going out. When I get on my 450 and kick out the back tire it doesn't stay out very long. It's like the bike wants to "right" itself. Am I crazy or what's the deal with the larger engine? Just curious...

The gyroscopic effect won't bring you back up, it will resist a change in the orientation of the rotational axis (of the motor, and more importantly the tire). But once that axis orientation is changed, that is the new "stable" orientation. So what has been said is ~correct, but I wonder if ...

1. Do you have the same tires on both bikes? Are the outer nobbs in the same condition?

2. What is the weight difference between the bikes? The 450 is probably much heavier and thus plants the back tire better.

3. I assume the 200 is a 2-stroke and the 450 a 4-stroke. Why that matters is the 2-stroke motor supplies a burst of power and slips the tire every crank revolution, whereas the 4-stroke supplies a burst of power every other crank revolution. I rememember years ago in Moab looking down at the tracks of Hayden in the sand and noticing the knobby pattern got blurred every foot or so ... that was the piston firing and breaking the rear wheel loose. In between those bursts is where the tire locks up with the dirt and provides the best traction. Static (non sliding) friction is always greater than kinetic (sliding, slipping) friction. A tire rolling on the road is actually static WRT the road if it isn't slipping.

4. Throw in too the differences in engine braking btw a 2 and 4, assuming you let off the throttle when the bike goes sideways. The 4 probably supplies more engine braking, so the rear wheel slows down, the side nobbs catch, the rear end slows down and gets pulled back in line with the motion of the bike (hopefully straight where you want to go).

[Savage]

I'm just thinking about holding a bicycle tire and spinning it how it doesn't like to change... I'm going to dig any deeper than that.

But to answer a few of your questions, my 200 is/was a 4 stroke, it weighed almost as much as my drz (lots of steel parts) and it had a newer and knobbier rear tire (trakmaster II).
Seems to me like the much more powerful engine wants to stand back up much faster when on the throttle.

[safiri]

my 200 is/was a 4 stroke, it weighed almost as much as my drz (lots of steel parts) and it had a newer and knobbier rear tire (trakmaster II).
Seems to me like the much more powerful engine wants to stand back up much faster when on the throttle.

Interesting. Got me thinking ...

[will_kc]

Hey savage! When playing with the spinning bicycle wheel, try turning it 90 degrees real fast. Betcha it won't stay in your hands..... Now try turning three wheels at varying degrees at the same time..... wowzzzaaa !

I did a little reading and the point of "precession" was left out of our discussion..... http://en.wikipedia.org/wiki/Precession

I agree with Safari on the gazillion of factors in the equation, but your on to it. Aren't we all just a gimble sitting on top of three gyros (two wheels and an engine) ?

OK, Safari, you can slap me now.....

[safiri]

Hey savage! When playing with the spinning bicycle wheel, try turning it 90 degrees real fast. Betcha it won't stay in your hands..... Now try turning three wheels at varying degrees at the same time..... wowzzzaaa !

I did a little reading and the point of "precession" was left out of our discussion..... http://en.wikipedia.org/wiki/Precession

I agree with Safari on the gazillion of factors in the equation, but your on to it. Aren't we all just a gimble sitting on top of three gyros (two wheels and an engine) ?

OK, Safari, you can slap me now.....

That is a good wiki article. No slap for excellent research!

At school I have ~bicycle tire~ with an axle that can be held on both sides of the spinning tire. The tire is actually solid rubber and heavy, so the rotational inertia is pretty large. I also have a swivel stool that is low friction. Now I am trying to remember ... Sitting on the stool, holding both sides of the axle with the wheel spinning, when I ~turn~ the wheel to the left (as if the rear MC wheel got kicked out to the right), my body and the stool seat rotate clockwise (so as to try to keep the axis of rotation the same, but IIRC the wheel also gets crooked in that the top doesn't kick out as much as the bottom.

On a MC or a bicycle, this would cause the bike to lean toward where it came from and would cause the side of the tire to be the contact patch. Those knobs are typically a lot fresher than the ones down the middle.

And with all this written, and my brain spinning (like a top), I am going to bed.

[will_kc]

I do believe it's time for a science experiment.

Needed parts :

100 ping-pong balls,
Super Glue,
High speed camera,
Troy and his new toy

We can glue the ping-pong balls to Troy. Set up the high speed camera and film Troy sliding around on his new bike. If we're lucky we can see the gyro effects just before he launches !!

[troy]

100 ping-pong balls,
Super Glue,
High speed camera,
Troy and his new toy

I WANT NO PART IN THIS! Dude, hold my beer--watch this!

[KC]

I do believe it's time for a science experiment.

Needed parts :

100 ping-pong balls,
Super Glue,
High speed camera,
Troy and his new toy

We can glue the ping-pong balls to Troy. Set up the high speed camera and film Troy sliding around on his new bike. If we're lucky we can see the gyro effects just before he launches !!

David H will do it He gets his bike up to 60mph, stands up on the seat and does the Macarena just to check his tire pressure See his post in "Newb with a DRZ" topic for clarification.

[MacWildcat]

Had a similar effect happen for me once. I bought a cheapo tire for a trip. When I would spin the rear tire the back end (bike's not mine!)would kick out about 4-6 inches always to the right. Checked alignment, didn't find anything wrong. When I changed back to a better tire - no problems. I figured somehow the carcass wasn't centered - some sort of tire flaw.

Uncle Dave's Macarena was also done while he was in a 80 degree wheelie, jumping a 16 inch ditch - he's the Man!

[Savage]

MacWildcat can you please swing by my house and check out my bike. I'd like your opinion on it since you basicly have the same bike. Too rich, too lean, etc.
Please email me at kansas_state@cox.net