Power vs. Speed

[Hillclimb#42]

 I have often been tempted with this concept, and try not to blurt out my ideals (opinion) on anyone else's thread, but am interested in your opinions, especially the ones based on facts about this. In hillclimbing, and I assume drag racing, along with many other forms of racing, the rear tire is spinning the whole race. No spin, or not enough wheel spin, will hook-up and wheelie which results in the on/off throttle, or crash, and you ultimately lose against anyone who didn't crash.                UNDERPOWERED or OVERGEARED

Flip side of this is too much wheel spin and your bike never accelerates, and the back end won't stay behind you.
            UNDERGEARED and NO TRACTION

Many factors are involved such as soil density, moisture content, and soil composition. The tire tread pattern, condition and air pressure, Gearing Choice, Power Supply, Suspension and Riding Technique are all factors really.

Power is basically Potential Speed in my opinion. Getting it to the ground is another art, also IMO, as with this whole thread, I guess. Far from an expert here. Presently, I have a basic set-up and will alter tire pressure 3-5 lb.s either direction, or switch 2 teeth either way on the rear sprocket, shorten or lengthen rear axle adjustment.

A little less air pressure and it will hook-up a little better, more pressure, it will spin a touch easier.

Longer suspension will help keep the front wheel down and help give a little wheel spin, shorter then would help give some traction to the ground ( I never try to shorten up a stock length bike)

2 teeth less on the rear and the bike is noticeably hooking up better, 2 more teeth and you will come out of any load sensitive bog and/or wheelie. (1 tooth bigger on the front is close to changing to three less on the back sprocket and vice versa, and is even more noticeable change than two teeth on the rear)

Suspension adjustments are aimed at keeping the rear tire putting power to the ground. Bumpy terrain needs a faster suspension and a big jump might need to be stiffer and slow to rebound. Suspension is an adjustment that I really need advice on. I usually leave it alone because of my ignorance of input and response with the adjustments to conditions, especially how it relates to the short hills that I race. The write-up by Paul, the former Administrator, about Race Sag and Static Sag really helped get the spring right and that made me alot faster. Thanks for that Paul.

[don46]

Kyle,

On my 4t I gear so that I'm almost or in some cases may hit the rev limiter, of course you have to know your power curve with the mods you have, some bikes fall flat on their face once you hit a certain rpm, in other words understand where peak hp/torque are generated and gear for it. On the 2t again the mods you have may dictate where you want to run, as an example my 500 on gas will pull 15 counter and anywhere from a 47 to 51 depending on the hill, and if I ever get the 250 ignition tamed a bit maybe taller. on a stock length bike try to run as far back in the slots as you can, and if your still having issues with the front end coming up, pull the fork tubes up in the triple clamps 10-15mm, that will help keep the front end down. I also like to run a wide rim, you can go all the way to 3.5" that will flatten out the footprint giving you more traction, doesn't corner well but hauls in a straight line.

Hillclimbing is about momentum,once you lose it your ride is essentially over.

good luck

[kaw rider]

Kyle
You what about 15% wheelspin and 25% overgeared.

[Hillclimb#42]

Very good suggestions, Don. I have seen the forks raised in the clamps a few times. Does that help a stretched bike also? I have seen the fat rims, (think I saw a 4" on a CR500)and the 18's with monster tread like the Terraflex on it. That's kinda THE hillclimb upgrade. I may get a fat rim eventually, just not ready, yet. When you say "depending on your mods" you still refer to me knowing where the bike pulls the best, right? Generally, tall enough to keep a load on the motor the entire climb, right?
  Do you have a source for figuring spring rates with the bike extended? Will race sag and static sag settings be measured to stock axle location? I have heard of revalves, spacers, heavier oil. Is there any reason the stock shock wouldn't work with a stiffer spring for 6-8" stretchers?
  Kaw Rider, not sure what that means, other than you are almost twice as concerned about being geared tall enough over having some wheel spin.

Thanks for your input guys. Working on some set-up plans, and need to be ready for adjustments.

[don46]

Many climbs dictate what the Max length you can run, so if you have issues keeping the front end down you need to figure out how to accomplish this, the easiest is pulling the forks up in the triples. I run 3.5" rims, not sure I could fit a 4" in the swingarm, a 2.5 will help more than you can imagine if traction is an issue.  I've been doing this long enough that I have a pretty good idea on what spring I need to run and have a fairly good selection to choose from. Revalves can be a great thing, the key is to find a suspension tuner that understand hillclimbing, typically you will run a stiffer spring and a little more compression and alot of rebound. You could go stiffer oil but I wouldn't go to stiff like 7.5 wt or maybe and thats a big maybe 10wt, there are some guys around here that are running 20 wt, but then you can see the results speak for themselves. I still set my race and static sag at the same position as if the bike were stock and look for the same numbers roughly 100mm race and 25-30mm static.

[kwakman]

im not particularly up on suspension stuff but remember if you have a lengthened swinger,it acts as a longer lever so shock spring imo would need beefing up a bit.

[cbxracer30]

You can put 4.25x18 sun rim on a K5 with no mods at all just shorter spokes , you can run the 5x18 excel on the K5 with an extended swingarm with a few mods, its what I run on the drag K5. You need to cut off an old spocket to use as a spacer to bring your spocket out for clearance from the side of the tire this will require yamaha sprocket bolts. then you need to mod the wheel spacers to move the rim to offset the rim to the brake side a quarter of an inch. the 5 inch rims put a whole lot of tire on the ground. the terra-flex is a little heavier tire if your interested in trying one I have 2 that are like new , they didn't work for drag racing my brother found out .CBX

[kaw rider]

Kyle
Also remember swingarm arm angle will affect the torque the motor has on tire. Just think about the angle you have going up the hill on the swingarm.   

[don46]

You can put 4.25x18 sun rim on a K5 with no mods at all just shorter spokes , you can run the 5x18 excel on the K5 with an extended swingarm with a few mods, its what I run on the drag K5. You need to cut off an old spocket to use as a spacer to bring your spocket out for clearance from the side of the tire this will require yamaha sprocket bolts. then you need to mod the wheel spacers to move the rim to offset the rim to the brake side a quarter of an inch. the 5 inch rims put a whole lot of tire on the ground. the terra-flex is a little heavier tire if your interested in trying one I have 2 that are like new , they didn't work for drag racing my brother found out .CBX

Yeah, maybe if your swing arm is wider than stock, All my swing arms are the same width as the stock swingarm, meaning there is no way you could add a sprocket width and clear, but I will keep that in mind if I ever want to go with a wider wheel. I use 530 chain on my bigger bikes, those that would use the widest wheel.

There is a balance between the traction and length, you can go more aggressive on the tire, and will have to go longer to keep a balance on the front end, shorter and a less aggressive tire will accomplish the same thing as a aggressive tire and length, the key is to know where that balance is. it does change from hill to hill and from morning to afternoon, you just gotta keep up with the hill.

[Hillclimb#42]

Kaw Rider, thinking about the angle of my swingarm to the ground? You think its better to be parralel to the ground or to always stay above parralel. I would think swingarm getting flat would take away from force applied to the ground, but think the sag settings set all of that up. Am I missing something there?
  I saw plenty of Terra flex tires on Hillclimbers. They are usually on big bikes. I don't think they work as well on 500's as a typical nobb. Its a very aggressive tread pattern and very heavy. It was too much traction for my buddies 750 triple, so I definately don't need that on my 500. Thanks for the offer, Cbx.
  I found out that the longest I can be, Don. The axle has to be inside of the tip of rear fender. I'm able to get out even with the rear '93 Fender mod with this new set-up for the 600cc Class. Looks like I'll be racin the fastest guys and the conditions of the hill. With Stewart Power and the new Stretchers getting set-up, I am graduating to the Insane Racing. Most Fast Times of the Day come from the 600cc Class. Alot of guys thought I was nuts Hillclimbing a stock length 500, wait till they see me on this Green Rocket.

If you noticed my brake line stretched out, I am going to get a green Brake line and install the chain today. I hope that the racing season goes as smooth as the build went for this bike. No stressin' when you do your homework. Thanks for all of the help guys, direct and indirect advice as well.   

[stewart]

bike looks real nice

[jfabmotorsports.com]

bike looks real nice

Yes,very cool. 

[kwakman]

looking good.how did you find the platinum pipe with fmf silencer when engine was stock?thats the combo im using next.did it make good top end power? decent overrev? thanks, k.

[Hillclimb#42]

Thanks guys.
kwakman, I started with a stock pipe and silencer, but eventually flipped the bike and destroyed the silencer, fender and sub-frame. Picked up the Platinum pipe after reading here on kx riders how well it performed. The FMF silencer was just a simple decision. I didn't like the pc silencer's looks or sound. I felt a noticable increase in power with the new exhaust, and it sounded healthy like I wanted. As far as overrev, I don't think I can give a good report. My 500 seemed to rev about 3/4 as much as my 250, so I had to gear it to be fast. This being my first 500, and every upgrade adding a little power, I really have no base reference. I had a crank issue that probably kept the motor from revving high, which has since been resolved, during the rebuild.
  Pro Circuit, V force Reeds, Wiseco, ...ect., everything Stewart has stated as being strong reliable performance upgrades has been just that.

[Goat]

Bike looks excellent. I agree with you on the pc vs fmf. I have a pc spark arrestor on one 500 and fmf turbine core on the other 500. I can't confirm performance exactly because of the different engines. Ones an 87 and the other is a 93. I am going to try swapping silencers and see which works better on what bike. I like the sound of fmf though. I'm looking forward to some hill climb videos Hint Hint Don't have much for climbing around here unless I go way north. Keep up the good work. Good luck in racing.