KX Riders
Maintenance & Technical => KX500 Original => Topic started by: tharden on May 09, 2009, 08:22:32 AM
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I have got to say I did not think this was going to happen. I thought I had my 500 tuned to make pretty good power, but my cousin just ran by me on a 07 yz250. He said his bike only has a pipe,wisco piston, and carb jetted. This is what my bike has gnarly pipe, k&n airfilter, and I leaned out the carb one point on the main jet. I just do not get it. The 500 seems to be running great, very smooth and powerful, but I guess not as powerful as I thought. I just do not know if my tire is spinning too much or what. I just put a new Kenda 771 on it. It seems where ever I go I leave a trench. One thing though, I think I am going to switch back to the stock filter. It seems to be better than the K&N.
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thats a sad story ,but to be realistic :roll:
an aged pretty stock k5 delivers about 58 HP
a modded fresh 250 goes up to 50 HP or more
take the riders weight and skills ,there you go
it can be true in other words i think :|
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I weigh about 30 pounds more than he does, but I do not think 30 pounds would make that much difference. As for the engine, it does have 162 psi which I think is pretty much where it should be stock.
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everything in good order ? kips working correct ?
muffler repacked ?
if so ,i can only suggest the magic hand of mr k5 stewart
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gearing is very important to go fast.
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gearing is very important to go fast.
yea definitely ,forgot to mention ,my dirtbike runs 15 /48 which i like for pull and topspeed
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I just picked up a KX5 today, and have to say that it accelerates a lot harder than my 07 CR250 or my tired CR500, so something is definitely wrong with yours.
...and YZ250's won't walk on either of the CR's.
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thats sad... somethings way off..
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could it be the gnarly pipe? my 2003 k5 seems like the power just flattens out on top. it has a gnarly pipe, stock silencer and stock gearing. it'll pull a wheelie in 1-4 and has plenty of compression (just been replated and new piston) i havent dragged raced any of my friends bikes, ive only opened it up by myself on country roads but it doesnt seem to be very fast on the top end. maybe 80 mph. so im guessing a gnarly kills top end??
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Throw alot of gear at the gnarly and she will be happy.
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could it be the gnarly pipe? my 2003 k5 seems like the power just flattens out on top. it has a gnarly pipe, stock silencer and stock gearing. it'll pull a wheelie in 1-4 and has plenty of compression (just been replated and new piston) i havent dragged raced any of my friends bikes, ive only opened it up by myself on country roads but it doesnt seem to be very fast on the top end. maybe 80 mph. so im guessing a gnarly kills top end??
like kawrider says ,what gearing you,r running ,
my circuit sm does rip my arms off ,and close to max rpm it needs to be shifted ,
id say ,try a 15 t instead of a 14 t,this way the bike ,s longterm breath gets alot bigger
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This is my gearing. 14 on front and 1 tooth bigger than stock on back. Also, the bike has a flywheel weight. How bad does this hurt the top end?
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I have got to say I did not think this was going to happen. I thought I had my 500 tuned to make pretty good power, but my cousin just ran by me on a 07 yz250. He said his bike only has a pipe,wisco piston, and carb jetted. This is what my bike has gnarly pipe, k&n airfilter, and I leaned out the carb one point on the main jet. I just do not get it. The 500 seems to be running great, very smooth and powerful, but I guess not as powerful as I thought. I just do not know if my tire is spinning too much or what. I just put a new Kenda 771 on it. It seems where ever I go I leave a trench. One thing though, I think I am going to switch back to the stock filter. It seems to be better than the K&N.
You have something very wrong with your KX500. Traction (lack of) as you claim, should have played a negitive role with BOTH bikes as well, so unless Bubba Stewart was piloting the KX250 you raced, you "should" rip a KX250 a new a$$ in every aspect of a drag race.
There can be som many reasons your KX500 is not running 100%, we need more details.
I've raced TON'S of other bikes/atv, and pretty much sit every one of 'em down. The only true challenges come from modded 450 4 stroke when we race in loose terrain, then I sometimes get beat in a race, but not by much..
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Tharden,
The gnarley is a great Torque pipe for Bottom & Mid, it signs off a little early up top. I think what they are saying is to gear the bike to ride the Torque Curve as your setup is not a RPM design. If you drop 4 teeth on the rear (or up 1 on the front) you will utilize the torque your motor is making & each gear will pull much longer opposed to just reving out.
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It isn't surprising at all you got beat by a new 250. We can stop pretending that 500s are that much faster than anything else. The YZ250s run so good rider ability will overcome horsepower everytime. You will never beat another rider as easily as you'd like to...if you beat them at all. I don't know how many of you race, but it's not uncommon at all for a 250 smoker to outpull a field of 500s to the first turn. Happened all the time on my KX, happens occasionally still on my CR. As the distances shorten to the first turn, it becomes almost impossible to get the holeshot on a 500. 250s are always quicker out of the hole.
You said so yourself the 500 is running great. So instead of trying to trouble shoot the bike, try leaving it alone for a change and improve your riding ability. That will almost curtainly allow you to beat your friend in the future.
The power of a 500 is it's best friend...you should also know it's a riders worst enemy. If you can't get all that power to hook up you're not going anywhere. I'd rather have 56hp I could put to the ground than 65hp I couldn't. You mentioned you run a Kenda 771 on it? I've never used a Kenda so I don't know how good or bad they are. But honestly my impressions are they aren't good tires. Regardless I would be more concerned with your size selection than anything. You say you dig a trench where ever you go? Not good. Sounds like your tire is too small. 100s, 110s are for mini bikes. I use a 2.50x19" rim, 120x90 D756 and I've got a prototype TuBliss core to begin testing as well. I don't get beat very often, and I don't suspect I'll ever get beat again with the TuBliss. In this sport racing is little a matter of horsepower as it is traction.
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thats a sad story ,but to be realistic :roll:
an aged pretty stock k5 delivers about 58 HP
a modded fresh 250 goes up to 50 HP or more
take the riders weight and skills ,there you go
it can be true in other words i think :|
220lbs K5 + 200lbs rider @ 58 hp = 7.24lbs/hp
210lbs ??250 +170lbs rider @50 hp = 7.6lbs/hp
You may have something wrong but if his tire is better than yours or if he has anything newer than a 1990 anything 250 2 stroke it will have a lot better traction than the K5. If he has 52.5 hp, and he could, you are even hp/weight and your but is kicked.
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WOW Mick, I was writing my post and you beat me to it. You said a mouth full. I race mx and everything you said is true. I can get the power of the KX500AF to the ground but it is because of the modern geometry, holeshot device 15/50 gearing and a million practic starts....as you said.
JFAB
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Yeah I've spent much more effort trying to get power to the ground than I have spent trying to increasing it. Holeshot devices, good tire selections, a wide rim and strangely enough even a CR250 ignition have all increased my AF's performance more than any cylinder porting could ever have done.
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I am running a 120x90x19 tire. I think my gearing is one of my problems.
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14/48 gearing is definately not the prob fo sho.
...it's a rider problem :wink:
practice, practice, practice...
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Tharden,
I agree that a rider can make a huge difference, BUT, there is NOT a 250 2 stroke that can hang with a 500 (red, green or orange) that is running properly (& geared correctly). I have a 250 drag bike that is pretty quick (it will run any 250 with just a pipe & reeds) & my STOCK K5 will MPH it in 300'. The 250 is lowered etc for this & the 500 is not so the 250 is quicker because of this, but if you add another 100' it is all over, the K5 ( or red or orange) will go by. I haven ridden 250's most of my life and they have plenty of power for most all situations, but if you drag a 500, and you get into 3rd gear the 500 is gone, I know this as my buddies had the CR500's and we would practice our starts from the gate on a MX track every week & it happens just like I mentioned.
Now let's try to get you whipping up on ALL 250's. Think of John Force running a 10.5 slick, his times would not be there as he is just spinning his tires, it sounds you are doing the same with the current gearing you have (adding teeth to rear is a torque multiplier) as the motor is over powering the traction available, digging a trench, not moving forward. Now take away some of that torque and spread it out longer you will obtain forward motion longer between gears. Try a 15 tooth counter shaft ( it's in expensive) to confirm you are on the right path & let us Know.
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I agree I am not the best rider but I seem to loose by the same margin every time. :-o I will try the counter sprocket. Also, is two cycle oil suppose to pool up in the boot in between the carb and air filter? I have not been home to look at the reeds, but I think they may not be sealing right.
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That sure would be blowback, pull the reeds and check them.
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You sure it isn't oil oozing off your filter after a cleaning???
I've seen ALOT of riders put the oil on too heavy, I'm guilty of doing this on occasion myself. Generally it just runs down into the airbox, but I've seen riders put it on so generously it ran into the carb as well.
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The air filter oil I use is red, but the oil in the air tube was green like the Golden Spectro.
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thats a sad story ,but to be realistic :roll:
an aged pretty stock k5 delivers about 58 HP
a modded fresh 250 goes up to 50 HP or more
take the riders weight and skills ,there you go
it can be true in other words i think :|
220lbs K5 + 200lbs rider @ 58 hp = 7.24lbs/hp
210lbs ??250 +170lbs rider @50 hp = 7.6lbs/hp
You may have something wrong but if his tire is better than yours or if he has anything newer than a 1990 anything 250 2 stroke it will have a lot better traction than the K5. If he has 52.5 hp, and he could, you are even hp/weight and your but is kicked.
im with you here, i too say what mick also says,and you ,that any recent 250 can outrun a k5 as described above .
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In holland you ride KNMV or MON. They are the 2 unions to choose from KNMV is the biggest and connected to the FIM.
You start lokal than district, junior, national, Dutch championship(ONK). Than you can go euro championship and GP's If your good enough :-D
I've ridden Junior 125 races and combined 250/500 on a cr250. I was about 15 to 23 place of 45 riders Top 10 could ride
top 15 national.
One race in memory of a friend I raced the top class with ONK riders Johan Boonen(ex GP) on his SXS540 even GP rider Mark de Reuver on his full factory sxf250 and many more fast riders. Some with 500 2strokes. I hole shoted It with my self tuned 2000 cr250 wich wassent the fastest ride.
Why Could I do this???? Good luck or good rider??? :-D Don't know
A good K-5 can beat everything, a AF even beat the factory 450!!! Seen steafn Everts do this by MILES!!!
Dutchie
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I once beat a Kawasaki ZRX1100 with a Harley Sportster 4 out of 5 times at a drag strip. :-o :-o :-o
The other guy had no clue how to launch on a christmas tree. By the time he left, I had 4-5 bike lengths on him. The one time he beat me, I pulled a red light. I would have won that race otherwise.
Not that you aren't a good rider, but as in most racing, it's 90% racer, 10% vehicle.
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Well this is what I came up with. The reeds and KIPS valves are working well. After I cleaned my air filter I did not spray as much oil on it. I then removed the flywheel weight. After I removed the flywheel weight I could tell a big difference. The bike does not vibrate near as much. Before removing the weight while riding at low rpm the bike would vibrate a good bit and I could feel it trough the pegs. Now it is much smoother. As for starting the bike I could not tell a difference, and the bike idles the same. The biggest difference was in power delivery. I could not believe it. Before I was able to sit close to the tank and gun the bike at a stand still and keep the front tire from rising up too high. Now I have to learn how to really ride the bike. I tried to do the same thing and I liked to have gotten thrown off of it. Really impressed. I also did not see any loss in torque at low speed either, and it still lugs good at low speeds. I believe since the weight is removed the engine can spin up quicker and the tire can deliver better traction.
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Tharden,
Removing the weight allows the bike to spin up RPM much quicker, getting into the Torque of the motor. If you were "Digging a Trench" before, it will happen even more without the weight. I still think you need to go up a tooth on the counter & try your cousin again. I seriously doubt a whatever year YZ250 with pipe, wiseco piston, head chambered is anywhere close to the 50 HP mark ( they produce about 44 @ the wheel stock / depending on who's Dyno) and nowhere near the Torque of a 500. It sounds as you are happy, & I reckon that's all that really matters.
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Tharden,
An article you might be interested in.
http://www.motorcycle-usa.com/276/1865/Motorcycle-Article/2009-Yamaha-YZ250-2-Stroke-Bike-Test.aspx
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I don't know how anyone can say for sure. I hillclimb a 250 and the 500. Often, I am faster on the 250. I don't think the power is the same at all. The 500 clearly has more ponies at the wheel. Traction, ergonomics, suspension and of course rider skill, all play a part. Even when I lay down a flawless ride on the 500, its not seconds faster, more like a tenth. Once your motor is running well, gearing is where its at. Optimum gearing choices change with every changing condition. Tire choice is another big factor. I would sell the flywheel weight to a tight woods rider, and ditch the reed spacer also, if you have one. I don't know about throwing a 15 on there, but I definately agree that the 500 can pull taller gearing than your buddies 250 will ever pull. I also agree that once you hit third, you should have all the speed you need to win, it would still be affected by your gearing choice as to when and how it got you to third.
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14/47 equals 3.357
14/48 equals 3.428
15/48 equals 3.2
14/44.8 equals 3.2
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I don't know how anyone can say for sure. I hillclimb a 250 and the 500. Often, I am faster on the 250. I don't think the power is the same at all. The 500 clearly has more ponies at the wheel. Traction, ergonomics, suspension and of course rider skill, all play a part. Even when I lay down a flawless ride on the 500, its not seconds faster, more like a tenth. Once your motor is running well, gearing is where its at. Optimum gearing choices change with every changing condition. Tire choice is another big factor. I would sell the flywheel weight to a tight woods rider, and ditch the reed spacer also, if you have one. I don't know about throwing a 15 on there, but I definately agree that the 500 can pull taller gearing than your buddies 250 will ever pull. I also agree that once you hit third, you should have all the speed you need to win, it would still be affected by your gearing choice as to when and how it got you to third.
Interesting post.
I'd be willing to bet you are "almost" as fast on a 250cc H/C for two reasons: 1) being chassis weight, i'll bet the KX500 has a good 20 lbs over your 250... (and 20 lbs that you are trying to drag almost verticle up a hill ) :(
2) "flickability", i'll also bet the 250 is way easier to keep charging straight up the nasty hill. KX500's are SO top heavy. Kinda like trying to get a bull to change directions quickly....
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I have enjoyed reading the post and would like to know what kind of techniques are good to develop when drag racing the kx500. I am always willing to learn and any knowledge that is offered is appreciated.
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I own a kx 500 with no mods ( to engine ) except gearing 15...44, I also own a KX 250 and 125. AS I dont race motocross on the 500 I am not sure about a 500 beating a 250 or even a 125 corner to corner on a track with lots of turns. I do know for a fact that the 250 and 125 will pull my 500 from the start somwhere between 2 and third gears the 500 catches up and walks away from them. The only bike I have owned that came very close was a KTM 390. As far as the earlier comment about big nasty hills, which I have seen lots of, there is no other bike I would want then the 500 on a long nasty hill. just my opinion
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I've had my KX500 out on the motocross track many times. It's NOT the KX500's strong point. A KX500 "drags" you around the track, rather then you driving the 500 around the track... however, talk about ROOST! Nobody ever follows directly behind me for some reason... LOL
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Hillclimb
what year 250 do you have. I'll run some sims for you. It's all in the set up.
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Are we still juggling the false presumption that more power = go faster in this debate???
Modern 250s are powerfull and incredibly fast, likewise a 500cc two stroke is even more powerfull. BUT THEY ARE NOT FASTER!!! Gernerally speaking...we can name niche applications all day :roll:
We need to realize an engine's performance on the dyno is absolutely, postively, in no way shape or form an indication to how "FAST" the bike performs in real world. Save of course for you guys thinking, "Well what about drags, the dunes, or hillclimbing?" I got it, nothing beats a 500cc two smoke. I'm talking about what the machine was specifically intended for. Track and/or trail use. Dodging trees, railing corners etc etc...
I wish 500s were as "fast" as some of you think they are :-D
My two 500s for example:
My KX makes more power everywhere than the CR, but the Honda is ALOT faster!
A modern 250 is as fast or faster than a 500 for the same reasons my Honda is faster than the Kawi. They put more power to the ground, they build power quicker, they're lighter and whereas they may not produce as much peak power...they still produce rediculous quantities of it non the less. It's quite simple. Matter of fact my Honda, and I'm sure the KX500AF, feel like a 60hp 250 MXer. Nothing at all IMO like the old steelies. And when you ride a 500AF, you will know the difference between "POWERFULL" and "FAST".
A KX500 is powerfull. A YZ250 is fast. A 500AF is both powerfull AND fast :mrgreen:
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Mick is right, you are compare old technology and new technology. Big differance.
250 new tech.
500 old tech.
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Hillclimb
what year 250 do you have. I'll run some sims for you. It's all in the set up.
Hey...Run a sim for me too, please....kx450f, 72 hp, modified to fire every stroke and runs on premix :-D
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Tharden
check the power valve arm , exiting clutch cover, pull pv cover off. Check and adjust shaft by loosening 10mm nut . my k5 is about middle of adjustment, it made a difference, I had no top end power. there is a hole in the shaft, by loosening 10mm nut, poke a small allen key in hole , and adjust the shaft then tighten , do this then ride if not happy try again , its a case of experimenting to suit you.
i found it best in the middle of adjustment.
my k5 blows off 250's and 450's in the sand up to fifth gear easliy, it will wheelstand in fourth gear in the soft sand .
let me know how you go
kxdino
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my k5 blows off 250's and 450's in the sand up to fifth gear easliy, it will wheelstand in fourth gear in the soft sand .
kxdino
Pretty wild claim.
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wild claims you reckon
It's probably helps my k5 is in a kx 250 (01) frame for a start. different geometry helps
piston had window mod, fmf pipe/muffler off a AF500, v force reeds ,and a good sandcross tyre
if you still don't belive jump on the plane and come to australia and see for yourself!!!!!
p.s your welcome to stay at my place so we can compare the 250's and the 450's
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I checked my power valve assembly and it is working fine. It was very smooth and tight in action. I went back to a 168 main jet and that seems to give it more grunt so I will try that on the long stretch. I feel though my loss is in my riding skills. I admit I am not the best rider which means I need more time out on the trails. Which is a plus for me. Another thing, we did a compression test on the yz250 and it had a whopping 240 psi. I could not believe it. That is 80 psi greater than my 500. But I do understand the 250 is compressing a smaller volume but..
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A KX500 is powerfull. A YZ250 is fast. A 500AF is both powerfull AND fast :mrgreen:
wild claims you reckon
It's probably helps my k5 is in a kx 250 (01) frame for a start. different geometry helps
piston had window mod, fmf pipe/muffler off a AF500, v force reeds ,and a good sandcross tyre
Thats why Service Honda makes AF bikes. Both of best worlds. If you believe that the technology of the 450 can use less power to go faster around a mx track than a 500, then its not a far cry to think a 250, which is comparable power to the 450 can keep up with a 500 that has not been changed for several years. Thats a very good point here. More power is not the same as more speed. They work together, but power is only one piece of the speed equasion.
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Hey Tharden, I didn't read anything about what gear you are starting in. Are you at least starting in 2nd? 3rd may even work depending on your gearing and the traction factor. Not to many 250s can beat a 500 beyond 4th gear,,, at that point you should be walking away. That is why the KX500 is King of the Desert. I raced a tight and short course last week and got spanked,,, not where the 500 shines. They had a 200' hole shot, and only one half mile place to hit 5th, rarely out of 3rd. I do well on the 500 on long 4th-5th gear races,,long hill climbs, and long WOT stretches and you are passing even 450 4strokes.
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heres a thought... race each other again on each others bikes. i mean you are family and all. thats a good test to see how much of the variable is actually rider skill/experience.
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It isn't surprising at all you got beat by a new 250. We can stop pretending that 500s are that much faster than anything else. :cry: shoot u can stop pretending because honestly kx5"s are one of the faster kinds. i mean it would take a shi* load of bike to pull on my stuff..personally i think kx 500s are bad in a line or through the dessert . scary fast
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It's not a matter of kips working smoothly, the actuating arm position has affect on the range of power . the position affect where power is produced. when you loosen the nut the shaft can be rotated to different preloads. if you don't have any preload on the shaft the kips won't fully open so you won't have any top end power . every time you take the cylinder off you must re set the preload on actuating arm.
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It's not a matter of kips working smoothly, the actuating arm position has affect on the range of power . the position affect where power is produced. when you loosen the nut the shaft can be rotated to different preloads. if you don't have any preload on the shaft the kips won't fully open so you won't have any top end power . every time you take the cylinder off you must re set the preload on actuating arm.
How much preload?
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it all about trial and error
you just have to experiment at the track , it's easy to do , i have mine set so i can just feel the tension, then tighten the nut up .
the hole in the shaft is parallel to the ground, and the bike is vertical, it just a case of playing with the adjustment to suit your needs . it's a 2 min job
dino