KX Riders
Maintenance & Technical => KX500 Original => Topic started by: John on December 07, 2005, 01:44:09 AM
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Has anyone investigated (verified) the opening times for the exhaust valve in relation to engine RPM?s?
If you are familiar with the principle of how the exhaust valves operate, you know that the opening times are controlled by a spring loaded mechanism.
It would be possible to change the opening times by fiddling with the spring pre-load and the K value of the spring itself.
I am not saying that this is something I particularly want to do, I was just wondering if someone has done anything in this area and would like to share their findings.
I think it would be possible to set up the whole axle with the balls and spring in a lathe and crank up the rews until it opens. I guess there are lot?s of opportunities for false reading given that the axle is not in its native environment - lack of friction and resistance and all.
Just wondering?
On the same subject;
Would there be any benefits in changing the exhaust valve timings? Maybe this could be a cheap (and easy) tuning tip?
//John
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john,good question to explore.my opinion is there should be some gains in changing the exhaust timings if other factors such as transfer hgts.,exhaust widths,intake openings etc.as well as pipe and intended use of bike. did not have time this year to experiment with governor spring or ramps to see what i could come up with.sure there are gains here.did tinker with rm250 spring and tension on return spring and it picked up revs quicker.i'm pondering blocking off the exhaust port drumm openings and center valve in order to control timing more for my use,which is drag race.this thread should be interesting.
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This would be an interesting test to do - running the gov in a lathe and watching the behavior at various rpm
I wonder how much the governor behavior (such as the RPMs when it begins to open, fully opens, etc)
I know the powervalve makes a HUGE difference in the way my bike runs. I should know, I had problems with mine for a while (dirty powervalve system, overclosing valves, etc), so I played around with it, disengaging it completely (leaving it closed), leaving it wide open, etc
This might be a fairly substantial reason why one KX500 runs differently from another
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Just writing something to keep the topic going. I can't be bothered to do anything myself . :oops:
//John
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john,i don't have a lathe here to turn it that fast.but i did take a look again at the rams and balls and decided to modify ramps some to see how it actually makes the bike react.i assume it will allow the balls to climb ramps faster and open valve sooner maybe getting motor on the pipe a little quicker.still plan to spinn it to visualize effect.
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If you alread have it apart, could you count the coggs on the different gears involved to be able to calculate the total ratio agains the crank revolutions. I assume it's not 1:1
Be careful so that you don't modify too much. One of these balls went through the engine cover on my 125, it did a nice big hole. That was due to wear / exhaustion rather than modification. Expensive anyway!
Cheers!
//John
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ok.will do that tomorrow.good point.won't grind on it too much.will make sure at full extension that the balls cannot come out.will also mike them for size as with lockup clutches, gram weight makes a difference with spinning mass.
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here is somespec's on 99 k5 governor : balls-7.9mm(.311)WASHERS-1.02MM(.040),same thickness as trans washers.spring hgt. uncompressed-25mm(.985)coil dia.2.04mm(.080).plastic gear was 18 teeth and 13 on the crank.looking for my angle finder so i can maybe get the degree of angle of the ramp.anyone know whether there are optional ramps available to the public.heard some factory sponsored bikes try different ones.
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Nice work!
This would mean that for every crank revolution the small axle will rotate 13/18 of a revolution. So if 6000 crank RPM's is the theoretical opening time for the govenor, it would calculate out as 6000 x (13 / 18) = 4333 RPM's on the small axle.
Does anyone know what the specified opening times (RPM's) are supposed to be for the exhaust valves?
Does anyone know what the ideal opening times (RPM's) should be for the exhaust valves?
Could anyone make a general statement of how the exhaust valve opening times affects the general behaviour of the engine?
I assume fiddling with the timing would require a different jetting - needle anyway.
//John
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Harder spring in KX250. :wink:
(Nearly the same maximum rpm for kx250 and kx500).
I have a kx250 spring for testing later in winter. :twisted:
//doordie
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let's say the harder spring will start the opening rate a little slower.would we then assume the motor will have a stronger bottom power curve yet still pull harder on top or slugguish thru the mid range transition.i guess the type of riding comes into play as well as the porting done to everything.i'm going to research this thing as far as i can.
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Hum,
I was assuming that a harder spring would change not only the timing (RPM) when the exhaust valves would open but also the time it takes for the valves to become fully open. Then I did the mistake of thinking again?
Once the engine reaches the critical RPM the balls are starting to move out from the centre of the axle. The further away they are from the centre of the axle the greater centrifugal force they will be subject to. This would mean that the opening of the valve would be almost binary (closed or opened). I don?t think it would ever be in a state of half open.
I don?t know if that?s good or bad or even interesting but it will simplify things?
A stronger spring moves the opening time further up the RMP?s and the opposite for a weaker spring. The opening times (time spent half open) would theoretically not change with different springs.
So the question remains; what kind of impact would this modification have on the behaviour of the engine characteristics?
Doordie, Mun, anyone?
//John
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I can't resist diving into this. In my experience, raising the exhaust roof increases the "pipe-iness" of the engine. In the KX, the powervalve also opens the sub ports, increasing the effective width. Both increase hp. I would expect that the stiffer spring would delaying the action of the power valve, and spread the opening over a wider rpm band. This would make the powerband more mellow but then make the top end rush a little more drastic as the engine RPM will be higher when the valve actually opens fully. I disagree on the binary opening. When riding you would feel a drastic step-change in the power characteristics when the valve snapped open. I think the increasing compression of the spring would balance the increasing centrifical force (not entirely unless it is a rising rate spring) and slow the action so that the full opening would take place over a few thousand RPM. This may be pure speculation but it's fun to analyse. Cam.
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More speculation.
(http://img408.imageshack.us/img408/7869/slechtenvsmunpipe0jo.jpg) (http://imageshack.us)
My story is easier with picture. There are old dynos of MuN old -86 KX with Slechten- and my own MuN-pipe. Power on my pipe came between 5500-6000 too fast. I even crash on tarmack track for this reason.
I ask multiple Finland Champ (iceracing, RR, dirt track, enduro,..) Ilkka Heinaaho: If i added washer to increase spring preload. He says: "Are you sure to add preload help you? My experience with KTM is different." How much i try to change washer? "1 mm is lot" he say.
I fix my problem with raising tranfers, so I don't tested with washer and have no experience with it.
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Cheers Mun,
When would you say that the exhaust valves are opening? Some drastic things happening around 5.5kRPM's (with your pipe that is...).
//John
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More to think about?
If the spring is pre-loaded it will take more power to compress it hence a higher RPM to open the exhaust valves. How will this affect the engine characteristics though? Will the power band be leaner or more aggressive?
Changing the spring to a weaker one will make the exhaust vales open earlier. How would that change the engine characteristics?
I am lost with two strokes; and a lot of beer doesn?t help?
Interesting thread though and a wonderful forum!
//John
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All this talk is reminding me of the centrifical (?) clutch on my gas powered R/C truck. You lighten the three clutch shoes so that the weight of the shoes doesnt carry them out to make contact with the clutch bell untill they are spun at a higher RPM... therefore the engine is making more power before it is sent through the drivetrain to the wheels. I think a heavier spring would slow the whole process evenly(higher rpm to open, but open at the same rate of speed) while lighter balls or steeper ramps? would cause the exhaust valve to hesitate opening until higher rpm is reached but sort of slamming the exhaust valve open creating more of a "hit" with the power band.
I could be totally wrong and far off base... just a little brainstorm I had when I realized this was all sounding like the clutch on my R/C truck. I really dont have any real life experience or knowledge with KIPS valves so hopefully this is of some assistance and not just a waste of space on the thread. :wink:
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never a waste.there is always something in thought that can be put to use.i would say you're probably on track with heavier spring bringing on harder hit.boy what a ride that would be! now how would it act thru the bottom range?what if we changed the number of teeth on plastic gear to spin it at a quicker rate.if we could find one.does a kx125 or 250 have same number of teeth.these should spin at faster rate or open quicker.man,now i've got to pull my cover off my 250 and 125.
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Mayby 2 dyno picture more explain better than i able write english.
(http://img235.imageshack.us/img235/8359/munkx500fuchspull6s4tm.th.jpg) (http://img235.imageshack.us/my.php?image=munkx500fuchspull6s4tm.jpg)
(http://img229.imageshack.us/img229/3941/munkx500fuchs7s7fv.th.jpg) (http://img229.imageshack.us/my.php?image=munkx500fuchs7s7fv.jpg)
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does it apprear that valve begins to open at around 4300-4400 and maybe climbs on pipe around 5300 are so.what would you say the reason for decrease in power with valve open constant?timing of power curve vs. type of pipe involve or not burning of as much fuel charge cleanly.where did the other 2. hp go from previous graph?interesting.there is a performance gain here somewhere in tuning of this valve with other mods. include in the equation.
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Mun,
Got it! These are nice graphs, thanks Mun!
Looks like the exhaust valves are starting to open at 4500RPM's and are fully open at 5500RPM's. There goes my theory of "never half-open"...
When you did these tests, did you increase the rews quick och slowly?
Do you agree with my interpetation?
//John
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You can use a extern spring attached between KIPS-wheel and cylinder, it?s very easy to "TEST" different springrates and see what?s happens.
After that can you test with preloaded stock spring or buy
a KX250 spring. :wink:
My own test will be with my third kx500 to get so much torque as possible,
spreaded for so long rpm-range as possible. :twisted:
(fourstrokes beware)
Recept: :idea:
Gnarly pipe with extension part
Powerblade
D-shaped carb.
Flywheel weight
High compression(wide squish)
Low exhaustport
Reshaped scavening ports
Modified KIPS
//doordie
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great.now we rolling.we'll say openning 4500.fully open @5500.now if we open it earlier @oh 3800 say will the power now spread more smoothly, at a greater efficently, maybe peaking a little more hp.
doordie, 1.5" added to head pipe should help torgue on gnarly.
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where did the other 2. hp go from previous graph?
Previous is with 490 main and this is with 500 main.
We start Slechten pipe with 500 main (57hp), what i use on tarmack. It's badly too rich on inertia dyno!!! (You can't find best jetting on inertia dyno! It has not enough braking to burning all fuel that you neet on track.)
Then 480 (65hp) and 460 (66hp), which was best of tested. But more smaller can be better, no time. Then MuN-pipe, start 490 (72hp) > 500 (71hp), no other :(. Powervalve testing (i quess again) we make with MuN-pipe and 500 main jet.
I remember that "powervalve OFF" mixture was very very rich.
This dynoing happend almost 5 years since and i don't remember all exactly. Some of those difference can be of dynos tolerances. Motor temp and pipe temp (it's most importing), ...
Looks like the exhaust valves are starting to open at 4500RPM's and are fully open at 5500RPM's. There goes my theory of "never half-open"...
When you did these tests, did you increase the rews quick och slowly?
Do you agree with my interpetation?
//John
John, your theory about "never half-open" is right. Please don't shut me, because i don't remember sure. If someone can take cover plastic of cylinder, so that KIPS moving arms is seeing. Raise rpm slovly and check what arms making. I'm so sick than i can't do now that. I last start my KX summer 2004 :(.
This dyno was PekkaP's Fuchs-dyno, http://www.pekkap.fi/fuchs.htm. That is acceleration, or inertia dyno. Pekka raised rpm slowly to 4000 and then wide open. We dynoing KX only one evening. If you want better results you need own dyno and eat and sleep in dyno room :).
Remember: My old -86 KX500 have KIPS only side exhausts, not in main exhaust.
There all rest dyno graphs:
(http://img324.imageshack.us/img324/8143/munkx500fuchs1s4yf.th.jpg) (http://img324.imageshack.us/my.php?image=munkx500fuchs1s4yf.jpg)
(http://img324.imageshack.us/img324/9168/munkx500fuchs2s2se.th.jpg) (http://img324.imageshack.us/my.php?image=munkx500fuchs2s2se.jpg)
(http://img324.imageshack.us/img324/7708/munkx500fuchs3s1hw.th.jpg) (http://img324.imageshack.us/my.php?image=munkx500fuchs3s1hw.jpg)
(http://img324.imageshack.us/img324/4187/munkx500fuchs4s0uf.th.jpg) (http://img324.imageshack.us/my.php?image=munkx500fuchs4s0uf.jpg)
(http://img324.imageshack.us/img324/7606/munkx500fuchs5s5jo.th.jpg) (http://img324.imageshack.us/my.php?image=munkx500fuchs5s5jo.jpg)
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Mun,you have a different carburator (mikuni 40mm) than we other so the jetting is not the same.
I?m up to 205 mainjet with ovalbored Kehin (39mm) at the same hp(70+) as you. :wink:
Hope you will get better soon Markku! :cry:
This test with KIPS should be done on a water or oil braked dyno for best result.
//doordie
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have set up date with Ms. Dyno for the sat. after xmas.its at a friends harley shop(he races top fuel kaw)for suppose to be 65.00 hr.but its likely going to two hrs. for that.we get to talking and trying things and you know.will be trying 3 pipes,keihin carb,44 lectron,stock flywheel,lighten one,ignition timing and of course exhaust valve washers,springs.sounds like three hrs.uh.anything else i should maybe check if time allows?
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YUNGGUNNAZ,
Different intake valves,stock or aftermarket(vforce,Radvalve),maybe borrow someones if you don?t have. :wink:
You should have O2-sensor to adjust right jetting (A/F-ratio). :wink:
A good chain and easy rolling tire. :wink:
//doordie
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ok. got a stock intake,vforce and mossbarger w/spacer on hand.his dyno setup should have o2 sensor wand or something i guess.will change tire to either street or enduro thread.we were going to do it today but it would have been a rush getting everything together.although i have the 99 already down to replace some trans. gears.he wanted to show me a VICTORY on the dyno but did'nt have time.boy this is going to be fun!oh might as well take some thermal wrap for pipes to see results.gonna get my money's worth.
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I would try each item one at a time only otherwise you will get lost, then wack the best of each option on and hopefully not go backwards. The thing i would like to see is a simple before and after reed block spacer as there has been much discussion on this and i would like to see if much top end losses.
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the spacer deal was another thing i was looking at also.i'll try each pipe, carb combo first starting with stock reed cage and either pro circuit or dyno-port up pipe i have.after plug chop,i'll change cages and carbs.getting the best pull with each after proper tune up.i'm looking for the most hp,torque #'s out of each combo.keeping curve in mind.will document each setup(jet,timing changes,temps,a/fr,etc.)
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I would like to go back to the core of this thread; will there be any benefits in changing the opening time of the exhaust valves?
The equation is slightly more complicated than I originally suspected?
I think I am more or less correct assuming that there are two major parameters involved in the KX5 exhaust; KIPS and pipe. The properties of the pipe are most likely more important that the timing of the exhaust valves. I can tell by looking at Mun?s diagrams.
Let?s draw two different scenarios / approaches;
1. The properties of the pipe are fixed ? exhaust valve timings are variable:
In this case, it would be possible to adjust / optimise the timings of the valve to fit the pipe properties.
2. The exhaust valve timings are fixed - pipe properties are variable:
Typically change the properties of the exhaust pipe until it?s optimised with the timing of the exhaust valve.
It probably safe to assume that the original exhaust pipe and the default exhaust valve opening times are optimised and tuned by Kawasaki..?
I don?t think it?s advisable to attack both approaches at the same time. Maybe choosing a pipe depending on the overall desired effect profile (and get the jetting right), then adjust the spring (exhaust valve timing).
I am not sure I fully understand how much or little the exhaust valve timing impact the characteristics of the engine.
Any thoughts?
//John
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i am hoping that once pipe and carb combo are chosen(fixed properties)then changing the valve spring,washer or both will show itself on the dyno graph.both in rpm opening and power curve andreaching peak hp. sooner(maybe).i believe it will start the hp. climb sooner.
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Guys,
You know that KIPS have one more dimension.... :roll:
When KIPS closes it makes your PIPE "fatter"!
You have a extra volume in a chamber in barrel to make more low torque.
It foul pipe to think it has more volume at low rpm and less in high rpm range. :wink:
"You eat cake and have it still"(sorry about my english,John don?t kill me). :oops:
(Kx500 have smaller stock pipes than Cr500)
//doordie
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"Have your cake and eat it to" :lol:
Your English makes more sense than mine.
Dale
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Doordie,
Don't worry, my English seems to be OK because I use an English spell checker and have lived in this rainy country for 5 eyars now. As long as you are making yourself understood you're fine!
I fail making myself understood on a daily basis - it's called work. Noting to do with the English language though, just the English people :(
I hope something good will come out of this thread. I am tooo lazy to participate with any real work, just stupid comments.
//John
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YUNGGUNNAZ,
Have you done any Dyno tests? I just read that you were planning to do some tests. Just asking...
//John
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john,waiting for new o2 sensor to come in.and hopefully weather won't change on that day.(live in the country 25 mi. away from dyno.)will post as soon as done.i'm going to try to post pic's of two cylinders tomorrow just for discussion.
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I've kept out of this thread because I've tried all kinds of kips timings, holding it open, shutting it, trying to space it a little, ect. I've really found very little effect in port timings with the KIPS and feel there is little benefit to doing major modifications to it. Stock is best that I've found and according to MUN it looks like it is pretty tuned off the bat. Now what can go wrong is your powervalves stuck or clogged with spooge or just crap from excess oil. Also your govenor spring worn out. Preventing it from opening or closing correctly. Those are the only issues I've found. I guess it depends on where you are looking for power. I'm questing for a spike, explosion type power while most are looking to smooth it down.. If this is the case (smooth power) I am of no help.. :-D
I would like to see HP differences with the pipes and valves. I've done my own little dynos, but that was quite some time ago and am due for another one soon (when it is warm enough to pull the bikes out and fire them up).
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I have measured with my tachometer that KIPS start opening about 4800rpm
and half open about 5000 and full open at 5300rpm,just wanna share info. :wink:
Most of our engines delivery most torque at 5500 rpm and hp at 6500 rpm and signing of at 7000 rpm.
This make you wonder if you change this ramp to......!!! :evil:
//doordie
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I just pulled the cylinder on my 97 K5. The K.I.P.S. valve on main exhaust port looks like it's not at max height with rod pulled out. Also seems to be excessive slack in the mechanism.
Should the valve be even with cylinder at top? Not sure if I should try and tighten up mechanism or maybe just de-carbon everything, grind the valve till it's flush and go with it.
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Redline,
It's the sides that matter most, not the top. The side spools open up ports on the side. You can remove the pins from the main top flap rotate them 90 deg and press them back in. Maker sure to meaure the pin height before you remove them. Grinding in the top flap is essentially porting and will change the power characteristic giving you more top end. Hope this helps. Cam.
PS one of the best things is to adjust the end stop of the horizontal rod with a small ball bearing. Space it until the side ports are covered. Stock the valves overclose makingone of them actually open again.
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I guess this will be one of the unsolved mysteries of life then - standard is actually OK...
//John
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Thanks for the input. As soon as my top end parts come in I'll adjust the valve and see how it runs. I did notice the side spolls over rotating at closed. The bike had an odd powerband in the sense it would hit the instant you cracked the throttle, pull for a short time then sign off, in my opinion too early, without much top end pull.
Once my valve is timed proper. Since my engine is already apart, what combo of mods between the reed valves, pipe choice, igniton timing, and head/base gasket combo will turn this bike into a mid-range monster?
Cylinder looked great so I ordered a wiseco piston kit and bearings thus far. Rest of the engine is bone stock. I don't use the low -end very much so that's not a concern.
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Just a little explansion about that "overclosing".
Kawasaki did this to solve the problem to start a big 500cc engine,at very low rpm
let compression go by in subexhaust ports and as soon over idle close the port again
to still have enough of compression for low rpm grunt.But when fireing 2 times per row it?s not so good, causes that surgering and backfireing when throttle is closed.
IF you CAN kick it already,get rid of that overclosing.... :wink:
(H..da CR500 have a different way,look at pic over exhaustport)
As always,just my 2 cent :-D
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found this on kawasaki website.
qoute
The stroke of the main Kawasaki Integrated Powervalve System (KIPS) valve has a shorter stroke so that it opens quicker to improve mid-range power