KX Riders
Maintenance & Technical => KX500 Original => Topic started by: Kawadougie on October 21, 2005, 03:15:52 PM
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I found this auction on E-Bay for a compression release for big bore 2 strokes. I won the auction and have since sent my cylinder off to be modified. I should have it back by next weekend. I will give a full report after I ride it. The whole point is to relieve some compression for starting only.
http://cgi.ebay.com/ebaymotors/Compression-release-KX500-CR500-LT500-RM500-CR480-Maico_W0QQitemZ4581489332QQcategoryZ10066QQrdZ1QQcmdZViewItem
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Yes I saw that a couple days ago and went back to look at it several times. Can't wait to hear how it turns out.
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Look forward to hearing how this works for you, Good luck. :D
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Theres your answer Quincy. Get that compression ratio back and no more busted kickers!
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My old montesas use to have one but I can't say I have had an issue with the huge KX compression. Just kick it with attitude (oh yeah and one of the new kickstart levers so it doesn't break off). Cam.
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I found this auction on E-Bay for a compression release for big bore 2 strokes. I won the auction and have since sent my cylinder off to be modified. I should have it back by next weekend. I will give a full report after I ride it. The whole point is to relieve some compression for starting only.
http://cgi.ebay.com/ebaymotors/Compression-release-KX500-CR500-LT500-RM500-CR480-Maico_W0QQitemZ4581489332QQcategoryZ10066QQrdZ1QQcmdZViewItem
I saw that! I've broken two **NEW** kickstarters. I've since had the head worked to lower the compression slightly and it is better.
I almost did a bid on that, but I was not intrested in a sleeve. But let me know how it works!! It might be a project for a upcoming stock 500. :D
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Gabe,
Do they break in the same spot? Cam.
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Cam, no actually it just takes a chunk out of the aluminum and rotates too far out to give it a kick without your foot slipping off and doing some serious damage.
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My KX starts easy and doesnt break kickers, but I am still interested in how it is installed and how well it works. I guess we all want a better mousetrap. Please keep us updated on how well this works short term and long term.
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Here you go. This is amazing. The compression release works. The mighty KX500 now starts as easy as a 125. You pull the lever and it kicks through like nothing and usually starts first kick. If you look at the photo, it is installed about an inch from the top of the cylinder. It still has enough compression to fire. I even put in the thinner head gasket. Best money I've ever spent. I was looking at buying a 250 but now I'm completely happy with my 500. :o
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Thanks for the update.
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I hate to say this but that mod would allow a s**tload of leakage past both rings when piston is rising and surely give far less power. I thought compression releases for two strokes were in the cyl head so as to give no blow by issues. 4 strokes (oops i said it, ten lashingsfor me) just push down on exhaust valve i believe to release pressure. I would like to hear how the ring longevity goes as all that blow by will be sure to heat things up well above std. But its selling point is starting easier and it surely will do that but i believe at a great cost.
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Also what is that brown colouring on the back of the two transfer ports?
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Epoxi :shock: :twisted: :wink:
//doordie
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Wow, call me crazy.. but did they not install a sleeve? Im either blind or I can't see, but it looks like they did not use a sleeve. If not, I'd like to keep up with this one. If I can get the compression down for starting, I could easily save $200 per year in kickstarters. Keep us up to date.
Did you notice any powerloss? Extra heat?
Maybe they installed it in the water jacket to keep the excessive heat down? This is now intresting.
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Kawadougie,
I can't see a liner either. Can we have a pic from the top looking down the two coolant holes over the release. Cam.
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The aluminum sleeve is what you see in the photo. The valve is back a bit from the cylinder and out of view. The brown coloration in the ports is probably from epoxy when Eric Gorr did his magic. :D I did not notice any change in power at all or extra heat. It was installed about 1" from TDC because you need to have SOME compression in order to start the motor.
Many years ago, the compression releases were installed directly in the head only to provide compression braking but you could not start the motor because there was no compression. I installed the thin head gasket and even ran 50/50 race/pump gas to test the unit. I don't believe it will add to ring wear any more than any other port in the cylinder. :lol: I'll put some more photos in the gallery.
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I say it will wear the ring more not because it is going over the hole but because of the leaking hot air blowing past on its down stroke. If you have ever seen a ring stuck apart from being a bitch to start they soon seize due to all the blow by creating overheated ring and piston. Yeah i imagine the decompression valves in the head give awesome braking as i had the unfortunate experiance of a sparkplug unwinding (yes slack pit crew work) and popping out at the end of a straight in my racing gokart and it was as if it seized, it basically locked up and spun me into the woodchips. Luckily the sparkplug didn't land in my lap and give me 16,000rpm's worth of zaps from a cdi ignition in the nether regions. Also for your sake i hope the bore lining doesn't flake aroun where they bored the hole through.
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Apparently this guy has been doing this modification for years. I'll let you know if I have any problems. Meanwhile, I think I'll install a kickstarter from a KX-125. :wink:
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Apparently this guy has been doing this modification for years. I'll let you know if I have any problems. Meanwhile, I think I'll install a kickstarter from a KX-125. :wink:
If I understand this mod correctly the blowby only happens when you activate the valve to start the bike. Is that not correct?
Also the sleeve the article is talking about is not a cylinder sleeve but the sleeve the valve fits into and that is what you see in the picture. Is that not correct?
I'll tell ya, you pretty much have me sold on this one.
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No the blow by is caused by the rings being over the decompression port which then leaves a gap for the compressed air to blow past. This is its (possibly only) major flaw. I'm sure kawadougie will let us know how it goes. You could potentially keep an eye on it by looking up exhaust port to see if any coating has flaked off and also through inlet port to see if any piston and ring scuffing.
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The release valve sleeve is installed by boring a hole through the water jacket into the cylinder. I understand what Brett is talking about but I didn't notice any change in compression or power. I installed this with my two year old old piston and rings to try it out. I've got a new Wiseco piston kit coming and I'll probably ride it a few more times before I install it. The only negative thing is that the decompressor valve blows some spooge over the back of the motor. I think I'll run a vent tube elsewhere.
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No the blow by is caused by the rings being over the decompression port which then leaves a gap for the compressed air to blow past. This is its (possibly only) major flaw. I'm sure kawadougie will let us know how it goes. You could potentially keep an eye on it by looking up exhaust port to see if any coating has flaked off and also through inlet port to see if any piston and ring scuffing.
My cylinder is steel sleeved so I would not have to worry about flaking. I will probably do this after I have new steel sleeve installed in mine since it is on it's last bore job. I already contacted the company and asked about boring out a cylinder with this mod on it. They said there would be no problem.
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The blow by should not be a problem because it's on the intake side(cooler temps.)In coming air is chasing burnt gas from this side to the other. Blow by on the exhuast port side know thats a problem.
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If only we could see a dyno graph of a before and after. ANY blowby will cause reduced power.
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He'll never notice any power lost. The above post are taking about ring wear and piston seizures. That's way I said on the intake side with incoming air and fuel blow by would not cause any piston problems. On the exhuast side blow by can be a problem with sticking rings, Hot combustion gases breaking down lube on the piston and cylinder wall and then piston siezure.
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Here's a quote from his E-Bay Auction:
Wiseco called me when they developed the KX500 piston because they were burning out starter motors on the dyno. They sent me the KX500 jug and I visited them to see the development work continue, their dyno was loving it and your feet will too!
I'm going to ride a District 36 Enduro tomorrow here in Northern California and I'll give you a ride report later. :D
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Can't wait for the report. GOOD LUCK.
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Unfortunately I came down with a flu bug the night before the enduro so I didn't go. :cry: But I have put about 200 miles on the release equipped cylinder and I can tell you that it works awesome! :D Even my friends who were reluctant to ride my bike are taking turns now. The photo below was taken yesterday after I ran a light hone through the cylinder and installed a new Wiseco piston. No flaking of the liner at all. Also, the piston was unmarked on the back of the skirt where it travels over the release port.
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Thanks for the update
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Why rebuild already, 200 miles is stuff all only 4 or 5 rides. Did you check the ring gap of the old rings. Thinking about it though the wiseco pistons are s**t and collapse readily. You should also measure the piston with a mic as i bet it is now oval the wrong way. Forged pistons of this size have no structural strength compared to a casting. I was even squeesed my old one in a vice to put back into original shape but it was too late though cos i had allready baught a new piston. Don't mean to bag ya but i just will not be convinced. I have to admit though it is good to see the lining hasn't flaked at all, any chance of a photo of piston on side where release valve is?
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Hmmm. Wiseco is my brand and has been for 15 years and no problems in every bike I've owned. :-)
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You didn't read my previous post. :o I've been running this piston and ring set for two years now. I ran the compression release for about 200 miles with the old piston before a rebuild. :lol:
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Did you realy put a smaller kicker on it? Evertone would think you were superman with a 125 kicker on it hehe.
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Thinking about it though the wiseco pistons are s**t and collapse readily. You should also measure the piston with a mic as i bet it is now oval the wrong way. Forged pistons of this size have no structural strength compared to a casting.
Hey, this might be a big piston for a motorcycle, but remember, this would be a SMALL piston for a good sized american V8 (the small block chevy 350 was 4.00x3.48" Bore/stroke - about 100mm by 87mm, if i remember correctly!) And IF you have a motor that will be leaned on hard - raced, nitrous, lots of blower pressure, etc - you should run forged pistons
Its one thing to say that wiseco pistons are crap quality. That may or may not be true, but I dont think you can say that a forged piston of this size has no strength. That doesn't make sense to me. There are forged pistons a lot bigger, they're tough as hell, and there are smaller forged pistons, also tough as hell........
Maybe i'm missing something, but i dont see what would make an 86mm dia forged piston weak - at least by design??
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Ahh, I think he has forged and cast confused. Because I've shattered cast pistons before from age, but have NEVER NEVER EVER seen a Wiseco collapse or even come close. They do freeze easier without proper breakin or not letting them warm up. Iridium is correct, when my dad and I built the motor on my mustang we used Forged. Extremely strong and will withstand much more than s**tty cast pistons.
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I find it hard to beleive that a company could stay in buisness as long as Wiseco has by selling a bad product.
2 cents worth
Dale
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Wiseco have served me well. Been using thier product for 20 years. Faultless!
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I have used Wiesco in every two stroke that I have ever took apart. I have never, ever had a piston failure or siezure. On another two stroke forum for non green bikes, they refer to Wiesco as "sieze-co" pistons. I guess some people have had problems, but I am guessing it is due to piston to wall clearance and break in procedure. Forged pistons are stronger, but they expand greater than cast.
While we are talking about pistons, how long do pistons last in the KX500? Do the skirts wear and cause the piston to get sloppy? Is the KX500 stock piston cast or forged?
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Um to answere your question.. I had a "Wiseco" in my 500 for about 2 years of every weekend hard riding (except rain) and just had it freeze this past summer and that was my error (no 2 stroke oil during a drag race) . So I'm assuming a good hard 400-500 hours is what I had in it? That would be 8 hour rides about every other weekend? And to be honest, I did not have any slop in the piston before locking it up. And the stock piston is cast.
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Ive used Wiesco's in every bike I have owned!
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I`m trying just now PROX in my MX-bike. :wink:
It`s lighter ,but don?t know how it last(only 4 hours on it) :?
//doordie
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The issue with forged pistons of this diameter 86mm + is that when forging it is basically a big dick of one piece that gets pushed into the ally blank. This method is perfectly fine and give great grain flow following the shape of the piston but being one piece has cannot give the webbing that a casting can. A casting is often a five piece inner core that after being cast they get removed in a certain order. due to this they can give very rigid design pistons with all the webs they have internally. Forged pistons are perfect for 4 strokes due to pistons being very short and they have internal webbing as they don't have to seal of ports with the skirt. Generally most racing 4 strokes have the gudgeon pin nearly touching the oil ring. From many two stroke race engine builders i have spoken to they all choose pro-x pistons for the big capacity two strokes as they don't go out of round the wrong way. Cast pistons being more rigid and often less ductile material which is more likey to shatter rather than oblong. Cast pistons are also prone to shrinkage porosity in the heavy sections around the pin bosses. You will get many hours out of a 500 piston due to the fact they put out stuff all specific power and also rev stuffall. They reckon the hand grenade style racing 450 4 strokes these days have less piston life than a 250 twostroke as they are revving so hard and everything is on the limit to try and get as much power as a twostroke.
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speaking of high reving 4 strokes, a dude from round here got shot of his CRF450 cause it stretched the valve stems! Not only once, 3 times!! A young chap I was talking to at the ride yesterday, said to me I,m saving up to buy one of those in a few years second hand. I told him there will be no running second hand ones worth buying...
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Here you go. This is amazing. The compression release works. The mighty KX500 now starts as easy as a 125. You pull the lever and it kicks through like nothing and usually starts first kick. If you look at the photo, it is installed about an inch from the top of the cylinder. It still has enough compression to fire. I even put in the thinner head gasket. Best money I've ever spent. I was looking at buying a 250 but now I'm completely happy with my 500. :o
Now that you have had this mod for a while, what do you think of it? Still no problems? I'm getting ready to make the plunge. :?:
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Still working fine?
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Is this mod for the K500's that are early models that do not have comp release in the KIPS?, or can you do this mod on the late models with the KIPS auto comp. release/
What yr. is your 500 beast?
Thanks