KX-500 Compression Release Mod! Easy Starting!!!

[KXcam22]

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.

[Kawadougie]

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.    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.    I'll put some more photos in the gallery.

[Brett]

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.

[Kawadougie]

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.  

[quincyman]

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.  

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.

[Brett]

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.

[Kawadougie]

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.

[quincyman]

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.

[hughes]

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.

[Brett]

If only we could see a dyno graph of a before and after.  ANY blowby will cause reduced power.

[hughes]

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.

[Kawadougie]

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.  

[hughes]

Can't wait for the report. GOOD LUCK.

[Kawadougie]

Unfortunately I came down with a flu bug the night before the enduro so I didn't go.    But I have put about 200 miles on the release equipped cylinder and I can tell you that it works awesome!    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.

[Torch654]

Thanks for the update