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11/8/2011
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Ascot Park, CA
US
KX500 PHATHEAD?
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That decompression unit looks like a cheap cast Chinese one . If that is the case, I would swap it for a CNC made one . Harley guys use the CNC type and I put one on my 1981 YZ465 and it cured the evil kickback problem. .
Do you have to reach down and push that button to release compression?
No, once it starts it releases. At least the ones I've seen.
That makes much more sense.
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The decompressor valve looks just like the ones used on chain saws?
Chainsaws, Lawnmowers, Compressors, HDs / Big Twins etc etc.
My Auto Decomp, that is Vacuum operated (no reaching down for a button, or a lever on the bars) , comes from old Victa Lawnmowers :
I found a picture of a remote, cable and lever operated set up for the 'pop off' decomps quite a few years ago, that someone had made :
Side note; the shape of that combustion chamber looks like it would have been punchy as hell. Know what engine that was off?
CR500, as far as I know.
There's a variety of heads over the years , ID'd by the middle 3 letters in the parts list, and, they ARE cast on the outside of the head - many argue about which is 'better'.
I've a few different heads - buggered if I know which one I've on there at the moment, and I'm too lazy to uncover the old beastie to check it. All I know for sure, is I've a decomp on them All.
And, of course, plenty of people re cut heads / weld and re cut to their preferred Squish and 'Tub' dimensions.
What 100 octane fuel do you plan to run ?
Most likely F&L SP-100, as I have a dealer nearby.
https://racefuel.com/products/leaded-racing-fuel/sp-100/
Tom Morgan will mod & decomp your OEM one for 1/3-1/2 the cost of a Phathead; can cut the head for race, pump, or whatever combo you want.
IMHO, he’s the only good primary source for K5 work. Don’t get me wrong, lots of other guys can do some great stuff on them… but the guy who built the last factory ones always has a few tricks up his sleeves. He has saved some parts for me that I would have bet money on could only be scrapped.
The one in the photo has a wide squish band that would make it super punchy, but it’s been laid back to avoid detonation.
That's my point but it appears by the down votes on my post that some people cant handle the truth. The cheapo chain saw ones have been known to break when used on motorcycles, but what do I know. 😆
I use these.
Stainless CNC machined body and internals
No kidding.
Why would you reinvent the wheel when round works really well.
I've never used one. What makes them close back?
Combustion pressure pops them back into the closed position.
lol, its the difference in quality which equals reliability and I for one wouldn't be stupid enough to jeapordize my engine by using a cheaply made part, that has been known to fail when used outside of the engine it was originally designed for, but obviously you like cheap unreliable parts.
Or, just maybe I can start mine in it's stock form just fine.
Pit Row
I hate to say the obvious...
Much appreciated Santa!😎
Give us a ride report when you test it.
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