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Author Topic: Kx500 head gasket cooling ports  (Read 535 times)
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Bcsnowbiker
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« on: May 13, 2019, 08:01:25 PM »

They're tiny!
What is the consensus on what to do with them. Add holes, match to cases?
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1901306708
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« Reply #1 on: May 13, 2019, 08:18:48 PM »

seems to work fine as is. you can jam a washer under your impeller to shim it out towards the cover. gets you way more flow. need to experiment a bit to shim it out but not touch
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Bcsnowbiker
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« Reply #2 on: May 13, 2019, 09:03:45 PM »

But the cooling jacket ports on both the head and the cylinder match yet the holes on the gasket are less than a third there size.
What good would improving your impeller be if those hole restrictions are your limiting factor?
I will post pics of what I mean tomorrow.
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Bcsnowbiker
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« Reply #3 on: May 14, 2019, 01:19:05 PM »

Head
Gasket
The two lined up


* IMG_20190514_110409.jpg (2904.05 KB, 4032x3024 - viewed 34 times.)

* IMG_20190514_110438_1.jpg (3358.21 KB, 4032x3024 - viewed 33 times.)
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Bcsnowbiker
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« Reply #4 on: May 14, 2019, 01:22:38 PM »

One more


* IMG_20190514_110546.jpg (3402.74 KB, 4032x3024 - viewed 35 times.)
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reklessj
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« Reply #5 on: May 14, 2019, 02:13:13 PM »

Wrong gasket bro!!
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My rides: 1994 KX500, 1988 T4, 1998, ZXI 1100 JETSKI, 2003 MOUNTAIN CAT 900
WIFES (Baby Fiver) rides: 2004 KTM 105SX,1992 LT250R, 1995 ZXI 900 JETSKI,  2011 RMK 600
SONS ride: 1995 YZ125,2002 RM 250
other rides: 2007 RMZ450 RC Ediition, 2003 RMK700
Bcsnowbiker
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« Reply #6 on: May 14, 2019, 03:34:34 PM »

Well that's the gasket that was in there and that is what my new aftermarket tusk one looks like, exactly the same.
Holes and everything line up right but the water jacket holes are small
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sandblaster
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« Reply #7 on: May 14, 2019, 04:16:32 PM »

There is a balance between too much flow and not enough.
There has been a lot of discussion on what is correct.
You will also note that the holes on one side is smaller than the other to force the coolant to cool the top end evenly shocked

I have thought some about changing the holes sizes but have never done it as I have always managed to keep my engine at a good operating temp.

If you experiment be sure to document what you do.
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The four stroke engine: That's one stroke for producing power and three for wearing the engine out.
Bcsnowbiker
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« Reply #8 on: May 14, 2019, 09:00:15 PM »

There is a balance between too much flow and not enough.
There has been a lot of discussion on what is correct.
You will also note that the holes on one side is smaller than the other to force the coolant to cool the top end evenly shocked

I have thought some about changing the holes sizes but have never done it as I have always managed to keep my engine at a good operating temp.

If you experiment be sure to document what you do.

Thanks for the clarification on that 👍
I hadn't gotten around to noticing that the holes were a different size yet
Speaking of head gaskets I measured my squish today at 2.2 mm with the 1mm head gasket. The 0.2mm head gasket would put my squish in the right zone. Do you typically run this gasket? Thoughts on the raised compression?
I know compression is usually good for bottom end, I want top, but is better for altitude, which I have, but also adds heat, never a great thing.
Gas wise I use avgas so 100mon is achievable though I typically mix with 95. thanks
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sandblaster
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« Reply #9 on: May 15, 2019, 07:47:43 AM »

Chuck that 1mm gasket and get a .2mm gasket.

Oh boy, I'm gonna start some controversy here  shocked
The number one thing to remember is trapped volume vs compression ratio.
In other words, how much air by volume are you compressing and how many times are you compressing it.
All other head design aspects are important but secondary to trapped volume vs compression ratio.
At sea level atmospheric pressure is 14.7 lb per sq in
At 5000 ft it drops to 12.2  lb per sq in
So lets say that you are compressing X volume at 13.7:1 compression ratio
At sea level that's 13.7 x 14.7 = 201.39 psi cylinder pressure.
At 5000 ft its 13.7 x 12.2 = 167.14 psi cylinder pressure.
The higher in altitude you go the lower your cylinder pressure is.
On a KX500 for good all around performance you want your cylinder pressure to be around 170-200 psi.
Unless your head, cylinder, or cases have been machined (and by your measurements they likely have not been) using the .2mm gasket is your wisest choice.
Otherwise you are lowering your compression over stock numbers as you are adding approx 1.5cc volume per .2mm gasket thickness... In other words you have raised the volume by a total of about 4.5cc greatly lowering your compression ratio. Then factor in the altitude and your gonna have a real lemon using a 1mm gasket...
« Last Edit: May 15, 2019, 07:52:19 AM by sandblaster » Logged

The four stroke engine: That's one stroke for producing power and three for wearing the engine out.
Bcsnowbiker
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« Reply #10 on: May 15, 2019, 08:37:54 AM »

Great info thanks 👍
I was going to have the head machined down to tighten squish and have the dome cut to maintain stock compression but seeing that the 0.2mm gasket is available it seems like a no brainier to try that.
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1901306708
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« Reply #11 on: May 17, 2019, 07:02:15 PM »

shouldn't be a problem.

mine ticked slightly in the midrange at part throttle when I wasn't running enough octane. gave me lots of warning to increase octane.

i have yet to find a point where increasing ignition advance or compression negatively effected power
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Bcsnowbiker
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« Reply #12 on: May 17, 2019, 09:19:16 PM »

Thanks for the fuel info 👍
When I got that stripped screw out I saw my timing was slightly retarded. I will try at the full advance mark.
Got the cases split today and things look pretty good in there 👍
Tranny looks good.RH main bearing had a hair of play and it looked like the LH seal was just starting to leak. So only big surprises was replacing entire clutch assembly and it looks like I'm shopping for a clutch cover. The big dent on the outside has some cracking on the inside 🤬
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« Reply #13 on: May 19, 2019, 12:34:54 PM »

ya pretty std. you can get a guy to weld it with a tig if you aren't too concerned with how it looks.
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