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Reducing the squish area

26 Mar 2020 10:09
mdscott
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Reducing the squish area #1
hello, I'm sending my cylinder head to my machinist to be surfaced so to get about .035 squish area. Obviously it will increase compression. I know a lot have done this, would I feel in the difference of power, if any when this mod is done. Any changing in jetting?
My KDX head has about 3mm of squish now.

inquiring minds what to know.

Thanks Mark
Roseville, Ca.

'76 Bultaco 143 Frontera
'06 GL1800
'01 KDX200
74 DT360
75 Norton
73 CB500K
63 C200
87 PW50
64 McClane Edger

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26 Mar 2020 15:40
GFrench
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Reducing the squish area #2
Which bike is this for? What is the stock squish area for this bike in comparison to the .035?

If head is milled... it will for sure increase you compression psi... if it gets to high could add some stress to the engine... but can easily be adjusted by adding an extra base gasket ect.

Proper timing will be needed to find the sweet spot and keep kick back to min.

Just speaking from my experience I have had doing this... for the 360's i have found 140 to 145 is where you would like to land and anything over is pushing it and need to make sure you give it plenty of fuel so none of those dreaded pinging sounds!

The Black Widow bike sits at 140 right now with an MX High Compression head and is dialed in.


If it ain't smokin', it's broken!
1970 RT1 360
1970 RT1 360
1971 CT1 175
1971 DT1 250
1971 DT1 250
1971 DT1 250
1971 RT1 360
1971 RT1 360 "Black Widow"
1974 DT 360
1976 IT 400
1978 XT 500
1980 YZ 465
1984 IT 490

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26 Mar 2020 16:34
RT325
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Reducing the squish area #3
Back in "87 i got my "86 KX125 taken down pretty close by memory & certainly sharpened it up. I'm sure i went up one size in the main & one notch richer on the needle just to be safe & think i left them set at that. Thing is, at the same time i would have replaced the piston & rings & new rings always sharpens the power up on a ring dinging 125 mxer. Loved that bike & funny thing 'was' the original piston lasted well & every regular change after that had elongated the small end hole in the piston & i knew because it rattled in a certain way & could grab the pin & move it vertically. I used the original piston with new rings at times if replacements were on a 'slow boat' arrival. & original never altered. Made me think replacement [genuine box] were made of cheese. Come to think--i'm sure i started using AvGas then, so power increase with more comp was really noticeable. 34 years ago--.

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26 Mar 2020 16:50
MarkT
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Reducing the squish area #4
If done correctly, it will make a very noticeable difference.

Water cooled is much more tolerant if compression is added... good shops that know the model will machine the combustion chamber to correct the compression if needed on that model... usually isn't needed.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

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26 Mar 2020 16:50 26 Mar 2020 16:52 by RT325.
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Reducing the squish area #5
My maths isn't good but you say .035 so is that 35 thou getting towards one mm. Not .035mm about 14 thou. I'm guessing the first one. Sorry if i sound thick lol but can be at times.

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26 Mar 2020 17:32
mdscott
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Reducing the squish area #6
Mr French my KDX220r is the bike i'm speaking of.
I know RB Designs and Fredette Racing along with shaving the head they configure the combustion chamber, plus they both bore and modify the carb.
I'm going the cheap route right now.
The cylinder lining was also flaking so as we speak it's being re-plated at Millennium Technologies, so that along with new piston, surfacing the head should make a fairly substantial increase in compression.
I might be heading to some desert in April to test it out.

So this is want I'm doing to maintain social distance and staying busy, I've also mowed my lawn 23 times.:ROFLOL

Thanks Mark
Roseville, Ca.

'76 Bultaco 143 Frontera
'06 GL1800
'01 KDX200
74 DT360
75 Norton
73 CB500K
63 C200
87 PW50
64 McClane Edger
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27 Mar 2020 08:28 27 Mar 2020 08:29 by Pillsbury.
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Reducing the squish area #7
The angle of the squish area needs to be changed with the machining. More important than milling the surface. Hopefully your machinest knows 2-stroke engine technology. If not send it to these guys. www.klemmvintage.com/ Here is a GYT head machined for 180 psi and a stock one for street and 91 octane gas

1970 DT1-C Grand Prix race bike
1970 DT1-C Street tracker
1968 Honda CL90
1973 Honda CR250
1974 Honda MR-50
1966 Triumph Tiger Cub
1970 Suzuki TC90
1947 Mustang
1974 Suzuki TC185

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27 Mar 2020 08:50
mdscott
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Reducing the squish area #8

Pillsbury wrote: The angle of the squish area needs to be changed with the machining. More important than milling the surface. Hopefully your machinest knows 2-stroke engine technology. If not send it to these guys. www.klemmvintage.com/ Here is a GYT head machined for 180 psi and a stock one for street and 91 octane gas


thanks Pillsbury,
just curious, other then taking the engine to him with cylinder and piston installed, how would you determine the angle of the squish area, pistons dome is arced.

Thanks Mark
Roseville, Ca.

'76 Bultaco 143 Frontera
'06 GL1800
'01 KDX200
74 DT360
75 Norton
73 CB500K
63 C200
87 PW50
64 McClane Edger

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27 Mar 2020 11:55 27 Mar 2020 14:48 by FrankC.
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Reducing the squish area #9
They (klemm) require your current piston to do the mods for best performance in terms of cooling and power. But, if you can't send them the piston the work will not be as good. They are top notch in deàling with detonation issues, whether your head is listed on there or not, you'd have to call them.

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27 Mar 2020 22:56
MarkT
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Reducing the squish area #10
KDX is a very modern engine compared to an old DT. Kawasaki knows how to make power. Angle may or may not need to be changed.

The biggest problem with excessive squish clearance is that there is a lot of mixture trapped there that gets "quenched" and doesn't burn. It's worthwhile to reduce that clearance. Factory doesn't do it because of mass production assembly tolerances.

If on a budget, reducing the clearance will make a significant difference in power... on squish angle, three experts will often have three different ideas of what is best. And you probably couldn't tell the difference between the three by seat of pants. Keeping in mind that Kawasaki engineers are experts too... :whistle:

Just my opinion and experience... and we all know what opinions are worth! :haha

:Buds

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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