"Decking" the cylinder?

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KDXDave
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"Decking" the cylinder?

Post by KDXDave »

I used the SEARCH mode with this term"decking the cylinder" and found no information. This is when you machine metal off the bottom of the cylinder. There may be another term for this and I'm not looking it up right? Has anyone done this to their KDX?
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Colorado Mike
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Post by Colorado Mike »

I haven't heard of this done on KDX's. I do remember on Team Green's MX racer support page they talked about doing that for the KX85. It would raise compression and change the porting characteristics.
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Post by fuzzy »

"Decking" at lease when you talk v-8/etc machine work is a process to ensure COMPLETE squaring of the cyl head deck in relation to crank centerline. I'm sure there is a factory tolerance here, and this process is to take it to some severe level of tolerance. Again, this being for solid block motors without removable cylinders.

I'm sure this coule be done on a 2-cycle just the same, but I'm sure they do a very good job of it at the factory, or else there things would be shedding pistons left and right. I've seen typical MX mills turn 12k with just porting, pipe, and a mag w/o reliability issues. HMMMM, Now that I think about it I'm not sure what you'd do w/ a 2T. Compression work is done at the head. If you were to square it off at the bottom or the top, yes port timing would be changed, but you'd also run into piston/head clearance issues without putting a plate (or mabe a bunch of head gaskets??) back in to 'shim' up the difference. Maybe on the 85 they did it for just that....To alter the port timing. Any compression increase would be made at the head.

I would leave it alone. 90% of performance enhancments are made in the ports, head, pipe, and intake (reed cage).
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Post by Julien D »

It would seem to me that you would be achieving the same result as you would from shaving the head. Smaller combustion chamber and higher compression. Only by removing material from the bottom of the cylinder you would likely be changing the porting characteristics. I would not even venture a guess as to what effect that would have as opposed to just shaving the head.
Last edited by Julien D on 09:14 am Dec 17 2008, edited 1 time in total.
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Post by canyncarvr »

>|<>QBB<
juliend wrote:It would seem to me that you would be achieving the same result as you would from shaving the head. Smaller combustion chamber and higher compression. Only be removing material from the bottom of the head you would be changing the porting characteristics. I would not even venture a guess as to what effect that would have as opposed to just shaving the head.
I'm guessing you meant 'Only be removing material from the bottom of the cylinder....'??

Not to pick, but removing material from the head is not the same as removing material from the top (deck) of the cylinder. If you're talking about .001" I don't suppose it would matter.......


What is it you're after with the 'decking' process? IS it to 'square' the cylinder, like fuzzy said? Or...are you looking for a performance tweak?

If the latter, have your cylinder head cut-n-shaped, as RB-Designs does.

Consider the former if you have had coolant loss problems, your bike has suffered a thermal meltdown..something like that.

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Post by KDXDave »

I already have Ron's head work, & carb, with VForce 3 and a torque pipe with spacer. & 12/48 sprockets, & advance the timing <1/16". I use Evans NPGR coolant & never over heat. What I'm interested in is changing to port timing to generate more torque down low. Most of my riding is in 1st & 2nd single track than a little 3rd & 4th on a forest road than back to the single track I seldom get a run at anything steep It's usually right left right left and UP. Sometimes I slip the clutch mostly not. All my riding is above 7000ft usually 8000-9000ft. I also read Canadian Daves Just KDX and I've never read anything about decking a KDX200? Is it just not necessary? What do you think? Thanks Dave
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Post by Colorado Mike »

Sounds like you might want to look into getting a 220 cylinder for your next rebuild.
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Post by canyncarvr »

Well...that 'splains some of it.

Like fuzzy said...the 'deck' is the TOP, not the bottom.

Anywhooo...

Re: 'Is it just not necessary?'

A whole lott'a 'depends' in that.

I don't know of a situation where it would be 'necessary'...and I understand that means diddle to you. I don't ride your stuff.

I've never heard of it being done (on a KDX).

If your 200 won't run to suit you, and the 220 does, Mike has it right. Removing 'some' metal from the bottom of the cylinder will: 1. Be completely experimental, 2. Change compression, squish band, and cylinder-to-head clearances in an unimaginable way, 3. Make a perfectly good 200 cylinder completely useless if you don't like it.

Sell the 200 cylinder, buy a 220.

I'd like to see what it is you ride in the 2-hunny won't do. I spent a few days riding in Idaho this past summer...and where there was a place my bike DID get ferried up (not me riding it)..that was rider error...not the bike's problem.

Well...it didn't happen to have any water in it at the time..was hotter'n hell..and had the bottom end of a completely useless pigmobile. The trip guide still rode it up on only the second try..with both of the tries apparently effortless on his part.

On this trail:

Image

..not that spot. It was 'better'n' that. I didn't have any trouble with this spot. :wink:

Oh...that's skipro on his autoclutched KX250 in the pic.

BTW...I run a -30 pipe on my woo-two. Used to change back and forth 'tween a -35/-30 depending on what/where I was riding. Stopped doing that years ago after a combination of modifications made it no longer necessary. BTW #2, the -35 pipe will like leaner jetting than the -30.
Last edited by canyncarvr on 06:29 pm Dec 18 2008, edited 4 times in total.

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Post by fuzzy »

Could have eric gorr do a 225cc to the 200....Arguabaly the best 22x cc setup as you don't start with what many consider to be crappy factory porting on the 220. Could also ask EG what we thinks about lowering the entire cylinder....I'm gonna guess that this 'decking' procedure isn't recommended on the KDX motor, or any powervalved 2-cycle for that matter.

Could also just have a plain old 'port job' done with an emphasis on low end. A lot can be done to the ports themselves without shifting the entire cylinder. Come to think of it the only time I've seen a cyl shifted/'decked' in this manner was to compensate for extreme bore change to keep the port timing correct. For all I know this is done on a 225 as adding 25cc w/ bore is a pretty large change. Got me.

I would imagine a 225cc with porting specified for low end would be a serious tractor....Not that I've ridden one.


Also, read this thread that's currently going on:

http://www.kdxrider.net/forums/viewtopi ... highlight=

Are you sure you're getting the most from your carb?
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Post by canyncarvr »

fuzzy wrote:..or any powervalved 2-cycle for that matter.
Excellent point. I hadn't considered that hassle.
fuzzy wrote:I would imagine a 225cc with porting specified for low end would be a serious tractor...

Yeah! Wouldn't that be nice to find out? :hmm:


:wink:

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Post by KDXDave »

GREAT PICTURE! Looks like southern Colorado stuff! Do you think an auto clutch would make this easier? I thought I remember reading that you had sent your cylinder to EG for a low end port job? How did that work? I also have a KDX220 with all the same mods & think that port timing has more to do with low end power than the difference in CC's. It's quite possible $ changing it to a 220 may be better spent. Thx Dave
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Post by canyncarvr »

I've been looking now and again for a 220 cylinder myself....just to see what these 220 guys think they're talking about. EGs overbores have had more'n one result of increased fuel octane requirements..even when 'pump gas' was specified.

The last 220 cylinder I found was a whole lotta money..something like $450. Too much for me. Heck...I could get a 225 overbore for that amount of $$.

I sent a cylinder to FRP for a 'moh better....woods' port job. Not EG. It was replated by USC..and came back not round. That I found after fussing with trying to make the thing work for well over a year....or two. I have no idea how the cylinder would run with a piston that had a seal to it. I took it off a couple years back..replaced it with a 'good used' OEM 200 cylinder.

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Post by Julien D »

I'm guessing you meant 'Only be removing material from the bottom of the cylinder....'??
Yep, that's exactly what I meant.
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Post by Mr. Wibbens »

>|QBB<[/url]
canyncarvr wrote:
Image


Oh...that's skipro on his autoclutched KX250 in the pic.

.
Always neat to see Jerry ON his bike rather than Vice-versa :razz:

Where is that olfart been anyway?
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Re: "Decking" the cylinder?

Post by RBD »

>|<>QBB<
KDXDave wrote:I used the SEARCH mode with this term"decking the cylinder" and found no information. This is when you machine metal off the bottom of the cylinder. There may be another term for this and I'm not looking it up right? Has anyone done this to their KDX?
I'm guessing you meant 'Only be removing material from the bottom of the cylinder....'??


Yep, that's exactly what I meant.
Yes Dave and juliend, removing a small amount of material from the base gasket surface will give you more bottom end torque.

I have always thought this would be a good thing to do to a KDX 200. I am not so sure about doing it to the 220's (except for maybe hard core trials riding)

Please note however, the head would need to be addressed as well for the changed deck height.

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Post by Mr. Wibbens »

That would be cool

Now all you need is a guinea pig :wink:
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Post by Indawoods »

I could send in a guinea pig head and cylinder.... :grin:
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Post by Julien D »

I have a cylinder I'll guinea pig if someone want's to get it plated for me :D


HA!


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