wornknobby

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Feb 5, 2004
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ok, i'm in the process of making a sweet motor for my 90'cr 125 :aj:
i received a whole new set of cases, tranny, cylinder, hot rod crank, and some more stuff for free!! :) (some one had it as extra and didn't have the frame of the bike anymore)

is there a bore bigger than the 144? i've heard of 155's
anyways, what do i have to do to run a 144or a 155 piston?
1. can i order a 144cc piston kit from some one?
2. do these usually come w/ rings,bearing, wrist pin?
3. can a sleeve take such a big bore? or is there something special i need to do to my cylinder?

right now i'm polishing/porting the cylinder, i don't want to shave anything off the head b/c i only have my original one.(i want to keep my original motor basically as is, just in case i screw something up i will have another motor to go back to.)

now say i shave alittle off the top of the cylinder, does that screw up where my rings go, and the ridge that is at the top of the cylinder(i didn't think this would work, but if some one knows something i don't and would like to share that would be awesome :cool: )

sorry for posting such a long thread, i'm just full of q's
 

robwbright

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Apr 8, 2005
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See http://www.ericgorr.com

144 is the biggest bore kit on most 125s. You can stroke to 155 or even bigger in some cases, but that tends to be VERY expensive.

Eric is running a special right now $450.00 for overbore, port, polish, 144cc piston ring, etc . . .

I'm hoping to send him my motor before the end of the year - am scheduled to get $400.00 from a class action suit on Monday :)

Rob
 

wornknobby

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Feb 5, 2004
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well , i have acces to many tools here at home, i.e. i do my own porting/polishing, but i can't do any work w/ the cranks, b/c i'm still in the learing process with these. thats why i guess i can only go to a 144, b/c beyond this you need to stroke the crank?

but i can't seem to find any one who sells a 144cc piston kit.

my cr also has non adjustable timing, would this hurt me w/ the 144?
 

oldfrt613

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Eric did a 155 for us ( without stroking ) but we had to buy the piston from Rick Peterson (RPM). Kustom Kraft has some unreal overbores.
 

wornknobby

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does kustom kraft have asite or something?

when you bought your piston from RPM, did you just call up Rick and tell him you needed a piston to fit your 155 bore? or did you have to go through other steps before hand? :coocoo:
 

Rich Rohrich

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Eric will sell you a 144cc piston kit for your bike but you'll still have to get your cylinder bored and have it replated to use the 58mm piston.
 

Rich Rohrich

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No you can't sleeve it. The OD of the sleeves is only 59mm. You have to plate the barrel to run a 58mm 144cc setup.
 

Rich Rohrich

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wornknobby said:
so that would mean that you could only safley over bore a sleeve like 50 thousands of an inch, am i correct?

I'm not a lawnmower mechanic so I'm not really up on all the specific low level details of steel sleeves in two-stroke engines. ;)
 

wornknobby

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ok, well this might be a stupid question,
-my cylinder is plated right now, say i bore it to fit the 58mm piston, now why can't you run the cylinder like this w/ out plating? i.e. is the casting not smooth enough even after a hone?
 

Rich Rohrich

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The raw aluminum is too soft to handle the job.
 

Chili

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I'm not sure why you keep coming back to a sleeve? You can bore the cylinder and the get it replated to accomplish your goal. No crappy steel sleeve to introduce all sorts of other problems to the equation.
 

Rich Rohrich

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wornknobby said:
ok so say worst case scenario i ran a sleeve w/ the od of 59mm,,what do you think would result from this.

It would ballon at the top of the barrel and the sleeve would be junk in a matter of hours. FORGET THE #@$%ING SLEEVE :bang:
 

SpDyKen

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Rich Rohrich said:
It would ballon at the top of the barrel and the sleeve would be junk in a matter of hours. FORGET THE #@$%ING SLEEVE :bang:
Or you can spend your money to learn a valuable lesson; try it yourself & see what happens. Think you got it figured W'naabie; let us all know how it works out for you. Trial and error is a great way to learn. Sometimes you learn the value of other peoples knowledge by doing things on your own!
I wouldn't bother asking questions here if you aren't interested in the answers you get. :clue:
 

wornknobby

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its not that i'm not interested, its that i'm on a very limited budget right now and i want to make the cylinder capatible w/ the 144 kit. but i don't want to fork out $250 for someone to replate my cylinder, just so i can have the kit, b/c no matter how big or small my piston is, as long as the bike runs i will still have the same amount of fun racin :aj: :aj: :aj: :aj:
 

SpDyKen

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So go ahead and try it; you'll certainly learn SOMETHING! :rotfl:
 

Masterphil

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Eric charges $450 for stripping your old cyl, bore, replating, porting and head mods specific to you, and a piston kit ready to install. If you shop around, you'll realize that's a damn good price, especially considering that Eric's one of the best 2-stroke tuners in the world.
 

84cr125flyer

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I've got the 144 kit in my 90 CR125 and absolutely love it. It doesn't pull your arms out of socket but suffice it to say, I've been able to keep up with guys on 450 4 Strokes on it. 'nuff said. :p
 

NM_KDX200

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The 144 kit sounds great for my KX125, but I'm worried about the reliability. What I'd LIKE to have is a more reliable engine- 2 piston rings, longer piston life, etc., and I'll sacrifice a little performance to get that.

How long do the rings actually last in your 144 kits?
 

Masterphil

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Stock Bore:
A 125 can be made more reliable by widening the exh. bridge and reducing the peak RPM, but you will take away everything that makes it a 125. It will lose a lot of top end power, for a little gain on the bottom. The only efficient way to make a 125 work is to rev it, at the expense of frequent ring/piston replacement.

144 Bore:
A 144 would make a slight left shift in the powercurve and allow you to make your power at a lower RPM, this would increase reliabilits some. I think Eric reccomends a 10/20hr ring/piston interval for mo-better porting on a 144.

144Bore + stroking:
How much money would you like to spend. A 155 ( 4mm overbore and 4mm stroke increase) will make a nice left shift in the power curve without losing much peak power, but it will cost you...$$ If you go this route, you're looking at the cost of overbore to 144, and stroking of the crankshaft, but while you're in there you might as well replace the rod, and main bearings/seals. This would be the most reliable, unless you start to have tranny problems because of the increased power.
 

MXP1MP

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Well providing I get the engine crate I requested EG this morning I'll hopefully be able to tell ya first hand on what it will do to my 06 YZ 125 making it a 144.
 

NM_KDX200

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Masterphil said:
Stock Bore:
A 125 can be made more reliable by widening the exh. bridge and reducing the peak RPM, but you will take away everything that makes it a 125.

I hear ya....

Would using 2 rings help? Not that I can find a 2 ring piston for my KX, but if I could, would it?

The 125's really not that bad maintenance wise. Rings, base gasket are less than $30. It's been much better on the clutch than I expected and tire, chain, sprocket wear are all better than on a 250.
 

arjay

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84cr125flyer said:
I've got the 144 kit in my 90 CR125 and absolutely love it. It doesn't pull your arms out of socket but suffice it to say, I've been able to keep up with guys on 450 4 Strokes on it. 'nuff said. :p[/QUOTE

Could you elaborate a bit on what the power feels like. Does it have a stronger pull off the bottom? Does it still have a 125 style top end hit? Where is the power increase most noticable?

Thanks

Any feedback on the 155 power characteristics would be good as well.
 
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