KLX 250 ( 300 ) camshaft mod by Marcelino
#282
07-21-2011 | 06:55 AM
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Senior Member
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Joined: May 2011
Posts: 123
From: Spain
I have the data that was missing from the original post .
The piston to valve clearance is 3.2 mm for the intake and 2.6 mm for the exhaust . These values are with the cam mod . With the original timing the values are 3.4 and 2.8 . These values are a whole lot higher than the minimal clearance required wich are 1.5 - 2 mm . This renders the argument of dangerously close valve to piston clearance mute .
On a different topic I have some other numbers for those who may wish to know :
The squish on the KLX is 1 mm . For those seeking more compression , let me remind you that you should not go under 0.7 mm under no circumstance !
The displacement of the combustion chamber in the head is 18 cc and it's the same for KLX 250 and KLX 300 .
The displacement in the squish volume is 4 cc . This makes the total for the combustion chamber on a 250 equal to 22 cc . 250 / 11 = 22.-something .
The 300 piston has a big shallow recess with a capacity of 5 cc .This makes the combustion chamber of a 300 reach 27 cc . 300 / 11 = 27.- something .
When measuring volumes one cannot get to under 1 cc accuracy without fancy lab equipment so please take all the volume measurements with a +/- 0.5 cc tolerance .
The piston valve recesses have the exact same depth in the 250 and the 300 pistons ( the original Kawasaki ones ) . The 300 recesses may seem smaller due to the big central recess that adds 5 cc to the combustion chamber .
I will update the original post with the valve to piston clearence data shortly .
The piston to valve clearance is 3.2 mm for the intake and 2.6 mm for the exhaust . These values are with the cam mod . With the original timing the values are 3.4 and 2.8 . These values are a whole lot higher than the minimal clearance required wich are 1.5 - 2 mm . This renders the argument of dangerously close valve to piston clearance mute .
On a different topic I have some other numbers for those who may wish to know :
The squish on the KLX is 1 mm . For those seeking more compression , let me remind you that you should not go under 0.7 mm under no circumstance !
The displacement of the combustion chamber in the head is 18 cc and it's the same for KLX 250 and KLX 300 .
The displacement in the squish volume is 4 cc . This makes the total for the combustion chamber on a 250 equal to 22 cc . 250 / 11 = 22.-something .
The 300 piston has a big shallow recess with a capacity of 5 cc .This makes the combustion chamber of a 300 reach 27 cc . 300 / 11 = 27.- something .
When measuring volumes one cannot get to under 1 cc accuracy without fancy lab equipment so please take all the volume measurements with a +/- 0.5 cc tolerance .
The piston valve recesses have the exact same depth in the 250 and the 300 pistons ( the original Kawasaki ones ) . The 300 recesses may seem smaller due to the big central recess that adds 5 cc to the combustion chamber .
I will update the original post with the valve to piston clearence data shortly .
#283
07-21-2011 | 08:53 PM
Senior Member
Joined: Mar 2009
Posts: 333
From: Quebec, Canada
1st Gear Member
I have the data that was missing from the original post .
The piston to valve clearance is 3.2 mm for the intake and 2.6 mm for the exhaust . These values are with the cam mod . With the original timing the values are 3.4 and 2.8 . These values are a whole lot higher than the minimal clearance required wich are 1.5 - 2 mm . This renders the argument of dangerously close valve to piston clearance mute .
On a different topic I have some other numbers for those who may wish to know :
The squish on the KLX is 1 mm . For those seeking more compression , let me remind you that you should not go under 0.7 mm under no circumstance !
The displacement of the combustion chamber in the head is 18 cc and it's the same for KLX 250 and KLX 300 .
The displacement in the squish volume is 4 cc . This makes the total for the combustion chamber on a 250 equal to 22 cc . 250 / 11 = 22.-something .
The 300 piston has a big shallow recess with a capacity of 5 cc .This makes the combustion chamber of a 300 reach 27 cc . 300 / 11 = 27.- something .
When measuring volumes one cannot get to under 1 cc accuracy without fancy lab equipment so please take all the volume measurements with a +/- 0.5 cc tolerance .
The piston valve recesses have the exact same depth in the 250 and the 300 pistons ( the original Kawasaki ones ) . The 300 recesses may seem smaller due to the big central recess that adds 5 cc to the combustion chamber .
I will update the original post with the valve to piston clearence data shortly .
The piston to valve clearance is 3.2 mm for the intake and 2.6 mm for the exhaust . These values are with the cam mod . With the original timing the values are 3.4 and 2.8 . These values are a whole lot higher than the minimal clearance required wich are 1.5 - 2 mm . This renders the argument of dangerously close valve to piston clearance mute .
On a different topic I have some other numbers for those who may wish to know :
The squish on the KLX is 1 mm . For those seeking more compression , let me remind you that you should not go under 0.7 mm under no circumstance !
The displacement of the combustion chamber in the head is 18 cc and it's the same for KLX 250 and KLX 300 .
The displacement in the squish volume is 4 cc . This makes the total for the combustion chamber on a 250 equal to 22 cc . 250 / 11 = 22.-something .
The 300 piston has a big shallow recess with a capacity of 5 cc .This makes the combustion chamber of a 300 reach 27 cc . 300 / 11 = 27.- something .
When measuring volumes one cannot get to under 1 cc accuracy without fancy lab equipment so please take all the volume measurements with a +/- 0.5 cc tolerance .
The piston valve recesses have the exact same depth in the 250 and the 300 pistons ( the original Kawasaki ones ) . The 300 recesses may seem smaller due to the big central recess that adds 5 cc to the combustion chamber .
I will update the original post with the valve to piston clearence data shortly .
One note, using a "squish" of 1mm gives me a volume of 2.94cc with the 61.2mm bore. I assume what you call squish is the distance from piston top to cylinder top at TDC. Is the 4cc you mention due to the additional tickness of head gasket?
#284
07-22-2011 | 07:51 AM
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Senior Member
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Joined: May 2011
Posts: 123
From: Spain
Good work. Did you measure those volumes yourself, or took these numbers somewhere on the net?
One note, using a "squish" of 1mm gives me a volume of 2.94cc with the 61.2mm bore. I assume what you call squish is the distance from piston top to cylinder top at TDC. Is the 4cc you mention due to the additional tickness of head gasket?
One note, using a "squish" of 1mm gives me a volume of 2.94cc with the 61.2mm bore. I assume what you call squish is the distance from piston top to cylinder top at TDC. Is the 4cc you mention due to the additional tickness of head gasket?
On a 250 the bore is 72 and the stroke is 61.2 . The volume of the squish is 4 cc as I said earlier .
The head gasket thickness is 0,75 mm and the base gasket has 0.5 mm .
#285
07-22-2011 | 02:34 PM
Senior Member
Joined: Mar 2009
Posts: 333
From: Quebec, Canada
1st Gear Member
I have asked a friend who is upgrading to 300 to do it for me . The data has been published in a spanish forum as well .
On a 250 the bore is 72 and the stroke is 61.2 . The volume of the squish is 4 cc as I said earlier .
The head gasket thickness is 0,75 mm and the base gasket has 0.5 mm .
On a 250 the bore is 72 and the stroke is 61.2 . The volume of the squish is 4 cc as I said earlier .
The head gasket thickness is 0,75 mm and the base gasket has 0.5 mm .
#287
07-23-2011 | 03:01 PM
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Joined: Jun 2011
Posts: 592
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Did you talk to him about doing the camshaft mod?
#289
08-02-2011 | 11:23 AM
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Joined: Jun 2010
Posts: 150
Quick question regarding the acr. Is it really that much harder to start without repositioning it? Does choking it help any? Im going to start this tonight. Will report back when its complete with a list of my mods and what i feel. Ill stack it up against my friends wr250.
#290
08-03-2011 | 12:03 AM
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Joined: Feb 2011
Posts: 628
From: Northern Kettle Moraine
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I did the acr as Marcellino described and it starts better hot. From what I have read it is near impossible to start hot without doing the acr. I did the acr myself by tapping it out with a large bolt and put it together in a vice very carefully, this method was posted by KansasKLX I believe.