KLX 250 ( 300 ) camshaft mod by Marcelino
#92
06-25-2011 | 03:46 AM
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Joined: Mar 2009
Posts: 333
From: Quebec, Canada
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That's a good point. Since the engine appears to have better volumetric efficiency with the new timing (more air is trapped when the intake valve closes), there is more pressure in the cylinder during compression. Might be equivalent to an increase in compression ratio by a few points (??). Thus it is possible that low octane fuel will show a tendency for pinging or detonation. Time will tell...
#93
06-25-2011 | 04:17 AM
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Joined: Jan 2008
Posts: 869
From: SW Ontario, Canada
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If I can add any validity to this mod, I am in the custom cam business, do a pile of cylinder head work, and it makes perfect sense. 110 degree intake centerline is a little late for a motor of this size.
I almost (the KLX is my reliable, leave it alone bike) feel embarrassed for not finding this myself first. It really never ocurred to me to look for it.
Search 3tech timing advance sprocket. 3tech is me. I've been doing it on the Suzuki's for 10 years.
I almost (the KLX is my reliable, leave it alone bike) feel embarrassed for not finding this myself first. It really never ocurred to me to look for it.
Search 3tech timing advance sprocket. 3tech is me. I've been doing it on the Suzuki's for 10 years.
#94
06-25-2011 | 04:21 AM
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Joined: Apr 2011
Posts: 99
After JUST doing the intake cam... its definetly..... different.
No more CRAZY intake resonance...but the exhaust is WAY louder.
Pulls the front tire up in first just rolling on the throttle.
When I get more time tomorrow I will take it out for a top speed run/WOT shakedown. I will without a doubt say that it actually pulls 6th gear with some authority now! I was cought off guard by it actually. I did a few quick clutch wheelies and almost looped the damn thing!! I figured that was enough for tonight.
No more CRAZY intake resonance...but the exhaust is WAY louder.
Pulls the front tire up in first just rolling on the throttle.
When I get more time tomorrow I will take it out for a top speed run/WOT shakedown. I will without a doubt say that it actually pulls 6th gear with some authority now! I was cought off guard by it actually. I did a few quick clutch wheelies and almost looped the damn thing!! I figured that was enough for tonight.
#95
06-25-2011 | 04:39 AM
Senior Member
Joined: Mar 2009
Posts: 333
From: Quebec, Canada
1st Gear Member
If I can add any validity to this mod, I am in the custom cam business, do a pile of cylinder head work, and it makes perfect sense. 110 degree intake centerline is a little late for a motor of this size.
I almost (the KLX is my reliable, leave it alone bike) feel embarrassed for not finding this myself first. It really never ocurred to me to look for it.
Search 3tech timing advance sprocket. 3tech is me. I've been doing it on the Suzuki's for 10 years.
I almost (the KLX is my reliable, leave it alone bike) feel embarrassed for not finding this myself first. It really never ocurred to me to look for it.
Search 3tech timing advance sprocket. 3tech is me. I've been doing it on the Suzuki's for 10 years.
Just kidding, I am in your very situation many times
So might be the Kawasaki engineers too. Possibly for this timing thing, but also, from my point of view, for the fork and shock valving. Would you happen to have anything to say concerning the reduced valve-piston clearance? I am tempted to do this mod myself (when I have time, which is not nowadays), but I am a little feared about that point. I expect there would be no issue, but I need insurance as I can't afford to put the time required for a repair if something bad happens.
#96
06-25-2011 | 04:40 AM
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Joined: Jun 2011
Posts: 592
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After JUST doing the intake cam... its definetly..... different.
No more CRAZY intake resonance...but the exhaust is WAY louder.
Pulls the front tire up in first just rolling on the throttle.
When I get more time tomorrow I will take it out for a top speed run/WOT shakedown. I will without a doubt say that it actually pulls 6th gear with some authority now! I was cought off guard by it actually. I did a few quick clutch wheelies and almost looped the damn thing!! I figured that was enough for tonight.
No more CRAZY intake resonance...but the exhaust is WAY louder.
Pulls the front tire up in first just rolling on the throttle.
When I get more time tomorrow I will take it out for a top speed run/WOT shakedown. I will without a doubt say that it actually pulls 6th gear with some authority now! I was cought off guard by it actually. I did a few quick clutch wheelies and almost looped the damn thing!! I figured that was enough for tonight.
#97
06-25-2011 | 05:43 AM
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Joined: May 2010
Posts: 494
From: Sydney
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... the KLX doesnīt have enough intake advance and has too much exhaust advance .
... can do the mod without modifying the sprockets at all ....
...Well , if we look CLOSELLY at a sprocket whe see that the distance between the two holes that correspond to " for INtake " and " for EXhaust " is two and A HALF teeth .
Well the solution is at follows :
For intake we give it 2 and a half teeth more advance by puting the screws in the position that corresponds to exhaust and then we retard the camshaft 2 teeth in the chain . The difference , as far as the cam is concerned , is a 1/2 tooth ( 10-something degrees )
For the exhaust cam itīs the same , but in the opposite direction : we retard the cam by puting the screws in the intake position and then we put the sprocket 2 teeth more advanced in the chain . This cam will de 1/2 teeth retarded ( 10.5 degrees ) .
...Most of us know that everything good comes with strings attached :
Modifying the exhaust cam advance / retard modifyies the ACR (automatic decompressor) advance/retard . In this case the ACR will release the exhaust valve it touches 10 degrees later loosing a little more compression ... The cold start is like an old bike ; the hot start is near impossible ...
... HAVE TO REPOSITION THE ACR ... A friendly word of advice : Donīt do this at home ! take the camshaft to a head shop and have them do the ACR. The camshaft is hollow and the ACR can be pressed out using a rod , it needs to be turned 6-7 mm ( 1/4 inch ) at the edge counter-clock-wise as you look at the ACR .
...
The bike really goes now. Have no intake grawl , even with the filter cover removed , just regular intake noise , no grawl , itīs imperceivable while the bike is moving .
...
Owners of carburates bikes may / will need rejetting the carb .
... can do the mod without modifying the sprockets at all ....
...Well , if we look CLOSELLY at a sprocket whe see that the distance between the two holes that correspond to " for INtake " and " for EXhaust " is two and A HALF teeth .
Well the solution is at follows :
For intake we give it 2 and a half teeth more advance by puting the screws in the position that corresponds to exhaust and then we retard the camshaft 2 teeth in the chain . The difference , as far as the cam is concerned , is a 1/2 tooth ( 10-something degrees )
For the exhaust cam itīs the same , but in the opposite direction : we retard the cam by puting the screws in the intake position and then we put the sprocket 2 teeth more advanced in the chain . This cam will de 1/2 teeth retarded ( 10.5 degrees ) .
...Most of us know that everything good comes with strings attached :
Modifying the exhaust cam advance / retard modifyies the ACR (automatic decompressor) advance/retard . In this case the ACR will release the exhaust valve it touches 10 degrees later loosing a little more compression ... The cold start is like an old bike ; the hot start is near impossible ...
... HAVE TO REPOSITION THE ACR ... A friendly word of advice : Donīt do this at home ! take the camshaft to a head shop and have them do the ACR. The camshaft is hollow and the ACR can be pressed out using a rod , it needs to be turned 6-7 mm ( 1/4 inch ) at the edge counter-clock-wise as you look at the ACR .
...
The bike really goes now. Have no intake grawl , even with the filter cover removed , just regular intake noise , no grawl , itīs imperceivable while the bike is moving .
...
Owners of carburates bikes may / will need rejetting the carb .
You have rocked the KLX world! Brilliant work and thatnk you so much for sharing it with us!
Anyone else second the motion for this mod to be called "The Marcelino Cam Mod"?
So here a controversial call... does this mod yield better power gains than the 351cc kit? Certainly sounds better bang for buck given it'll only cost getting the ACR timing sorted.
Last edited by Arctra; 07-03-2013 at 10:08 PM.
#98
06-25-2011 | 05:55 AM
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Joined: May 2011
Posts: 123
From: Spain
Awesome Marcelino!
I've got to go back and re read your first post now.
I do hope that others will post there results and help make it even clearer for me.
I've only timed one cam before and it's very difficult for me to get all the things straight in my mind.
I'm really courious about doing just the intake and how that works out.
Is 87 octane fuel still going to be OK?
I've got to go back and re read your first post now.
I do hope that others will post there results and help make it even clearer for me.
I've only timed one cam before and it's very difficult for me to get all the things straight in my mind.
I'm really courious about doing just the intake and how that works out.
Is 87 octane fuel still going to be OK?
#100
06-25-2011 | 05:58 AM
Thread Starter
|
Senior Member
1st Gear Member
Joined: May 2011
Posts: 123
From: Spain
Now i gotta do this.
im going to have to take a day off work now
how much pressure was needed to press out the ACR? can a hammer and wooden dowel get the job done or do i need to take it to the shop and in the press?
Same question for reinstall? did you need to really crank on the press to get it in?
im going to have to take a day off work now
how much pressure was needed to press out the ACR? can a hammer and wooden dowel get the job done or do i need to take it to the shop and in the press?
Same question for reinstall? did you need to really crank on the press to get it in?