KLX 250 ( 300 ) camshaft mod by Marcelino
Feel free to correct me if i'm wrong and my understanding of the mod is inaccurate.
If someone were to go through the trouble of timing the cams by the book, they should also notice that the bolts are in the wrong holes. If they don't notice that, god help them!
Bolts for the exhaust cam are in the intake holes. ACR is on the exhaust cam. Kind of obvious something is going on to anyone with a little expierence. I used the manual to replace the jug and piston on my bike. I took pictures of the timing before tear down. Sometimes I do it at work too. Digital is the *****, way better than my old drawings. Sometimes I wire the chain to the cam sprockets.
David
David
As I write this there have been 5,030 posts since Marcelino first rocked the KLX250 world this time last week. Took a day or two but it really took off.
Maybe there should be some kind of cake or award presented or something.
I've had the full mod applied for a couple of days, now, and am presently messing with the air box lid to see how that will do but regardless, to all those who are unsure or waiting, it is a pretty good (and free!
) mod that adds a little pep to the lower and mid ranges. I can only speak for my 250 engine with stock 42/14 gears. Others will have to speak for the 351 and 250's with different mods/gearing applied.
Thank you Marcelino. What's next, a free mod for supercharging to 50hp?
Maybe there should be some kind of cake or award presented or something.
I've had the full mod applied for a couple of days, now, and am presently messing with the air box lid to see how that will do but regardless, to all those who are unsure or waiting, it is a pretty good (and free!
) mod that adds a little pep to the lower and mid ranges. I can only speak for my 250 engine with stock 42/14 gears. Others will have to speak for the 351 and 250's with different mods/gearing applied.Thank you Marcelino. What's next, a free mod for supercharging to 50hp?

Also, the stator output is 39 VAC ('wires with AC coming into the regulator')..not sure where you got the 12V figure from. I have the DC CDI for the KLX250ES adapted to my later model KLX, and while you don't get the 40 deg total advance of the KLX300/250R, you still get an extra 10 deg over stock. A rarity here in Japan is to find the CDI for the KLX250SR, where you get the same advance as the old AC CDI's on the 300/250R's
Last edited by tremor38; Jul 1, 2011 at 06:33 AM.
Yes what I am saying is if someone timed it by the book after the mod(becuase they never heard of the mod) They could destroy the engine. No ones going to forget about it now becuase its the shiznit but 3 years from now when you sell the bike?? or when you give it to your oldest boy and he has one of his mates work on it with him?
I may be an idiot but I will admit that I did not look to see which holes the bolts were in ANY of the times I had the cams out. Why would I expect the bolts to possibley be in the WRONG holes on a working engine if I did not know about this mod?
I am suggesting marking the sprockets for the benifit of future owners or yourself if you think you might EVER POSIBLY have a shop work on your bike. I think you would be hard pressed to get a Kawi dealership to fix the damage if you did not alert them to the mod. Probably depends on the dealership and your relationship but good luck.
What I propose is to mark a line where the sprokets now line up with the head and put a single line thru the original. That would be enough for me to say WTF & I would apreciate
Dont get me wrong I think its a GREAT mod and plan on doing it.
Flame away.
Cheers Jim
I may be an idiot but I will admit that I did not look to see which holes the bolts were in ANY of the times I had the cams out. Why would I expect the bolts to possibley be in the WRONG holes on a working engine if I did not know about this mod?
I am suggesting marking the sprockets for the benifit of future owners or yourself if you think you might EVER POSIBLY have a shop work on your bike. I think you would be hard pressed to get a Kawi dealership to fix the damage if you did not alert them to the mod. Probably depends on the dealership and your relationship but good luck.
What I propose is to mark a line where the sprokets now line up with the head and put a single line thru the original. That would be enough for me to say WTF & I would apreciate
Dont get me wrong I think its a GREAT mod and plan on doing it.
Flame away.
Cheers Jim
I think what Jim was saying is that if someone attempted to time the engine to spec using the cams with the sprocket mod done they would be two teeth out since the camshaft/sprocket relationship has changed.
Feel free to correct me if i'm wrong and my understanding of the mod is inaccurate.
Feel free to correct me if i'm wrong and my understanding of the mod is inaccurate.
Are you sure you wouldn't opening a can or worms with that? None of the 3 phase load is distributed prior to going though the Reg/rectifier. Unbalancing the phases by loading one of them might be asking for some problems. I've been known to be wrong though
Also, the stator output is 39 VAC ('wires with AC coming into the regulator')..not sure where you got the 12V figure from.
I have the DC CDI for the KLX250ES adapted to my later model KLX, and while you don't get the 40 deg total advance of the KLX300/250R, you still get an extra 10 deg over stock. A rarity here in Japan is to find the CDI for the KLX250SR, where you get the same advance as the old AC CDI's on the 300/250R's
Also, the stator output is 39 VAC ('wires with AC coming into the regulator')..not sure where you got the 12V figure from. I have the DC CDI for the KLX250ES adapted to my later model KLX, and while you don't get the 40 deg total advance of the KLX300/250R, you still get an extra 10 deg over stock. A rarity here in Japan is to find the CDI for the KLX250SR, where you get the same advance as the old AC CDI's on the 300/250R's

You can take one of the phases and do as you please with it , who said the consumption has to be balanced ? Most triphasic loads are imballanced . The generator just supplies 3 independent phases with the same voltage on each and every one of them . The older bikes and many of todayīs MX bikes supply only 2 phases , one with 12 V and one with 48 volts ( under load ) , and with the bike in 4000 revs ( and under load ) 14 V and 56 V .
I have put a 1X5 transformer in my earlier post out of my gut , Iīm not actually sure what the loses will be on a 50 or 60 Hz transformer when itīs running in a variable frequency 150 or 200 Hz to a few thousant Hz ( I really donīt know how many poles the rotor has ) . Maybe a safer approach is to use a 1X4 transformer , see where the voltages are under load and start fromm there . The voltaje that gets to the old ignition itīs not stabilized , it varies greatly from 40-something ( at idle ) to more or less 60 at full revs .
Another approach would be to rewind one of the three phases with a smaller wire , but double the number of winds , the output voltage is proportional to the square number of winds , given the same magnetic flux ( induced by the magnets in the rotor ) .
That 40 V figure given in many bikeīs service manual is measured with a digital voltmeter and absolutely no load . If the output would be actually connected to something you would get more some 12 V ac. or 14 V ac with a little revs .
The problem you comment on about the inertia of the reciprocating mases is a non-issue in the KLX250 , for example the KXF 250 has about the same mases ( lighter piston and heavier rod ) and itīs a happy reving engine up to 13000 RPM . There are a lot of engines with 35* max advance and while quite a lot heavier do not experience a power loss after 7500-8000 RPM they rev quite happily up to 9000-10000-11000 RPM . 25 degrees of maximum advance is totaly inadequate after 7000 RPM . Look at the power graphs and see where the top power would be if the graph would continue to rise up to 10000 .
Could you please try to find out something about that Keihin racing ECU ? Iīm at a dead end over here , and Iīm really fed up with dealers that have the " I know whatīs best for you atitude " . Itīs my bike and if I choose tomorow to put NOS on it itīs my choice to make not anybodyīs else .
Last edited by Marcelino; Jul 1, 2011 at 08:50 AM.


