So for me the ACR is on the exhaust cam, or i have a special model

 

It's on the exhaust cam.

Some people have done only the intake cam and gotten satisfactory gains.

Us new guys gotta stick together...since no one wants to answer questions; I'll just go ask the local mod shop owner. He probably only earns a few hundred dollars a month here in Asia-but he knows engines and won't chide you for asking questions

Enjoy yourselves

 

+1

Doxbike, Do not touch your poor KLX

 

Doxbike, you need to really read and understand the mod, or take your bike to someone that does. You can choose to do INTAKE Cam mod only, or BOTH.
You cannot do exhaust Cam side only. If you choose to do Intake side only, no need to reposition ACR.
Doing intake side only seems to benefit the 300 cc engine. ( I have not read any reports about doing only the intake side on a 250 )

I attempted to do this mod 2 times on my own, and both times I put it all back to standard as I was experiencing a clatter noise on start up. I was making an error somewhere maybe. So now I have gone 331 cc with Webcams.

 

Sorry if I misunderstood, maybe I misheard the guy on the video talking about working on the exhaust cam. I'll go listen to it again.

OK, I listened again to post 428 and unless I'm not hearing or am misinterpreting, the guy doing the video only is doing the exhaust cam. (on the cylinder closest to the front of the bike). I haven't torn into anything yet, that's why I am asking. And to belay your fears, I have already talked to a local mechanic-I just want to know enough so I can verify that he knows what he's doing.

Thanks for your input

 

Grahamgower, about your startup noises... I was overly meticulous in performing my mod - marking positions on components, taking before and after pictures on everything, turning engine by hand and then by starter (w/o the spark plug installed of course) before the first startup, etc etc .... While my first startup was flawless, additional startups were not. I had to go back into the engine many times to try to figure out the cause of noises. I ran the engine without the cam cover numerous times to track down the sounds. The first event seemed to cure itself and I believe was the ACR sticking and not functioning correctly until it received a good bathing of warm engine oil.
The second noise event was very different from the first. It was associated somehow with the cam chain. After many hours of observation and testing the result was that the tensioner adjusting screw had to be set about half way out. Re-setting and installing with the screw all the way in would somehow cause the noise- leaving the adjuster off the bike allowed some cam chain whip but no noise. Perhaps the cam re-time mod changed the dynamics and requirements demanded from the tensioner.

I cannot fully explain the causes of these noise events. Each sounded like I had trashed the engine. I will be bothered by this for the foreseeable future.

The bike now has about 150 trouble-free miles on it since the mod.
I just wanted you to know of my experience with engine noises after the mod.


Yall please don't anger me with accusations of having dropped things (like the two index pins on the camshaft upper support casting) into the engine.

 

Video of new found power after the mods. I admit that I unknowingly, automatically, pulled on the handle bars to assist the wheelies but I do not think it is required. The clutch WAS NOT used to assist in the wheelies.

This is what you'll get from this cam mod , a slip on , Dynojet stage 2 as per instructions , and the airbox lid removed , on an otherwise stock 2012 KLX250S.

KLX After Mods Ride - YouTube

Please read my previous posts before commenting as I am old an crotchety.

 

I keep thinking about doing the cam mod, but I have some niggling doubts….

1) Comparison of power curves (ref posts #1 & 5):

If you overlay the standard KLX250S EFI power curve on the CRF250X vs WR250F curves it all looks very believable – the KLX makes more power (and therefore torque) up to about 5.5K then the CRF keeps climbing to reach 26HP a 10K rpm, whereas the KLX peaks at 19 @ 7k5.
However the MCM (Marcelino Cam Mod) has more power than a CRF250X right up to 8K rpm and the peak is only 2HP less. Also at 7.5K the MCM produces 24HP versus a WR250F producing only about 14HP.
Incredible!!

2) Cam timing and angles (all figures are “advertised” not at 0.050”, so somewhat moot. However I cannot find 50 thou figures for the KLX and the relative difference between KLX and MCM should provide useful info):

The cam sprocket holes don’t look exactly 2.5 teeth apart to me. I did some measurements and a bit of geometry and worked out they are ~30.6° apart (in terms of crankshaft angle) and 2 teeth = 22.5°. Therefore the MCM mod changes the crankshaft angles by ~8°, not 10° as suggested.
KLX standard timing, inlet: 22° BTDC & 62° ABDC = 264° duration and mid at 110° ATDC
KLX standard timing, exhaust: 62° BBDC & 19° ATDC = 260° duration and mid at 111° BTDC
Therefore LSA = 110.5° and overlap = 41°

MCM timing, inlet: 30° BTDC & 54° ABDC = 264° duration and mid at 102° ATDC
MCM timing, exhaust: 53° BBDC & 27° ATDC = 260° duration and mid at 103° BTDC
Therefore LSA = 102.5° and overlap = 57°

A quick look at the Webcams site reveals:
LSA 110-112 = moderately wide
<104° = extremely tight!!

Looks like a good thing the MCM only changes the timing by 8° and not 10°!

As a sanity check, Webcams 101 grind:
Inlet: 21° BTDC & 49° ABDC = 250° duration and mid at 104° ATDC
Exhaust: 51° BBDC & 19° ATDC = 250° duration and mid at 106° BTDC
Therefore LSA = 105° and overlap = 40°

2a) Concerns:
The MCM has “extremely tight! LSA which could result in the valves hitting each other (in a worn engine). This sort of LSA is regarded as a very “hot” cam i.e. narrow powerband.
MCM has very wide overlap which is good for high RPMs and bad for fuel economy and emissions. Quote from Zomby Woof, post #125:
https://www.kawasakiforums.com/forum...13/#post258116

“Because of the large valve area, the 4 valve/cylinder motors are much more duration sensitive than the 2 valve/cylinder motors.In other words,the same cam will net very different results on the two motors. The 4 valve motors produce more power with less duration, and overlap, but will also start to lose low RPM power in a real hurry as duration at .050" increases beyond 210-220 degrees.!

3) My conclusion (based on lots of internet reading and zero experience!!!)

Advancing the inlet valve closing will help power at all revs due to an effective increase in compression ratio, with the trade-off that the engine may not tolerate very low octane fuel.
All the other MCM timings will narrow the power band and may lead to a more noticeable step in power in the midrange. Could it be that people feel this step as more power, when it’s just less power below the step?
I am somewhat worried about engine damage due to the tight LSA.
I cannot find any other cams for any type of engine that have 57° of overlap.
M’s dyno curves seem too good to be true.
M mentions the KLX cam timing seems to be more suited to >10K RPM. I would like to know why this is the case.

Overall, I think I will leave well alone…… although more (mid range) power/responsiveness would solve the biggest niggle with the KLX – difficulty lofting the front wheel over trail obstacles – so maybe I need to investigate just advancing the inlet valve timing?

Have I got this all badly wrong??

 

I did just the inlet valve timing and it did a great deal of difference i have a lot more low end and top end tork

i am so happy with doing the intake only that i wont do the exhuast

i'm getting 50 mpg on the trails (deep sand hill climbs and mud )

and thats the only place i ride the klx

 

DT175MX, your opinions based on your own assumptions and observations ( i.e. ~30.6°) make for an interesting read. I appreciate you for your post, your effort, and especially - " 3) My conclusion (based on lots of internet reading and zero experience!!!)".
I would expect damage done to our bikes by this mod would have been reported on this thread during its' 2+ year existence. That is why I performed the mod after reading every page over and over looking, in part, for damage reports.
I'm sure all of us would agree that intake cam re-time alone provides benefits and is a snap to perform for those not able/capable of the exhaust cam and ACR.

However, part of your conclusion - "M’s dyno curves seem too good to be true. " goes to casting dispersions. Please dyno your bike, do the intake, dyno again, add the exhaust mod, dyno again. Do this with either a 100% stock bike or one with a slip-on, stage 2 dynojet kit, and airbox lid removed. Post all results and conditions.

Until then, I believe the answer is that, yes, you have this wrong.