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I've edited this pdf in order to try to make the installation of the MCM easier to understand from a conceptual standpoint.
NOTE: In this image, the gears and the indexing marks on the gears are NOT accurate enough to be used as a precise visual guide for this mod.
While I do give "Tips" for when the cams are fully removed from the head, one at a time, and repositioned - this PDF does not attempt to detail the different methods, complexities, and all steps needed for manipulating the cams and gears.
For instance, if you choose to do the mod without removing the cams, you will be manipulating a cam gear first, then re-bolting its' cam to it..
Careful and intelligent Grease pen (white) marking of starting positions and the required final positions- of each gear/chain relationship is needed to insure correct end result..
Additional info:
While it is useless information for doing this mod correctly, some will want to know that the chain rotates right to left - counterclockwise...
The cam gear bolt holes give a 2.5 tooth change. This is too much. We need only a 1/2 tooth change in the cams. So the gear/chain relationship has to be moved 2 teeth. The text below should help with conceptualizing the mod, as well as help to understand where to (grease pen) mark the gear/chain "current and target" relationships..
The intake cam: This is the cam on the left. Changing the gear bolting to "Ex" moves the intake cam 2.5 teeth clockwise(which is advancing the cam)... This is too much advance, so you must move the gear 2 teeth counterclockwise on the chain - the result is that the intake cam is left 1/2 tooth advanced/clockwise from stock (100° instead of 110°)..
The exhaust cam: This is the cam on the right. Changing the gear bolting to "In" moves the cam 2.5 teeth counterclockwise (which is retarding the cam).. This is too much retard, so you have to move the gear 2 teeth clockwise on the chain - the result is that the exhaust cam is left 1/2 tooth retarded/counterclockwise from stock (100° instead of 110°)..
The alignment marks on each gear will visually show the 2 tooth change - instead of lining up across the top of the head casting (stock) the marks will be splayed equally (and approximately two teeth "up" from stock).. While not a precise method for measurement, if one were to mis-index a gear, the index marks would not appear to be symmetrically changed. Remember, this diagram cannot be used as a precise visual guide for the gear/gear index marks/head casting relationship. The diagram is not depicting these components precisely/correctly enough to be used as a precision visual guide for identifying a correctly done MCM..
The original done here was on an EFI model by Marcelino.
Yeah, I read that. Didn't know if there may be any differences in the bikes that would make a difference. Looks like I have a nice little winter project.
Worst case scenario, provided that you do all the work properly of course, is you don't like the results and you take it apart to retime it back to stock. But you still benefit by disabling the compression release.
The MCM has taken a bit of life again in the ADVrider forum after I mentioned it. Here is one of my posts:
SR56, post: Marcelino Cam Mod....hmmmm, retarding the cam should give the engine more high rpm power at the expense of losing low rpm power.Not saying it doesn't work but I'd be real skeptical without some dyno data to back it up.
Funny, there's a rider at the Kawasaki forum that doesn't believe the dyno results that were published. She wants someone to drag race a non-MCM bike versus an MCM bike up an on-ramp. Can't win...
Marcelino had his results published, but due to his removing the pictures from whatever the source was, they are now gone. But KLXter has the dyno results he got and published in his signature at the Kawasaki forum.I found this from Marcelino,
"When they teach you the ABCs in mechanic school they teach you that reducing the centerline of a intake cam (having it open earlier and close earlier) increases the torque and power in lows and midrange . Why ? Because the engine gets more air and because you increase the dynamic compresion (the real compresion of an engine , not the advertised/static one).Reducing the centerline of the exhaust cam (having the exhaust open later and close later) means an increase in lows and midrange . Why ? because the pressure of the gases stays in contact with the piston longer , pushing down on the piston for a longer time .This is ABC for ANY KNOWLEDGEABLE MECHANIC , and it doesn´t matter if it´s a Kawasaki or Lexus or Ferrari engine .As far as the theoretical top end that we lose by changing the centerlines from 110* to 100* here is some food for the thought :The KX250F has 35 HP at 13000 RPM with centerlines of 105* for the intake and 100 * for the exhaust ."
Thing is I believe he got it backward a bit, according to Star Racing Performance's Doug Meyer found here...
The usable range of lobe center values for just about all commonly used engines is only about 15 degrees wide from about 98 to 112 degrees and for the engines we use, the right spread is even smaller than that (note: they build lower rpm reving Harley V-twins, so this kind of validates the comparison of the KLX250 to the Ducati - klx678). Small changes of one degree can have considerable effect on the power delivery characteristics of an engine.Very generally speaking, the effect of moving lobe centers is as follows:Advancing the intake and retarding the exhaust (“closing up the centers”) increases overlap and should move the power up in the RPM range, usually at the sacrifice of bottom end power. The result would be lower numerical values on both intake and exhaust lobe centers.Retarding the intake and advancing the exhaust (“spreading the centers”) decreases overlap and should result in a wider power band at the sacrifice of some top end power. This condition would be indicated by higher numerical values on both intake and exhaust lobe centers. By moving only one cam the results are less predictable, but usually it is the intake that is moved to change power characteristics since small changes here seem to have a greater effect. With twin cam engines we have the luxury of moving the cams independently.
It seems all sources I found voiced that information. I think Marcelino fitted the cam timing to the KLX design with appropriate cam timing, if nothing else, by comparison to the KX250F timing.Judging from the dyno charts previously posted by Marcelino and those of KLXter any loss of low end occurs so low in the range that it is also an area of performance loss based on other factors like displacement along with intake and exhaust efficiencies.
There are advantages to the larger spread of the lobes, but none that really affect the KLX250.In reading I found note that the advantages of the wider valve angle stock on the KLX will slightly lower true dynamic compression, less likely to detonate, able to run lesser grade gas. It also will crank easier for starting and idle smoother. None of which really seemed to matter in my personal experience. OEM timing is essentially detuned in comparison to what should be. Heck, it may be contributing to better emissions by the lower compression and all, but I don't know that and never saw it noted.
I just bought a 2016 KLX 250 S with EFI in France with 1500km (940 miles) on the clock. It's a great all round bike and I like it a lot. I'm looking to give the bike more power for overtaking on the road but I don't want to make it louder. I like keeping the peace in the neighbouring and not pissing off other countryside users and residents when riding green lanes. I'd also like a bit more low down torque for getting over (wheelie-ing) obstacles.
I'm reading through the threads now and trying to make sense of the Marcelino cam mod:
-- does it provide a real improvement to power?
-- any longterm drawbacks to engine life?
-- what happens if I only advance the inlet cam and leave the exhaust cam?
I notice that the older KLX250 has more power -- around 27bhp. I'm guessing mine has less (21bhp) to comply with Euro 3 regulations. I'd love to get it up to the sort of power of the early KLX. However, I want to keep the standard exhaust and airbox so as to keep the bike nice and quiet.
Also, I would like to understand how and why the clutch switch mod works. It does appear that my bike will not rev above 8000rpm in the top 3 gears. What is the point of that?
Your feedback and suggestions from personal experience is very welcome.
12-09-2018, 10:50 AM
