Well he did say his was a stock bike that gained the 5hp or whatever it was after the mod, and that if you'd already done a lot of the standard mods the gain might only be 1hp. I can't find it now but I do recall reading it before.

I have reinstalled my 34 CVK carb and will start on the MCM after I do a timed sprint with the 34 to compare it to the 36 (which I've never done). Probably doing the intake cam first just to see how performance and jetting goes etc.

 

Other than some big bores, the biggest issue I've seen people have with the cam timing change usually ties into jetting. Same with big bore issues.

The only way to know for sure is to do one change at a time. As Richard is doing, go to the base line for comparison. Once all is proven either good or bad, then other changes should be made. Massive overall changes set up for failure and I, for one, consider any kind of jetting changes to be a major change that should be done after getting a baseline for performance, even if it is "seat of the pants, up the street".

I haven't installed an aftermarket exhaust yet, it's still sitting in the garage, because I want to make sure the carb is right to start. I did do the cam mod at the same time I jetted in the carb, but I did the most common recommended jetting for the average KLX. My brother had done his and it worked fine stock. Since we are only 110 miles apart and virtually identical altitude, I figured it would be darn close. I did the cam mod too.

My only mistake was cheating, running a stock main jet, figuring the Dial-A-Jet would cover for it, but it was too big a change for the richest setting, causing a surge. My first possible fix was the ground wire addition, which didn't take out the surge. But I already suspected it wouldn't since pulling the enrichener would smooth out the surge by slightly richening the mix. Knowing the suggested jetting with a Dial-A-Jet worked great on my brother's 06 I simply added the larger main jet and it worked. Surge was gone.

Still haven't had the opportunity for a "race" with my brother to see if the cam mod did much. Broke my ankle before we could run them off. My brother did ride mine briefly and thought it might pull stronger lower. So I'm running on "blind faith" keeping it as such.

When it comes to wheelies, I tend to keep the rpm high enough when rolling and I also tend to sit up near the tank, so they don't come easy. I can do one heck of a nice one starting out on the 650 gently applying throttle as the clutch is let out when leaving a stop - jades one's experiences on a 250 really badly.

I will say even with the lean jetting on top, when we were running in the deep sand in Michigan I never had any issue with getting rolling when it came to power. The real problem was steering in the stuff. I had 13/47 gearing and needed only to gas it up a bit, let out the clutch and work the throttle, spinning the rear wheel some. I could catch second without bog until the steering got wonky, forcing me to slow drastically and downshift or just plain stop. Learned my lesson about sand on that run... treat it like eastern Ohio muddy clay - realize when you start into it if it you can't see the end of the tough stuff that it likely won't get better. Turn around and get out!

 

I don't believe there is any reference to only 1 hp gains - under any circumstances - by Marcelino or anyone else.

Also, the thread indicates that intake cam alone doesn't produce the MCM power increase.

 

2 HP then

" Read the OP slowly and carefully. The 5 HP gain was a combination of air filter lid removed , exhaust mod and cam mod over a completly stock EFI bike . On a bike that has allready been moded at the air filter and exhaust level the gains will be smaller . You have probably gained allready 3 HP . On a carburated bike the results will vary greatly based on your ability to correctly retune the carb ." - Marcelino

KLX 250 ( 300 ) camshaft mod by Marcelino - Page 2 - KLX/KLR 125/140/250/300 - ThumperTalk (post 25)


Get the MCM re-jetting wrong on an already modded bike, and the gain might be zero.

 

Just reviewed the MCM thread again since I'm on break and goofing off way too much.

There were two references to 1 to 1.5 hp, one was the difference running with and without an air box lid, the other referring to possible gains from muffler modifications. The big gains had to do with cam retiming, small gains from some restriction changes.

It was kind of interesting to reread the stuff. Seems most issues always centered on running rich or lean as opposed to actual cam timing. Problems sometimes were situations where jetting was comparing Dyno Jet to Kiehin or Mikuni, numbers only - without reference to the actual product. Hard to translate and never actually resolved in any sort of clear way.

Some other issues appeared to be dealing with proper set up of cams - one reason I did the summary of the original to make steps and images clearer to understand. Not the author, but rather the editor and narrator in the document. From personal experience I know it was easy to be off a tooth or possibly not get the cam drive tight in the right direction to make sure the cams were right (pulling slack to the back chain run). It took me like three or four tries to get the cams aligned properly due to moving the wrong direction or not enough teeth on the chain. I knew to make the front chain run tight to check timing, thus seeing my errors.

All in all, a fun review.

Summary -

• Do the mod on a decent performing 250 stock lean conditions, or if jetted it should be running cleanly),
• Disable the compression release or remove it,
• Do NOT do any other changes at the same time,
• Run the bike for a bit to see how it performs.
• Then perform any jetting or other modifications.

As Marcelino recommends, do the starting adjustments with the needle to see what direction need be done, it makes sense, or do known changes that will work in your area, like those in the cheap mods listing.

 

MCM effects:

The intake closing point has more effect on engine-operating characteristics than any of the other three opening and closing points. The earlier it occurs the greater the cranking pressure. Early intake closing is critical for low-end torque and responsiveness and provides a broad power curve. It also reduces exhaust emissions while enhancing fuel economy.

As rpm increase, intake charge momentum increases. This results in the intake charge continuing to flow into the combustion chamber against the rising piston far past BDC. The higher the engine's operating rpm, the later the intake closing should be to ensure all the charge possible makes it into the combustion chamber. Of course, closing the valve too late will create significant reversion. It's a fine balancing act.


Overall, the exhaust valve opening point has the least effect on engine performance of any of the four opening and closing points. Later exhaust valve opening helps low rpm performance by keeping pressure on the piston longer, plus it reduces emissions. On the other hand, late closing events can help purge spent gasses from the combustion chamber and provide more vacuum signal to the intake at high rpm.



http://www.hotrod.com/how-to/engine/...amshaft-power/

 

Richard, apparently your reading Thumper Talk stuff.. I only know our MCM thread..

The mod makes noticeable power without any jetting change on a dead stock bike with 0 mods. I can attest to that.

 

In quick afterthought, one problem some have with modifications is the whole idea that they are plug-and-play. Not all are, especially when it comes to carburetors relating to jetting. Too many variables to expect perfection in one shot. So the rider has to know a bit or know of someone who can help. One blessing of EFI up to a certain point where modifications go beyond the compensation capabilities.

 

Well I'll wait till spring to re evaluate. It's not that I didn't notice any change, just that the subsequent constant playing with the settings gets frustrating at times.
I did get the bike started (finally) in the cold weather. Seems the pilot was rich and unless I was 1 turn out, it wouldn't start (put back the 38)
Oh spring. Wherefore art thou??

 

My experience is that if your bike runs correctly before MCM, it runs correctly after MCM..
I know the MCM does not require changes in jetting/fuel screw/pilot jet/needle clip/drill bits/kitchen sinks/ etc, any more than any other KLX. I suppose any previous carburetion issues, however minor, could be magnified as the TRQ comes on strong by 4k...