I found the mod fairly easy to do even though I managed to muck up disconnecting the ACR, but with some suggestions from klx678 I was able to correct my screw-up. The screw-up made the engine sound like it had tappets on steroids. When I corrected that screw-up the bike started well and sounded ok, but it did not pull well at all from 3000 rpm on moderate uphills. It felt like it was starving for fuel. So it was put back to the OEM cam configuration. Now its back to running pretty darn smoothly and strong from 3000 rpm on up. I have detailed pictures of the cams before and after; and they appear to look like the photos in other threads that show how to do the mod. So I'm puzzled, but also happy that it is back to running like it did before I started monkeying around with the cams.

Not having anything to do with the performance, but more of a heads up, I noticed that the little allen bolts that hold the cam gears on will loosen up even when torqued down to spec. I noticed that when I tore it down to fix the ACR issue, not when I tore it down to go back to stock.

 

I'm sure you know that the MCM is not an experimental mod. It is a leap in power production from off idle to 6500 rpm - proven with dyno charts as well as years worth of member dynobutts.

You do the retime accurately, pull the spring off the KACR, correctly replace the tensioner, and you are done.. If the fueling is set up correctly before the mod, it does not require a change.. If the fueling is borderline improper before the mod, the increased requirements placed on the carb may create problems. However, retuning for the MCM will always be "best practice"..

 

Did you do any jetting from stock with the carb before doing the cam retiming? I agree with KLXter, it needs rejetted and may need it even more so with the cams retimed to give more midrange. I had my bike rejetted with the Keihin/Kawasaki brass, KLXter did Dyno Jet. I had tried going on the cheap originally, doing a shimmed needle, but had to put in the N1TC adjustable needle. I don't remember for sure but I believe I have the .040 pilot, N1TC second notch from the top, a 125 main (normally too lean, my brother runs the 128), and drilled slide. I use the Dial-A-Jet fuel adder to cover for lean spots.

I will also tell you I virtually never will try to accelerate hard from 3000 rpm even with my KLX650 or my Yamaha SR500. They stumble all over the place. 3000 rpm s too low to pull well in anything but first or second. Even then with the 250 I stay above 4000 rpm and with the 650 above 3500 rpm. They just do not pull strong down low, regardless of jetting. Only time I'm accelerating below that is if gently picking up speed. Been riding the 650 for 30,000 miles, it's jetted well and will pull strongest if around 4000. Only have about 5000 on the 250 (not much riding the last two years for a variety of reasons) and find it best to be more around 4500 and up, 5000 rpm is the best back roading and off roading for my experience. They aren't exactly tractors.

Now for your other issue,cam fasteners. You need to use some thread locking agent like Loctite blue 242 when putting the cam fasteners back in. I did that and would not trust reassembly without it. Too many risks doing the job without Loctite. If you want to be really assured, cross drill the heads and safety wire the fasteners.

 

 

Well, the way you are attempting to "frame it" is incorrect. The MCM, radically increases power below 6500 rpm and maintains power levels within 1 hp from 6500 - redline..

All mod combos have trade-offs compared to other mod combos..

The only reason to not perform the MCM would be for a bike that is specifically modded for only top end power ( 7000 - 10500 rpm).. However such a mod combo would suffer a significant loss of power below 7k rpm..

Combining a lidless airbox, proper lidless CVk setup, full performance exhaust system AND the MCM creates significant increases from idle - redline and is the best "overall" power curves available for a stockbore with CVK.. And don't forget that such KLX's have a top speed of over 100 mph with standard sprockets..

 

klxster said:

"You do the retime accurately, pull the spring off the KACR, correctly replace the tensioner, and you are done.. If the fueling is set up correctly before the mod, it does not require a change.. If the fueling is borderline improper before the mod, the increased requirements placed on the carb may create problems. However, retuning for the MCM will always be "best practice".."

Because I turned the motor over by hand to make sure there wasn't any interference and when doing this re-set it to TDC and then verified everything looked like the "successful" pictures; I'm fairly sure the retime was done accurately. As to the fueling setup beforehand, I purchased the carb from GBAUTO three years ago, it came from him with the Dynajet, Stage II kit installed. Precisely how he set the carb up when installing that kit, I don't know. When installing that carb I remove the snorkle. I do know that the bike started easily and ran like a champ at 4,000 to 6,000' where I do most of my riding.

After doing the cam mod, the bike continued to start real easily and for the most part was running well except as noted when doing a moderate uphill, it wouldn't pull cleanly from about 3,000 or so rpm's. I was concerned that I did something else in the process of the teardown to muck up the fuel delivery system, but when I went back to the stock cam timing the problem went away. As to performance in other areas of the rpm range, my dynobutt is not refined enough to tell the difference. I put on about 90 miles of both FS roads and highway riding.

When I went back to stock I didn't re-activate the ACR.

At any rate, I'm back to being a happy clam.

 

klx678,

I think there are some inaccuracies and assumptions in your response that need clarifying. What klxster said was: "If the fueling is set up correctly before the mod, it does not require a change.. " I never said anything about accelerating "hard" in my original post, but I should have said while slowing accelerating. But irrespective of accelerating technique, the bike no longer performed as it use to before the cam mod. As to cam fasteners loosening up, Locktite was used, however I may have used blue vs red, or vice versa. When going back to the stock cam timing, after torquing down to spec, I also used the torque wrench in my wrists and snugged them down a little further. In a week or so, I'll do a mini teardown and see if they are still snug.

 

Again, the MCM is not experimental - it is proven.. Any running/operational issues that arise after MCM are due to a fault in fueling that is made worse by the increased vacuum signaling and/or the significant increase in the volume of airflow through the carb..

From your top post, I could have predicted that your CVK is running a setup that is unknown / unverified ..

 

I can certainly verify that it is unknown/unverified. But I can verify is that it runs like a top throughout the rpm range with the stock cam setup and the sparkplug is a nice looking tan.

 

There are no inaccuracies. I never said you did anything, only that if you did those kinds of things the results may be what I have had in the past with three different singles. From my own experience with a decently jetted carb I did not have to change anything. I also pointed out that trying to accelerate - especially if at bigger throttle openings, stumbling can occur. That is from experience with a 250, a 500, and a a 650 single. From experience I learned that the best performance was over 3500 with the 500, around 4000 for the 650 and 5000 rpm for the 250.

We used to have riders complain about Gold Wing 1100s not pulling cleanly from 2500-2700 rpm, bucking and not getting good mpg. Honda's response was that the engine performed best when over 3000 rpm and the sweet spot for mpg was between 3500-4000 rpm. I personally found I would get 50 mpg on my 83 GL by keeping it around 3500 rpm regardless of what gear. I would venture to guess that the KLX250 has the best performance between 4500-6000 rpm from personal experience and the power curve. I could not expect a 250cc single to pull lower than my Wing or big bore singles. Smaller engines need to spin. I found when accelerating on a Honda 250 Reflex scooter that happened to have a tachometer, it would be reving around 5000 rpm when accelerating and more like 6500 when accelerating hard. Kinda told me a lot about how Honda expects a 250 to operate. So I passed that information on. It is amazing how many people expect essentially high performance engines to pull like a John Deere.

As for your experience, sorry it wasn't as good as some, myself included, have had. I don't see it as any big negative on your part, it just didn't work as you expected. Seen that before, over the years in the bike shop. Some like certain hop ups, others don't. Either way, if it makes one happy, all is good.

I don't trust my "torque wrench" arm or wrist when it comes to internal engine bits. I don't want to snap anything off and don't want to have anything back out. Seat bolts, no problem, but not cam cap bolts or sprocket bolts. I don't do enough mechanical work to develop any sort of touch, plus when doing set up on Hondas, back in the 80s at the shop, I got in the habit of always torquing fasteners so if there ever was a problem it was highly unlikely that it would be due to my work. Please post if the bolts are loose after using the LocTite, I'm interested. If they are, I'm gonna cross drill for safety wire next time I'm checking valves.