Well, tried to start the motorcycle today with a fully loaded battery and with a temperature of -4 degrees celcius. Nahhh, It feels like the starter having a hard time to turn the motor. It fires up quite fast but it feels like the battery was empty and doesnt have the power to crank the motor. My best guess its because i have disabled the kacr. Anyone having the same issue?

 

Instant starting means you did the MCM correctly ( Standard result on a bike that has no issues and a properly done MCM. ).
No one has ever had the "same issue". KACR deactivation on a KLX250 does not over-stress the starter.
It has been surmised, by a member whose starter failed, that over years, the starters' life may be shortened. But this was one (and only one) reported event, many years ago, with no subsequent support..

Surely you are aware of the effects cold temperatures have on a battery's CCA ( cold cranking amps ) ..

 

Well, is not a battery issue, battery worked before mcm and I fully loaded after because I mention the struggle.
FRom the other hand the kacr is what exactly do, releases compression!. Maybe my starter is weak and shows on my motorcycle more. I have never replace brush carbon or something since i bought it, maybe its time!

The start this morning:

And today noon

You can hear and see the struggle, the lights never turned completly off in the past for such long time.

 

Sounds like a weak battery to me. How old is the battery? Try it with a car battery attached.
You know batteries only last so long & just because they appear to have voltage sitting there, underload they fail due to one cell being failed.

 

Battery is checked and its ok. Today i tried it a bit and i noticed also an instability of the idle rpm. Was changing idle everytime i was twisting and leaving the throttle. So, just took it back to stock settings and voila, everything works as it should. Interestingly when i put it back and started the motor, it was a knocking sound that strangly disappear after a while. I hope i havent destroyed something!

 

FWIW Idle should be around 1250 rpm. Never had a problem without the CR, even in sub freezing temperatures. If carbureted, a properly jetted set up will fire up near instantly and require minimal choke. Most of the time I had the choke off within less than 30 seconds from starting.

I just thought about it, with the MCM change the overlap is longer, so actually the setup would have less compression than the OEM, possibly having over-lap as long as the KACR might hang open, offsetting the KACR delete. That overlap may also cause a slightly rougher idle than stock, but I don't remember that.

 

Dunno really, but I don't think it worth to mess more. Mine is efi version(as Marcelino's). 1250 is correct. It fires up good now that I changed it back to stock and not a single issue with idle.

 

You may not have done the MCM exactly correct. I say this because of the following:

1. Your idle issue could certainly indicate that something was not done correctly with the retiming.
2. There have been no other reports of the issues you've reported, from the MCM .
3. Due to many years of membership usage and testing, the MCM is not experimental. It is wholly effective.

The photo you posted above shows a correctly done MCM , IF the engine was at TDC on the power stroke when the picture was taken.

 

Good point, It might be the timing was off at the crank. It may not have been on the T mark when the MCM was done. Not being able to actually be there and look makes it hard to troubleshoot things.

 

This week I left my bike to install 300cc AHL big bore kit and do MCM (trustworthy garage!). I also provided garage with pdf from @Klxster and video from from @SaltyDitchDr . Today I came to collect my bike, but mechanic told MCM didn't work well. Indeed the sound from the engine was weird. Then we've opened the head to see cams. Guess what - instead of 2 teeth they've rotated gear 3 teeth! Luckily it didn't damage the head as they checked valve clearance before starting the bike...
Long story short - it's easy to screw up even for experienced mechanic.. It worth to double and triple check everything.

I've put stock cam timing today as I was tight in time and need my bike to be ready for trail ride on Sunday.

I will do MCM and measure effect on dyno in a couple of weeks.

P.S. 250->300 upgrade is quite amazing (see here)!