I have been lurking/reading for months and finally got off my butt and did some mods this past week on my 09 KLX250S (only 2500 miles). The MCM tread has been great and just made so much sense I had to try it. I thought it was quite easy to do and the mid-range change is very noticeable and makes it so much nicer for this old age pensioner. Here's what I did for riding at 500 ASL with stock exhaust.

MCM
DJ 2152 - main 128, fuel screw out 3 turns
Removed smog crap
Added ground line to rectifier
Changed out shift star

I've worked on many 2-strokes over the years but this is the first 4-stroke top end my tools have seen. I would have had these completed in a couple of hours except the original valve cover gasket was shrunk like all the 09's have been. It took 5 days to get a new one in.

Maybe when funds allow it I'll go with a nice FMF full system but for now I'll probably just go with manual cam chain tensioner, some suspension and seat mods before I do the FMF.

The improved performance seems to be well worth the little money it cost to do it. I've got no hesitation all the way up to 9K and crusing at 6-8K seems to be smoother than before which may be from the ground change. I was kind of concerned about getting the jetting right but it's a piece of cake just twisting the carb, removing the bowl, and changing the main jet.

Thanks to all you guys for the info, it made the work quite easy.

 

Always great to hear from folks that jump in and tackle the work instead of hauling the bike to a shop. There's very little that can't/shouldn't be done at home with basic tools.

Ride on
Brewster

 

Nice Barebow, you did put in the DJ slide spring and needle, right?

Your "Stage 1 + MCM" makes a really fun bike outta the KLX.. I remember doing the MCM on my 100% stock bike - what a rush to feel MCM powah for the first time!

Hey, ya don't have to get the full FMF stuff, you can go with a Four Strokes Works KLX300R header and a KLX300R muffler with a Ebay end cap/tip..

 

Tip - Next time you do anything requiring the cam cover to come off if it has to sit for any length of time put the cover back on and snug up the bolts a bit. When I did the MCM and valve shimming I had to wait to get the shims. I put the cam cap back on with two bolts snugged up, cams out, then put the cover back on. Gasket can't shrink if in place.

 

Yes, I did the DJ spring and needle (3rd groove from top). The KCR wasn't removed, just disabled with the spring removed and wire through the holes. I had earlier drilled the enrichment jet out and put the Thermo-Bob on it.

Apparently many of the 09's had an issue with a supplier or material. There are multiple threads about them leaking and when taken off they were found to no longer fit into the cover grove. Mine had at least a 1/4" difference in the half moons compared to the head. That was about 30 sec. after taking the cover off.

 

Are there any good youtube tutorials on how to do this MCM mod?

 

I don't think so QOS, there is at least one really bad one that'll likely have you looking for a replacement engine.

 

Not seen a video. I did condense down the Marcelino Cam Mod into a Google Doc that can be shared. It is a link in my signature. It is the mechanical work minus all the numbers and theory. Check it out, it may work for you. Print it off if preferred.

If you have good mechanical reasoning and skills the MCM is not mechanically extremely difficult. But having the details correct - aka cam positions per the mod - is highly critical. It's just about attention to detail. From what I've read and seen you appear to have the ability and reasoning skills.

Read the article a few times, absorbing the details and thinking it through, it helps to have good understanding before doing the work. Saves a lot of time. It is essentially the same procedure for shimming valves. The detail is getting the timing marks in the right place after changing the sprocket positions.

Sometimes it is the goofy stuff that gets you - having the cam one or two teeth out of position. I'd think I have it right, put the cams in the journals, look and I'm off by a tooth or two. Change it up and find out I moved the wrong way. After a couple times I finally had the cams in the right place. One other note if you do it - loosen the cam sprocket bolts before pulling the cams.

I was shimming valves at the same time, so I don't know if the change can be made without removing the cams. I think it could be done after removing the OEM tensioner or backing out the manual tensioner if there is enough slack in the cam chain. Just don't drop a sprocket bolt into the engine and pay attention to the cam timing marks - the detail.

Feel free to share the link.

 

This doc is exactly what I used, as well as reading the long MCM thread about 3 times. KLX678's write-up is quite clear and easy to follow ( I thought). I compared his final photo with my finished work about 5 times, went back about 2 hrs later, rotated the engine by hand twice, rechecked. Didn't hear anything bad, cranked it with the plug disconnected, no bad sounds. Put the tank on and it started right up.

I'm mechanically inclined with an assortment of tools and slightly OCD (according to my wife) but a novice with 4-stroke heads.

I forgot to mention I had also swapped the snorkel out with the KDX 200 one.

 

Look forward to hearing your ride reviews post-MCM. Did you notice reduction in intake grawl, etc?

Thanks in advance!