@Klxster , Do you know if the Aussie and US carbs are the same? When I did all my mods, the carb was de-restricted by the shop and they said they also re-jetted it (but wouldn't tell me what they put in). It runs pretty well and you can get the front wheel up in 1st. But would be prepared to pull the carb apart if there is a reasonable amount more to unlock.

 

Klxster, I'll remove the airbox and set up the EJK as described. As far as the exhaust, it's the stock KLX300 muffler and stock KLX300 header. It came with 2 tips. One is about 1"dia and the other is 2-3". The bike seemed to run better with the smaller tip. That's before I did the MCM. I have the larger tip on now.

Looking forward to trying out the new setup on some harder trails this weekend.

Toph

 

Thanks Klxster, I really appreciate your offer, AND all the informative posts you submit to this forum!

 

@Topher749 , got it.. If it were mine, I'd use the prescribed settings for aftermarket exhaust and lidless airbox BUT I would add 1 light to all three RPM ranges and also to the transition zones. And, of course, pull off the airbox lid..

The MCM is a very significant - even radical - increase in volumetric efficiency from off idle to 6500 rpm ( IIRC).. and the KLX300R exhaust system (stock with the large endcap) is going to help everywhere in the RPM band..

Should be a real "eye-opener" ....!

 

If you are running the airbox lid, there is more power to be found with a lidless setup.. If you decide to try out lidless, send me a PM..

 

yep been running lidless from new. Did all the mods in my signature in the first 2 months of getting the bike earlier this year. Will PM you.

 

Hi, and thank you to everyone for their contributions on this very active thread.

I live in France and early last year (2019) I was fortunate enough to come across and buy a near new (2016, 900miles/1500km) KLX 250 with EFI where I live in France.

After reading articles about the Marcelino cam mod last year and recently reading the review below:
https://bikesandtravels.com/biker.aspx?ride=7193
I finally decided to take the plunge.

The above article recommends only changing the inlet cam, replacing the inlet snorkel for that of a KDX200 and l leaving the EFI alone (why and how are described in the comments section of the article). This is what I did as well as bridging the clutch switch.

Ideally what I want is plenty of low down pulling power while maintaining the low noise of the the original bike. All on a shoestring budget.

Before buying the KLX I tried the Suzuki DRZ400: I loved the engine but did not find one with low mileage and in great condition. Also it feels a bit long in the the tooth. The KLX looks and feels more modern. It also seems more adapted to dual sport riding: the DRZ seems more at home on the dirt but less so on the road. But I really miss that engine (could it not be fit into the KLX 😁?).

With the above mods now done (inlet cam and snorkel removed while awaiting delivery of the KDX200 snorkel) there appears to be an improvement in responsiveness. Although the power now disappears at 9000 rpm. The snorkel-less inlet box is too noisy however.

But I am still left wanting more power; I am guessing that 30bhp would be nice (but still a long way from the DRZ400’s 40+bhp). I believe the original exhaust can be modified? Anyone tried this?

And I am looking into the 300cc upgrade using Kawasaki OEM parts (for reliability and so as to not mess with the EFI). But will there be a worthwhile gain?

Your advice and experience would be most welcome 😁

 

My village in Southern France

Hi All!

I’ve spent some hours reading through this thread and other threads and your contributions including videos. You have a lot of experience, of which I have little (I used to have mostly two strokes back in the old days including an RD350LC, an RD250, an RM250, a Maico 440, a DT400 but also a Tenere 600 and a BSA Bantam to name a few).

My experience is mostly riding and racing track and rally cars. Although I’ve carried out a number of mods on my cars: a Mitsubishi Evo VI; performed a complete engine rebuild for a group N engine on my Subaru Impreza turbo GT; a complete rebuild of my MGF race car and installed a race engine in my Mk1 Golf GTI after an Irish ‘friend’ borrowed it without first asking and then blew the engine while driving up the steep incline that is the motorway from Nice to Monaco flat-out and shifting from 4th into 3rd instead of into 5th... Gee, with friends like that who needs enemies?

I’m used to, and like small bikes that give a bit of a kick in the ***. The LC was a real wheelie monster — ah such good memories. But now I’m an old geezer... still if I can get my lovely little KLX packing a punch I’ll be happy.



Step 1 complete: Inlet cam only modified. Works well: better initial and mid-range pull. Power drops off noticeably above 9000rpm.



Standard KLX250 EFI airbox inlet pipe on the right. Cross sectional area is around 720mm2 (1.12inch2). The new replacement inlet pipe (on the left) is from a KDX200/KL650a (part number 14073-1577) and has a cross sectional area of around 1550mm2 (2.4inch2).

The cross sectional area of the 34mm intake of the EFI model is 908mm2. The standard inlet pipe/snorkel cross sectional is significantly smaller.



Inlet pipe mounted in the airbox lid.



Step 2: The airbox lid fitted into the bike. Air flow capacity is now more than double but noise levels are barely increased: essential for keeping environmentalists complaints to a minimum and keeping country lanes open to motorcycles. And for having fun!

So I will try the new inlet pipe/snorkel soon and then step 4 will be modding the exhaust cam. Followed, perhaps, by step 5, the exhaust muffler mod. If I think I can do it... I found some pictures here:




Link to pictures of standard muffler cut open

Also, it seems Marcelino’s first post has information about the standard exhaust mods which seems necessary. And some dyno runs he did. The photos are no longer there. Can anyone on this forum help me in finding those photos? Perhaps there is an archive somewhere?

I want to keep a standard exhaust so I don’t get set upon by local ramblers and bird lovers, bless them, and also because I am now an old fart. Is it enough to mod the KLX250 muffler (seems pretty involved)? Can I simply use a KLX300 exhaust system? Does that flow better/sufficiently?

All contributions are welcome.

 

KLX300R complete system will bolt on. But it does not offer performance increases until the endcap is removed or replaced with a performance KLX300R endcap - which makes the system about as loud as a Q4 slipon on your stock header, but a KLX300R system will have a "stock" appearance.


A "uncorked" KLX300R system with the KDX snorkel WILL provide noticeably more power once the bike is retuned with an EJK or PCFC.

 

Hey,

I plan on doing the cam mod soon, everything has been explained really well so I don't see any issues there.
One question I do have is "Should" the cams be removed to perform the mod, my concern is the torquing down of the cam gear bolts potentially harming the cam bearing surface when the pressure is applied?
If it's a non issue i'd rather complete the mod with the cams in the head.

Cheers