You should probably research flame propagation rates / burn rates of various E10 AFR. It'll take a few months but well worth it. But the short story is that fastest rates occur around 12.4. From that point, rates get slower as AFR gets leaner.

Adding to this is that a ignition scheme designed to properly ignite a (stock) AFR of lower 12's will be increasingly retarded for increasingly leaner AFR - the leaner the AFR, the more power is lost due to improper ( retarded) ignition timing.

If you wonder why you've never heard of this before, it's because it is obscure "proprietary" knowledge that lives in realms not understood or available to most all.

 

Hi folks. I'm running 355 kit from Keng for quite some time now. While the power is really good, keep in mind that engine vibrations are definitely increased (i regret I didn't re-balance my crankshaft). Nothing extraordinary, but I can't agree with the folks running 351/355/402 kits and saying they didn't notice vibrations increase - not my experience.
The engine still didn't reach full potential as I didn't have a chance to completely dial fuel at high rpm. I won't have access to the dyno in the near future, so I post intermediate results "as is".
Mixture is quite rich after 6500 rpm which definitely doesn't allow to achieve max power. For the reference AFR is about 11:1 at 6000 and goes all towards 10:1 at higher rpm that's why torque drops quite sharply at 6500.
Nevertheless results are quite remarkable - about 35hp and 35Nm. With correct fueling I believe the power will be 38+ hp. Below dyno comparison between my latest klx300 (292cc) setup and new 355 set up. I still run my 3d printed snorkel, 38mm throttle body, klx300R airbox and JDM ECU.
Changes over 300 set up:

1. 355 kit (86mm piston). Higher compression piston - 12:1 vs ~11:1 on klx300
2. Slightly ported and polished head. Nothing extreme. Standard valves 29mm intake 25mm exhaust
3. New header + midpipe. Also Megabomb, but larger diameter. Now its 36mm (before megabomb expansion) -> 38mm (after megabomb expansion) -> 40mm (midpipe to muffler). Same KTM excf350/500 / husqvarna fe350/500 muffler (it's amazing!). Header and midpipe are very important. My previous set up which worked well on 300 was 32mm -> 34mm -> 36mm. I also made dyno run with old header+midpipe on 355. Max torque was 32Nm. So new larger header on 355 added almost 10% max torque. Standard header on klx250/300 is 28mm which is very limiting. I feel it's likely much more limiting than the standard muffler.
4. As of now I run oversized injector from ~2011-2016 KTM excf/sxf 350/450/500, part number 77741023044. From what I found it supposed to be 450cc/min. I run no fuel controller at the moment and low-mid rpm fueling is very adequate (but keep in mind that my set up has really high flow intake, ported head and large diameter header). High rpm it's still rich, I'm waiting PCFC to correct this.

 

Is the JDM ECU the rare one you got from Japan?

 

Yes. But Not so rare, sometimes I source them from Indonesia, sometimes from Japan. But overall I believe sourced about 20pcs already.

 

Thanks for the update!
I see Keng is adding heavy metal to counter weight the flywheel now.
I'm still waiting for a fully programmable ECU before I make the change.
I have removed all testing equipment from the bike and plan on just riding for a while.
Thanks again for the update.

 

TSC,
Looks like you're making great power.

Why aren't you running a fuel controller currently? Couldn't you use the controller you sell to richen up the AFR in the high RPMs? Why are you choosing to go to the PCFC ?

 

Thats a good question! For some reason it didn't work well on 355. Even with minor adjustments 1-2% bike worked significantly worse than just with injector. I'm not sure honestly what was the reason. I thought maybe bad ground wire of the fuel controller and connected ground to the battery - didn't help.
Second reason for PCFC is that it has throttle position sensor input additionally to RPM. 355 needs more fuel correction at lower throttle response and less fuel correction at larger throttle openings. For example: wide open throttle is rich and I remove some fuel to make it 12:1-13:1. This cause hiccups at low throttle so it's not possible to really ride the bike smoothly... So fueling on 355 is more tricky than on 250/300.

 

Hey folks! I don't login here frequently, but I have some big news: I’ve moved from Bali to London—and the bike made the trip, too!

While dyno runs will be rarer in the UK, I’m sitting on some KLX355 charts with perfected fueling that might surprise you.

What’s new:
- Major Site Overhaul: https://planetklx2.com has been reworked with streamlined guides.
- Community: I’ve started a Discord and a mailing list for all KLX fans - https://planetklx2.com/join-discord
- YouTube: This remains the most complete record of my developments: https://youtube.com/@planetklx2

I’ll be sharing the full updates and dyno data across those channels.

Best, Dmitry

 

Hi everyone!
I’m glad to see that my previous info about the Japanese ECUs helped the community. It’s great to see that knowledge being put to good use!
I want to propose a new experiment for those looking to optimize their performance. We’re all familiar with the 'Marcelino Cam Mod' (MCM) on both intake and exhaust, and some have tried the 'lazy' mod on the intake side only. However, I’ve noticed that many riders with 300cc+ big-bore kits aren't entirely happy with the standard MCM results.
Here is my suggestion: Try the cam mod on the Exhaust valve only.
The Theory:
By adjusting only the exhaust timing, we should be able to increase torque across the entire powerband. Unlike the intake-only mod, this shouldn't 'choke' the engine or restrict high RPMs due to lack of air. It could be the 'sweet spot' for those who want more grunt without sacrificing top-end flow.
If anyone is currently working on their valves or is up for a bit of testing, it would be very interesting to see the results (especially on 300cc+ builds).
Let me know what you think