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The MCM doesn't have much of a "butt dyno" difference anyone noticed, but then again not everything is readily apparent by feel. One of the Kevin Cameron columns dealt with that. He was doing jetting on a two stroke road racer and his rider, pro racer Cliff Carr, was doing the riding. They were struggling, because the clock was the measure of the results. He did one last change. Carr came in Cameron asks how the bike felt. Carr said it felt slow off the corners and not impressive. Cameron then told him the lap time was the fastest he'd turned all day. Sometimes what seems uneventful may be a significant change, because its easier to go quicker. I've not read where anyone actually did a dyno test between the bigger bore stock versus MCM, only the 250s.
Dyno Butts come in all different flavors and calibrations - none can be trusted.
Luckily, no one here has to as my posted dyno charts comparing before and after MCM proves the effectiveness.
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.
I don't really think it was wrong set because then I turn it back to stock from that point with just counting 2 teeth each side and worked like a charm. And yes it was at t mark. If it was wrong I would have problems with the stock setting also.
Last edited by cycloholic; 01-25-2024 at 10:19 PM.
Ahh, I hope you mean you reset each gear on each cam, back to the standard bolt holes, and moved each gear 2 teeth in the proper direction..
Assuming you did the MCM correctly, the increased cylinder filling ( increase in effective compression ratio and increased vacuum thru-out the induction tract) seems to have uncovered a fault that is not apparent with the lower performing standard cam timings.
Certainly, any air leaks would be exacerbated by the MCM.
I've finally made cam mod and measured effect with dyno. I've done only intake part. Two reasons for that:
I've studied quite a lot of material for cams LSA, intake timing and exhaust timing. With both intake and exhaust the LSA will be ~100 degrees which is very narrow and won't promote torque to high RPM.
In this thread Marcelino told intake and exhaust might makes sense for 250 cc and recommended to try only intake for larger bore set ups.
My bike setup
klx250 EFI
300cc with AHL kit
secondary throttle blade removed
Full custom exhaust with custom "megabomb" style header and straight muffler
Open airbox ("lidless")
AFR tuned to approximately 13:1 separately for both cam mod and stock cam timing
I did several runs for cam mod and double checked AFR to make sure it's properly fueled. Here is a comparison of the best cam mod run vs stock cam run.
As you can see cam mod has a slight edge in torque (0.5Nm?) before 6500 rpm, but it drops quickly after. So stock cam timing gives extra 1-1.5 hp at the top end around 7500 rpm. In the end I reverted to stock cam timing.
I believe this is important result supported by dyno. I did dyno runs with stock cams before cam mod and after I reverted from cam mod to stock cam timing. In both cases stock cam demonstrated 28.5hp+. The best hp with intake cam mod was 27.5 (see second image below)
.
It would be interesting if the charts were actually reasonably easy to read. So tell me, stock has 1 hp more at the peak, what about the rest of the range from there down? One of the key factors in a narrower LSA with more overlap is a rise in the torque in the mid and upper range, not so much a rise in peak power. Which colors relate to what setup on the charts?
I wish the charts Marcelino had run were still online.
1 question
If my klx has 24 hp , does mcm works?
I think mcm just calibrates cams and ignition.
This engines build for 24 hp at 9000 rpm
They cut off ignition so left just 20 hp at 7500 rpm
When cams go thair optimum rpm we hawe no ignition.
mcm just calibrates cams optimum rpm whit ignition rpm
I think so )))
It would be interesting if the charts were actually reasonably easy to read. So tell me, stock has 1 hp more at the peak, what about the rest of the range from there down? One of the key factors in a narrower LCA with more overlap is a rise in the torque in the mid and upper range, not so much a rise in peak power. Which colors relate to what setup on the charts?
I wish the charts Marcelino had run were still online.
Lines with more hp at the top are stock cams. I would say mcm has a slight edge at mid rpm 5500-6500 (0.3-0.5hp?).
TSC, you wasted your time and resources proving what's already been proven long ago - Doing a 1/2 MCM is pointless.
Way back, peeps did "Intake only" in order to avoid dealing with the KACR attached to the exhaust valve - sure this didn't have anything to do with your choice to not complete the MCM correctly ?
01-20-2024 | 12:13 PM
