klx678, you mean advancing the intake and retarding the exhaust.. The MCM way! LOL

Ya mite wanna re-edit-upon that last post..

 

Ok, so I've broken the cardinal rule of jetting and done several changes at the same time. Twice. Jaja.

1st: Screw from 2.25 to 2.5, Needle from 4N to 4N plus a washer underneath, Main from 126 to 128. Low end was rich; bogging off idle, I think mid range was a tad rich; stumbling just a tad when cruising at 6k rpm, top end felt real good; no bogging, no surging either at 8k rpm cruise or snap to WOT thru the rev range.

2nd: Screw back to 2 using the midpoint test, Needle back to 4N, main still 128. Top end keeps feeling good. Low end feels good, better than before no bogging or stumbling. Mid range has no stumbling or bogging but feels real flat.

3rd: Keep screw and main settings, Move needle to 5N. Findings to come soon.
3.5: The screw likes to be at 2.5, surging and bogging at 3 or 2 turns, but it's not cruising as well as prior to the MCM at 2.25 turns. Top end still good as expected as no change was made to the main. The mid, sigh. It's better at 5N than at 4N; more power and better response, but it does feel rich because 1) snap to wot causes a stumble at 4k or 5k rpm, 6k rpm feels ok. 2) slight stumbling when cruising between 3k and 6k rpm.

4th: Went back to 126 main, kept screw at 2.5 and needle at 5N. Notes to come later today.

 

Neonarc, you broke the rules - do the crime, do the time..lol

Perhaps some worthless observations.. You found a great setup before MCM. The MCM should not have needed a change in your main jet. The needle positions "uncover" the main jet quicker or slower during a WOT snap as well as changing the fuel curve richer or leaner while moving toward the full up position at WOT. (5N seems to almost provide an accelerator pump type "jolt" of fuel with a snap to WOT.) But, if you can't find a needle position you like, you can always re-adjust the float level to modify the low to midrange AFR of a given setup - lower for leaning , higher for richening.

 

yeah, no kidding, jajaja. I thought I might get a better "bang" with the 128 since it had been almost identical to the 126 before the mcm. At least I know the outcome now.

So today I test 126 and 5N. I hope it works, but if it doesn't, I was considering changing the float level. Why would the mcm affect this? does it have a better "pull" of gas from the carb at low rpm? I never had cruise issues prior to the mcm with either 126 or 128 after correcting the float level.

cheers

 

" does it have a better "pull" of gas from the carb at low rpm? "

Yes it does "pull" stronger from the carb at lower RPMs relative to non-MCM..

The MCM doesn't require a new float level - It's just that in order to get the full benefit from the MCM we need to retune to provide a little steeper fuel curve lower in the RPM range. I'm thinking this is usually a little richer on the fuel screw and maybe a notch lower on the needle - but if that doesn't get you where you want to be then throw in float level tweaking to richen (raise) or lean (lower) the low-midrange AFR for a given setup.. Sound about right?

Also, I don't understand "stumbling".. Are you referring to the momentary ignition glitch ?

 

For instance - if 4n is flat, 5N too much, and 4N+washer is still not right - you could lean 5N or richen 4N with the float level.. Just be sure all internal parts are clean and clear of clogs and that the diaphragm is intalled properly and working right.. Also some members have not quite gotten the boots re-installed correctly causing leaks - this is usually the boot to the airbox..
The bike should have run perfectly fine with your original carb setup, just pulling harder below 6500 rpm with the MCM..

 

By stumbling I mean bogging when it's pulling then bogs, pulls, bogs, etc. Carb is clean and been put together correctly. Yeah, the carb/airbox boot is a B to put together correctly but I always check it on all sides before and after tightening the clamp.

Could be that the previous jetting was just right at my altitude. It sucks to rejet so many times but at least I'll be sure I have the best jetting at the end.

 

Oh man, what your describing pegs my weirdsh$t-o-meter.. That doesn't smell like a jetting/setup issue at all to me..- but more like a faulty component/circuit..

Becareful with your thinking, If your bike carbs correctly before MCM - It will after MCM.. The mod does not require a different carb setup.. However, the mod makes more if you richen the low and mid range (with the stock header) - this is assuming your main jet is already correct.

 

I'm probably explaining it wrong. It's definitely rich carb setup. I'm thinking this way because it also behaved this way without the mcm and with the 5N. I messed up by changing so many things at once and I'm paying for it. In the end, jetting is gonna be very close to or the same as prior to the mcm, just like you say. No regrets as this way I'm sure I'm not missing out on more power by going richer.

cheers

 

Yeah... Probably go back to original setup, , verify functioning, then try a washer, a slight float height change (1mm or so?), a little more "out" on the fuel screw,,etc etc - BUT one at a time! LOL