Z start pro stalling on my 10 yz450

Don't know exactly what's going on but from quick snap of the throttle in gear to let off it stalls. Breaking into rock sections it stalls. It's driving me literally insane. I've tried 24 ball c200l5 and c150l4 springs 27 ball same set up c150l4 27 ball. All with the same exact effect. Stalls in quick snap of the throttle to slight let off like as if your in a rock section. The whole purpose of this clutch is to eliminate the stall. My riding style is pretty much like a worcs race. Rock section single track and the occasional motocross section.

The problem is in the way that the engine idles down during such maneuvers.  If it were a carb'ed bike, I would recommend making the pilot circuit leaner to address it.  Raising the idle speed may help, and definitely using the 24 ball setup rather than 27 will help also.  From that point, you might take it to a dealer and see if they can back off the CO setting on the ECU at idle about 5-10%. 

Yeah I'm rocking the Jay marmont map on my bike with the c150l4 27 ball. With the low engagement rpm soft engagement rate is gonna wear my clutch fast and heat my motor up faster?

From what I've seen 4 strokes stall pretty easy at very low rpm, especially with a chopped throttle. It has to coast 1 revolution out of 2. I'd increase the engagement rpm and increase the idle speed, just a bit.

The difference between the "quick" and "slow" engagement rates (27 or 24 balls) is not huge.  I had this same problem with my '06, and a big part of the problem was fixed by going to the slow rate (24 balls).  I also use the mid speed spring combination for the engagement RPM setting.  No issues with clutch wear. 


I'm also using different plates than the bike comes with.  The stock stack in yours is 8 5TA-16321-00-00 friction plates.  Because of a parts guy mix-up I ended up with a kit for a quad, which has two of the 5TA plates, one for the bottom of the stack, against the boss, and the other to sit on top against the pressure plate.  The other 6 are 5VY-16321-00-00 plates from an R-1.  Rather than send it back, I decided to try it out, and it works great.  Interesting it is now to see Yamaha adding the 5VY plates into the current YZ450 clutches.  Hmm.


Using the more gradual engagement rate and the mid speed engagement rate will allow the clutch to release a little sooner on maneuvers like you describe.  Helps on the sudden need for power when you're a gear too high sometimes too.  It's easy to change and change back.  I recommend you try it out.

I just wanted to say thanks gray. I'm rocking a 24 ball with the small and medium spring all adjusted perfectly. Everything worked out beautifully. Check my video I just added on here. I'm gonna have to look into upgrades fiction plates eventually.

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