Bike Dies During Hard Stops

[corey]

I noticed this evening, and over the past few weeks since my carb rebuild, that when I apply the brakes hard while traveling forward the bike will die. At all other times the bike functions fully and smoothly. What causes this? Is it just something these bikes do?

[T748]

Float levels too high maybe?-Tom.

[Pat Kelly]

Possibly float level too low? Hard braking, fuel sloshes to front of float bowls causing fuel starvation?
Waddya think guys?

[prometheus578]

Oh oh, I can see it coming!

(Sounds like another thread where I sit with a cup o' coffee and burn through half a pack o' smokes, thinkin' and theorizin')
Yeah, always was told 'twas caused by low float level. But... bikes lean forward when braking... how about rearing up when accelerating? What about wheelies?
Cars do the same thing during panic stops. Dying, I mean
Theory: Cars die during rapid deceleration 'cause the engine has dropped down to idle (lowest power), but the tranny is sort of fluid-locked due to the wheels not really spinning like they were, thus suddenly putting a quick, extra strain on the engine that it can't handle.
Theory: Idle may be set too low. If I'm not sadly misshapen, when you blip the throttle, the rpms jump up, but on the way back down, dip below idle a little, then come up and stabilize. Panic stop: slam on the brakes prior to pulling in the clutch and releasing the throttle, the strain of which gets the rpms shooting downward faster that by just releasing the throttle alone. Rpms dip way low (due to incorrect base idle) and don't recover.
Of course, it could be the float level. He did just have carb work done.

[corey]

I think the floats are in the right spot. I measured them and what not. However, I did not carry out the clear tube test, so who knows what my actually float level is. Those porus plastic floats might have absorbed some over time, resulting in a low fuel level (???).

The RPM dump makes sense to me. Any other thoughts?

[DiverRay]

If the floats have absorbed fuel, the level will be high.

[TopCatGr58]

Also,
Applying the brakes hard causes the rear wheel to lift up more easily, and when hitting ALL the brakes, it's easier to come closer to locking up the rear, or at least slowing it down more than your actual travelling speed. And the rear wheel being linked to the drivetrain, could be slowing down the engine to the point of stall speed?

Corey, you didn't mention whether when hard braking if you're pulling in the clutch lever or not? Like Prom said, bikes slosh fuel during very hard accel, wheelies, etc., so I don't think it's the carbs loosing fuel from the bowls, but slamming shut the throttle plate during hard braking while the engine was still revving faster could cause it to be too lean to support combustion? SO, perhaps a higher idle setting is in order?
T.C.

[corey]

Mmm Hmmm... I think the idle needs bumped up. During the hard stops I'm pulling in the clutch and releasing the throttle. Regardless of what that indicates, I think the idle is a little low. 1050-1100 RPMs is ideal, no?

[TopCatGr58]

Well,

Ideal is what works for you! Mine idles around that range, never dies when I hit the brakes hard! Worth a try, can't hurt!
T.C.