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267 Posts
98' M900 with racked 41s, Keihin blue velocity stacks, very short/free-flowing exhaust. Generally speaking there is backfire when decelerating from 4k+, or at least a deep burping sound.
When at WOT for a few seconds it feels as it the bike is running out of fuel and the motor will die within a matter of a few more seconds if I continue to keep the throttle pinned. When it dies all electronics remain on. After a few seconds of the motor being off the motor fires right up again and operates normally.
If, however, I immediately let go of the throttle completely while it begins to feel like the bike wants to die and then wait a second or so and gently get back on the throttle just a bit it then the bike will ride just fine. It's as if we gave it time to replenish the the float bowls.
When I had 39s this issue did not exist. This leads me to believe it is probably not the fuel delivery pre-carb, and instead is related to fuel circuitry in the carbs themselves; the only thing that has changed has been the carbs (and the exhaust).
I have rebuilt most of the easier to access gaskets, seals, and float valves + accelerator pump. I should mention that I slightly damaged one valve seat, then used a dremel to smooth it again and tested the operation of the valve by holding the carb at the angle it sits on the intake and ensured the most gentle touch to the float would push the valve into the seat without any resistance. But let's say that valve was stuck inside the valve seat. There would be no fuel for one cylinder, but wouldn't it still run on the other cylinder? And if the valve was stuck outside of the seat, there would be a lot of fuel, but since the bike is already at WOT wouldn't it consume all that uninhibited flow of fuel anyway? If not, it'd be a rich condition for one cylinder, but the other cylinder would still have to run, no?
I'm buying a set of new set of seats anyway, but I am not yet convinced the seats are playing a dominant role in this.
Running 155 mains with "W" heads.
Cheers.
When at WOT for a few seconds it feels as it the bike is running out of fuel and the motor will die within a matter of a few more seconds if I continue to keep the throttle pinned. When it dies all electronics remain on. After a few seconds of the motor being off the motor fires right up again and operates normally.
If, however, I immediately let go of the throttle completely while it begins to feel like the bike wants to die and then wait a second or so and gently get back on the throttle just a bit it then the bike will ride just fine. It's as if we gave it time to replenish the the float bowls.
When I had 39s this issue did not exist. This leads me to believe it is probably not the fuel delivery pre-carb, and instead is related to fuel circuitry in the carbs themselves; the only thing that has changed has been the carbs (and the exhaust).
I have rebuilt most of the easier to access gaskets, seals, and float valves + accelerator pump. I should mention that I slightly damaged one valve seat, then used a dremel to smooth it again and tested the operation of the valve by holding the carb at the angle it sits on the intake and ensured the most gentle touch to the float would push the valve into the seat without any resistance. But let's say that valve was stuck inside the valve seat. There would be no fuel for one cylinder, but wouldn't it still run on the other cylinder? And if the valve was stuck outside of the seat, there would be a lot of fuel, but since the bike is already at WOT wouldn't it consume all that uninhibited flow of fuel anyway? If not, it'd be a rich condition for one cylinder, but the other cylinder would still have to run, no?
I'm buying a set of new set of seats anyway, but I am not yet convinced the seats are playing a dominant role in this.
Running 155 mains with "W" heads.
Cheers.