[46VR]

Hey
I have read around and about that the 848 is prone to stall for no reason but as yet dont know why it does it. I was out Yday and it did it to me twice - anyone know whats up ?

Thats issue one, issue two - and not related to the 1st

When sat on the bike, balls against the tank sometimes you feel as if within the tank something shoots towards your balls/stomach and is stopped by the inside of the tank.
You hear it and certainly feel it - its a noticeable jolt.

I know exactly what Im describing but it could be a crappy description.

Any ideas on either anyone ?

 

[[email protected]]

The "jolt" sounds like a backfire up the throttle bodies. I've experienced it myself. As for the stalling.....the debate is out on that one. Mine stalled twice before the first service and hasn't stalled since.

 

[46VR]

Do I need the throttle bodies replaced or adjusted ?

 

[FallenHero_08]

mine has stalled out mid corner before. only once and it started right back up. i wondered if it was the ECU getting hung or something. it was before my 7,500 mile service, hasnt done it since.

 

[tye1138]

Yep, its backfiring through the throttle bodies, which is a sign of a mixture which isn't burning properly. I've never been able to fully resolve the issue running street gas. But with my fully tuned 848 race bike with race fuel, the problem disappeared.

Remember, the fuel is sprayed over a CLOSED throttle plate, so how does the mixture get into the cylinder? It goes through a little tunnel/cut away in the side of the throttle body, which is controlled by two little screws on the side. Similar in function to the air screw on a carburetor, this system takes the mixture and moves it around the throttle plate. But there isn't enough space for the fuel and air mixture to atomize properly, so if the mixture and environment isn't perfect, it can very easily stall. It doesn't help that the stock mapping on these bikes is very lean at idle, thats just to pass emissions.

You can't ever eliminate the issues with a shower injector type system. The Japanese bikes use dual injectors, one below the throttle body and one above, to help eliminate these issues. Ducati has never done that, so the more modern superbikes suffer from this malady. Its very easy to reduce the issues by calibrating the air screws AND throttle plates. Plus, raising the idle (increasing the vacuum on those air screws) helps a bit as well. A lot of people find the idle raise to help greatly, without resorting to replacing the fueling map.

 

[46VR]

what a ball ache.
Thanks guys

 

[FallenHero_08]

does using a powercomander and tune eliminate this? and what are you guys raising the idle to?

 

[tye1138]

does using a powercomander and tune eliminate this? and what are you guys raising the idle to?

Not really. My bikes were very well tuned and they still did it.