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Discussion Starter #1
I swapped to a 900ie engine and ecu from 2000 from my 1998 750, and I kept the 38 tooth rear sprocket since it is standard equipment on both my original 750 and on the 900. I rode around for a while with the stock front 15t sprocket and soon switched to a 14 tooth. I never went all out on the highway with stock gearing but with the 14t I seem to be hitting the rev limiter on the highway at around 114 mph indicated in 6th gear. I didn't expect this... I figured it would 1) go a little faster and 2) run out of steam before hitting the limiter. What's up with the gearing..dropping 1 tooth in front shouldn't do that I thought

Anybody else hitting the rev limiter on the highway? To add the the problem, I'm not using a tach but it feels just like the limiter on my car...could be my feuling?

Oh yea, I'm also using the older mechanical speedo
 

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Speeddog said:
Perhaps your clutch is slipping.
Maybe, I would have thought the symptoms described were at the wrong end of the torque curve though... I'm gonna guess fuel flow problems - a kinked line from the tank or a dirty filter...

Have you got a tach on it? How many rpms are you doing when it happens, and does it do the same thing at the same rpms in 5th?

big
 

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bigiain said:
Maybe, I would have thought the symptoms described were at the wrong end of the torque curve though... I'm gonna guess fuel flow problems - a kinked line from the tank or a dirty filter...

Have you got a tach on it? How many rpms are you doing when it happens, and does it do the same thing at the same rpms in 5th?

big
man, never thought about feuling..always thought it ran out a bit early even in the other gears. Problem is I don't have a tach so I can't say when it happens really. Its definitely not the clutch. I'll have to take a look at the feul hose..but come to think of it I'm running an autozone feul filter which only has the same appearance of the original 750 carbed filter...
 

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whited3 said:
man, never thought about feuling..always thought it ran out a bit early even in the other gears. Problem is I don't have a tach so I can't say when it happens really. Its definitely not the clutch. I'll have to take a look at the feul hose..but come to think of it I'm running an autozone feul filter which only has the same appearance of the original 750 carbed filter...
What did you do for a fuel pump?
 

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Discussion Starter #10
yeah, I'll have to check out which filter the 900 uses. I don't know what else would cause the engine to cut like that....There's no pop like a backfire, just cuts very briefly
 

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whited3 said:
yeah, I'll have to check out which filter the 900 uses. I don't know what else would cause the engine to cut like that....There's no pop like a backfire, just cuts very briefly
FWIW the stock setup has the filter after the pump. The fittings are also larger than the carbed plastic filter.
 

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Discussion Starter #12
hmm, I will try a higher capacity filter, but I think I'll keep the filter before the pump unless someone can convince me otherwise. Thanks for all the great help btw
 

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I would suggest removing the filter and trying it. If the problem isn't fixed you can put it back. Insufficient fuel volume in will equal insufficient fuel volume out. This would be a lot easier than doing a volume test, assuming you can find a volume spec.
 

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That pump is capable of supporting roughly 500HP, so unless something is *way* out of whack, there shouldn't be any delivery problems.

What kind of fuel pressure regulator are you using?
 

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Speeddog said:
That pump is capable of supporting roughly 500HP, so unless something is *way* out of whack, there shouldn't be any delivery problems.

What kind of fuel pressure regulator are you using?
True, but the rating is with adequate supply. If the small diameter fittings are reducing flow the spec could drop off rapidly.

Most pumps are better at pushing than sucking. That's why our cars have low pressure high volume transfer pumps to supply the high pressure pump. Maybe gravity isn't adequate in this scenario.
 

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Discussion Starter #16
Oh that's true, the pump is probably designed for pushing. So in any case ill have to try without the filter to see if its starving my pump. Oh, and the regulator is standard ducati equipment, along with the injectors and all the other fueling stuff which came with the engine. Only thing I did was add the filter and pump and fuel lines which are basically same as the originals.
 

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ducpainter said:
Most pumps are better at pushing than sucking. That's why our cars have low pressure high volume transfer pumps to supply the high pressure pump. Maybe gravity isn't adequate in this scenario.
Yeah, keep in mind all the factory Ducati FI systems seem to use the pump in tank trick - no "sucking" required at all...

I also wonder if the pump does a fair bit more work than the motor power suggests - I recall talk of a return line in the FI tanks - how much of what the pump puts out just gets sent back into the tank?

big
 
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