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Discussion Starter #1
I finally got my new gauges and ECU in for the bike and got it started. It ran ok for maybe 5 or 10 minutes, then i started to have problems. It's a 2002 M750

When I start the bike it will rev out and run great for about 10 seconds, then slowly begin to rev out less and less, stutter more and generally run crappy. It will eventually get to the point where it won't rev past 2,000 RPM or so and will stall out. I took off the airbox cover and watched what was going on- as it starts to stutter it misses and is backfiring slightly out of the throttle bodies.

I changed the plugs and there was no difference. Both cylinders are hot and I can see the backfiring, stuttering, etc coming from both cylinders. The plugs don't look overly rich or lean, but then again I can't really get a good run in to see what they truly look like

I have a suspicion it is a bad fuel pump- does this make sense as a diagnosis? I can hear the pump prime, and continue to run once the bike is running.

Anything else I should maybe look at? I checked all the fuel lines, they seem to be hooked up correctly and there is no pinching that I can see. When it first ran I took it for a short spin and it seemed to have good power. The fuel is new, just got it in the tank today.

How much is a new pump going to cost at the dealer? :p

Thanks

Reid
 

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Discussion Starter #3
Good call, I will give that a try.

I also have a hunch it might be the Throttle Position Sensor, Although I've never had one on a car make THIS big of difference in running. How big of part does the TPS play on the Monster Injection system? Is there a test I can do with an Ohm meter to see if it's still good?

Thanks for the clues, keep them coming.
 

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Discussion Starter #5
I'm leaning towards the TPS being out of wack/shot. Anyone ever open one up and clean it? Considering it's just a potentiometer, I might give it a try then reset it all from the beginning.

I did some more riding, basically if i start it i can tear ass for a block or two and it runs well. Then it just starts to sputter out, die, etc. killing it and starting it will give it a little boost, but not much. I was listening to the fuel pump when it was running and startting to sputter badly, it didn't sound like it were cavitating or anything of the sort, it sounded the same as always.

It strikes me odd that it will run great for a bit, then once it starts to get warmer it runs crappy. This happens quickly and the bike runs VERY poor. It's not even driveable after 4 or 5 blocks. Makes me think TPS even more, rather than fuel pump/pressure.

Thanks

Reid
 

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Isn't your bike under warranty? Anyway, the TPS, unless they have been changed, has 16 contacts. It is also not cheap and if you take it apart you bought it instead of Ducati. It also is not a likely cause of your problem. If opening the gas cap doesn't work get the bike to the dealer. They should be able to solve the problem quickly with the DDS tool if the problem is FI related.
 

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I've had similar symptoms in a few carbed bikes i was restoring from water in the gas but I don't have a lot experience with FI. This isn't likely since your bike probably hasn't been sitting in a field for the past 20 years. It sounds kind of like a vacuum leak so maybe you could check for a leak in the throttle bodies (possibly the vacuum fittings or air bleed/bypass screws).
 

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The TPS guess is right on, It will need to be reset. I had the same symptoms on my M800 after replacing the ECU. Reset the TPS aqnd VIOLA!!! Ran fine.
 

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Discussion Starter #9
No way I'm gonna pay for this to go to the dealer...

It was a salvage bike that needed a few things and was missing the keys. It was cheap and I'm trying to keep it that way....I guess I'm just cheap.

Anyhow, I'm about to reset the TPS to 150 M.Amps with the throttle body ALL the way shut, and 350 M.Amps with it set at idle speed.

This sound right?

Thanks


UPDATE: fiddled with the TPS, set it to spec, also tried moving it in increments of 10 Milli amps both up and down , from 50-250. NO appreciable change. When it started to cut out/run very poorly I gave it a small shot of starting fluid into the airbox, it then revved right up. It's looking like a fuel issue, I'm going to try to rent or buy a Fuel Pressure tester this afternoon and check it.

Should fuel pressure be about 3 bar or 5 bar? I searched and seemed to find both as the answer....

Thanks
 

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Ah, salvage, so there is no warranty. Ah, double doh!! '02, I was thinking '06. Don't forget to look at fuel quality also. Did you pull the plugs? If they are gas fouled it could be the cylinder temp sensor reading cold.
 

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Doesnt the 750 use the 5.9? Never fiddled with one, as its kinda a one year deal with the 750 and FI. If so the only way top reset or adjust the TPS is with the Mathesis or teh Technoresearch software.

Mine needed to be reset so it knew where 0 throttle was. After the reset it was just dandy.
 

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Discussion Starter #12
I was thinking the temp sensor too. I might try unplugging it and see if it makes any difference.

I think this bike uses the same style TPS as all the bikes that were Pre-06. The non "linear" or whatever it is. It can be manually rotated and is adjustable, unlike the brand new bikes that require the computer to be programmed to match the TPS instead of actually doing anything to the TPS.

Ducman how was your bike running before you reset the TPS? Mine will run decent/rev nicely for a block or two, then it starts to crap out QUICKLY. And this is all from a cold start (it's in the 40's here), i wouldn't imagine the temp sensor would even have a chance to pick up much of a temperature change in this short short period of time.

After that block or two it starts to buck, miss, and wont rev or really make any power. If you give it full throttle it will shut off and die completely, but if you feather it it will sort of stumble and stay running.....

Off to do more tests,

Reid
 

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Mine would start and idle, but if you gave any throttle input it would stumble, miss and stall. After the TPS reset it ran beautiful.
 

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Open up the tank and check the fuel lines as well as filter. The pumps are reasonably stout. If it is the pump, just get one for a 5.0 ford mustang.

imho, this sounds like classis 748SBK "split fuel line" issue.
 

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Discussion Starter #15
Update: Hooked up a fuel pressure gauge.

Upon turning the key on I have about 30 PSI of pressure. Start it, at idle it stays about 30. Rev it up, by about 3,000 RPM fuel pressure has dropped to about 20 psi.

This sounds WAY too low. I'm going to pull it apart tomorrow, check the lines inside the tank and install the mustang fuel pump I got. Hopefully that will clear up the issue.

Reid
 

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Discussion Starter #17
Pulled the tank and took it all apart.

Put in the Mustang 5.0 fuel pump, NAPA fuel filter, and new fuel lines. Also a new fuel pickup sock.

It runs good now. Still might need to adjust the TPS again, but overall it's damn close.

Looks like my front rotor got whacked and is bent, It'll need a replacement....IT's SOOO close.
 

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hollowellreid said:
Put in the Mustang 5.0 fuel pump, NAPA fuel filter, and new fuel lines. Also a new fuel pickup sock. It runs good now. Still might need to adjust the TPS again, but overall it's damn close.

Looks like my front rotor got whacked and is bent, It'll need a replacement....IT's SOOO close.
ooo, good to hear about the running, sorry to hear about the rotor. We're about to have an Xmas sale that's pretty insane on some stainless rotors with wavey outside, great looks, and "smart" looking carrier. If you'd like info sooner than later, please e-mail me at [email protected]
 
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