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Author Topic: Low power due to fuel pump?  (Read 998 times)

Paulio

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Low power due to fuel pump?
« on: April 25, 2014, 06:36:52 AM »

Hi! I bought a 2008 MS3-250 that was not running due to a problem with the fuel pressure regulator. I fixed that, and installed a new strainer. I got it running, but I was under the impression that it should top out around 90 mph. The best I've been able to get is 60. I checked the fuel pressure, and I have about 40 PSI. The manual calls for 53. The only other problem I could find was the TP sensor out of range, and I fixed that. In your experience, will a 15 PSI difference in pump pressure cause my  performance to drop this much? Are there other things I should look at, like a restrictor in the exhaust, or something in the clutch?
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Cloud

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Re: Low power due to fuel pump?
« Reply #1 on: April 25, 2014, 12:25:19 PM »

We used to run boosted fuel pressure on the cars, and it does make a difference.

53psi seems like massive pressure for a 249cc engine, I'm just guessing here but there must be a reason it runs that, and I think possibly you are finding out what that reason is.
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Paulio

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Re: Low power due to fuel pump?
« Reply #2 on: April 25, 2014, 02:33:14 PM »

Thank you Cloud! I think I will try changing the fuel pump and maybe an adjustable regulator, if I can find one.

Also, let me rephrase my question a little bit--When I bought this baby I was sceptical about its ability to actually run on the freeway. So does anybody on here own an MS250 that will easily run 70 mph? If so, it affects my decision on how much time and money to spend trying to achieve the same result with this bike.
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Cloud

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Re: Low power due to fuel pump?
« Reply #3 on: April 26, 2014, 12:20:33 AM »

Putting the number aside for a moment, think of it like this: if it's working, you should be able to wind it out to maximum revs at maximum gear, and run out of gear ratio and revving capability, before you run out of power to get there. As standard, almost every bike or scooter is able to redline in top gear. You should be able to hit that, regardless of the numbers on the speedo. If not, then you have problems.

As for the number, yes, it should sit at (actual) 70 comfortably, 85 is a stretch. You can probably bring 90 up on the dial but it's unsustainable as a cruising speed.
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Paulio

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Re: Low power due to fuel pump?
« Reply #4 on: April 26, 2014, 02:43:54 AM »

Bangin'!! I'm looking for a fuel pump to install. I was able to get a little better acceleration by restricting the return line with an adjustable flow valve, so I am on the right track, but I don't think the pump is making enough pressure. I'll update if that works.
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Cloud

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Re: Low power due to fuel pump?
« Reply #5 on: April 26, 2014, 11:50:20 AM »

(less pressure = less speed) = (more pressure = more speed)

So 190psi and ride at 210mph.
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Hylife

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Re: Low power due to fuel pump?
« Reply #6 on: April 26, 2014, 02:15:24 PM »

Quote
Also, let me rephrase my question a little bit--When I bought this baby I was sceptical about its ability to actually run on the freeway. So does anybody on here own an MS250 that will easily run 70 mph? If so, it affects my decision on how much time and money to spend trying to achieve the same result with this bike.

Hmmm, 165kg, single cylinder, water cooled, auto transmission scooter, with all the aerodynamics of a brick, geared down with a tiny 13 inch rear wheel and a 9 litre fuel tank.
I doubt this is truely freeway material but you could perhaps get it up to 80mph at 8 to 9,000rpm with the right tail wind.
With about 25% LESS horsepower than the Hyo GT250 twins but more weight and smaller wheels with a pitiful tank I really think it is aimed at commuting through the suburbs rather than hitting the motorways.
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