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Old 11-01-2012, 04:18 AM   #31330
fred flintstone
Studly Adventurer
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Joined: Apr 2009
Location: Above 7600 ft.
Oddometer: 531
Originally Posted by Mikef5000 View Post
The only one of those factors that would effect the pump itself is (b). Modifications and riding style make no difference, the pump is either on or off, not variable. Hot climates (or running hot) could be a factor as well.

This is quite common with FI dirt bikes though. A small amount of fuel (which acts as fuel pump coolant), mixed with lots of heat (stuck/slow riding), is going to be bad on a fuel pump, period. Regardless of bike/brand etc.
Thanks for your reply. Yes it is either on or off but it cycles to maintain pressure faster or slower depending on engine load. What I was getting at is any electric pump has a max flow rate, and at that point the electric motor inside it is cycling at its design limit to maintain fuel system pressure. This generates a certain amount of excess heat. Part of the design of an in-tank pump is that heat is dissipated by the fuel in which it is immersed.

Performance mods + hard riding + heavily loaded will cause higher demands for peak flow rate out of the pump. Low fuel levels + high engine & ambient temps & low speeds also increase heat effects as the fuel cannot dissipate the heat from the pump as well.

I was just guessing that many folks ride the shit out of these bikes loaded & modded (which is a good thing believe me) but maybe the fuel pump is too often at or beyond its design limits in a situation with a low fuel ( so poor heat sink) and so it fails. It would be nice to have a higher capacity aftermarket pump available or at least understand what factors are causing this so as to minimize the likelihood of occurrence. Then again I would expect Athena big bore folks to have the most failures if this is a correct thesis.

I am purposely not modding the engine til I understand this better, much of my riding is way the hell off and gone solo in the mountains and I really don't want to have to deal with a fuel pump going out @ 12k ft 30 miles from anywhere. High elevation makes heat problems worse as the ambient air pressure is lower, so its ability to absorb radiated heat is less.

Anyway so far the take away message seems to be, do not run out of fuel or get too low, esp while riding hard & slow, and if you do maybe ride more conservatively to minimize heat build up.
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