Author Topic: Bike hard to start when itís hot???  (Read 613 times)

Online Perazzimx14

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Re: Bike hard to start when itís hot???
« Reply #30 on: May 19, 2022, 08:47:18 AM »
There's a clear misuse of terms in this thread.

Vapor lock is when the fuel boils within the system, and displaces liquid fuel at the engine entry point.

Tank vacuum is when the pressure in the tank becomes too low to feed the carbs or pump. Seems unlikely in an EFI system, but still to be verified.

I think you quoted the wrong post??
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Online PJPR01

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Re: Bike hard to start when itís hot???
« Reply #31 on: May 19, 2022, 09:01:17 AM »
Very unlikely. That fuel pump is submerged under liquid fuel. That pressurizes the entire system down stream from there. Even if the tank does not vent properly, the pump will typically keep pushing out fuel. Very difficult to get a vapor condition in a system with a submerged pump. Now in the systems with the external pump sucking on the lines, that is very common.

From personal experience on my 08 Norge, it's behaving exactly as I've described - I understand the above statement, however opening the gas cap, relieving the pressure  and the bike runs fine again immediately, so....This only occurs on extremely hot days, and not very often.  Which sounds like what Bob is experiencing.  Either way, it's one alternative for him to explore...hopefully he finds the root cause.

Paul R
2015 Red/Black Griso
2008 Silver Norge
2002 V11 Scura


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Harper's Moto Guzzi : Go Ride , Break Parts, Call me!
Harper's Moto Guzzi. Where we still answer the phone, use the highest quality parts, and also do Transmission, rear drive, and carb rebuilds fast. Call us at 816.697.3411 and get your problems resolved.
http://www.harpermoto.com
Advertise Here