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Fuel tap causing flooding?

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350Simon:
When I bought my 350f the dealer said 'always run these old bikes in the reserve position'....... in other words there's a problem with your fuel tap but I don't want to tell you haha

Anyway it runs great so no issues there, yesterday out of interest I thought I'd put the tap in the on position and see what happened. Literally 15 seconds later fuel is pissing out all 4 overflows onto the drive. Turn it to reserve, fuel stops flooding out the carbs.

Started engine with tap in reserve, lovely idle and good response. Turn tap to on position, bike starts spluttering and flooding carbs again.

Could it be that the tap is broken? It seems very odd to me as you'd expect if it was a float / seat issue it would also flood in the reserve position. Anyone had this before?

Cheers
Simon

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McCabe-Thiele (Ted):
That's weird as if the tap internals are as they should be you would have a greater fuel  pressure in reserve - lower in normal ON position.
Out of interest what happens if you are on reserve and open the filler cap.

350Simon:

--- Quote from: McCabe-Thiele (Ted) on August 07, 2022, 01:18:26 PM ---That's weird as if the tap internals are as they should be you would have a greater fuel  pressure in reserve - lower in normal ON position.
Out of interest what happens if you are on reserve and open the filler cap.

--- End quote ---
Yes that's exactly what I thought. Pressure should be greater on reserve setting than 'on'.

An internal restrictor perhaps broken down? Someone has rebuilt it back to front maybe? Is that even possible?

Not tried with the cap off yet I will try that shortly!



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Laverdaroo:
Wonder if the rubber diaphram/gusset thingy inside is split or in back to front as you suggest (if thats indeed possible) weird it behaving like that!

McCabe-Thiele (Ted):
If the tap is switched off whilst the engine is running to empty the carb bowls you can sometimes get flooding when you open the tap again if the valves stick a little. Before my rebuild I found rocking the bike whilst on the centre stand would fix the flooding immediately.

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