Petcock on reserve...fuel flow?

[steve murdoch icoa #5322]

How does the fuel flow change when the tank is switched to reserve?
On my '81 with 6-6 Pipemasters, the fuel line diaphram rremoved and otherwise stock carbs, and inline fuel filter, whenever i switch to reserve the bike coughs/stumbles and runs like it is being starved for fuel. Sometimes it will clear itself after a few seconds but mostly it continues to run like crap until i can stop and refuel.
I thought it could be the Pingel 2-valve petcock acting up but after replacing it with the stock Honda one the problem remains.
Is the flow different? Any thoughts?

[alimey4u2]

With the valve in the run position, it opens up the top port & when in the reserve position it opens up the lower port. The lower port then has access to the remaining fuel left in the tank that hasn't been scavenged by the top port.
From what you describe, my suspicions would be that you have blocked "in tank" fuel filter or a layer of crap (sediment) in the bottom of the tank restricting flow. And/Or... your "inline" fuel filter requires a greater head ( pressure) to pass flow. This could be because the design is somewhat restricting or it is partially blocked.

However, seeing that you have switched petcocks ( & strainers ? ) it could be sediment accumulation in the tank or your inline fuel filter.

[Terry]

I have an inline filter on my 79 but not the 82 but my guess would also be the lower pickup point in the tank is partially blocked. I routinely run the bike from the reserve position every time I ride just to insure its kept open and free of crud. I occasionally run some gas treatment thru them too. BTW, I have the original petcocks on both bikes and although the 79 has a much higher level of fuel in it when it goes on reserve, both petcocks work perfectly.

[Don #6141]

I routinely run the bike from the reserve position every time I ride just to insure its kept open and free of crud

That is very, very good advice - Maybe run the first 20 miles of every tankful through the reserve and then switch to the 'main'

I usually shut off the petcock every time I get off the bike, so it would never be a problem leaving it on reserve for too long and running out of gas

Don

[steve murdoch icoa #5322]

Thanks for the input, guys.

I had thought the two petcock ports may have been a different size or that the removal of the fuel line diaphram hay have created a different fuel draw..
I will drain the tank, check for a layer of crud and change the inline filter.