Topic: CB750 fuel petcock neck- can it be shortened?

[Bduck72750k]

I tried to search around the forum for an answer, but can i shorten the petcock neck inside the tank? Im not looking to have it sit right above the bottom of the tank, but at least reduce it by half the length. Anyone have input on this? It is a 1974 CB750

[HondaMan]

I tried to search around the forum for an answer, but can i shorten the petcock neck inside the tank? Im not looking to have it sit right above the bottom of the tank, but at least reduce it by half the length. Anyone have input on this? It is a 1974 CB750

You can, but it shortens your "Reserve" range a lot. When on Reserve it only drains both sides until the 'hump' in the center is dry, then the far side gets trapped and the Reserve side becomes quite short, like 15 miles.

[Bduck72750k]

I tried to search around the forum for an answer, but can i shorten the petcock neck inside the tank? Im not looking to have it sit right above the bottom of the tank, but at least reduce it by half the length. Anyone have input on this? It is a 1974 CB750

You can, but it shortens your "Reserve" range a lot. When on Reserve it only drains both sides until the 'hump' in the center is dry, then the far side gets trapped and the Reserve side becomes quite short, like 15 miles.

Gotcha! Appreciate the response. Ill probably leave it be. I read an older post you wrote on how to petcock works. I think it was an older post from maybe 2008 area. Very helpful!

[ekpent]

 Just curious as to why you need to do it. Need more clearance for some knee dents or other custom mods ?

[Bduck72750k]

Just curious as to why you need to do it. Need more clearance for some knee dents or other custom mods ?

No just wanting to get more out of my primary tank and seems like the reserve uses too much real estate. Lol also am quesioning using a license plate bracket that would attach to the rear axle on the left hand side. Would this interfere with anything?

[RAFster122s]

Most states require plates to be illuminated, so there is that added complication.

[TwoTired]

No just wanting to get more out of my primary tank and seems like the reserve uses too much real estate.

What?
The stand pipe only determines when reserve needs to be selected, as it is fed from the tank bottom.  The pipe has nothing to do with the amount the tank will hold, just how far you can drive after you NEED to switch to reserve.

The stand pipe length has no effect on total tank capacity.

[Bduck72750k]

No just wanting to get more out of my primary tank and seems like the reserve uses too much real estate.

What?
The stand pipe only determines when reserve needs to be selected, as it is fed from the tank bottom.  The pipe has nothing to do with the amount the tank will hold, just how far you can drive after you NEED to switch to reserve.

Right; and in previous posts Hondaman has gone into detail about driving with reserve selected, and im trying to see if reducing the length of that will allow me to drive a longer range with it in the “on” position, and ill obviously aknowledge i wont have the same amoumt of miles on reserve.

The stand pipe length has no effect on total tank capacity.

[Bodi]

And, depending on your rate of acceleration and braking while on reserve, you can get a few miles more after running dry by tilting the bike as far to the left as you can manage to let any fuel still in the bottom of the right side go over to the left where it can be used. Under acceleration and braking the fuel sloshes back and forth and will tend to equalize the two sides but there's likely some left over there, I have had to do this a few times to try to get to a gas station. You appreciate having a motor if you ever have to push the bike very far at all.

[Don R]

 I once owned an F with drilled jets and high fuel levels, it got awful mileage before my buddy figured out the jets had been drilled. I had to give it the "lean" a couple times. 

[ekpent]

 Seems like I've noticed I think that 75-76 F bikes hit reserve sooner then K bikes. Maybe my imagination 

[seanbarney41]

Just curious as to why you need to do it. Need more clearance for some knee dents or other custom mods ?

No just wanting to get more out of my primary tank and seems like the reserve uses too much real estate. Lol also am quesioning using a license plate bracket that would attach to the rear axle on the left hand side. Would this interfere with anything?

I would try to avoid axle mounted and/or vertical mounted license plates altogether.  I have had one and it is just a lazy solution to a cosmetic problem that just causes ground clearance problems, rider seat accessability problems, and or rear wheel serviceability problems, in addition to legal problems.  Find a way to cleanly mount it in the proper location and your custom project will be that much ahead of everyone else on the internet.

[Don R]

Seems like I've noticed I think that 75-76 F bikes hit reserve sooner then K bikes. Maybe my imagination 

I agree with that assessment, the tank appears bigger but is it really?

[ekpent]

Seems like I've noticed I think that 75-76 F bikes hit reserve sooner then K bikes. Maybe my imagination 

I agree with that assessment, the tank appears bigger but is it really?

or the stand pipe sits taller in it ??

[Bduck72750k]

Just curious as to why you need to do it. Need more clearance for some knee dents or other custom mods ?

No just wanting to get more out of my primary tank and seems like the reserve uses too much real estate. Lol also am quesioning using a license plate bracket that would attach to the rear axle on the left hand side. Would this interfere with anything?

I would try to avoid axle mounted and/or vertical mounted license plates altogether.  I have had one and it is just a lazy solution to a cosmetic problem that just causes ground clearance problems, rider seat accessability problems, and or rear wheel serviceability problems, in addition to legal problems.  Find a way to cleanly mount it in the proper location and your custom project will be that much ahead of everyone else on the internet.

Right i got ya! I live in a small town in VT and its pretty relaxed. Right now im not running a plate, but its registered. I totally agree and i think with winter coming i actually will swap to building an actual cafe style cowling and seat. This is what i am running right now…

[Bduck72750k]

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