fuel line question

M

miikeflynn

New Member
I just replaced the petcock and fuel lines on my cb350. I used a new oe style petcock a short fuel line that runs into a fuel filter, then another short line that runs into a Y connector and then two lines off of that to each carb.

here's my question; since the previous lines were black I never saw what happened inside of them. The new lines are clear so I was a little shocked to see the lines were not completely full of fuel. there are a couple of spots in the line that hold air. Is that normal? The bike runs great, so I assume this is normal but it was a little off putting so I wanted to check with you guys. Sorry if this is a dumb question but this bike is really my first venture into engine mechanics.
 
Fairly normal in my experience.
My 350 did the same thing.
It always annoyed me.
 
Yeah it seems weird. I'm not looking at the bike right now but i think there was a small pocket of air right before and right after the filer. I cleaned the tank at the same time (so much crud came out it was crazy) so now its nice clean fuel all the was to the carbs. It seems to run so much better now. So I guess i'll just leave well enough alone.
 
AlphaDogChoppers said:
Maybe you are easily annoyed? :D
Click to expand...

I am
thefinger.gif
 
The rate of fuel flow is pretty small. Not enough to purge air bubbles out of the line. You get a capillary flow on the sides of the tube along side the bubble. It's enough flow to satisfy the need. If the engine needed to draw fuel faster than that, it would draw the bubble through.
 
AlphaDogChoppers said:
The rate of fuel flow is pretty small. Not enough to purge air bubbles out of the line. You get a capillary flow on the sides of the tube along side the bubble. It's enough flow to satisfy the need. If the engine needed to draw fuel faster than that, it would draw the bubble through.
Click to expand...

Ok that makes sense.

Now for another question as a novice mechanic how hard is it to pull the carbs off of this bike and clean them? Any good step by step guides you can recommend?
 
You could install a EFI pump, to get the pressure up to 50psi. That will force all the air bubbles out.

Then, just before the carbs install a 4psi regulator and a return by pass valve/hose back to the tank.

;)
 
ako said:
You could install a EFI pump, to get the pressure up to 50psi. That will force all the air bubbles out.

Then, just before the carbs install a 4psi regulator and a return by pass valve/hose back to the tank.

;)
Click to expand...

Completely nonsensical
Overly complicated
Impossible without supporting modifications

I love it!

But id bet 4psi is still way more than is needed.
 
AlphaDogChoppers said:
Step 1: Download the service manual.
Step 2: Follow the instructions in the service manual. :)
Click to expand...

I have a shop manual. It says "disassemble and clean carburetors with gasoline...reassemble, install and adjust carburetors" Then goes through the steps of adjusting the idle and pilot screws. Is that pretty much what I get to go on? I think I can follow those steps ok but what about the disassembly and reassembly? Is it one of those put everything back where it came from deals or is there more to it than that?
 
ako said:
You could install a EFI pump, to get the pressure up to 50psi. That will force all the air bubbles out.

Then, just before the carbs install a 4psi regulator and a return by pass valve/hose back to the tank.

;)
Click to expand...

I may not know much, but I know thats not the way to fix it. haha

:D
 
AlphaDogChoppers said:
That ain't gonna cut it. Is it a factory manual?
Click to expand...

I think so. It was a PDF I found online where someone scanned in an old manual. It's got some pretty good info on some things just not the carbs. Is there a good manual out there for the 350?
 
If gasoline would clean the carbs, then you wouldn't need to clean them, would you?

You have to disassemble the carbs. Get two kinds of carburetor cleaner. There is one in a one gallon can with a basket inside, and get a can of spray carb cleaner.

After dissassembly, put the carb parts in the basket and soak them in the cleaner. DO NO soak any parts that have non metallic parts. If you are having trouble removing a gasket, (such as the float bowl gasket,) it's OK to soak it for a minute or two to get it separated, then wash the carb cleaner off of it.

After they soak for a bit, pull them out and clean with a brush. Then take the pieces outside and squirt spray carb cleaner through all the passages. Take special care to be sure all passages are clear. While you are doing that, study where the passages go to develop some understanding of how the carbs work. If you have compressed air, use it to blow out all the passages.

Before putting the float needle seat back in, use some metal polish on a wooden match stick to polish the needle seat.

Follow the manual instructions for setting the float height.
 
@alphadog thanks a lot for the help. I found a much more detailed manual last night. Looks like it would have probably been something issued to a Honda service department. I think between your advice and that manual ill be ready to tackle that soon.
 
Your in luck if it's the one issued to a Honda service dept. That goes way more in depth then any Clymer or owners manual. But it does not give you obvious answers because it kind of expects techs to have some idea of what their doing. If this is your first bike read as much as possible it really helps.
 
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