Fuel Leak

Well, I have had a bit of a weep for a while now.
Last night it was pouring out.

I had a look tonight and I was hoping it was just coming from where the fuel pipe joins the pipe that puts fuel to the carbs.
But I can't tell for sure.

The pipe itself gets wet on the top but slowly.
(well, quite quick, but not flowing, you know?)

I think it might be coming from where the pipe enters the carb.
https://www.lingshondaparts.com/honda_motorcycle_parts_selection_pfk?block_01=13MY5WEA&block_02=E__1900&block_03=1554&block_04=xx&block_05=hmc

Looks like there is a gasket at the end there.

How hard is it to do a bit of an overhaul on the carbs?
I have been thinking I would like to do it at some point anyway.

I have only played with one car carb and a couple of mower carbs before.

If you're going to overhaul the carbs ensure you've got a blowtorch and a JIS screwdriver. If you use a philips or a pz drive it'll round out the heads so make sure it's a J.I.S once. I ordered one from amazon called "Vessel 900 Megadora +2x150" and it actually came from Japan!

As for where you think it's leaking from do you mean the part numbered 3/4? within part number 2?

Nice one, thanks James.
I had never heard of JIS before.

A blowtorch eh?
I have one, but that makes it sound a bit interesting.
Is it a fairly straight forward job?
Just stay organised.

I can't see where it is actually coming from.
I shall have another try today hopefully.
It only comes out with the engine running and it gets wet quite quickly.

I 'think' it is coming from number 3 in this:

Screenshot_1 by chuffedas, on Flickr


I was thinking I might just change all the gaskets, but having ooked at the prices, maybe not.

I reckon I best have a read up.

If it's coming out of the number 3 part (the fuel union)  then the carbs will need to be split to replace the O rings.
It's actually the first time that I have heard of these failing, I believe that it is just be the fuel line from the tank where it joins this part. Which would be much easier to fix.

OK, thanks.
It has always run a bit rough as well anyway.
Plus it backfires a fair bit.
So I was pondering looking at it anyway.

But I could do with an easy fix for now I guess.
Get me back on the road.

The pipe was my first thought, but the tube it goes into gets wet on top pretty quick.
Plus the right hand side carb is wet on the side.
Perhaps first thing to try is pull the pipe off and have a look.
Perhaps it is spraying eh?
Even that doesn't seem that easy to get at does it.

Right, I shall report back.

Petrol like any other liquid will track to the lowest point so if it's on the top of the union the it's unlikely to be the O rings. As that would most likely be coming from the bottom of the union. The hose is not easy to get to granted, but it is by far the lesser of the two evils.
If the bike has been running rough then the carbs probably need cleaning out and balancing, but the fuel leak would have no effect on the running of the engine I'm sure.

It's not too difficult cleaning the carbs and quite satisfying once done knowing they are all good. They come off the bike easier than I expected when I did mine. From memory I rounded a couple of soft screws but they were easily drilled out without damaging anything. If they have never been off the bike before you might find bits of sub air filter in there (I did) and the gaskets may need replacing on reassembly. I got cheap ones and they have help up fine for two years now judging by the date on that thread.

If you have never done it before I also found these 3 part vids very useful:
https://www.youtube.com/watch?v=J8gXnaJr2J0
https://www.youtube.com/watch?v=yd3TL4yIzl4
https://www.youtube.com/watch?v=7rtNABYbpmk

You might wonder why I'm linking videos from the States about an old Goldwing engine but the carbs used on that bike seem pretty much identical to the ones of the CB500 as you will see!

@ceejay wrote:It's not too difficult cleaning the carbs and quite satisfying once done knowing they are all good. They come off the bike easier than I expected when I did mine. From memory I rounded a couple of soft screws but they were easily drilled out without damaging anything. If they have never been off the bike before you might find bits of sub air filter in there (I did) and the gaskets may need replacing on reassembly. I got cheap ones and they have help up fine for two years now judging by the date on that thread.

If you have never done it before I also found these 3 part vids very useful:
https://www.youtube.com/watch?v=J8gXnaJr2J0
https://www.youtube.com/watch?v=yd3TL4yIzl4
https://www.youtube.com/watch?v=7rtNABYbpmk

You might wonder why I'm linking videos from the States about an old Goldwing engine but the carbs used on that bike seem pretty much identical to the ones of the CB500 as you will see!

Nice one.
How on earth did you work out that bike's carbs were similar?
Random youtube searching?

@ANDYC wrote:Petrol like any other liquid will track to the lowest point so if it's on the top of the union the it's unlikely to be the O rings. As that would most likely be coming from the bottom of the union. The hose is not easy to get to granted, but it is by far the lesser of the two evils.
If the bike has been running rough then the carbs probably need cleaning out and balancing, but the fuel leak would have no effect on the running of the engine I'm sure.

I went out with a second pair of eyes and hands.
It had dried overnight.
You can see where it gets wet by it soaking into the gunk.

I was hoping to see that it was where the fuel line joined the part.

Question:
Should the part wiggle about?
Mine does. quite freely when you move the fuel pipe.
Where I gave it a wiggle, there was less fuel coming out this time.

I had a pair of eyes on the top and underneath.
The part moistens from one side along the top (difficult to see the bottom).
This happened before the fuel pipe got wet.
The carbs were dry above the part.
The fuel pipe was dry this time so not much was coming out.
(apart from where it accumulated at the top, but we still couldn't see it running down the fuel pipe.) 

It really did look like it came from the join of the part to the carb.

The part should move as it's only held in place by the O rings when the carbs are joined. 
Replace the fuel hose as it is probably well past it's best anyway and take it from there.

If you heat up the alloy then the corrosion/chemical reaction that builds up in the threads probably will crack making it easier to remove the bolts/screws. Putting them in boiling water would work just as well.

If you need to keep the bike on the road and have no other transport I've got a spare set of carbs you can borrow - no idea on their history though.

@Grarea wrote:
Nice one.
How on earth did you work out that bike's carbs were similar?
Random youtube searching?

Pretty much, I was actually watching his vid on sealing the tank on that same bike but watched the carbs one anyway as that was the next job for me too, thinking it might be helpful even if they are completely different... then when I got my carbs out it turned out they are not so different...

I guess it was a reliable and well developed carb design at the time when the writing was on the wall for carbs..

@ANDYC wrote:The part should move as it's only held in place by the O rings when the carbs are joined. 
Replace the fuel hose as it is probably well past it's best anyway and take it from there.

Thanks for that.

Also, agreed.
I tried to get some on the way past earlier, but they didn't have the right size, bugger.

@Jameshambleton wrote:If you heat up the alloy then the corrosion/chemical reaction that builds up in the threads probably will crack making it easier to remove the bolts/screws. Putting them in boiling water would work just as well.

If you need to keep the bike on the road and have no other transport I've got a spare set of carbs you can borrow - no idea on their history though.

Nice tip James, thanks.

That is incredibly generous James.
Thanks so much for the offer.

I can cycle about at the moment without too much problem.

If I missed the post I would struggle to collect it on the push bike.

Well, I learn something every day.
Turns out you are meant to have an accelerator and a decellerator cable.

100_7216 by chuffedas, on Flickr

Boy, everything I look at on this poor bike......
100_7223 by chuffedas, on Flickr

I had the carbs off.
It is definitely coming from that joint.
Both sides.

It is p***ing out.

New o rings are the answer.
That's the easy bit,
Separating the carbs to put them in is the fun part.

Is it that bad?

Not really, 
Remove the sliding plate that operates the choke plungers. Taking care to note which washers go where and the fixing of the return spring.
Loosen off the synchronizing linkage, just enough to be separated when the time comes. 
There are two long narrow bolts that run through the spacers that hold them together,  once they are unfastened the two carb bodies should pull apart. Remember to take note of which way the breather vents and the offending  fuel  union are pointing otherwise they would have to be separated again to correct it.
(I speak from experience).
The carbs will need rebalancing once put back together. 
Regarding the return cable, I haven't run one for decades. They were mainly for the slide carbs from days gone by. CV carbs are a different thing completely. This is why these days a broken throttle cable is a rarity.

Nice one, thank you very much.

Slowest Carb taking apart ever going on at my place.
Grabbing a bit of time here and there.
Thanks for the JIS suggestion James.
They really fit don't they?

IMGP2094 by chuffedas, on Flickr

Quick question. What is all the sawdust type stuff in there?

IMGP2097 by chuffedas, on Flickr



Edit: Oh, just thought, is that the residue of the disintegrated filter that I replaced?

That's just debris that accumulates over the years from petrol. Rust from the tank etc.
The debris from the filter will be in the top part with the diaphragms.

Thanks again for that.
I do appreciate the responses. 
Gives me confidence to carry on.

Now, I did an oops.
IMGP2099 by chuffedas, on Flickr

I hardly put any pressure at all (twice) and it broke of two of the 'bits'.
Any better suggestions than a hacksaw into the turret to create a groove for a straight edge screwdriver?

Same sh*t happened to me when I did it a few month back (first carb disassembly ever), I made a notch with a dremel (or was it an angle grinder? x)

Yeah, that's what I was thinking.
Seems a shame to cut into the case though.
That will be the job for tomorrow.