Topic: fuel line and filter positioning

[petercb750]

Howdy all.
I have noticed that my bike, 750 K2, with in-line filters between tap and carbies, has one of the lines and filter sitting on top of the air box - ie there is a section of the line that therefore runs up hill a bit before it loops back down to the carbies on the left hand side. Do you think this will cause a problem? I have an idea that if the level of fuel in the tank gets low, there will be less pressure of fuel from the less weight, and therefore maybe not enough pressure to get the fuel up hill before the in-line filter, thus causing an air lock? Or am I dreaming and letting paranoia set in with the 50+ years?

The reason I ask is that today my bike seemed to run out of fuel with fuel tap at "on" and despite turning to reserve didn't want to run, until I coasted into a servo (very quietly  ), put in a few litres, and away she went, as good as new. Therefore, reserve didn't seem to work. It's a new fuel tap, and I've just had the carbies cleaned and tank cleaned and cream coated.

Now that I've written this I might have answered my own question - bike runs out of fuel, meaning carbie bowls are empty, switch to reserve, not enough weight of fuel to go uphill and therefore fill bowls again to get it going - sound feasible?? And to add weight to that, the bike seemed to be trying to run on 2 cylinders, which I guess would be the other 2 not fed by this line?


Any thoughts? Oh it should be this simple...............

Peter.

[keiths]

I've seen the same thing. I removed the filter and the problem went away. Mine wasn't going up hill but it was mounted flat.

[Raul CB750K1]

Been there done that. Due to the length of the filters, I have them besides the carbs but the fuel line makes a pretty nice "U" shape.


For that reason, the filters never get completely filled with gas, but anyway and due to the laws of physics, the gas manage to climb up and reach the carburetors. There is an air bubble in the filters that stays there.


A few weeks ago I couldn't for the life of me start the bike. I was having problem with the battery, so I decided to kickstart it because it always works even whith an almost-flat battery. Sweating like a roasted chicken and the bike didn't even make a single explosion.

The battery was completely dead and, as I had tried all possible choke positions and wide open throttle, I couldn't smell gas so I put the blame on it. My bike never take that much to start, so I put the blame on the lack of gas. But there was gas on the tank and the petcock was on!!!


So I thought what you think: the gas was not able to reach to the carbs. I was in my parking, so I thought of an imaginative solution: put the mouth on the tank opening and blowed inside, forcing pressure. When I looked at the filters they had more gas than before. A couple of kicks and the bike started....


I will probably get rid of the filters, but the truth is that the petcock filter can't cope with all the particles and I had a problem sometime ago with a stuck float needle and flooded air filter and cylinders. Anyway, in a month or so I will replacing the battery and battery leads -a previous owner replaced them because the battery had the terminals the other way round-, replacing the master cylinder and probably coating the inside of the tank, so I will then decide what to do with the lines.

My bigger problem (CB750) is that when I used short lines with no bends, it was almost impossible to disconnect the lines out of the petcock when I wanted to remove the tank...


Raul

[Terry in Australia]

F*cking hell, Raul, no wonder you ran outta fuel mate, those lines are about a foot too long! I had a similar problem on my GS1000 Pete, and my fuel line that I fitted was only an inch or two longer than the one I replaced, it went up slightly before it went back down to the carbs, and that was enough for it to conk out.

One day I conked out on the side of the Hume highway, and a car full of Arab terrorists stopped to help me out, (well, not everyone in Al Queda is an #$%*, is he?) as I'd flattened the battery they tried to push-start me, well, they pushed and pushed, for maybe twenty minutes, but it didn't even fire, then just as we were about to push my bike off the side of the road so that Ahmet and Ahkmed could blow it up and I could collect the insurance, I noticed that I'd accidentally moved the kill switch to "off"?

Hmmmnnn........... I didn't tell the rest of my red-faced new "friends" that I'd f*cked up as they were looking pretty angry by now, and muttering things about "May the fleas of a thousand camels infest Mr Suzuki's armpits" so I suggested "what about one more go guys" and within a couple of yards it went "Varoom", so I didn't stop to thank them all individually and offer to strap on a couple of pounds of C4 and stop in at McDonalds on my way home, I just buggered off! 

It was all because I thought (like Raul) that I'd add a little more line to make it easier to remove the tank, but it drove me nuts until I finally removed the OEM "Vacuum" petcock (great in theory, miserable in practise) and replaced it with a Pingel, then all was well with the world. Cheers, Terry.  

[Raul CB750K1]

Well Terry, now that you mention it, let me share with you a true story. When I was 18 I had an old car whose battery was flat every other day. I used to park it facing a downward slope so in case the battery fails I just had to let it go. That day it was cold and it refused to start even after the "pushstart".

Well, I was in a little hurry and needed to start the car. Looked around and found a couple guys inside a car. Got near, knocked at the window and that was when I saw them smoking a "chinese" -spanish nickname for smoking a heroin cigarette in aluminium foil-. I didn't know what to do, so my reaction was to ignore what I was seeing and pretend to be natural. They rolled down the window and I told them. Hey guys, my car wont' start. Would you mind to give me a push start? 

They guys told me: "Give us five minutes". Believe it or not, in ten minutes they came to my car, pushed it and it started. I waved my hand and thanked them. What I don't know is what happened with them after the exertion....


Raul

[Terry in Australia]

"and that was when I saw them smoking a "chinese" -spanish nickname for smoking a heroin cigarette in aluminium foil"
Raul

Geez mate, you'd have to be desperate wouldn't you? Man, I couldn't put aluminum foil in my mouth, let alone smoke heroin outta it? Of course, I could drink Jack Daniels out of an aluminum foil cup all day long, but we both know that's good for you! Ha ha, Cheers, Terry.

[Master Ted]

How odd it is that heroin is not phisically damaging - sure, it has killed many from needle sharing: hep C, HIV, and assorted rot. But, the actual drug itself is quite easy going on the constitution. How else can one explain the life span of Keith Richards, Bob Dylan and Eric Clapton?

[Raul CB750K1]

"and that was when I saw them smoking a "chinese" -spanish nickname for smoking a heroin cigarette in aluminium foil"
Raul

Geez mate, you'd have to be desperate wouldn't you? Man, I couldn't put aluminum foil in my mouth, let alone smoke heroin outta it? Of course, I could drink Jack Daniels out of an aluminum foil cup day long, but we both know that's good for you! Ha ha, Cheers, Terry.

I hasn't been very accurate, and doesn't know the "procedure" either. You make some kind of cup with the foil, put the drug on it, use a lighter underneath and when the drug smokes you use some kind of rolled paper to breath it. Something like sniffing cocaine but through the mouth. Sorry I'm not very well informed when it comes to drugs...

[petercb750]

ummmm, I think somewhere we lost the plot with this thread..............

[Nate]

How odd it is that heroin is not phisically damaging - sure, it has killed many from needle sharing: hep C, HIV, and assorted rot. But, the actual drug itself is quite easy going on the constitution. How else can one explain the life span of Keith Richards, Bob Dylan and Eric Clapton?

When i was in the Air Force i was told by a Doctor at a anti-drug briefing, "if your going to do drugs and ruin your career, for gods sake go with heroine. If you're somewhat sensible about it and use clean needles it won't harm you a bit. Only downside of it is you typically have to hang out with other heroine junkies."

[Klark Kent]

http://en.wikipedia.org/wiki/Chasing_the_dragon
-KK

[Raul CB750K1]

So "chasing the dragon", from chinese origin. It explains why is it called the "chinese" in spanish. Thanks for the enlightment Klark Kent.


Funny thing is that in the wikipedia it warns about aluminium foil with plastic coating, reccomending to burn it first to avoid "inhaling dangerous plastic fumes". As if inhaling heroin was harmless... 

[Geeto67]

Getting back on topic for a second.

One of the reasons I bought my DOHC cb750 so cheap ($350) was that the owner couldn't get it started. After a friend and I were futzing around with it for a good long while I was about to give up when I looked under the tank and saw a mile of fuel line.  I told the seller I would give him $350 for it not running (he was asking $500 but the ad said running) and I was going to push it to my friend's shop which was a couple of blocks away. He did the deal and I pushed it around the corner - once around the corner Took the tank off, cut the line down to the shortest possible length, and re connected it. The bike fired right up and didn't miss a beat - I rode it home.

If you can help it the fuel line should not be level or uphill. 

[petercb750]

Ok, thanks Geeto - I've got some repositioning to do.
While we're on the subject again, another theory put to me is that the tank is not venting properly.
This might sound pretty dumb, but where do these tanks vent? I assume it's through the cap, so what should I be looking for in the cap? If there is meant to be a pinhole in it, this may have become blocked when I had the inside of the tank cleaned and lined at the same time the new filters were put in. Maybe??
Yesterday, when trying to go to a bike show about 100k from home, it wouldn't run for more than a kilometre or so before chugging to a stop, despite full tank. Could see fuel in the filter that was suspect before (so assume fuel is getting through ok), took out a couple of plugs (nothing too bad with those), checked inside tank to see if the new coating was perhaps "melting" into fuel (don't think so, running finger around inside tank didn't produce anything other than fuel that I could notice). From memory, I reckon each time I opened the tank, the bike started and ran ok, but this was probably not consistent, as I wasn't thinking about that as a problem, just gazing hopefully into the tank cos I didn't know what else to do! 
After much stuffing around, and several false starts I decided to take it home, and go the bike show two-up on the wife's 400/4, but as an experiment I turned the tap to reserve despite tank being full - ran like clockwork all the way home (about 10k from where I gave up), and revved out to redline no worries. Now this would give an obvious solution to my problem - blocked fuel pipe in the tap - but the day before turning to reserve made no difference. So this venting theory is starting to look right?? (and of course the placement of the lines).
Any thoughts?
Peter.

[Geeto67]

Ok, thanks Geeto - I've got some repositioning to do.
While we're on the subject again, another theory put to me is that the tank is not venting properly.
This might sound pretty dumb, but where do these tanks vent? I assume it's through the cap, so what should I be looking for in the cap? If there is meant to be a pinhole in it, this may have become blocked when I had the inside of the tank cleaned and lined at the same time the new filters were put in. Maybe??
Yesterday, when trying to go to a bike show about 100k from home, it wouldn't run for more than a kilometre or so before chugging to a stop, despite full tank. Could see fuel in the filter that was suspect before (so assume fuel is getting through ok), took out a couple of plugs (nothing too bad with those), checked inside tank to see if the new coating was perhaps "melting" into fuel (don't think so, running finger around inside tank didn't produce anything other than fuel that I could notice). From memory, I reckon each time I opened the tank, the bike started and ran ok, but this was probably not consistent, as I wasn't thinking about that as a problem, just gazing hopefully into the tank cos I didn't know what else to do! 
After much stuffing around, and several false starts I decided to take it home, and go the bike show two-up on the wife's 400/4, but as an experiment I turned the tap to reserve despite tank being full - ran like clockwork all the way home (about 10k from where I gave up), and revved out to redline no worries. Now this would give an obvious solution to my problem - blocked fuel pipe in the tap - but the day before turning to reserve made no difference. So this venting theory is starting to look right?? (and of course the placement of the lines).
Any thoughts?
Peter.

the vent depends on the bike. the later ones have vents in the tank tunnel, earlier ones in the cap. consult your manual. A good way to see if your tank is not venting is when it starts chugging, open the fuel cap. if it smooths right out then your vent is clogged - if it doesn't then the issue is something else.

if you turn the petcock and it solves the problem then your petcock is probably clogged in the main event (not the researve vent). Take it out clean it and see if the issue is still there.