Topic: Fuel Starvation?

[Frankenkit]

I'm stumped.  So yesterday, I put a new inline fuel filter on and when I turned my petcock to 'on' and 'res', nothing flowed.  I have about 3 gallons in the tank, so I'm a little surprised.  Today I siphoned the tank, took the petcock off, and...
it's flowing easily.

I blew it out with compressed air, but I'm still at a loss.  It seems free and clear.  Lines are clear, too.  The only guess I have is that the washer that fits inside the petcock is torn a little bit, buckles just a little where an eighth of an inch of the rubber on one side is missing.  I doubt it's enough to impede fuel flow, but it could be, so I'm getting another one to replace it. 

If it's a sticky float needle, wouldn't  the fuel still at least fill the fuel line and filter? 

Bike's empty now, so if it's the float needle etc, I'm in a good position to fix it... 

[OldSchool_IsCool]

I'm not a big fan of in-line filters.  I had one that filled with air and prevented sufficient fuel flow to hold even 3/4 WOT.  Inspect, replace your in-tank filter and trust that.  If you must run an in-line, mount it vertically, like standing on end on top of the carb fuel gallery.  Your hose should have no high spots, sloping gently down to the carbs.

Your problem sounds different, no flow at all!  Could it have been that all four bowls were full thus no call for any fuel to flow?  If it happens again, open a bowl drain and see if you get flow.

 

[martino1972]

yeah,trust your intank filter......

[Frankenkit]

no in-tank filter. For whatever reason, when I had the tank coated, the internal diameter of the petcock tap was so narrow as to pinch the filter and tube so nothing got through.  (that was the first time it started acting like this...)  so I had to hook out the intank filter (it was jammed by that point) and put in the petcock again- that time it worked.  Maybe I should buy another in-tank filter?  how would you suggest I get it to work with the tank liner, w/o disrupting the liner to the point that it starts releasing?  The liner is blue 'red-kote' according to the radiator shop.

[woody1981]

This might be a stupid suggestion, but have you checked the vent hole in your gas cap? Does the fuel flow with the cap open?

Just a thought.

- Woody

[Raul CB750K1]

My brother has a Kawa EX500 that starved at WOT. I suggested him to remove the inline filter. No more problems after that. The EX500 has a petcock filter.

Kitsune, you sure your filter is in the petcock tube? Does your petcock have a fuel bowl? If so, then the filter is on the bowl -so you can clean the sediment in the bowl-

[eurban]

Raul those type of petcocks were sooooo early to mid seventies.  Late seventies and eighties, inside the tank filters were the rage.

[Tower]

Perhaps a naive suggestion...but, is the fuel filter in the right orientation to fuel flow?  If fuel is supposed to flow in the opposite direction you may be getting air lock, or a check valve preventing flow.

[NickC]

I was going to suggest the same thing. I had some inline filters that had no markings on them (or so I thought) until I looked real close and saw a 1&2

[Hush]

Is the fuel filter fitted upside down?
They only flow one way so try fitting it other way round.
I have no filter on mine Kits, the tank one seems to either be missing or never fitted.
Don't think I'll bother unless I run into debris problems, the tank seems very clean and crap free at the moment.

[Frankenkit]

I'm going to try the in-tank filter again... just buy another one and get it over with.  Petcock was clean inside, everything flowed smoothly once it was off the bike.  I *thought* I had it in a very gravity/flow conducive configuration, but maybe not?  Cleaned out gas cap too, but that was also clear to air flow, so no idea.  Going to buy some fuel line again and try to route it better (this time, until the in-tank filter arrives)... but as I'm in the work week right now... it might be until tomorrow or so before I can do anything again.  

If my tank has just been coated, should I bother with a filter, then?  (potentially dumb and/or loaded question, but thought I'd ask...)

[martino1972]

yes,you do need a filter...
unless you get a kick out of removing and cleaning carb's....
no filter at all makes you at risk for every little partical that could and WILL end up in your fuel tank,nicely going down your system and plugg up your pretty little carb jet's...

and martino's law......oh,eu,murphy's law will make sure it happens on a pretty road trip,leaving you with a crappy runnig bike in the middle of nowhere....

[TwoTired]

If my tank has just been coated, should I bother with a filter, then?  (potentially dumb and/or loaded question, but thought I'd ask...)

So, you are saying that you trust every gas station to provide perfectly clean fuel?  Has cleaning the carbs become a joyous endeavor?

If the red coat is a hard liner, rather than soft, I would use a reamer to skim/trim the coating to a point where the in tank filter will once again fit.

Cheers,

[Raul CB750K1]

Who say that the inline filters allow fuel only in one direction? They allow fuel in both directions; it is only that the filter, instead of being a simple mesh screen, is a bigger funnel to maximize filtering surface, therefore maximizing the fuel flow even when there has been a lot of particles filtered. The "flow in" tube is always the tube connected to the outside chamber of the filter, for the simple reason that this way the user can see how much sediment there is. Otherwise you would never see how much particles there has been filtered. But the fuel can flow in both directions.


Seems that we have busted another myth of "conventional wisdom"......   

[Tower]

Raul, there are some filters that have check valves.  Some will create an air lock if not oriented right, and they all will hide and concentrate the sediment (as you said) if flowed in the wrong direction.

[goon 1492]

I saw your thread earlier today describing the tank liner, and I would reccomend taking off the inline filter they are tricky to get all the air bubbles out of, and if you don't they will cause an air lock, I would listen to TT if its a hard type of liner and ream that bugger out alittle. Possibily ream out just enough to slip the filter/petcock assembly back in..........And then drive it like you stole it!

[Raul CB750K1]

Raul, there are some filters that have check valves.  Some will create an air lock if not oriented right, and they all will hide and concentrate the sediment (as you said) if flowed in the wrong direction.

Never seen one with a check valve. Are they suppoused to be used with motorcycles? The valve mechanism must be real weak, otherwise the gravity would not be able to open it.

I use a petcock in my Sanglas bike, the mesh in the filter is so thick that I don't trust it -and the filter residue shows that I was right. It has air sometimes, and some others not, and the bike runs like a champ with no hesitation. If the filter is in vertical position, you probably don't have air, but if it is in any other position, there will always be a chamber above that will keep the air trapped. No problem at all, as long as gas can come in and go out.

[neudl]

For what it's worth, I was using an in-line filter to deal with a rusty tank.  I recently treated my tank with Por-15, ditched the in-line filter, and replaced the worn-out petcock with a new one with a new in-tank screen.  The difference in performance is amazing.  I never appreciated how much the in-line filter was interfering with the fuel flow.

[Frankenkit]

OK, bought fuel line and ordered a filter. A real, spankin' in-tank filter.  TT, do you suggest a regular rat-tail file, or something finer, like a pencil with sand paper wrapped around it?

[goon 1492]

there is also smaller jewelers files you can get at any hardware store, or hobby lobby. that would get the fine touch your probably gonna want to get, or a fine tooth rat tail like what you said. Either that that way you don't take too much material and go all the way through the liner back to metal.

[TwoTired]

OK, bought fuel line and ordered a filter. A real, spankin' in-tank filter.  TT, do you suggest a regular rat-tail file, or something finer, like a pencil with sand paper wrapped around it?

The "Most Correct" way, I imagine, is to measure the O.D. (outside diameter) of the fuel strainer you wish to insert.  And, then get a straight flute Reamer with the same O.D.
http://en.wikipedia.org/wiki/Reamer

I still don't know if your red coat remains soft.  If so, a reamer may grab it in a big bite and tear it off entirely.    Then perhaps a taper flute reamer would be a better tool for the job.

Depending on your skill, you could take a smaller diameter wood dowel, and cut a slit in one end with razor saw.  Then cut some fine sandpaper the width of the slit and insert it into dowel end.  You just made a cylinder hone.  With the correct size dowel and the right length of sand paper, you wrap the sand paper you put into the dowel slit around the dowel, and insert it into the hole you want to abrade.  Twisting the dowel now abrades the hole I.D. (inside diameter).  If the paper clogs, change the paper.  When the hole has enlarged enough, you're done.
There is a lot I don't know about Red Coat.  Might be able to chuck you newly made hone into a drill.  But, heat from the friction might melt the red coat and fuse it onto the hone.
You'll have to use some judgement.

A rat tail file can also work, provided you have good hand fine motor skills, don't select a too aggressive cutting tool, and can keep the entry hole round to fit the filter snugly, without cutting through the red coat.

Good luck!

[martino1972]

i would like to add,that if you use a rat file,that you only stroke outwards....
if stroking inwards you might lift up the liner and break of a piece inside the tank....
so,insert the rat file gently without touching the liner,and then push against the liner abit on the way out,that way the pressure on the liner gets suported by the tank wall...less change of liner failure...

[Frankenkit]

The cylinder hone idea was pretty much exactly what I was thinking of, actually.  It'll take a week to get in, but then again, I've got work and the lead-up to finals week anyway.

[mrbreeze]

I also tried an in -line a few years ago and felt that it restricted fuel delivery to where I noticed it. Just remember....Its gravity feeding 4 carbs.

[Frankenkit]

My local Honda shop *finally* got my filter in (and didn't bother to call me...) so today I put it in and noticed I had two problems:
1) I can tighten the petcock down to 'relatively firm' which is the far end of 'finger tight' before it jumps the threads, loosens and pisses gas all over everywhere...  I've bandaided the problem with teflon tape just in order to keep the gas in the tank and start up the bike, but have no intention of making that a permanent fix unless you guys say that's my best recourse...

2) Second problem is, I got the bike started, but the idle was really low and boggy.  I choked it and it brought the idle up a bit, but it wouldn't take any throttle until after a couple minutes when it was warmed up a bit.  Any throttle would kill it, and later, if it didn't kill it, I could give it just a touch of wrist, the rpms would rise, then drop while I still had the throttle open.  Not sure wtf that is supposed to mean.  After I got the idle going good, it eventually started accepting throttle decently... but I'm not sure if that's a "These bikes are old, so unless you did xyAND z with it, it'll kind of act like that" thing, or a "It's running rich/lean/etc because previously it didn't have any gas and now that it does, it's set wrong" or "you have a stuck float needle so it's effed up" or whatever...

I'm strongly considering taking off my carbs (again) and looking over floats/needles, checking passages and jets, and doing the best bench synch I can with whatever directions I can find here (I know there are some instructions in the FAQ)  I don't have the carb-tune, and unless I feel real confident in whatever directions I receive, I'm not sure I'd feel comfortable trying to make one at home.    I also know there's a possibility of an air leak at the carb boots, so that's also on my fixit list. (for now, just putting some high-temp sealer on the inside mating edges of the boots, as there are no visible cracks...) then spraying with some wd-40 or a touch of ether to see if I have a change in RPMs...

I just want to do this as well as possible (and in as short of a length of time as possible) because I'm just waiting on my riding buddy to recover from her recent surgery, then we're going 2-wheeled full-time.  (provided my bike behaves...)