damned small fuel filter almost ate me

[ohgood]

So not long after buying the gs I installed an in line fuel filter. It's been fine n dandy until yesterday:

While cruising (80+/- mph) on I-4 the carb's starved. If there is ever a good time to starve carbs, this is definetly not it. So I slipped off the next exit and examined the visible filter. Empty. Bone dry. Notta.
Flip it over to prime, and watch the trickle start.
The always typical (since the headlight interrupt anyway) 1 and 1/2 revolutions with the starter and it fired up fine.
Road the rest of the way on prime, till I exited the 'state.

I suppose it could be contaminated with about 10,000 miles on it, or maybe I should just slam the biggest possible filter in there also ?

This is the first time I've noticed a starving problem, ever.
filter is approximately 2" long  X 1.125 diameter.

Any comments welcome. Thanks.

[makenzie71]

Okay the bike dies and you put it on prime...you ACTUALLY WATCH the fuel flow through the filter on prime, yet somehow you decide it's not working?

Fuel starvation isn't uncommon with the GS and there are several fixes...my favortie to date is putting gas in the tank.  Who'd a thunk.

[ducati_nolan]

Yeah, if the bike ran on prime and you saw fuel going through the filter, then that obviously isn't the problem 

you probally either ran low on gas or had you vacum line come lose/break. The fuel valves on these things is really too complicated and has several ways of failing.

[krypto35]

the way I am reading it, you either added a filter to the "ON" fuel line, or replaced the existing filter in the "RES" line? -- on my GS there is only an in-line filter on the RES fuel line - probably because the bottom of the tank has all the dirt.  My filter is pre-petcock, so a single fuel line feeds from petcock to carb.

If you ADDED a filter to the ON fuel supply line, and it ran dry -- you most likely were too low on fuel -- or you're experiencing fuel starvation, which you would cure with larger fuel lines or a slower cruising speed 

search the forum for info on larger fuel tubing choices

[ducati_nolan]

It only really makes sense putting the filter on the line going to the carb, that way all the fuel gets filtered ON PRIME and RESERVE. and a 2" filter is pretty big for a bike. Unless you tank is really rusty

[ohgood]

Okay the bike dies and you put it on prime...you ACTUALLY WATCH the fuel flow through the filter on prime, yet somehow you decide it's not working?

Fuel starvation isn't uncommon with the GS and there are several fixes...my favortie to date is putting gas in the tank.  Who'd a thunk.

Not working and not working _fast_enough_ to prevent starving are two different things, I believe.

The tank was actually very close to full, only 18 miles on the tank.

The filter is pre-petcock iirc.

I haven't noticed any vaccum lines astray befor.

Rust is always there, just noticable so I'd call it 'mild oxidation' and not full on 'rust' with my calibrated eye. (Yes i know oxidation and rust are the same. Actually seeing a mildy oxidized peice of metal and a fully delapidated 39 ford is what i'm refering to.)

So the size seems to be large enough to allow free flowing fuel. I'll search the forum for other common causes. thanks

[Wrecent_Wryder]

T4

[ducati_nolan]

I'd try a new filter. If you have it between the tank and petcock make sure you have one on both lines too. What Wrecent_Wryder said about the car style filter is a good point too. I use a sintered metal fuel filter on my bike and get good results even though it's pretty small, the only downside is that it lets some very fine stuff into the carbs. It isn't enough to clog the jets but if I pull the carb bowls, there's always a little bit of stuff stuck to the bottom of them.

I'd try switching to a less restrictive sintered metal or screen type filter and then clean or replace them when you change your oil, before problems develop. Or just cary a spere.

Good luck 

[tussey]

While cruising (80+/- mph) on I-4

Where on I-4? Do you live in Orlando? We should ride sometime. 

[ohgood]

The situation you describe is still confusing. What was it that you watched "the trickle start" in after switching to "Prime"?

A lot of people have gotten in trouble by putting the wrong kind of filters on motorcycles. Most automotive filters assume a LOT more pressure, coming from a fuel pump. Fuel-injected motorcycles also have fuel pumps.  We just have gravity feed with a drop of, what, less than a foot? The pressure drops as the fuel level drops, so sometimes this is "cured" by filling the tank, not because it was empty but because the weight of the gas in the tank increases the pressure in the hoses, and the owner ends up thinking that they just have an awfully high "reserve"... for a while, until the filter gets a little more clogged and the situation worsens.

If you have ALMOST but not quite enough flow, you may not have any problem at all at low speeds, or with a full tank. Any marginal-flow situation will probably show up with a lowish tank at prolonged high speeds. Having the tank petcock not lined up just right will do it too, but switching to "Prime" won't help in that case.. though just being pulled over long enough to do that might.

Lots of variables.


Sorry about the delay.

The 'trickle' I was refering to was the gas into the filter. Odd, I guess I've got a couple of things contributing here. Given what others have discussed, my problem sounds like:

a) petcock clogged with alien snot
b) petcock damaged by alien snot slingin food fight
c) petcock in dire need of replacement befor the aliens assemble a snotting party and get me

d) some water in the tank, combined with alien snot in the tank filter.

I'll be draining my tank tonight, hopefully finding the culprit.

Today, while cruising at <50MPH it starved again. Took 5-10 seconds on prime to get something that likes to burn flowing again. Weirdness.

[ohgood]

Man, I always fudge the quotes, sorry bout the last one.

Actually, my end of I-4 is always around Tampa. Orlando isn't really that far, and as soon as I solve my starvation problem(s), it'd be cool to take a trip.

ALSO

My little brain has decided it's found a pattern:

Stock/Modified/whatever bike + stock petcock = eventual starvation.

Blame the petcock gasket, gunk in the tank, gunked up lines, water or whatever, but I'm thinking it's the whole "not enough volume in the tank to push the gas past the gunked up petcock flapper".

How's that sound for a theory ?

I'm going to drain my tank tonight or this weekend and see what I can pull out of the petcock. Running on prime is still a possibility, but if the fix is a simple petcock replacement, I'm there. I'm not going to let a $40 part fuckup a really fun ride.

While cruising (80+/- mph) on I-4

Where on I-4? Do you live in Orlando? We should ride sometime. 

[NWDave]

Yes, all stock bikes will suffer fuel starvation at continued high engine speeds.  The fix to simply to switch the fuel valve to prime before, durring or after.. whenever you start to notice the effects.

[NiceGuysFinishLast]

Yes, all stock bikes will suffer fuel starvation at continued high engine speeds.

Not necessarily true. My stock '02 has never had a fuel starvation issue, and I've done 300 miles at 85-90mph in a day.

[Wrecent_Wryder]

[5

[NWDave]

Don't mistake MPH with RPM... go to you favortive strait and leave the valve in the ON position.. then try to max her out and hold her there.. lemme know how that works..

[Jarrett]

Don't mistake MPH with RPM... go to you favortive strait and leave the valve in the ON position.. then try to max her out and hold her there.. lemme know how that works..

It works great.  You're confusing "running lean" with starvation.  Not the same thing.

[NWDave]

Just run her into the ground, then back off and you'll see it... it doesn't die but you can hear the engine struggling to keep a coast.