inline fuel filter routing

[DeanR]

Is this the preferred way of adding inline filters? For a Special, if it makes any difference.
My petcocks do angle down, rather than to the side.





Damn, my perfect original condition tank, isn't anymore. It's been empty for the winter, in the house on the floor, and an ST driveshaft managed to roll off the top of a chest and bounce off the tank, Small dent right on top....

[DiverRay]

That is NOT the way I would route it! That loop in the line is Trouble! I would plug the prime, front nipple on each side, and run a single line from the Right side, inline filter, and feed the Left side carbs. Then the Left side, inline filter, and feed the Right side carbs. Inline filter can go between carbs, but you do NOT want a fuel line going over two carbs, under a carb, and then back over the carbs again. Just NOT the proper way of running fuel lines.
The dent, if it's a small, dish shape you may be able to pull it out with a suction cup. If it's one of those deep, small diameter dings, Oh well....

[DeanR]

This method is what is in our tech tips section.
with no need to plug the prime.

[DiverRay]

OK, I just go on the K.I.S.S. method. I have not looked at the tech tips for fuel in quite a while. And, as I only have one Special, and it still has the octy, I have not worried about it. I DID re-plumb Special Ed's bike, so it's not like I have not done it before.
The great thing about these machines, there is ALWAYS more than one correct way to modify them.

[DeanR]

The great thing about these machines, there is ALWAYS more than one correct way to modify them.

Yep, that's kinda why I posted the question. Wasn't sure about going with 'tech tip' or not.

[ViperRon]

I do not have a special I have the standard no octy and I tried the routing method from tech tips with 2 different style filters and had flow problems. To get it to work no problem I routed from one side to filter between carb 1 & 2 down under to feed carbs 3&4 from other side to filter between 3&4 under to feed carbs 1&2. Do not use regular auto store black hose the rubber dissolves. Do not leave large loops or slack it seems to collect air bubbles and can cause flow issues. I think as mentioned KISS is the way to go at least it is for me.

[jetmechmarty]

I used two of these. I mounted them between the carburetors. They are about two inches above the tees between the carburetors. Yes, the carb bank has to be removed to install them. You need more practice anyway.

[Rasputin]

All fluid will find it's own level. I disagree with anyone who says fuel line routing is a problem. The gas will find it's own way to the carb even if it is routed below the bottom of the frame. It is simple and true that fluid will find it's own level and that if the tank is higher than the carbs, it will flow. Simple physics.

[ViperRon]

Ras
I agree to a point but gravity is not the only law at work here and just as the clogged vent in the gas cap will cause fuel flow problems air in a line between the carb and tank can cause flow problems. True gas will flow but at a reduced rate which is what causes the issue with running. This problem seems to increase depending on the type of filter being used. Some filters clear and wick fluid threw easily and others will not. I suggest that no loops be created that air can be trapped in or a vapor lock condition can cause fuel flow issues.

Ron

[Rasputin]

I guess that may be true Ron but I have had those bubbles of air in my fuel lines for years and nothing has gone wrong. I have my 79SF plumbed so far down that the lines hit the engine case, air bubbles and all, yet it still rides like it should.
One can take the time to get rid of those bubbles but there is really no need. If one wants to be picky....well go ahead, as it is simple enough.

[DeanR]

Good thing I like fiddling with my bikes,
but
my patience is running low with this carb work.

To review. Cleaned carbs over the winter. Got the carbs and airbox back on eventually the other day. Just hooked up tank and fuel lines with the new inline filters for a start attempt.

Left petcock leaking. Took apart, cleaned the innards that look brand new, back together, seemed better.
Tank is now off the bike with still a very slight dribble in the off position.

Main problem now…
After many start tries (never did start up), looks like #3 is leaking into the airbox. That boot is gassy. I had left the bottom of the airbox loose and the front of the bike propped up as much as possible. (on centerstand).

So right now I have the tank off and all fuel lines off again. Do I need to drain the carb bowls, leave the front elevated, take the carbs back off????
Pretty lost at the moment.

I did hook the lines up this way, but will next just do a direct hookup until I get the rest fixed.

[DiverRay]

fuel petcocks first.
Tilt tank so fuel is below petcocks and remove the two small screws holding the lever on.
Polish up the inside surface of the lever. I start with 1000 grit, go to 1500, and then metal polish.
VERIFY the rubber o-ring with the three holes is NOT bad or torn.
put it back together and test by watching for weeping from the petcock.
Tap on the float bowls when you first start to fill from the tank. That will usually free up a float that isn't doing its job.

[DeanR]

Had already done the petcock work Ray (except the polishing part) and like I said, they looked about new. The slight dribble was there. Have since taken them apart again, now they are, I think, ok.

So right now the tank is hooked up simply (it's sitting in the seat position), no inline filters. Bottom of the airbox is off. After about a half hour, with the petcocks having been in all positions, the airbox boots are dry. Did not drain any carbs, only changed the line arrangement and banged that number 3 bowl a few times.

Sound like I'm good to go?

fuel petcocks first.
Tilt tank so fuel is below petcocks and remove the two small screws holding the lever on.
Polish up the inside surface of the lever. I start with 1000 grit, go to 1500, and then metal polish.
VERIFY the rubber o-ring with the three holes is NOT bad or torn.
put it back together and test by watching for weeping from the petcock.
Tap on the float bowls when you first start to fill from the tank. That will usually free up a float that isn't doing its job.

[sail4free]

Direction of Flow Through Inline Filters?

Ras
True gas will flow but at a reduced rate which is what causes the issue with running. This problem seems to increase depending on the type of filter being used. Some filters clear and wick fluid threw easily and others will not. I suggest that no loops be created that air can be trapped in or a vapor lock condition can cause fuel flow issues.

Ron

==========
The diagram we used has the gas flowing UP through the inline filters to keep any air bubbles from languishing *inside* the filter and blocking proper flow through the filter itself -- though it is easy to see how bubbles can -- and likely will -- 'stagnate' in the highest portion of the line between each filter and the Tee which feeds each pair of carbs. The theory is that flowing fuel will eventually absorb these air bubbles and/or move them to the carb so they can burp out the float bowl vent and be gone with their bad selves.
==========
I have seen clear water siphon tubes (a container gardening experiment) where air (from unknown sources) would accumulate until the bubble of air gets so big that the natural siphon is lost. I realize this is a different deal because the elevated gas tank provides modest pressure to encourage flow at all times.
JIM P.
==========

[DiverRay]

DeanR:

Sound like I'm good to go?

Yes, I would go with it.
Jim P. :

I have seen clear water siphon tubes (a container gardening experiment) where air (from unknown sources) would accumulate until the bubble of air gets so big that the natural siphon is lost. I realize this is a different deal because the elevated gas tank provides modest pressure to encourage flow at all times.
JIM P.

Remember, you are talking about 1-2psi from the weight of the fuel, add heat to the air bubble in the gas line, and you can be talking 3-4psi. VAPOR LOCK....