My brother has a modified (raked and stretched) '74 Low rider. It has a '76 FX engine on it and he has been having some issues with it. This is one of those, what I call "garage bikes" from the '70's. Tins and fuel tanks were homemade, we don't know by who.


Neither he nor I are what you could call great mechanics, so I thought I would throw it out there for you guys.


The bike will start and run like a champ for a while and then the fuel flow just stops, as in the fuel line is empty although there is gas in the tank.


Bike has a S&S carb, new vented gas caps, new clear in-line fuel filter, new petcock, and the tanks were taken off and cleaned not long ago. When it stops, you can pull the fuel line loose from the carb and gas will flow immediately. Hook it back up and you are good for about 15 - 20 miles before it does it again.


We re-routed the fuel line (was going between the heads) to try to eliminate any excess heat that might result in a vapor lock. Same deal.


I say it has to be developing a vacuum somehow, but he thinks its the carb. I just don't see how the carb could be the problem if the gas 'aint getting to it.


Ideas and suggestions appreciated.


LiiT

 

Fuel cap vent is plugged.

 

Or the screen in the tank.

 

Both are new and if you take the caps off when it does this it makes no difference. Fuel flow is restored only when the line is taken off the carb.


LiiT

 

New petcock.


LiiT

 

I guess I should say that we have not pulled the petcock since it was installed so I guess it's possible it's become clogged, but the tanks were supposed to have been cleaned when he took it into a local indy shop not long ago just before we installed it. So there really shouldn't be any dregs left in it to plug it up. It makes sense to me that when the line is pulled from the carb the air bubble going back up the fuel line to the tank would temporarily move a clog.


Maybe we need to drain the tanks, yank it out and see.


Thanks guys.


LiiT

 

Did the vent on the carb bowl inadvertently get plugged?

 

Here's what I do in a situation like this.

Drain the tank and clean it. Look for rust and gunk. Take the petcock apart and if it's really yucky looking, replace it with a Pingel.

Replace the gas line and filter. Pull the carb and rebuild it (about $15 for a kit). Replace the intake seals and just for fun, clean or replace the air filter.

You said you had a new gas cap. As long as it's clean and vents well, you should be good.

Now you have a clean fuel delivery system. If you did the job right, you "should" be able to say any engine problems aren't the carb or gas.



Carl

 

It might not be your problem but take a flashlight and check the tank for something that may float for awhile then get sucked into the petcock outlet. When you pull off the fuel line it breaks the vacuum and it floats away again.

 

Bit of an update on this bike. I found out that a few years ago he had a guy to do one of those tank lining deals on it to stop the rust inside. I finally talked him into pulling the tanks (bike has two half tanks instead of one single) and lo and behold pieces of that **** come pouring out with the gas. Been trying to tell the ******* that it had to be something like that, but he never was a good listener. I did get a free steak dinner for being right about what was causing the problem all along. Score!


Maybe he'll learn to listen to his big brother for a change. Nah, probably not...


LiiT