TOPIC:

There have been many comments and questions regarding less then acceptable engine operation due to suspected fuel delivery related concerns. The topic is inclusive of the STRONGLY recommended removal of the electric fuel shutoff. This is another carb. related topic which has initiated a strong opinion from me.
I have previously submitted several fuel-line routing revisions which eliminate the problems associated with what i commonly refer to as 'the convoluted" stock routing. I stand by these suggestions with a strong conviction to their success.
This bore itself out with the recent carb-rebuild that I was setting up and test driving prior to their sale. The stock fuel "Tee' was retained. Because my own carbs had been converted to a two inlet fuel feed setup (can be found in the related thread some time ago) the fuel line connection for this set of carbs was made with a length of 5/16" fuel line which came off the tank-valve, through a filter and then DOWN and UNDER the carbs and back up to the fuel "tee" between the left and center carb. In this configuration the engine would start to die and quickly quit every 15 - 20 Kilometers. Within 20 - 60 seconds I could start the engine and ride the same distance before this repeated itself. I returned to the shop and re-routed the fuel line. To start: The fuel "tee" was turned to an upward position. The fuel line was then routed directly behind the diaphragm covers and to the right, around the right hand end-cover and paralleled the choke-shaft to a filter and then directly to the tank-valve. To keep the fuel-line under control and neat, several appropriate sized plastic wire clamps were anchored with existing diaphragm screws. In other words - The fuel-line is all above the "tee" and is for the purposes of this description - level for it's entire run !

Problem solved !

There has been a relatively recent thread started regarding this issue and the owners suspected "vapor-lock" / "air-bubble" theory.

My definitive answer for this is: Do Not Allow Any part of the fuel-line to be routed below the carbs. PERIOD.

Hope this helps solve some issues and mystery's.

Herewith picture of my routing. Although it routes under the carbs to the T, I have had no problems with "vapour locks" and fuel starvation at high speed. I have a Pingel Hi Flow pet cock, 8mm fuel hose and a hi flow filter and have removed the electric solenoid valve as seen in the pic and never had a problem. On a recent rally in Zimbabwe I hammered the old girl for about 50km's at 190 - 210kph non stop, much to the amazement of others with no hassle or fuel starvation!

I noticed what appears to be a unique Drain-bolt on the left hand carb. Any chance of getting a better/close-up photo of this ?

scotch wrote: I noticed what appears to be a unique Drain-bolt on the left hand carb. Any chance of getting a better/close-up photo of this ?

Like a Kid in a candy store Eh Scotch???

Gotta agree with Craig. I've got a stock solenoid in place (what? I like 'em as stock as possible), with routing that's very nearly identical to the photo posted. While I do have issues starting it if it sits for an extended period of time (which I attribute to the solenoid), once she's going she'll run like stink. This includes several extended stints on the freeway as well, at a speed of at least 70 mph.

Now, I'm not saying that this routing is perfect- I'm just saying that eliminating kinks in the fuel line is more important than keeping the lines above the level of the carbs.

But, as always, to each his own. My bike is my bike, yours is yours. Modify it as you will.

One thing that is important is to be sure not to have air trapped in the filter, it will slow the flow especially when there isnt much fuel in the tank.