Petcock or Vacuum... You be da judge

[ratbyk]

No, he means that if the fuel enrichment jets in the well at the bottom of the float bowls are plugged that even though you are turning the choke on the carbs will not be providing an enriched mixture to allow starting and running while cold.
Ken/Sooke

[John]

Mike, I don't think it will start any easier with out the choke, but you can try it. The choke really is an enrichening circuit. That is, instead of restricting the air supply, like the choke on an older car, it adds more fuel to richen the mixture. I can't think of any way that the bowls can empty over night. Mine can sit for days, and with out turning the petcocks on (I have removed the octopus) it will start right up. I never even use the choke. Foster Child is the same way, only it needs to be choked, but it starts right up.

[fxrer]

Mike,

From your description of the problem, I does not seem that your enricher circuit jets are clogged because, as you point out, the motor starts instantly, then quits after a couple seconds. My bike had clogged jets, as diagnosed to me by Ken Talbot with a super clear picture in a post back on 4/16. Look here for the picture

http://www.xs11.com/forum/showthread...8512#post48512

The symptom my bike displayed, with these clogged jets, was that it was VERY hard to start when cold, using the enricher. After cranking for many seconds, it would catch on one or two cylinders, cough and sputter for 30 seconds or so until the next cylinder would catch, and another 30 seconds before it ran roughly on all four. When warm, it ran fine.

So, after following Ken’s expert advice, I took the carbs off, removed all four float bowls, and cleaned those jets - Two were very clogged and I had to use a needle and lots of carb cleaner, but finally got fluid squirting through all four of the circuits (I sprayed down in the pickup hole and it came out through the jet).

When I put it all back together, the bike started instantly, just like when it was new (and like your does). So, that was the cure for my problem but it doesn’t sound like the same as yours.

I would question the operation of your diaphragm (octopus). There are many threads on this subject. First, check the fuel line routing. Again, Ken posted a diagram of this on 4/06. Go here to see
the diagram.

http://www.xs11.com/forum/showthread...&threadid=6581

You mentioned that the vacuum line to your octopus was connected to the second carb boot from the left. I assume you mean carburetor #2, which is the second carb from the left? The line is supposed to be connected to the port on the #2 intake manifold, not the tube in the carburetor body - that is for the vacuum advance.

If not connected properly, maybe there is not enough vacuum at start up to open the diaphragm, and hence let fuel flow properly to the carbs?

If it is connected properly, maybe there is a small hole in the diaphragm or in the line, which is causing the problem? There are also many threads about testing the diaphragm.

Since it runs fine on “Prime”, and later on “Run”, I would concentrate on the diaphragm.

Good luck

[excess11]

Reply

Just a thought, did anyone have your petcocks apart, If you switch the left and right petcock handles you will have problems.They will not work properly.

[Michael March]

Thanks for the thoughts. The vacuum tube is connected correctly, but it acts like it isn't. As for the petcocks, they have not been apart. I think the problem must lie in the octopus, which is stingy with fuel. Running on prime seems to help, and if that cures it, I'll probably just run on prime and then fill up quickly when the fuel light comes on.

Does anyone know if running on prime or run or reserve effects when the fuel light comes on? I figure I've got about ten miles once the light comes on when I'm in "run," so if that's the case running in prime too, I don't really need the reserve. No matter what I'm running on, if that light comes on at the same time, I know I'd better get gas in ten miles or walk!

[TopCatGr58]

Michael,

Since I've removed my Octopus, I have been running on Prime for years. The Reserve light still comes on at the same time since it's controlled by how much fuel is in the tank. I, too, then start looking for a station, I don't miss Reserve at all! I also use my Tripmeter as a second monitor to how far I've gone on that tankful, so that just incase I don't see the red light, I'll still know when it's getting close to fillup time!!
T.C.

[John]

Hey TC. What kind of range do you get with the Big Bore? I only get about 85-90 miles, max, to a tank after my BB.

[TopCatGr58]

Hey John,

Yeah, about 30 to 32MPG is about right, I've stretched it to 108 in a tank, but that was with the Evil Red Eye glaring at me for a while!!

Of course I'm not as well tuned as I could be, will be probably building that home made synch tool, and having a go at it!
T.C.

[John]

30-32!
The best I can get on the freeway is 28, and maybe 31 on back roads. I used to get 33 on the freeway before the BB, plus I have a full windshield on it too. That can't be helping any. I have a couple of spare tanks, that I'm going to try to cut up and make one large tank with. 6 gallons would be nice. Having to stop every hour for gas is a PITA.

[TopCatGr58]

I've got a spare XJ tank that I'm hoping to put on Godzilla, supposed to hold a bit more than the Specials, but I don't mind stopping after an hour and a half, my back and bottom side actually appreciate the breaks!!

Yeah, I see those guys on Discovery channel hammering out those tanks, doesn't look too hard!! :P Instead of trying to make it nice and curvy, I could probably come up with a COFFIN shaped thing, nice straight lines and such, easy to weld and bend!
Hmmm, maybe next year?? Good Luck.
T.C.