Correct fuel pressure for dual carbs? Options

[terrymason]

I'm having alittle trouble getting my dual carbs dialed in, the 1st is rich, and the second is lean. My fuel pump was putting out 3.5psi, but the guy I bought my carbs from said I should run 2.6psi instead. What do you guys think?

I've got 60 idle jets and 180 mains, which I thought was overkill, until he told me that I should run 2.6 instead of 3.5 psi.

[type11969]

If you have the dellorto superperformace tech book, it is definitely in there, I don't have the book in front of me though so I can't quote the page. I believe it is after the troubleshooting section for the DRLAs. There is a small diagram indicating the height needed at open/closed positions.

It is easy, potentially time consuming though to get dead on. All you have to do is pull the carb top, measure the float position at the extents of its travel against the bottom of the carb top, and set the position to be 5-6mm from the bottom of the carb top in the float highest position, and 12-13mm in the lowest. You change the highest position by bending the forklike tabs that engage the needle valve, and you change the lowest position by bending the tab that contacts the part of the carb top that retains the float (opposite side of the float from the forklike tabs). I pull off the carb top gasket to get an accurate reading. Be careful that the spring loaded pin in the needle valve is not compressed at all during the stroke of the float. This will close the valve prematurely. Make sure it is the forklike tabs that close the valve.

If one float is set to high and the other set too low, one carb will certainly be richer than the other due to the different fuel levels in the bowl (and may also cause fuel to dribble out of the bowl down the carb throat).

I've been fighting with my dells for the past few weeks too, so I feel your pain. I think I solved my biggest issue by realizing that the needle valve were getting closed before I thought because I was compressing that spring loaded pin. The symptom was a high rpm leanout like I was running out of fuel. The way the floats were set, basically I was.


-Chris