How to fule while tuning polit screws and syncing?? & tuning advice?

[Phil_B]

Just got my crabs cleaned and things are looking good. I am missing the tiny (1mm x 3mm) O-ring in one of the pilot screws but put it back together until I can get hold of one in the next few days. Its currently idling high/erratic, but I can imagine that is due in large part to the missing o-ring. It will also need to be tuned as I have rebuilt the OEM air filters with Uni-foam with K&M oil and so am likely pulling less air than the OEM oil-less filter...

So, my main question is how do i feed the crab fuel while I am tuning it? Just a tube with a funnel and a bit of fuel going into the carb? Kind of like having it on prime? Or will that give too much fuel?

Also, any advice for tuning the pilot screws? What am i looking for? I won't know where I am till I get that O-ring in, but imagine it will be running a bit rich given the new air filters are likely a tad more restrictive.

Greatly appreciate any advice!

 

[XSLeo]

I use a temporary test tank. Find a place near by that works on small engines, like lawn mowers, rototillers and such.
They may have a small tank from something that can easily be adapted for a test tank.
I used a couple of U bolts from the hardware store, some old hose and strap steel. A enough fuel line to reach from the test tank to the carbs and have a shutoff valve inline. Most places that sell small engine stuff sells plastic shut off valves by themselves or in a kit with some fuel line.
Use the hose to pad the U bolt to minimize paint damage. Put the U bolts around the frame. Drilled holes in the straps to match the U bolts. A bit of hose around the strap or black tape for padding. Leave the straps long enough so you can attach them to the test tanks mounting points.
This way you can mount the test tank on the backbone of the frame setting far enough forward to have plenty of room to reach the carb adjustments. If mounted well enough you can even go for short rides with the test tank installed.
Might even get the tank for free. Often times people leave dead lawn mowers out for the garbage man. Pick one up for the tank.
Leo

 

[XSLeo]

Almost forgot, on tuning, www.amckayltd.com/carbguide.pdf is a carb guide written by the carb Guru's over at our sister site XS650.com The 80 up XS650's use a BS 34 carb very similar to the XS400 carbs.
In the guide is a "Tuning for Mods" section It works for stock bikes to.
It lists test to do. then using the results of the test tells you what adjustment to make.
Carb tuning isn't magic or even really hard, it's just trial end error. Test, make one change, test, make one change. repeat till you carbs are where you want them.
Just make one change at a time. If you make two changes you won't know which change caused the effect on running.
Leo

 

[sandmanred]

Or if all you are doing is setting the air screws and syncing the carbs get a long piece of fuel line and set your tank on a table nearby.

 

[Phil_B]

I just ended up loosening the tank bolt and pivoting the back end up and propping it on the lid of a spray can. Just enough room to get at the screws with a bit in my fingers. Worked perfectly since the pins have little resistance.

Thanks for the advice guys! I'll check out the guide XSLeo, thanks.