BS38 Trouble

half_whit

XS650 New Member
Messages
4
Reaction score
4
Points
3
Location
Pennsylvania
Hey folks, I'm in a pickle with my carbs here. Just finishing up a custom build on a 73 tx650 frame with a mid 70's xs motor. I'm using the BS38's (for looks, against my better judgement). I have rebuilt and cleaned them, replaced bowl gaskets and float valves jets etc. Didn't mess with the choke assembly at all as it seems proper. Fuel is being delivered through a pair of brand new gravity taps with in line filters. I can NOT get the fuel to stop gushing from the carburetors. Took them apart and checked/adjusted float levels. There is no sign that the needle valves are shutting off gas flow at all. I might as well bypass the carbs and pour a can of gas on the ground. What am I missing here?
 
I disagree - If anything gives trouble it's usually the floats and last time I checked the Needle & seat
assemblies were about 45.00 each so you better check that. Also check if they have stock.
 
The link says they're about $16. I know they're not $45 because I bought some recently.

My dealer told me he quit using aftermarket float needle and seat assemblies because too many of the bikes came back to him leaking. He was losing money because he had to fix them on his nickel.
 
I've had floats that wouldn't float - not hard to fix if you can solder. Float valves are easy to check. Put a length of fuel line on the inlet nipple. With the float bowl off and the float and valve assembled, hold the carburetor in your hand, right side up, and blow on the line. Then turn the carburetor upside down and blow on the line. Upside down you should not be able to blow past the float valve. If you can, inspect the needle and seat with a magnifying glass to try to find the problem. Sometimes a minor re-finish and clean up will fix things.
 
Hi folks, I wish I had happy news but I seem to be getting nowhere. I checked the seal on the float needle and it passed. Replaced them anyway, passed the test, and it still leaks. I now have the bowls off full of water to see if maybe the overflow tube is leaking, but it doesn't seem to be. One float was replaced pre-rebuild. The other has a little tarnish, but nothing crazy and I dont hear anything rattling around inside. I threw it in a cup of water (more dense than gasoline, I know) and it floated just fine. I am at the end of my clever ideas on how to diagnose this one.
*edit* I just plopped both floast in a glass bowl full of gasoline. they bob around at the same height
 
Last edited:
With a float bowl removed and a catch container under the carb, gas on, can you lift and lower the float with your finger, shutting the float needle on and off? Does the fuel flow stop when you lift the float and push the float needle into it's seat? This should verify whether or not the float needle and seat assemblies are working right. The only other thing that comes to mind is a float hanging up, not rising up as it should either because it's binding on the pivot pin or maybe rubbing against the sides of the float bowl.
 
I also just purchased 2 new needle/seats from Partzilla and they cost about $40 with shipping and tax.......

tim
 
With a float bowl removed and a catch container under the carb, gas on, can you lift and lower the float with your finger, shutting the float needle on and off? Does the fuel flow stop when you lift the float and push the float needle into it's seat? This should verify whether or not the float needle and seat assemblies are working right. The only other thing that comes to mind is a float hanging up, not rising up as it should either because it's binding on the pivot pin or maybe rubbing against the sides of the float bowl.
This might have done the trick. I found that the floats opened so much that one of the needles was getting jammed at an angle, unable to close. I'll button it back up in a little while and see if that did it
 
Back
Top