Float Bowls Don't Get Fuel

[Farm Mechanic]

Hey, I'm new to the motorcycle world and wanted some help with my 1979 XS 650. I recently did a cleaning and replaced a couple parts because the bike seems to be getting too much fuel all the time making it hard to ride and carbonizing everything. I think I am running stock BS 34 Carburetors, but after I did a cleaning the left carburetor started leaking. I readjusted the floats using a clear hose in the bottom and the first time fuel was getting through. After adjusting less than 1mm tried again and no fuel came through. This goes for both sides even though I didn't adjust the second yet. Fuel is getting through all the lines just wouldn't reach the float bowl. Didn't put a new pin in, but replaced all the jets and the floats. Both floats are currently set to 25mm to deal with the overfueling problem while the manual says that they should be at 24mm give or take 1 mm. If anyone has any advice for a rookie please let me know.

 

[Wingedwheel]

If the float needles are working (moving) then you may have some crud in the fuel passage. Try blowing it out with carb cleaner.

 

[Raymond]

Hi, how would you like us to call you? Plenty advice here for rookies. My tuppence worth, if you have a vacuum petrol tap, are you putting it to Prime to measure the fuel height?

 

[Its been a long time]

First suggestion I have is to identity for certain what carbs are fitted and from what year. That's very important because they changed every couple of years. As far as I know, a '79 bike would originally have had BS38 carbs not the BS34 stated in the first post. Perfectly possible BS34s are fitted but it affects everything, so need to be absolutely certain what type and year carbs are fitted.

 

[Adamc]

Hey, I'm new to the motorcycle world and wanted some help with my 1979 XS 650. I recently did a cleaning and replaced a couple parts because the bike seems to be getting too much fuel all the time making it hard to ride and carbonizing everything. I think I am running stock BS 34 Carburetors, but after I did a cleaning the left carburetor started leaking. I readjusted the floats using a clear hose in the bottom and the first time fuel was getting through. After adjusting less than 1mm tried again and no fuel came through. This goes for both sides even though I didn't adjust the second yet. Fuel is getting through all the lines just wouldn't reach the float bowl. Didn't put a new pin in, but replaced all the jets and the floats. Both floats are currently set to 25mm to deal with the overfueling problem while the manual says that they should be at 24mm give or take 1 mm. If anyone has any advice for a rookie please let me know.

Welcome.
Tons of useful information in the Tech section.
Also a wealth of knowledgeable members willing to offer good advice.
Just be sure to ask sensible questions, provide images of the bike / parts in question; and importantly act upon the advice given.
We all love to see new members develop with their bikes.

 

[Farm Mechanic]

These are the carbs. You're right they should be BS 38s just want a second opinion because I'm not sure how to tell.

 

[Its been a long time]

View attachment 353160
These are the carbs. You're right they should be BS 38s just want a second opinion because I'm not sure how to tell.

Look like 78/79 BS38 to me. Check the carb guide in the technical section for tons of information on setting them up.

 

[Tiggertoo]

Hi and welcome, definately look the same as my '79 BS38's. My floats are set to 25mm.
So if I'm reading correctly first they overflowed then after adjusting the float heights theres no fuel going into the bowls (using clear tube method).
So the obvious things that spring to mind is that either the fuel tap not open (as Raymond says if it is a vacuum tap try it set to prime), blockage in the fuel pipe or the float heights have been incorrectly set, try retracing your steps until you have fuel flowing. Incidentally when setting the 25mm height you need to measure without the gasket fitted in case you were not aware.

 

[Farm Mechanic]

Yes, I was aware thank-you. Just cleaning them again more thoroughly I'll see if that helps

 

[Mikey]

You could remove the fuel line at the petcock to see if fuel is getting past it and trace your way foreward

 

[Farm Mechanic]

Ok, finally got it figured out if anyone else ever has the same problem. I put in some after market floats that weren't built correctly and they would stay closed from the float bowl pushing them in which didn't allow gas in. Put old floats on and no longer a problem.