Interesting noob mistake: float needle valve.

[nakedGS]

I am new to the forums and to the GS twin, but I have done alot of work on carbureated VW engines and I had to fix the family Harley after it sat for a few years causing gunk to build up in the jets.

Anyway, I got a decent price on a GS500E a few weeks ago because it wasn't running properly. I figured that it needed a carb clean and set about removing a disassembling the carbs, replaced a few o-rings, and put everything back together. The bike ran better, but it was exhibiting symptoms that seem rather commonly seen around the forums on this site (which rules, btw). It had a hovering idle (around 3000), and a ugly flat spot between 4.5-7k RPM. Power seemed low too.

I wasn't sure what I was going to do until I came across a picture in one of the threads on this forum (I tried to find it again so I could post it here, but couldn't). The picture showed the bottom end of the early GS carb, with the float tab INSIDE the wire spring and touching the needle valve directly. In my reassembly, I had just inserted the needle valve and then the float assembly on top of it, so that the float tab was touching the OUTSIDE of the wire spring. Anyway, I figured that this caused the needle valve to shut off way too early, meaning the level in my bowl was low and thus I was running a too lean condition.

I took the carbs apart again today and reassembled them with the tabs inside the wire spring, and it rides 100x better. Idles steady once warm at 1300 and has consistent power to 11k.

I posted this here, because it didn't seem intuitive to me that the float tab be set up that way, and it didn't mention it at all in the carb disassembly/reassembly section of the service manual I have. If your bike is showing lean symptoms and you're not sure you've put the float system back together correctly, this could explain your problem and save you a rejet.

[Jenya]

May I recommend to consider using the clear tubing method of veryfying that the float level is set correctly. Had you done that, you'd discover that the level is off.
http://www.gstwin.com/float_height_check.htm

Unfortunately, it still wouldn't have hinted that the spring has to be outside the metal adjustment tab.

[nakedGS]

Thanks for the tip Jenya, I saw that technique a few days ago and thought it was pretty clever. I plan on doing it pretty soon to make sure that both my float bowls are set at the same level and around 14mm.