The last float height thread
This is how I originally set float height when I bought my bike. I turn the carb at about a 45 degree angle to JUST engage the float arm with the spring inside the needle valve.
This is how service manuals have specified to adjust it for other bikes I've worked on.
However, someone mentioned that this was not how to do it. I brought my floats about 3mm lower in the bowl when I adjusted them... and guess what? The bike feels like it has a stumble (ever so slight) when you're crusing at about 15%-20% throttle.. That whole pilot-to-main jet handoff. The sort of feeling that shimming a needle typically irons out.
Well I have my needle shimmed about one click higher than stock already.
So I wanted to get opinions on the proper way to measure float height. Zero spring tension at the needle valve, or do I want to have the carb perfectly upside down with the full weight of the floats pushing on the needle valve?
It's been a while...
Here's how I checked the fuel level in the bowl... with a clear plastic tube attached to drain outlet:
Bike should be in the vertical position, not on the side stand.
On the '01 and newer CV carb, the fuel height should be about 1 mm ABOVE the float bowl seam.
On the older slide carb, the fuel level should be about 8 mm BELOW the bowl seam.
Float height (newer CV carb) 10 mm:
Sorry... Just noticed you have the older slide carb...
Personally, I am not too concerned about the float height. I think the fuel level in the bowl is the important thing.
I would set the float at whatever height necessary to get the proper fuel level.
2018 Triumph Street Twin..............2016 CB500F
2014 XT250 ..................................2008 H-D Softail Deluxe
2008 SV 650..................................2007 DR 650..
Good deal. I will check it using tubing from the outside. I'm picky enough that I want it exactly at 8mm so I can proceed to tune the carburetor where it needs it. My bike is running fine by most peoples' standards but I am a bit OCD about things.
My bike was dying on me at idle today (about 45F when I went to work and 60F right now.) Still too lean without the enricher when it's cool outside.
So.. I pulled the carburetor, removed the #42 pilot and put the #40 back in. The #40 has an extra hole drilled into the top part so I just trust it since it's OEM.
Backed the air screw out from 2.5 turns to 3 turns.
And more importantly, lowered my float height from 25mm to 23mm based on my fuel tube height measurement. This got me to that 8mm below the seam of the float bowl measurement.
This lets gas sit higher in the needle jet and makes the transition from pilot to main noticeably smoother. The bike runs smoother all throughout the rev range now, in fact. I'm going to do some plug chops after work to see if I'm running richer. All signs already point to yes though.
So my float height is 22mm which is out of spec, but gets the fuel level to where it should be. Most likely has to do with the needle valve spring getting weaker with age.