won't idle, Carb sync, mixture screws, head temps

So I rebuilt my carbs because I had an overflow from a leaky float. I cleaned them without separating the bank or removing the fuel lines and I replaced on choke plunger. I have pods and an open exhaust so I upped the main jets and pilot jet (from stock to a 117 and a 37 I think).

bike really came to life but a little squishy in the midrange at constant throttle and she needs choke to idle..

well I never took out the mixture screws so I did that today and cleaned them up and squirted carb cleaner and air down those holes.. but she didn't get better. mixture screws were 2 3/4 and one was at 3 and I didn't count the middle ones. I read 2 1/2 to 2 3/4 so I tried that but she didn't want to idle without choke, I know this is sounding like a pilot circuit issue... I did try a procedure to find the sweetspot but seems she's too far off to matter.

I just got an infrared temperature gun so I shot the exhaust flanges and saw my number 1 at 160F, #2 180F, #3 around 250F and #4 even higher (like 300?).. I'm thinking whoa, the mix cant be that far off.. checked the number 1 plug and it looked nice tan, not wet/fouled. So I'm thinking could the sync be that far off and now with the rejetting, it just matters more? so without a manometer, I backed off #4 and #2/3 a little (they are together?), and screwed in #1 a little (and then more to see if I could hear something). \

I never got her idling and wonder if the sync could be the problem.. got to make a tool.

 

what did the other plugs look like?

 

I didn't look at the other plugs. They have been out recently but I'll check tomorrow.

 

haha, I still didn't look. I had intake leaks at the manifolds last fall and snugged them up for some good running so I mentally had that out of my mind but then seeing as I rebuilt the carbs and didn't do the throttle shaft seals, I got to thinking maybe a propane test. well the propane revealed leaks at almost all the manifolds to head and the allen bolts were loose. rather than tighten them up like last time, I disassembled and saw some of the gaskets torn/tired so I made new gaskets and assembled with rtv hi temp copper (yea, they will be tough to get off but they wont leak!!). when I took the carbs off I saw the intakes almost all looked kinda wet (fuel level high in bowls?) and the #2 & 3 looked worst. Well I didn't mess with the floats during the rebuild but I probably mixed them up and then I have new aftermarket float needles too so I figured I better measure the float levels. On the bench all levels were about the same (within a couple 64's) but the #4 level was markedly low, about 1/8" below the lower limit. so I bent that float tang to bring it up and yes, now that float was markedly lower than the rest but I go the four bowls about same on fuel height (with carbs level both ways). bike idled much better but still a tad soft/sluggish when I whack the throttle.. from my last play time I had the mixture screws set 2 & 1/2 turns out (factory I think is 2 & 3/4, so I could bring them all out more and then in more to see but I also had screwed with the syncs (when I was looking at head temps thinking the sync was driving it) and since I never synced this bike I figure I better do that first. anyway, this thread was just to see if anyone else had even float heights with markedly different fuel heights...

 

float heights do not set fuel heights it is just a starting referance point. when you do a fuel height measurment with the clear tube you go back into the bowls and adjust the tangs which control the needle valves.then you can check the float heights to see if you actualy made an adjustment.

when you say float tang do you mean the one above the needle valve or the one at the post? you should be adjusting the one above the valve.
the one at the post keeps the floats from dropping to low in the bowl and possibly sticking keeping the valve open

 

I think we're talking the same thing. the tang that contacts the needle gets bent to adjust the sprung height of the float and moving that up or down changes the fuel level which will cause the needle to stopper the needle valve seat. All things being built approximately the same, I expected comparable fuel heights for comparable float heights... oops, just realized now maybe that valve seat isn't fully seated in the body!!!

 

I recall chasing the tune on my carbs on my '80 xj650 after a fresh carb rebuild. I had one carb flooding, so I checked float heighths. Good. Ran the bike, then a different carb would flood. and so on, and so forth.

My issue was the 'open-ended' float hangers. REPLACE them with 'closed' hanger float valves. They are now standard in most rebuild/replacement kits.

 

sometimes when you first fill the carbs the float will stick in the down position due to the inrush of fuel and air, a few taps on the float bowl with a screwdriver handle fixes this. i went through this and adjusted the other tang near the post to stop the floats from dropping to low when empty.

some aftermarket needle valves are 1mm longer than oem, so if you replace all the float valve assemblies you may get the same float heights, provided the floats themselves have not been bent up while someone was trying to adjust the float valve tang.
with tolerance specs being what they are you could have 4 new floats and 4 new float valve assemblies and not have the same dry float height. when you add all the + & - for the mtn posts hole location, floats and valve set ups 3+3 does not equal 6.

 

So what you're saying is, you knew that you didn't do things right in the first place and neglected to tell us that when you asked your original question?

 

Nah, K-Moe, that wasn't an engineering quiz. I couldn't understand why but the possibility of the seat seating just dawned on me. I seem to remember either #2 or 3 carb fuel seats didn't press in and stay seated all the way down but there is a hold down screw which took out that play and so I'd think the hold down also socked down that #4 fuel seat. I'll look next time the carbs are off.