Carb Troubles ? Quick Thoughts..

[b.walker5]

Before I get too carried away and pull things apart that may not need it, are there any thought on what this means... (#2 Slide colour)



Engine has been running a little rough and using a lot of fuel. I'm thinking leaking diaphram but open to other suggestions..

[rpgoerlich]

Looks like some fuel residue maybe? If so I cleaned mine with some carb cleaner and it came right off. If the slides are moving freely, the carbs might just need a good cleaning. While they are off the bike is a great time to go through them. Completely Clean them & set float levels.

[Larrym]

Minimalist Approach...

Brian,

Apparently the #2 slide is getting doused with fuel: Varnish/residue. Since the only place that the fuel can be coming from is through the overflow vent at the inlet of the bell....I'd say an examination of of the float, needle and seat is in order. Maybe there's a ring around the needle like I found when my #4 carb showed a little "seepage" around the float bowl gasket.

Might I suggest that you lift the #2 slide and then plug the atmosphere vent orifice at the inlet bell? If the slide stays up (in position) then it's an indicator that the diaphragm is OK and no need to disturb the integrity of the diaphragm set-up. (Just being a minimalist is all...)

I addressed the "ring" around the float needle with 600/1500 grit carbide sandpaper. Chucked the needle in a hand drill and then touched up the surfaces till the ring was gone then polished with the 1500 grit paper. As I had the bank off and all bowls off I did the same to all needles as #4 was the first to show signs of needing attention but the other three were in a similar condition.

I'm sure you'll confirm all your float settings/float functions with an inverted bench test along with the usual upright bench test. Better to see if anything's wonky before installing on the bike.

Two more things:

1. Nice to see how the later carbs with that float bowl vent hole in the carb itself "display" when in an overflow scenario. (The earlier carbs dump the overflow into the airbox...)

2. Ain't it great that for all their complexity these carbs can sometimes be diagnosed with the troubleshooting equipment built into your face? (eyes and nose...) Not exactly true for the FI systems IMO.

[b.walker5]

Might I suggest that you lift the #2 slide and then plug the atmosphere vent orifice at the inlet bell? If the slide stays up (in position) then it's an indicator that the diaphragm is OK and no need to disturb the integrity of the diaphragm set-up. (Just being a minimalist is all...)

Good Plan.. I Like it...

I addressed the "ring" around the float needle with 600/1500 grit carbide sandpaper. Chucked the needle in a hand drill and then touched up the surfaces till the ring was gone then polished with the 1500 grit paper.

Good fix.. I like it too... , except I got rubber tipped needles..

Ain't it great that for all their complexity these carbs can sometimes be diagnosed with the troubleshooting equipment built into your face? (eyes and nose...) Not exactly true for the FI systems IMO.

I'm hearin' ya, 'cept sometimes I cant see the wood for the trees.. I hadnt thought of the diaphram test. Thanks

Brian

[mack]

Discoloration

Did it show up all of a sudden or has it been quite a while since you've had the carbs out. If you had an octy, I'd say check it for leaks. It sits right above your discoloration.

[b.walker5]

It's been a while since the carbs have been out, but the rough running appeared just recently. First I attributed it to bad gas from sitting in semi retirement for a few weeks after I bought the XJR.

I changed the gas a couple of times before taking the carbs out, but it made no difference, and the octy went west many moons ago.

I havent pulled the carbs apart yet (got another bike to ride ) but I suspect a cleaning coming up. I was mainly interested if anyone else had come across similar discolouration and symptons before and had a quick solution.