Intermittent carb overflow

TexasChris

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Hello,

Real minor issue, just looking for some thoughts for others

Bikes running and riding fine (actually pretty good if i do say so), but its started dripping gas out of one of the carb overflow tubes when its sitting. It isn't a constant drip, seems to drip some then stop...then a little while later drip some more out. Always out of the lefthand carb.

Now because the bikes running so well, i'm trying to avoid tearing into the carbs needlessly (i dont think they need a total clean out, cause it starts first kick, idles great, pulls fine). However, first thoughts were debris in the float valve preventing a full seal? I've drained the floats, blasted carb cleaner spray in the fuel inlet and out the drain plug, drained a bunch of fuel through the carbs to try to flush anything out...and I've riden a couple of tanks worth of gas. but its still dripping.

Is it likely that there is still something in there stopping a full seal? and i really gotta pull it apart to clear it...or could it be something else? It seems to have started when i finished its dirt track conversion (mostly invovling bigger wheels and tyres) so the bike leans more when its on its side stand now, towards the dripping carb. Could it be fuel from the right carb flowing into the left causing it to overflow? (but it still dripped when i had it in the back of the van this weekend and that was stood pretty much straight up).

I'm going on a bit about a quite small issue, just wondering if anyone had any thoughts. If the consensus is 'float related' and i got to open it up, thats cool. but anything else you think i should try first??

Cheers,
Chris
 
Hey dude,

1976 bike, stock carbs to the best of my knowledge, so BS38 (???feel free to correct me??).

I did notice a tiny drip from one of the petcocks when it was in the off position (the carb drips even with the petocks off) but surely a properly working float valve should be able to handle holding back the fuel? or do y'all think a slight drip from a petcock could be the source??

Cheers again,
Chris
 
Float needles and seats are a fuel metering device, not a total shut-off device. Yes, parked on the side stand and leaned over, fuel from the right carb could transfer to and over-fill the left one. You have the metal needles and seats. It's possible the left carb's set is worn out and needs replacing. Also check that dripping petcock to make sure it's fully shutting off. Pull it's fuel line and see if it's really off or still dripping a bit.
 
I had a similar problem in my '71 carbs, traced them to splits in the bowl's brass overflow tube.

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Have a look at this album pic, and hit 'previous' for another 4 pics:

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Hi

Just to add a note also check your petrol (Gas) taps. I had 2 of left and right hand side vacuum taps, both leaked. Let fuel into the crankcase over time. Not good. I replaced the vaccum type with one single new fuel tap non vacuum, run new fuel line, all good now.
 
Cheers Gents.

I pulled the fuel taps to make sure they were sealing properly. found one to be a little gunked up, cleaned it out and it seems to have resolved the issue.

I'll know for sure when i get home later if there isnt a little puddle under the bike.

I appreciate the tips guys,
Chris
 
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