SV650 breather for fuel tank

[kenny]

After several months of fault finding and fixing to fix various problems i have finally got them down to just 1 fault now its my breather on my fuel tank its not working if i run the bike for 5mins it starves itself of fuel and if i leave the fuel cap open when running it it will stay running.

My Question is on the tank where it sinks in for the cap to fit there is a small hole about 3-4mm wide next to where you put the fuel into the tank which i can see runs in the tank, is this my breather pipe or just an out let for over flow of fuel when filling up as i know the breathers are some times in the actual cap itself.

Any info would be great, thanks
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KeNNy 100cc peugot speedfight 125cc Honda NSR125R 650cc suzuki SV650R 125cc suzuki GZ125 600cc yamaha YZF-R6

[UnknownStuntm...]

That's the overflow I think, there's a pipe that pops out just around the swingarm pivot that dumps excess fuel. I'm not sure if it'll let air back in, there may be another pipe for this, but I reckon you're spot on with your diagnosis, I had a similar issue on my Hornet last week.

[kenny]

i have been reading some posts on sv650.org and they say its a outlet for rainwater so it does not build up and sit in the well of the tank, they say they can rust through and leak fuel but as i can tell its ok so it must be in the actual cap itself. can the cap be fixed or is it a case of get new one.
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KeNNy 100cc peugot speedfight 125cc Honda NSR125R 650cc suzuki SV650R 125cc suzuki GZ125 600cc yamaha YZF-R6

[finpos]

The hole in the tank is a drain for rainwater as you say, and the air bleed for the tank should indeed be in the cap although it's not often obvious where it is (i.e. It may not be an actual hole somewhere you can see). It's usually a bit smarter than that because it's got to stop water getting in.

The other slightly more hideous prospect is that on some very new bikes the cap is completely sealed and there is an emissions reduction system that the tank must vent through - that involves a lot of tubes, electronics, solids and other nonsense. Refer to you manual

f.

[kenny]

i've tested the drain hole thats fine so i stripped down the actual cap and there seems to be a ball bearing that seats over a hole which i think must be the breather hole so i have removed that rebuilt it and will test it to see if thats makes a difference at all.
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KeNNy 100cc peugot speedfight 125cc Honda NSR125R 650cc suzuki SV650R 125cc suzuki GZ125 600cc yamaha YZF-R6