After some expert help!
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I may have left the choke on yes, as I came from a WR I maybe forgot to turn it off. I'm not sure if it was leaking before or not although whenever I would take it out the garage in a morning it stunk of petrol so could possibly of been leaking before. What damage could leaving the choke on cause? Thanks for your reply! 
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@ricky0115 No damage, it can cause bore wash but I doubt there will be any problems here. Choke on to start, then once the revs die down, take the choke off and that's it. 
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Thanks I will give it a go. Any idea on the carb overflow? Tried tapping the float end in case it was jammed but no luck. Thinking about taking it to a garage and having all the seals replaced. Noticed a threaded bolt on the reed block, would this cause an air leak? 
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Okay so I just tried kicking it up and on the third kick I heard a puff of air like a blow off valve letting out pressure but I'm unsure where it came from it sounded like it was somewhere near the carb or air filter @ricky0115 Probably tried to fire up but failed. You haven't blown a hole through the piston have you? It does start right? 
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A couple of my bikes used to occasionally make that sound when I was kicking them. I'm sure it only happens on an engine that isn't perfectly set up / running little bit lean or little bit rich? Either way the bikes ran okay. @mightyman I've only known 4 strokes to make that sound 
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I'd say piston rings at a guess maybe just a cracked ring would cause issues 
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I'd say piston rings at a guess maybe just a cracked ring would cause issues @andrewj1680 thanks 
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@mightyman I've only known 4 strokes to make that sound 
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@declan I think it's drawing in way too much air, everything is standard air intake wise. How can I find the piston size I know it's been bored out but I'm unsure of the size @ricky0115 markings on top of the piston should give you the size or measure the bore with calipers, either way it's the head off, not a big deal. Personally think your problem lies elsewhere but expect to be proved wrong, see what the garage says, hopefully something simple. Good luck 
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Just had a quick Google and first couple of results suggest worn rings / not correctly sized piston, which makes perfect sense because the sound will be the air squeezing through the ring seal when compression is happening. I suppose this means my bikes could have been a bit down on power not having a correctly sized piston  
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I've had this before on a high mileage DT125R and due to being poor I left it with dire consequences. Basically the piston tried to make its way out via the exhaust port. I went from a standard bore to 2.00mm oversize in one go which made me cry when I realised. 
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Just had a quick Google and first couple of results suggest worn rings / not correctly sized piston, which makes perfect sense because the sound will be the air squeezing through the ring seal when compression is happening. I suppose this means my bikes could have been a bit down on power not having a correctly sized piston  @mightyman dt125r puff of air from top end didn't find any matches for me  





