OP, a couple of things...
The 7 day time limit the seller told you for returns is exactly the same as the story they told you about the fuel crystalizing overnight, complete **bleep**. They are no different to many other businesses who only give minimal time limits for returns/refunds for faulty goods that were purchased new, they know full well that for items such as that bike, their legal obligation under Australian & NSW consumer guarantee laws to accept returns & either repair/replace/refund extends considerably longer than just one or two weeks.
They are merely trying to dupe uninformed buyers into believing those minimal time limits they give (along with also trying to bluff buyers like yourself with the bogus claim the item was damaged through misuse) They get away with this because it's technically not illegal of them to do so. Firstly, in the case of warranties they can say it's only 1hr to return if they wanted, and that's all you get, but warranties are voluntarily offered by suppliers/manufacturers so they can set the terms of it however they want (they can’t change those terms after the fact though). But warranties do not supercede statutory obligations regarding consumer guarantees, and the relevant government authority/laws set those terms.
Even so, under cg's the seller can still advertise any time limit they want no matter how unrealistic it may be, or how much BS it is in practice... simply because the cg regulations do not stipulate an actual time limit for accepting returns to repair/replace/refund, they merely state it's to be a 'reasonable' period of time. When push comes to shove the seller/manufacturer doesn't get to decide what constitutes a reasonable period of time, that decision is made by the relevant authority, or their inspectors. It is subjective and can differ considerably depending on the type of goods it is and/or the circumstances of the transaction & problem/fault, and who the seller/manufacturer is.
As Harley said, In NSW it's the NSW Dept of Fair Trading, and for a pocket bike purchased new from a business seller, you are most probably looking at between 30 - 90 days for returns for r/r/r. 30-60 days is what I would usually expect though. If the seller is/has been on FT's radar due to numerous complaints (and I can assure you a good many established B&M sellers of pocket bikes are very liable to be) you will find the FT inspectors will be very generous on the time limit in favour of the buyers. They don't usually feel too kindly towards repeat offenders that keep wasting FTs time because they keep trying to dodge their legal obligations by attempting to dupe their innocent victims (customers) out of their legal rights.
As Harley suggested call the NSW Dept of Fair Trading (if you have not already done so) and lodge a complaint with them about the seller. Usually FT will simply give the seller a 'friendly' call to discuss the situation & more often than not... hey presto the seller will suddenly be only too happy to help you, & it will be sorted right away. They're just trying it on in the hope you don't know the score, it's just business... nothing personal (there's some huge retailers that do exactly the same)... but the moment FT calls they know the gigs up and you'll find that they can't make good fast enough. If they're a veteran seller of pocket bikes they'll know FTs next move is to have an inspector or two drop in on them for a 'chat' which 9 times out of 10 will also include an inspection looking (ie. knitpicking) for breeches, and @ a minimum of $500 per breech, well... let's just say a veteran seller knows it's in their best interest to avoid FT dropping in on them like that.
OP, one thing I very much suggest, if at all possible do not accept a repaired pocket bike back... & only accept it back repaired if you've first contacted FT and they insist that's your only option. These bikes are notorious for having a high proportion of them prove to be lemons. and any fixes performed on them are often bandaid fixes that mask an inherant defect for a brief period only. This is because the cost of the bikes to the importer is so little that anything other than a bandaid/simple fix is almost certain to exceed the replacement cost of the bike for them.That doesn't mean though that they'll readily replace a faulty bike with a new one if they can help it, as the new one represents a $200 sale to them, whereas your used bike has little/no resale value to speak of for them.
These ($200) bikes arrive from China at a cost to a very large volume importer/seller of between $20 - $30 per bike (possibly less, it's been nearly 10 yrs since I last priced them by the 40' container load, so...). As the aboveThey are cheap AND nasty. The raw materials used are very low quality as are the production processes involved all along the line to produce the component parts & the finished product. Due to the poor quality of material & processes the steel/alloy components in particular very often contain defects (bubbles, stresses, hairline fractures, etc..), the machining is equally low quality, and quality control is virtually non existant through all stages of manufacture. Nothing is checked, nothing is tested (when you're talking about precision engine parts, a cursory glance with the naked eye to see if it roughly looks the right size/shape is not quality control).
With pocket bikes, that old saying you get what you pay for is especially true.
