scooter bogs down when trying to use full throttle

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scooter bogs down when trying to use full throttle

my huatian ht 125 t-25 has started to bog down when trying to use full throttle, its fine when you start off but as you try to build up the revs and the speed it just stops at a certain point and wont get any faster and sounds as if its going to cut out but it doesn't. any ideas

Well I looked it up and it's a 4 stroke which is a shame as the two stroke diagnosis would have been easier. Look for the obvious things first :- 1/. Brakes binding, or wheel bearing shot 2/ Fuel starvation (does it rev ok out of gear?) 3/. Mixture wrong 4/. Induction leak (although more liable to misfire) 5/. Lube oil not circulating - I hope not. So lets try to narrow it down :- Does the engine rev freely when stationery and not in gear?, no strange noises?, Do the wheels spin fairly easily with brakes off? Is there a misfire? Have you checked the spark plug? Is the throttle cable working properly i.e. full travel, check these simple things first and we'll go from there, anything else you notice?

the engine revs fine when its on the stand with no strange noises. it only seems to happen when driving the bike. wheels are moving fine, there is no misfire and throttle cable is ok i haven't checked the spark plug yet as i wouldn't know what damage to look for  

OK only two things can be wrong it's not developing the power or it is and something physical is holding it back. 1/. Not developing power, have you took on a bad batch of fuel or does it have water in it - can happen, change if you can. If it has a fuel filter is it clean? my suspicions for this type of thing where no misfire tend to lie with poor combustion, which in practical terms means fuelling, timing and good spark. 2/. Try going down a hill, knock the engine off, does it freewheel easily?

If you have checked your carb condition and your fuel system eg filter or fuel leakages, blocked jets, float level etc and also condition of spark .Your next step may be to check the condition of the rollers in the variator( do they have flats on and should be round) this will inhibit your acceleration and top speed, also check the belt condition.

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