4 stroke 125cc scooter problem

[ct7acg]

I have a Kenos 125cc Maple scooter which has developed a problem.  At 55Kmph it starts to buck then makes a a lot of rattling kind of noise. The speed will then not go above 60Kmph up or down hill or even on the straight it makes no difference.  I am no expert but I have taken a look at the pully system and it seems okay I do not see anything obvious that might be causing this the engine etc looks the same as the GY6 150cc bike on u tube but followed instructions from there to take a look at things but all looks the same and nothing found.  Can anyone make a suggestion as to what the problem might be please?

[Rebel]

I want to suggest checking your valve adjustment, is it backfiring as well?

[ct7acg]

no have not heard it back fire

[Rebel]

Ok, i still would suggest checking the valves, first of all it is free, next they need regular adjustment. If they are good you can do a compression test, especially if it has been smoking.

If that all checks out inspect fuel lines/filter. Then go to ignition system.

[jmkjr72]

Ontop 8 the valves did you pull the varatior apart you could have a jammed roller that isn't letting things mover free

[ct7acg]

Thats interesting though Rev commander I have not done anything with the varatior - what is that and do I pull it apart? At 55kmph it starts to buck then goes no faster than 60kmph making a rattling noise. Now there is one other thing the exhaust is in need or replacing as nothing inside it all fell apart and removed so only outer casing no CAT! This scooter has some kind of feed back system to the engine from the exhaust not sure how that works but not got that anymore either so need new exhaust cannot find one anywhere that gives me that feed back thing I am told this could be the problem but would that give the rattling sound?

[Rebel]

The variator is the transmision located on the left side of the bike. It has a self adjusting pulley system and uses a belt to rotate the rear wheel.

[poppawelee]

May 16, 2015 8:30:29 GMT -5 ct7acg said:

Thats interesting though Rev commander I have not done anything with the varatior - what is that and do I pull it apart? At 55kmph it starts to buck then goes no faster than 60kmph making a rattling noise. Now there is one other thing the exhaust is in need or replacing as nothing inside it all fell apart and removed so only outer casing no CAT! This scooter has some kind of feed back system to the engine from the exhaust not sure how that works but not got that anymore either so need new exhaust cannot find one anywhere that gives me that feed back thing I am told this could be the problem but would that give the rattling sound?

Recently read about this style of exhaust elsewhere. The feedback to that USA owner was how overseas where traffic jams are thousands of scooters the more stringent exhaust control has a definite need. But in the USA where cars reign supreme many scooter owners by-pass the additional canister (but not the CAT). If I'm permitted to mention, I think I found the how to bypass advice thread on the scooter professor site. Owner used a dime, JB Weld and the scooters own suction to bypass then allowed the JB W to set up for a few hours. Also - I've found there are a lot of helpful how-to Videos online, maybe there's one on variator that will point you in the right direction. Best of luck.