my suzuki cs125 wont go beyond 40mph on the flat, its a 3 speed twist & go 4 stroke scooter starts first go every time no miss fire but on hills is really sluggish at times 20mph is all it can do!. Ive had 100cc whip past me on hills before now .. Gratefull for any ideas

gaz, January 2010

my cs125 is doing the same, 55mph on straight and 15-20mph on hills regardless of air filter. its getting worse it seems. if you manage to fix it, please let me know how. thanks tom

iow tom, February 2010

your welcome gary.good luck

adam bike doctor, January 2010

thanks 4 your help , its 27yr old but in excellent condition im pretty sure it has 1 inlet valve & 1 outlet valve , exhaust isnt that old so will check air filter as i was given a piece of like filter sponge 2 cut out make a diy job not had chance 2 look yet but im hoping its the problem but big thanks cheers gary

gaz, January 2010

could be one of 3 things,
1, the air filter is blocked of the airflow to the carb is restricted for some reason
2, the exhaust has a collapsed baffle or an interal part is basically blocking the flow of gases for the engine
3,the rocker arm has broken for one of the valves (if it has more than 2 valves only)it will still run with only 1 inlet valve for instance opening but be slow.i have seen it before on honda and aprilia scooters.

adam bike doctor, January 2010