1998 suzukilt-f4wd 250 cc

[searsmonkey]

bought above machine after a 1989 of same make , model. wish i had keep old one. new one will not perform near what the old one did. 15 to 20 miles an hour in speed ,going down hill and on streight. difference is the carb i has a mikiuni BST31SS .old one had a mikuni VM24SS am thinking and want to replace with a bigger throated carb.am i thinking along the right lines or way off?

[DirtDemon]

I think your old one probably ran better because the motor was in better shape. Check over your motor real good, you may just need to do some minor repair work or make some adjustments. Make sure all the filters are clean, fresh fuel and oil, pull the carb off and make sure everything is clean in there, do a compression test, check the valve adjusment, new spark plug.

[searsmonkey]

no unit ran this way right from dealership.took it back four or five times dealer said it was due to EPA rules. motor is rebuilt now with a high compression piston.still runs bad. have put the bigger carb on it . does starts 100% easier but lopes at high RPM. have not had it at on dirt. also been to busy to miss with it.put new fuel pump rated as 14 liter an hour.looking for more if's? could be's.

[DirtDemon]

I imagine the cam profile is less aggressive, if a cam from an older model fits that may help you gain a little power. I would imagine that the jetting was leaned out for the tighter EPA regs too. Might look into intake changes, the newer design may be more restrictive than the old one. They probably made changes to the timing curve too, if an older CDI box will work, that would probably help wake it up too.