will the 300 motor drop in with no mods needed to the exhaust as i have a line on a one that needs a top end rebuild and thats my cue to bore it .40 over or more and port the head possibly

is the carb the same or will i need that also

if it needs mods what do i need to do to make it work

thanks for looking

 

Exhaust systems are slightly different as the 300s' head fins are larger then the 250 and the muffler is slightly slimmer to accommodate,but possible that it could work with the 250 exhaust.The main thing if you switch to the 300 you'd need the stator,cdi,and harness as some of the electronics are different. The only common modules between the two engines are the stator exciter coil,regulator and reverse limiter module.Timing advance is slightly different between the 250 and 300,the main reason for the cdi difference.

 

well i might still buy the motor but will just the cylinder and head with the piston bolt up to the 250 lower end, and will the piston fit the 250 connecting rod as i can always mod the head fins for the 250 pipe as i have a racing DG National pipe on it already

 

Only difference mechanically between the 250 and 300 was the bore size,piston and cylinder.Rod lengths the same,so probably will work. I've just never tried it myself..

 

man you have been a big help, thank you alot,

 

one last quick question is the carb the same size bore on the 300 as the 250, if it is bigger i will grab that carb also

 

Sorry wasn't fully awake on the swapping of the cylinders! Won't work as the 250 has a 72mm stroke X 60 mm bore versus the 300 which has a 74.5 mm stroke and a 65mm bore. Both engines use the VM30 mm carb. 145 main jet on the 250, 155 main jet on the 300.Sounds like you're either going to have to use one or the other engines,not a mix of both..

 

Okay thanks again, i will grab the motor and look for the remainder of th parts