Quote:
Originally Posted by bruce71198
OOps missed the rod length difference in the OP. So they ran shorter rods in the 300 but shortened the piston by 5.2mm to clear the counter weights maybe ?
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The shorter skirt does help clear the weights but the main concern would the be clearance of the piston below the pin hole. The stock 250 piston with 300 rod and crank pratically sits on the counter weight of the crank at BDC.
300 below pin thickness: 4.5 mm
250 below pin thickness: 6.36 mm
265 below pin thickness: 4.5 mm
This is the 300 piston/rod/crank at BDC:
250 piston/300 rod and crank:
Wiseco 265cc 64mm/300 rod and crank:
250 vs 265 64mm
CRANKCASE HALVES
The location of the oil pressure sensor for your dummy light is located differently as well as the neutral position switch. The 250 oil pressures sensor is located inline with oiling tube at the front of the case. On the 300, it's located on the lower half towards the rear. Sprocket covers will not interchange. There are noticeable changes on the top halves. The 300 has a more opened and clearanced area for the cylinder block base and rotating assembly. Also noticeable are the changes in the crankcase breather design toward the rear of the case.
250 and 300 lower bottom:
250 and 300 upper top:
300 pic 1
250 pic 1
250 pic 2
Left side Lower (300 top, 250 bottom):
Left side upper (300 top, 250 bottom):
right side lower (250 top, 300 bottom):
Right side upper (300 top, 250 bottom):
Opened up area to make room for the new 300 cylinder block design:
CHARGING SYSTEM
300 puts out 21 Amps vs 19 Amps at 5k RPMs.
250 puts out 40+ volts at 4k rpms vs 35+
a. Alternator rotor
Different amounts and sizes of pickups on the circumference of the alternator rotor.
Outer diameter of the rotors are the same.
The 300 rotor is more of a bell shaped with deeper dish.
250 rotor is a different type of material than 300.
b. Stator and crankshaft sensor
2010 250
2013 300
Starter gear:
250 left, 300 right:
TRANSMISSION
a. gearing
1rst and 6th gear are different between the two.
250
1st 2.600 (39/15)
2nd 1.789 (34/19)
3rd 1.409 (31/22)
4th 1.160 (29/25)
5th 1.000 (27/27)
6th 0.893 (25/28)
300
1st 2.714 (38/14)
2nd 1.789 (34/19)
3rd 1.409 (31/22)
4th 1.160 (29/25)
5th 1.000 (27/27)
6th 0.857 (24/28)
b. Shifter drum cam
More adaptation from the bigger bikes can be seen here. The 300 utilizes a
gear positioning lever with a spring to give tension on the shifter cam/stop on the drum. This holds the shift drum from falling out of gear. Factory Pro sells shifter springs with higher spring rates for the 250 and 300. On the 250, the shifter cam is located on the opposite end of the shifter drum as compared to the 300. The spring for it is easy to replace as all you need is to remove the bolt on top of the upper crankcase. Replacement of the shifter spring requires more work by having you drain your oil and remove the case cover. Also, the drum is held in place by a plate with screws vs allen head bolts like on the 250. These screws/bolts have threadlock on them. I used an impact wrench and almost stripped the threads on the screws.
300 shifter cam and lever
300 left, 250 right:
The protruding tips are what activates the neutral position switch
250 vs 300 shifter cam
c. Clutch
The 300 utilizes a slipper clutch which makes the shifting more new rider friendly. The clutch slips when downshifting preventing wheel lock up and jerkiness.
*disclaimer* I did not have a 300 slipper clutch to play with since the original owner had to reuse it for his new motor. I am going off pictures on Ebay.
The clutch baskets are the same between both models except that the 300 basket springs uses thicker and less coils. The 250 utilizes needle roller bearings for the basket and the 300 uses a crossdrilled copper bushing. I am not sure what the logic is behind this change.
