Naked Arborist
Hack from way back.
This thing runs like no other 025/250 I have ever handled after only 2 tanks. Some numbers taken from the AM kit and the OEM. Some are mm and some are inch measurements. Don't ask, just the way I do things.
AM/OEM
wrist pin end play spec is 0.010
0.020/0.008
Wrist pin size
0.391/0.390
flat top to wrist pin bore 13mm
quench, squish
0.036-0.040 average 0.038 AM
0.052-0.058 average 0.055 OEM
piston skirt thickness
intake 1.20/1.50 mm
exhaust 1.75/1.56 mm
AM piston has a overall 0.020 taper from widest to crown.
AM rings were a nice cast set gaped at 0.008 0.0095
AM piston skirt to crank counter weight clearance 0.075 on both sides
AM outside ports sizes out of the box
exhaust width 24.1/ height 16.7 mm 0.030 wider than OEM
intake width 21.3/ height 16.75 mm 0.005 wider than OEM
Compression is at 130psi and sure to climb with use.
The intake roof entry angle is 10 degrees higher on the AM jug. Most everything else can be considered well with-in spec. :msp_biggrin: The fit and finish of this kit was good IMO. The plating was decent. The ports were nice and had plenty of meat in them all around. One last note, the combustion chamber is keyhole shaped in this kit.
I have many more pics. Most are blurry.
AM/OEM
wrist pin end play spec is 0.010
0.020/0.008
Wrist pin size
0.391/0.390
flat top to wrist pin bore 13mm
quench, squish
0.036-0.040 average 0.038 AM
0.052-0.058 average 0.055 OEM
piston skirt thickness
intake 1.20/1.50 mm
exhaust 1.75/1.56 mm
AM piston has a overall 0.020 taper from widest to crown.
AM rings were a nice cast set gaped at 0.008 0.0095
AM piston skirt to crank counter weight clearance 0.075 on both sides
AM outside ports sizes out of the box
exhaust width 24.1/ height 16.7 mm 0.030 wider than OEM
intake width 21.3/ height 16.75 mm 0.005 wider than OEM
Compression is at 130psi and sure to climb with use.
The intake roof entry angle is 10 degrees higher on the AM jug. Most everything else can be considered well with-in spec. :msp_biggrin: The fit and finish of this kit was good IMO. The plating was decent. The ports were nice and had plenty of meat in them all around. One last note, the combustion chamber is keyhole shaped in this kit.
I have many more pics. Most are blurry.
Last edited: