YZ360A vs YZ360B engine differences?

[Tahitian_Red]

What are the internal and external differences between the YZ360A and YZ360B engines?

[Davey Crocket]

A has sand cast alloy clutch cover, alloy mag and clutch actuator covers, B has all 3 out of magnesium, B has later style ign system,  B went back to DT1 style shifting forks and drum (A had swiss cheese type), I think 1 of the gears was upgraded, and that I think is it.....you don't mess with a good thing.

[JohnnyO]

The B also has different porting to the A.. I have a magazine somewhere that goes into detail about their porting specs.

[Davey Crocket]

I thought that was only on the 250.

[Freakshow]

i think the 360 has the noraml drum and shift gears.  they were all the same part but the number changed for the 250A only because of all the holes in everything. My 360's look the same in the box.

[firko]

.My 360's look the same in the box.

But what about when you take them out of the box ?

[Freakshow]

Sorry in the Gear box case.

[OverTheHill]

Any 'old' selector drums out of the dt/rt series used to be hard on the high point of the track where it's held in gear, they all eventually flatten that high point off on 3rd gear [worst one] by memory to the point of loosing dog engagement [or not enough engagement to be safe] then just push on the selector until it cries enough. Not sure if the YZA/B use better material but anyway--have a yza one full of holes in one of my bikes so must've decided it was ok at the time. Remember someone at work building up the track high point with work hardening bronze on a bad one in the early days--not sure how it lasted!!.