There is a lot of opinions out there about these two, but what is actually the same, and what have people found is different? The obvious are suspension , carbs and close ratio gearbox but what else?

Wider 17 inch rear wheel, single seat no rear foot pegs,

Thanks, The engine seems the same other than the gearbox, valve train and cams all measured the same in my std and sp engine. I have an sp race bike and building another 400 race bike for a friend, I have never had a complete road bike. What about the ignition?

previous post by mofrockband,


moforockband
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Bike owned: GK73a SP CRM250 mk3
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Re: GK73a sp rocker arms/valvetrain

Post by moforockband » Sat Nov 14, 2020 11:27 am
Finally received a 73SP head. I've pulled it apart and found the reason the valve gear is different, is that the springs are physically smaller, but have more tension, hence the need for different retainers and seat washers.
The rockers have a '13' marking, and weigh exactly the same as std counterparts. These differ in that they have a slight cutout in the middle of the the rocker, not sure if they have the same ratio..

Cheers, my gk73a sp race bike (89) has the smaller springs.
The 88 gk73a engine doesn’t.

The valve springs are more durable in the sp, so i have been told. But as long as you are running std cams, you will be ok with either set.
It's usually the valves which fail 1st, and munch the top end.