Mk1 1200 bandit oversized valves.

[Alex]

Hello all. Going to big bore to 1216cc. Is it worth putting big valves 26 ex 30 in I think while everything is apart? Taking head to machine shop anyway. Putting 38 mikuni flatslides on. 12-1 compression. Road bike. Would just like to know pros and cons please before I go down that route. Thanks Alex.

Edited January 29, 2023 by Alex

[DAZ]

Sounds great especially if you fit some cams to make use of the extra flow(you are having it gasflowed aren't you ?) and bigger carbs

Edited January 29, 2023 by DAZ
Bleeding predictive text

[Alex]

3 minutes ago, DAZ said:

Sounds great especially if you fit some cams to make use of the extra flow(you are having it gasflowed aren't you ?) and bigger carbs

I’m port matching it and I already have Kent reground cams degreed in.

[wraith]

I'd go for a flow job first, then big valves but ever way with big bore, cams and carbs it will benefit.

[DAZ]

11 minutes ago, wraith said:

I'd go for a flow job first, then big valves but ever way with big bore, cams and carbs it will benefit.

Your going to have to port it to some extent (beyond port matching the intakes) if you have bigger valves fitted ,if you don't open up and blend the bowls into the seats then you'll never see the potential of the bigger valves ( a set of valves from kibblewhite  or ferrea is close to £800 ) or your investment 

[dupersunc]

I'd optimise the ports and combustion chamber shape first, before going oversized valves.

 

[george 1100]

The oil cooled engine was undervalved imo. It's the single best mod with a compatible port job, you can do. Expensive though