RGS Head Off, Hi-Comp Pistons?

ksoholm

Full member
Location
Seattle
Lads,

I'm having the head off my RGS for head work & light porting, and several mizewells (might as well) are presenting themselves. So:
1. Is it worth it to widen intakes to 35-36mm? I have Red's Mikunis RS36s already (best things ever). I appreciate intake velocity for torque; this is not a race bike.
2. Is it worth it to pop some 10:1 pistons in there? Are stock rods good enough, and does it make a nice difference?

Thanks all -

Kristian
Bellingham, WA
 
Last edited:

GregT

Hero member
Location
Hororata NZ
I'll offer an opinion on the porting anyway. No, don't enlarge the throats. Just clean up the first inch under the valve heads.
For a road motor, never sacrifice gas speed if you can avoid it. You'll lose out everywhere.
 

Laverdalothar

Hero member
Location
Germany
Lads,

I'm having the head off my RGS for head work & light porting, and several mizewells (might as well) are presenting themselves. So:
1. Is it worth it to widen intakes to 35-36mm? I have Red's Mikunis RS36s already (best things ever). I appreciate intake velocity for torque; this is not a race bike.
2. Is it worth it to pop some 10:1 pistons in there? Are stock rods good enough, and does it make a nice difference?

Thanks all -

Kristian
Bellingham, WA
Hi Kristian,

it's always a question of "how far do you want to go". If you touch one thing, it might cause you to alter several other things. Basically, it depends on what you want to achive.

I did everything that experts told me would normally make the engine lose torque and it has more torque than ever before. That said, I did not stop only at porting and higher compression or bigger carbs, I also changed the exhaust massively (which is needed if you want to find especially midrange torque on RGS/SFC engines).

So - if you just want to optimize and not to really increase power and torque and do want to keep the bike halfway standard, I agree, you should pop out the valves (especially the inlet valves, move the finger through the valve seat into the intake and feel where the edges are and remove them gently (or at least smooth them out). Replace the valve seals (as they are hardened and will soon leak) but stay away from putting some on the exhaust valves!

Now take some 32mm tappered billet manifolds to mount the carbs (from Red) that open from 32 to 36mm and you improve a lot the transition from 1.500 - 3.000

If you want to go bigger, you need the full program and would need to go for 40,5mm intake valves, too, with according seats. The 1000 SFC produces roughly 10HP and a bit more torque by the larger inlet, inletvalve and the increased compression combined with different carb settings, extra airbox and exhaust modifications.

Rods: there have been some RGS engines that broke rods and destroyed engine cases. I am not sure what circumstances lead to this but for sure it is NOT a good idea to increase power and torque on an engine without checking the big end bearings and at best even replace them. Depending on what millage the engine has, I would consider a complete crank overhaul. If you want to go down the road.

the increase with all operations can be tempting and produce well over 100HP and 100 Nm (like my engine did), but all components must play together. This is still a very good street engine with smooth but permanent power development. really fun to ride...

so - depends all on what you aim for and what you are willing/able to invest.
 
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