Exhaust yamaha 70ces

[mobil1]

In the exhaust chest from the bottom cilinder, you have on top a longer quidance then the above cilinders.
Anyone that know\tested the effects if you grind it away? The omc 's did not have those i thought.
Portwork is done, nothing special. Transfers set @ 120 , exhaust higher & wider, cut heads @ 1.8:2 ratio.
Expecting around 180/190 psi, 90hp carbs, cnc machined flywheel...
Will test the mods this year/summer, maybe next winter i will try some more.

[Fast Fred]

there is a cleft cut into number 3 cyl exhaust on that moda, if your goin to spin it big numbers , low timin, like 16deg max., 180 - 190psi needs 100+ octain

[mobil1]

Yes, from factory they already cut a little piece (cleft) out of #3 .
I am thinking to grind it completly level.
But not sure of effects on performance, did you try it or have an opinion about it?
Not going to spin big numbers, want to stay under 7500.
With that compression ratio i will be able to still run europe 98 fuel.
Only 16deg?

[Fast Fred]

she does not like timing, weld the crank or she will separate, known to cut through the case when separation happens. there is no power to be had by grinding the exhaust runners. finger ports make it go. the ces head has a negative squish band if not corrected best run fat. (fat = rich)

[mobil1]

Did planned to make fingerports but running out of time. That will be for next winter... This year testing with new mods.
I cut the squish band same as original, this is not so good? Can you explain a little more regarding the effects of negative squishband?