Rough edges inside Mikuni intake

fiatfan · Feb 6, 2019

Got my new Mikuni single conversion kit today. Not that happy with the way the intake holes facing the head looks like. I don´t think it´s a big deal though, and will use the Dremel or a slightly bigger grinder to make the holes match the intake ports better. The question is; Will hours after hours of grinding to an absolute perfect match make a difference that I will notice? (Will just be cruising with this bike.) Or is it enough to just take off the worst?
Tommy

Triton Thrasher · Feb 6, 2019

Your bike will be slowed down by the single carb conversion, not by a rough edge on the casting.

concours · Feb 6, 2019

Think water pipe, t-y, threaded flanges.
If you do invest that time, be happy you know you did it. No one else will.

Fast Eddie · Feb 6, 2019

Spend an hour or so fettling, you’ll feel better knowing it’s done. I certainly would.

Nevertheless, I’m with TT in thinking it won’t make a blind bit of difference. The bottleneck is further up stream with the single carb itself, and with the tight bends in the manifold.

acadian · Feb 6, 2019

Just to throw another wrench in the works, it was reported in a previous discussion on port matching that the "step" may actually increase power. Some other chatter also suggests leaving the rough intake surfaces rather than polishing them out.

https://www.accessnorton.com/NortonCommando/carb-intake-manifold-intake-port-matching.19035/

fiatfan · Feb 6, 2019

Triton Thrasher said:
Your bike will be slowed down by the single carb conversion, not by a rough edge on the casting.

I know that, it´s not the issue.

fiatfan · Feb 6, 2019

This is not a big issue, just wondering, thanks for the input.

fiatfan · Feb 6, 2019

acadian said:
Just to throw another wrench in the works, it was reported in a previous discussion on port matching that the "step" may actually increase power. Some other chatter also suggests leaving the rough intake surfaces rather than polishing them out.

https://www.accessnorton.com/NortonCommando/carb-intake-manifold-intake-port-matching.19035/

Interresting.

Danno · Feb 7, 2019

Jim Comstock has said, regarding dual Amals, that port-matching can benefit a 750 motor, but and 850 not so much. So apparently, uninterrupted intake flow is more critical in some engines than in others. This is not hogging out diameters, bu merely smoothing the transitions from port-to-manifold and manifold-to-carb.

eskasteve · Feb 7, 2019

My Mikuni intake was clean but If it wasn't I'd clean it up just because. I don't ride a 46 year old motorcycle for performance just for fun. Clean it up, stick it on, and enjoy the simplicity that it offers.

Lineslinger · Feb 7, 2019

eskasteve said:
My Mikuni intake was clean but If it wasn't I'd clean it up just because. I don't ride a 46 year old motorcycle for performance just for fun. Clean it up, stick it on, and enjoy the simplicity that it offers.

What he said.

jbruney · Feb 7, 2019

Uh huh.

Rough edges inside Mikuni intake

fiatfan

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