Mild Port

[GuzziNZ]

Looking at the 850T head ports for the first time it would have to help to blend at the sharp edges like below the valve seats and the base of the intake as it turns down to the valve.

[Lannis]

I think that it's true for almost every production motorcycle engine that you will increase mixture flow and engine power by cleaning up the intake tract and valve ports, something that the factory would never have time or reason to do, unless it were a race engine.

As long as you don't make big increases in port size, carb size, etc, I can't see how it could possibly hurt.  Might only be noticeable at high RPM though.

Lannis

[nc43bsa]

I think that it's true for almost every production motorcycle engine that you will increase mixture flow and engine power by cleaning up the intake tract and valve ports, something that the factory would never have time or reason to do, unless it were a race engine.

As long as you don't make big increases in port size, carb size, etc, I can't see how it could possibly hurt.  Might only be noticeable at high RPM though.

Lannis

Which is why the factory didn't do it.  The 850T engine was not intended to be operated at high RPM.

[RinkRat II]

   You'll get just as much out of it by matching the ports. My $.02


       Paul B

[Lannis]

Which is why the factory didn't do it.  The 850T engine was not intended to be operated at high RPM.

I understand that.   The Guzzi engine is designed as a tourer, and any port work without changes in carburetion, exhaust, cam timing, etc is likely to have little effect.

But for someone who is itching to do a little clean-up work with a Dremel or something, it's not going to make it worse and might make it run a little better.

ALTHOUGH ... Guzzi engines are designed to run at higher RPM than most people think they are.  My Centauro used to get its best fuel mileage in 4th gear on the highway at 5000 RPM or more, and my Stelvio is happier in 5th gear on the highway than in 6th ... newbies seem to try to make a Guzzi "chug", and it's certainly not meant for that.

But I'll leave any further development to someone with a flow bench!   

Lannis

[wirespokes]

That's been my experience too, Lannis. The best fuel economy with the T3 was the tankful that spent 45 minutes at 5K in fifth.

[Turin]

Been there done that.  I did it backwards. Would have been more cost effective to do it all to my 850 T at once.
I started with 36mm carbs and just dremeled the intake where the head meets the manifold. bike ran well.
Later I installed an megacycle x-9 cam. better still reved higher and the power delivery felt more " meaty".
Again later when I went to gilardoni barrels ( still an 850 ) we ported the heads and replaced the valves and seats.




 Also increased the compression ratio with thinner head and base gaskets ( 0.042 squish )
It's a lot more fun and makes more power everywhere up to 7,000 rpm. I wasn't out to build a radical road burner, I as already have one of those.

[GuzziNZ]

That looks very nice work there Turin.
I am not looking to throw bigger carbs or hot cam into this T just smooth the ports enough to remove some pretty big sharp ridges and then match and dowel the ports.
While on the subject of ports the twin fibre insulating gaskets between the head and intake are a pain. I was thinking of making a Phenolic insulator and machining an
O-Ring groove on each side. Anyone see a problem with that?

On the subject of fuel mileage versa revs my 1200 Sport get better mileage at 70 mph than 60  in top.

[Rough Edge racing]

You should do research on modern porting and valve jobs...Sometimes the sharp edges are not removed...Proper valve work done by an experienced person can add power  at all engine speeds....