Something Failed, let’s find it! Transmission Analysis.

Claviger said:

Aaaand I’ve hit an impasse

Not having any of the Triumph cash cow special tools I cannot remove the rotor for the alternator.

There’s 1 bolt back there holding the stator in that threads into the bottom 1/2 of the cases.

No way to get it out as it intereferes with the rotor when trying to unscrew it.

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Yep, you require the tool.

Paul Bryant said:

That is a Carpenter ported Head ???

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It is, the rubbers are matched to the runners in the head as well. The texture is what's left from being CNCd.

Just my opinion, and not much of a technical one as it has been a long time since i've done the work myself. But, you'd think someone setting up a head to machine it for flow purposes would run a bore hone through it while it is already setup on the mill.

I read somewhere it was mentioned Bob can make more power in the r3 engine, but it is not streetable. Maybe this is part of dialing it back.

Claviger said:

It is, the rubbers are matched to the runners in the head as well. The texture is what's left from being CNCd.

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That's pretty poor.



Should look more like this.



Even the above leaves room for improvement, and it's not about being shinny, it's shape and contours.
Look at how the light travels along the port.
If this was a road and you were hitting these contours at 100+ MPH, how smooth would your exit be ?
One thing that I did when I was porting my Trident Head was to hold it up with the Combustion Chamber pointing to the Sun.
The light then traveled down the port and I could see the exact shape of that port.

This was the first "head that I had ported.
I did the R/H port and thought that was O.K.
I then moved onto the Center port, this I did better than the first one, so went back and did the first one again.
This was now better than the second one, so re did that !
Now onto the third port ...... I think I did about 11 ports on that 3 cylinder head.
I then built a simple flow bench and checked it there ..... more tweaking .............

Oh, my "Tutor" at the time was an Ex Mechanic specializing in cylinder Head work from the Old BRM Racing Business in the U.K (Well retired)

Also, I've broken a few bits along the way .....

I agree 100 percent. Actually it should be smoother than your last pic. Done right looks like it is polished with no lines at all.

I’m not disagreeing but I wonder if it’s a case of “good enough”? Like, nothing was gained going further, or,

I know there’s more power available to be made from the motors, there are still a few cam sizes up, but, I wonder if the way he does the head supports more flow than the 2305 cam so it’s a moot point.

When you consider 265whp vs displacement, hp per liter isn’t high at all for a motorcycle motor, but, we have a lot more frictional loss than most bikes so actual flywheel power is probably more like 310-320. I don’t think hitting 300-310whp would be impossible, if, your willing to get peak power at 8500ish RPM instead of 7600 or so where mines at now.

At 8600-8800 with a bigger cam I’m sure the head will be critical.

sonny said:

I agree 100 percent. Actually it should be smoother than your last pic. Done right looks like it is polished with no lines at all.

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Mirror finish intake runners are bad, on the exhaust it’s great. Years ago it was accepted as best practice on the intake side, but it’s been proven over and over that some texture is desirable on the intake side.

@sonny Just had a thought about HD specifically regarding intake runners: head temperatures. I imagine they get hot as far cylinder heads go, possibly hot enough to ever prevent fuel from sticking to the walls, just a guess but that would explain why they do best with mirrored runners.

I do feel the need to point out, they could look like the texture of the moon, the bike made 240/179 untuned with 15:1 AFRs...

Never heard of that. Not saying your not correct but a lot of Harley guys pay big bucks for the polished including myself.

sonny said:

Never heard of that. Not saying your not correct but a lot of Harley guys pay big bucks for the polished including myself.

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I do not believe it be universally true from engine to engine that a certain finish works best, however, I know in some flow challenged applications where the runner area can’t be increased one of the tricks used is to apply enough texture to break up the airflow sticking to the walls.

It’s counter intuitive but works in the same way a perforated straight through muffler does in high flow situations, dealing with laminar flow vs surface area, all very technical crap I don’t completely remember the details of

Here’s a video I quickly found showing the difference. The dimpled vs wave thing, whatever it’s bull crap, but you can see both the waved and dimpled runners beat the polished runner.


Little something I found on the matter by mototuneusa

Why Not Polish The Ports ??
Doesn't Air Flow Better on a Smooth Surface ???

Remember that the ultimate goal isn't "flow" ... it's POWER !!

The intake port is going to flow both fuel and air. The problem with fuel is that, since it weighs more, it's difficult to keep it evenly mixed with the air as it follows the contours of the port.

Boundary Layer

The next time you drive a car in the rain, notice that when the car is going 60 MPH, the rain drops go up the hood of the car at walking speed. That's because the smooth surface of the car creates what's known as a boundary layer, and the portion of that layer of air that's nearest to the surface is almost still.

The same thing happens inside an intake port. Except instead of raindrops, it's fuel droplets that will run down the port wall slower than the air. That causes a serious change in the fuel air mixture by the time it reaches the cylinder, ruining much of the engine's potential power.
Polishing the port walls will ensure that this happens.

The phrase "Port & Polish" always makes me laugh ... I think the idea came from 70's Hot Rod magazines or something. Anyways, the last thing you want to do is polish your ports !!!

Instead, by making a series of rough 60 grit lines that purposely go against the flow, the "boundary layer area" will be turbulent, and the fuel will stay suspended in the air.

Remember: Rough is Good !!