After reading DragBikeMike's technical articles I decided I should pick up a spare Savage head to inspect.
Peering into ports (the cylinder head people I've known usually don't look, instead they insert a finger and feel around in the port) can be a difficult way to tell the shape of them. What is helpful is to pull a mold from the port. 2 part rubber compounds are often used. What I have is a product called "Vinamold" which is vinyl based and can be melted and reused many times. The white compound is of medium stiffness. It also works well without additional powdering when doing a 3D scan.
Last week I ran the spare head through the ultrasonic cleaner many times to get the ports as clean as I could, heated up the Vinamold and poured it in. The intake mold wasn't too difficult to pull out, but the exhaust port took a lot of work as I didn't want to pull too hard and tear it.
I also have some Aprilia/Rotax RSV 1L twin port molds to compare the Suzuki molds to. The Aprilia is a 500cc cylinder making 61.5hp @9500 (per cylinder), and 37.5 hp @ 6500 RPM. The Suzuki is reported to max out at 31hp @ 5400 RPM. The Aprilia is 123 hp/liter, the Suzuki is 47.7 hp/liter. Power will vary with RPM, but the 50% increase in RPM of the Aprilia gives a 2.6X increase in power over the Savage, so it is breathing much better.
Valve sizes (Savage from DBM) and horsepower/RPM:
Suzuki
94x94 (single)
IN 33 x 98 x 6.96mm
EX 28 x 91.5 x 6.95mm
31hp @ 5400 RPM for 47.7 bhp/liter
Aprilia
97x67.5 (twin)
IN 35.89 x 90.33 x 5.97mm
EX 30.95 x 90.56 x 5.94mm
123hp @ 9500 for 123 bhp/liter
from a dyno chart, 57hp @ 5400 RPM (Savage power peak)
75hp @ 6500 RPM (Savage reasonable redline)
But those are best cut by 50% to compare a 500cc cylinder to the Savage's 650cc. The Savage is tuned to make more power down low compared to the Aprilia.
I was surprised to find the Savage head had the longer valve stems. I had expected them to be short and contributing to the port needing to bend.
First the intake ports (the molds with a valve in them are the Suzuki ports):
![](https://motoconstructor.com/graphics/Suzuki/LS650%20Savage/ApriliaSuzukiIntake_3867.jpg)
The Savage doesn't benefit from the sidedraft intake, putting a bend in the port, but the shape doesn't look bad.
Now the fun stuff, the exhaust ports:
![](https://motoconstructor.com/graphics/Suzuki/LS650%20Savage/ApriliaSuzukiExhaust_3860.jpg)
I showed photos of the Suzuki exhaust to a knowledgeable friend who remarked "It is amazing just how bad manufacturers can make things. It looks like the performance chaps had a reasonably good port design, very steep upwards but then the valve chest designer came along and put his dents in it. I sometimes saw this back when I was gainfully employed, two designers at odds with one another or that they just never got together for a chat." Another friend remarked that "good intakes/bad exhaust" has been a combo he's seen on various engines.
Unfortunately, a 7mm thick layer of aluminum can't be easily added in the floor of the trough above the exhaust port because the valve springs are in the way. A quick measurement with "finger calipers" doesn't seem to show the floor of the trough being very thick, though there's probably enough metal to shave a bit off the bottom but a person would want to be pretty cautious when doing that.
At this time in the project I'm not going to worry about it. DBM and others have probably found all the reasonably easy gains. I'll still plan on digging out my Audie FlowQuick test equipment and test this spare head, but I'm not going to be in a big hurry on that.
The Aprilia ports show that much nicer ones can be had, but it would probably take a redesign of the Savage cylinder head to get them. I'll put my time into the chassis first.