Topic: Bonneville

[Don R]

 Tuning for that density altitude is a challenge if you haven't seen it before. Most of us haven't.

[scottly]

The 1220cc bike seems to have a rev limiter at 9,500 when trying to go faster than 147.

The great white dyno is saying the HP peak is at 9500 RPM. Hopefully the gearing change will raise the speed.

Dennis, I misspoke; the dyno is saying that the HP at 9500 is enough to push the bike through the air at 147, but the peak HP may be at a much lower RPM, especially with 1220 CC. The head, even modified, can only flow so much air, so the peak will be lower than a smaller engine with the same head. Your motor, for instance, had a peak at 9500 or so, IIRC. What was the RPM at 150?

This is a straight spigot, big valve head. I asked the original owner about flow numbers but he never got around to running it on a bench. I'd still imagine it can move a lot of air. He had a special cam ground just for this stroker.

Frank, what do you mean by "straight spigot"?
The bike ran 147 at 9500, and 150 at 9000. The great white dyno says this engine makes more HP at 9000 RPM than at 9500 RPM, and the actual peak RPM may be even lower, given that it is a stroked motor.

[gschuld]

Straight port head.  This means the intake ports are modified to have them go from angled (needing angled boots to allow straight carb racks to work, to parallel to each other so the carb flow doesn’t take the turns you get in a stock setup.  Carbs need a wider rack spacing to compensate and use straight boots.

CycleX road race head was both straight ported and raised intake ports.

The pic below is an example of a straight port mod(RPE work in the pic I recall)

George

[Old Scrambler]

Observations regarding the 1220cc bike:

Based on the 'post' locations in the head-fins, this is NOT an F2 head or later K model. That leads me to think that the valves are not significantly oversized. Side-winder pipe is oversized vs. smaller diameter. The Lectrons are open with no air-filters, and appear to be no more than 31 or 32mm. The 'gas-tank' is a less than 2-inch square tube 'back-bone' so it may be starving at the 3-mile. May be 530 0-ring chain which takes a few horses to turn. Lots of nice looking weld around the jugs

I did not measure anything........just looking

[Don R]

 That's a pretty head, the last few horsepower are surely left on the table with the use of stock intakes and rubbers.  I've done a tiny bit of welding on cast and know what a challenge it can be.  Clean, grind, weld, grind, clean, weld, grind, etc.