Is it just me????

Production K Models

Re: Is it just me????

Postby wz507 » Thu Aug 16, 2018 7:09 pm

Dirty dave wrote:Ok I see the sporton here . I’m building one myself with a 1966 Sportster motor that I want to hot up so what’s a good formula for a good strong running Iron head motor ? Also what about gear ratios obviously a higher gearing over all but what’s the best way to close up the big gaps in the box ? The bike will be used for fast road and maybe a bit of track work . I own some pretty fast evo Sportsters so am looking to build something that will scare me without blowing up . I know you know what I’m saying. Interested to see what you suggest .

I guess it depends how strong you want it to run, but this one would scare you a bit without blowing up. Back in 1976 a friend and I both built 76” iron head Sportsters (4-5/8” flywheels) with essentially the same internals - with the exception of the heads, where he thought small ports were good and I thought big ports were good (and of course we were both wrong). He ran a mag, I ran a battery ignition. We employed Sifton +H cams, Branch Flowmetrics 44mm Mikuni carb and intake kit, and straight pipes.

After we got them running he could always beat me in 50-60 mph roll-ons in the lower gears. He was running a 24T CS sprocket and I ran a 23T. I reasoned that if I ran any taller gearing he’d beat me even worse, but to put it to rest once and for all, I purchased a 24T CS sprocket. From that moment forward both bikes were identical, so evidently the higher gearing made better use of the engine’s power in accelerating the bike. Both bikes ran 11.70 sec 117 mph quarter miles, which is unremarkable by today’s standards, but back then these bikes would pretty soundly spank anything we ran into on the street. If you rolled it on at 80 mph in high gear it would stutter once or twice from reversion, then clean out, fully extend the front end and pull right through to an indicated 6500 rpm.

Here’s a few grainy old images of the bike.
76 inch Sportster0002LR.jpg
76 inch Sportster0002LR.jpg (280.17 KiB) Viewed 3749 times


76 inch Sportster0003LR.jpg
76 inch Sportster0003LR.jpg (453.48 KiB) Viewed 3749 times


76 inch Sportster0004LR.jpg
76 inch Sportster0004LR.jpg (249.28 KiB) Viewed 3749 times
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