Bonneville Question "Just the Facts"
My QUESTION: Seriously, how many rpms can a 5" stroke iron Sportster on nitro turn? I know it depends on balance and strength, but - One guy said his motor at Bonneville (stroker Sportster, a shorter 4 3/4" stroke) rev'd to 6800 rpms - and when he hit slick spots in the track - it revved up even higher. How many rpms do you think Manning and Riley spun that streamliner?
REPLY: I saw the pictures of the streamliner on your blog just a few minutes ago and laughed at your comment about "7,8,9 grand." Reality is, at Bonneville an ironhead stroker doesn't like to rev over it's torque peak which is about 5700-6000. I've ran mine over 7200 at the drags, but when I had my motor in Leo's bike we had it geared for 210mph at 5800 !
The rest of the story, is George Smith never ran much over 65% nitro and they hurt the front piston in the motor on the first run for the record, so they did the return run only using third gear (close ratio KR road racing gears) and never put it in high, so they turned it 6000 or 6200? The lower gear lessened the load on the motor and they got lucky and it held together long enough. Leo always thought that if they would have jetted it up and put 90% in it - it would have went 280 or 290 maybe? Anyway, they set the record and that was a big deal though. Jeff said, "I was there in 1970. I was a young punk, age 19 at the time, and my 75cu in. XLCH ran 152.8mph on gas - unstreamlined. My bike was the centerfold in Street Chopper Magazine in October or November that year. I didn't know the magazine had taken the picture, and I went to the store to read the new magazines and was shocked to see my bike in the magazine. As Paul Harvey used to say, "Now you know - The Rest of the Story."
Just for the record, I (Noot) always like to get my facts straight, and this is one way to do it - talk to people who know or who were actually there that day. It's the foundation of good reporting.
Posted by Noot