One rod cleanly separated itself at 10,500rpm and swung through the transmission (located in the crankcase).
We made it to Bonneville Speed Week in August 2017, very exciting, first time out on the salt. We roughed it in a tent at the KOA. Tech went well, no issues. Both Sean and I made our rookie runs and got our licenses, running in the 110-120 range. That course was very rough and was an eye opener to say the least. We moved over to the short course and I made several passes over the next couple days tuning and making an attempt at the M-PBF 500 record of 126.9mph. Monday the bike qualified and went to impound. Tuesday morning we experienced acute rod failure on the record attempt after I over-revved the engine at the top of 4th gear(oops). One rod cleanly separated itself at 10,500rpm and swung through the transmission (located in the crankcase). The countershaft sheared clean in half. We went back to the pits and swapped in the low compression engine and got back in line. We made the last pass of the day with Sean riding and requalified. The next day the bike ran 141mph and set the new record at 133.1mph. Good times!
Unloaded "over-rev" connecting rod tension loads @ TDC overlap can be fearsome. Use one of the engine analysis programs to calculate the load in G's. The piston in the photo looks like it might be a bit on the heavy side, but it is hard to say for sure. You are going to need very light, premium quality parts for reliability at high revs.
:cheers:
Wobbly, the new 500 is nice, but since it is OHC, it runs with the big boys in G, good try trying to get all of us CX guys out of the pushrod classes.
That is interesting that they took away the shaved V rated tire rule, can anyone shed light on this, was there a problem? There are a lot of the smaller bikes that run narrow tires and the selections are very limited when you get narrower than a 160.
I'm curious about the shaft drive possibilities. Are there other makes of shaft drive bikes that have a taller drive ratio, and if so, how difficult is it to transplant the entire rear drive assembly to the Honda?
Tom
P.S. In regards to narrow radial tires/wheels, I've gone to 17" cast wheels and have found some 2.5" wide rims on which I can run 110/70 ZR17 w rated tires for the front, and 3.5" rims on which I run 120/70 ZR17 W rated tires on the rear.
Here's the part that makes this even tougher, I just had Nate Jones shave my 23" V rated tire 3 weeks ago before I saw any rule change, so now my tire is shorter and still not allowed over 150mph. There is a Guzzi final drive that exists with a better ratio - 2.91:1, my Honda has a 3.09:1 ratio. That would be great but now I must run a smaller diameter tire with a z rating, so I'm right back where I started.
Unfortunately the Factory CX650 Turbo primary gears that would solve the problem are unobtanium, I will probably have to end up buying a complete CX650T, take what I need, and part out the rest to recoup the 3-4 thousand it costs to buy one, which would be a shame and I would rather not do.
Open to any ideas on gearing, does anyone know of a machine shop that makes one off transmission or primary gears?