Part 1 Getting the bike ready
(Hey, it’s not salt this time, but the 750 bike is putting on a different hat for dragracing. No matter what kind of track, we take the opportunity to learn more about the bike and engine and tuning. This is all on the road to Bonneville)
Having returned from Bonneville it was time to clean up that mess and prepare for another. In a few short weeks it would be time to head south for the Manufacturer’s Cup Race at South Georgia Motorsports Park in Cecil Georgia. It was huge in 2011 and promised to be even bigger this year.
This would be a piece of cake since we planned to take only one bike down with us, right? Well it seemed so at first when we planned this whole thing out earlier this year. Based on last year’s efforts I figured things to be a reasonably big push to change the bike over and be ready for the trip south. What must have slipped my mind was that we were rained out last year. With the event being run in its entirety this year, and the bike going down the salt twelve times, I completely overlooked the time needed to clean the bike, front to back, top to bottom, and inside out. Silly me.
Once back in the shop, and the trailer unloaded, the task of sorting out the hurt from the good and cleaning off the salt that encrusted the bike began. Start with extensive bathing in the driveway and then on the lift. Put some Salt-Away in the bug sprayer and deploy with zeal.
Then began the task of disassembling the bike and converting it back to dragstrip trim. This involves stripping the eighty pounds of ballast off, changing the 22 lb. BMW battery out for the usual 1.7 lb. primary battery, removing the cooling system and its requisite plumbing and then moving to the front of the bike. Here, the full front fender is removed, along with the front wheel assembly and the brake mounts. The shroud for the barrel valve attached to the bottom of the steering head area of the frame comes off and then the clutch master cylinder and all the related parts of the stock type clutch release. The smaller lighter fender is installed after cleaning the wiring and connections, the front fairing is attached to its bracketing again.
Working our way back, the stock type clutch was removed and the slider centrifugal assembly reinstalled. All the pack heights clearances and setup data from the last runs at the dragstrip are set and the outer cover reinstalled. The addition of two small washers when the outer basket was bolted up will help keep the oil seal in the hub in place in case we put a hole in another piston. A small but valuable lesson. The tunability of this type of clutch helps to reduce the variables introduced when the run starts, and simplifies the operation of the bike under the differing conditions of the various surface conditions at different tracks. While South Georgia has one of the best surfaces we have raced on in recent memory, consistency in the first 60 feet helps set the tone for the rest of the pass.
As the light parts went on the bike we always are looking for ways to improve the package. That is one of the hallmarks of a successful team. I have learned the hard way that if you are not moving forward you are moving back. Assuming that your competition is working as hard or harder than you are helps add the spurs. That is the reason we tried four different cylinder head/camshaft/valve/piston combinations this year. The time needed to make the valves, pistons and other parts, and work on future designs was time not spent at home, sitting on your butt watching TV or playing a video game. A four hour round trip drive and a day at the dragstrip to test these ideas is how you spend your Sundays. When you are the only one in the world running this type of combination, there aren’t a lot of other people to call and certainly no one to just buy what you want from. It is mostly best-educated guesses that precede the trial and error portion of testing. Hopefully the error part isn’t too great. I can only thank Fred Weege, Nick Moore, Jacki Whisenant, Bill Shields and my wife Patty for their help and patience in sorting this combination out. These are many of the same people that made our Bonneville successes possible.
One of the areas that I felt we could improve on was the power output of the motor. I was hoping for better 60 foot times and a little more mile and hour. The 172 mph at Bonneville was encouraging and looking at the tuning sheets there seemed to be some of the salt flat tuneup that could be used in Georgia. Granted there was a nearly 4,000 foot altitude difference, but the basic behavior of the platform was showing through. A spread sheet of the tuning variables can visually show patterns. There are twelve or more gross tuning variables that can be used in the adjustments to the systems on the bike. Which ones you change under what conditions is one of the spins of the roulette wheel where experience can be helpful in shifting the odds in your favor. Luckily we keep pretty good records of the atmospheric conditions and the position or calibration of the tuning variables. Some of the variables like gearing and the particular motor are not often changed once a good combination is found. Others, such as fuel percentage and tire pressure can be changed to accommodate the racing surface or atmospheric conditions of the day. The individual, smaller variables can be adjusted from run to run during the day and often are as the air density, humidity and temperature changes throughout the day. Luckily the Ducati motor we are using has a rather wide sweet spot in the tuning of it that helps you look perhaps a bit more adept than you really are.
We also were confronted with fixing the parts that we hurt out on the salt. This involved two sets of cylinder heads and finding cylinders to replace those we hurt, as the plating was scorched on a couple and rubbed through on a couple more.
The cylinder heads showed a characteristic retreat of the areas of the exhaust valve seats near the center of the combustion chamber. This was a characteristic we found on the Suzuki SV-650 motors when they started to make some power. The exhaust valves were a bit tweaked, but everything came back in with just a light touch-up of both the valves and the seats. The intakes were pretty much fine. This may be a very good trait to play off of with the supercharged version as a leaky intake valve can result in a rather spectacular explosion in the blower manifold.
The cylinders were replaced with new players and the motors were assembled. Trying a page from John Gregory’s book we upped gearing to a 39 tooth rear from the 43 we were running earlier in the year. In case you are wondering, the Bonneville gearing ran a 32 tooth rear sprocket. Putting more fuel into it and tugging on the motor seemed like a good idea so why not try it. Once again, I had Nick and Fred there to clean up the mess I might make and we had plenty of parts.
One of the major changes we were wanting to try was to run a solid motor. Filling up the cooling system with concrete sounds a bit daft, but it was something that if you read the Bonneville blog you will see we already had one head with a hole in the exhaust port floor that was just begging for concrete and maybe the solid motor wouldn’t have the exhaust seat retreat that water-cooled one did.
It was definitely a mess of the first order with the buckets, concrete and water. Tipping and jiggling and tapping and drilling bleed holes on the fly added a whole new dimension to motor prep. I was sure glad when it was over. Coming back to it two days later it looked like we were pretty much good to go. A little cleanup of the water port surfaces and back together the motor went.
Time to start packing to go to Valdosta and see what she’ll do!