Get It Done 12/1/2005
HO HO HO, Merry Christmas! ‘Tis the season to get those upgrades done. A little more throttle response for those 70 mph role on or to make that pass on two lane roads. Big Nick, alias St. Nicholas, Santa Clause, you know who you are, needs a fun ride. Maybe you need some scheduled maintenance to end the year keeping your ride ready for the next big riding opportunity. Point being, December/January aren’t prime riding time making these months good for maintenance, engine, transmission, or drive line restoration and upgrade time. For example, twin cam chain tensioners have a life expectancy of 20 to 30 thousand miles around town on short trip bikes, and 30 to 40 thousand miles on long distance cruisers! If your machine is in this mileage range just have the cam chain tensioners replaced, its much cheaper to do it before they fragment, sending hard delron pieces to cam support bearings and oil pump. If you wait too long you will have lateral choice of gear drive with a little oil pump on the side. By the way gear drive is the ultimate solution. With the right cam profile for pulse timing much can be achieved in your desired range of operation. Cam changes can be complemented with head changes. NOT ALL HEADS ARE CREATED EQUAL! There are different port and chamber works for upper RPM screamers. Big exhaust big chamber works for EFI torque application at low RPM. There are too many head theories to go into. I hope you will find a tuner to help select what will fit your riding style and budget. This can be a place where a lot of money can be misspent and not get your desired results!
Air into the engine is very important. In the carburetor world, bigger is not always better. You can’t tune a summer breeze through a barn door. Remember, the chamber shape, the port design, the valve size, the cam profile, and now the intake manifold shape, size and length will play a large role in efficiency range of operation. Some builders will chose a constant velocity (CV) carburetor because it is forgiving to oversight and operator mistakes. Other builders will use butterfly type carburetors because of their higher cubic feet per minute (CFM) capability but intake calculations must be correct to get desired results. The other thing on butterfly carburetors is the operator must learn throttle control. These are the trade-offs for more CFM of air movement. By the way, EFI is butterfly type.
Air cleaners can and will play a significant role in air flow. Some engines like smaller air cleaners while other want larger air cleaners. What I have found to be very interesting is there is no set rule in this area. While some stock 88 CID bikes will take a standard size K&N air filter, others will perform efficiently with the high flow K&N, and yet others will want the really large super sucker. All of this goes back to not every head created at Milwaukee is equal.
This brings me to exhaust, which can be an exhausting debate, I care nothing for. It’s like this 2-into-1 is a torque pipe and 2-into-2 is a high RPM pipe. A Harley is a torque design machine so you chose what you want and some tuner somewhere with an eddy current capable Dynamometer will tune what you have to the best of your equipment’s ability. We tuners can only do so much with equipment already in place. Engine, drive line and chassis must all work together to have a total package working to your expectation.
The last thing to consider if your particular package is a little lower in projected output numbers is to first find out the exact package you are comparing your machine to. Any substitute made will change the outcome, and I do mean any change! To find out if you are close to what was proposed for a certain upgrade you will want to bring it to a Dyno operator who will use the Society of Automotive Engineers (SAE) correction factor, which is a standard that is very respectable. If you are a low or mid range rider and care nothing for wide open throttle (WOT) just ask the Dyno operator to steady state load the machine 25% and test for your riding range in high gear, say from 50 mph to 80 mph and this will keep the RPM down, for those of you who care nothing for top horse power. Top horse power is measured at WOT when top RPM is achieved. Realistic tuning occurs from lower RPM to mid range. This is where you will spend the majority of your riding time. You can know if your tuner has hit the mark with the package set up you purchased by having it tested. I have seen some pretty good ones and have also seen some mismatched components fighting each other to the point of losing power. Sometimes, it just takes a little tweaking or minor change to get the desired response. Sometimes there is a component beginning to fail that can cause problems for the new products put into play. These are real issues that a treadmill and stress test will help to discover on your motorcycle by using a Dyno. The Dynamometer is just another tool we tuners have at our disposal for diagnostics. The winter months are a good time to get these lengthy upgrades and rebuilds performed, waiting until spring may cause longer down time for you and your machine.
Wishing all a great holiday season and a Happy New Year!
Good Riding and God Bless
Steve Caldwell - steve@precisionvtwins.com
877.429.0399