The Melting Pot!
Contribution:Philip Small
Setting up a speedway bike is a lot more than just a few factors individually addressed. It's a whole "melting pot" of things, all combined and inter-twined to provide a massive combination of bike handling and performance characteristics.
So, how does one convey all that information to a newcomer?
Well you have to start with a few "key" things that really make a difference, and explain them one by one.
Some of these important factors have been well documented in the posts above, especially by Aaron. Some of the things I've had to say have been mostly correct too (although I'm far too modest to admit it)!
Certainly gearing, jetting, tire pressure, ignition timing etc are major factors. Only years of plugging away and trying different combinations for different track conditions will really show you what works for you.
Another major factor (and one more piece of the complex puzzle) which is well worth mentioning is rear wheel position.
We've all seen the "slots" in the rear frame loop where the rear wheel axle or "spindle" goes through. These slots are not just for achieving the correct final drive chain tension. They play a major role (again, in conjunction with all the other factors) in the rear tire grip or "hook-up" one can expect to get. In other words, the back tire's ability to grip on the track and drive the bike forward.
Of course, it is very important to insure the final drive chain tension and alignment is correct, but if that results in the rear wheel of the bike being positioned too far forwards or too far backwards in the slots, then that's a big "no-no"!
The chain length will have to be adjusted by adding or removing a small number of links, to achieve optimum rear wheel position.
General rule of thumb is the further forward the rear wheel in the slots, the more grip will be gained. This makes the bike much more difficult to slide in the turns for a newcomer, but gives a more experienced rider much more drive and speed.
Conversely, if the wheel is near the back of the slots, it will make the bike "longer" and breaking the back wheel free to slide will be easier. The end result, a slower lap time, but an easier bike to ride as a beginner.
Newcomers, try to follow the general guidelines in previous posts. In conjunction with that, insure your back wheel ends up about three quarters of the way back in the slots. At the very least, definitely behind center! Don't dare go in the front half of the slots, or you may not be around to read my next posting! LOL!
Of course, don't loose sight of achieving correct final drive chain tension (about 1/2" play up and down on the "top" run of the chain at a point half way between the top of the countershaft sprocket and top of the rear wheel sprocket).
Also, last but not least, insure correct final drive chain alignment. Unlike lots of street bikes, speedway bikes do not have "markings" on the rear adjusters to help with wheel alignment.
During rear wheel adjustment, walk behind the bike while it is on a bike stand and look straight down the top chain run from the rear sprocket to the countershaft sprocket. Everything should be dead straight and in alignment. (If necessary, get an assistant to hold the clutch lever in and spin the rear wheel so you can see it moving.
Don't listen to some advice that a "slightly" misaligned wheel will help you slide the bike easier.
This is BS. Make sure alignment is dead nuts!
A **** up here will almost certainly result in a "thrown" chain in the middle of a race. Not a good experience!!!! |
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