Stan Bradbury's Speedway Training Notes
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Many riders suffer from chain problems despite using the so called "best" chain lubricants. Other riders are unaware that they have chain problems until these cause other, more serious problems (which they may still be unaware are caused by lack of, or improper maintenance). Some of these problems are: Broken or seized primary chains, worn sprockets broken housings, worn or broken engine main bearings and components and, worst of all, broken drive-side engine crankcases.
Some years ago, we were lucky to have a very good quality primary chain made in Britain by Renolds. That chain is now made in France to different specifications and is no longer satisfactory for speedway use. Added to that are such factors as, more powerful engines, tacky track surfaces, soft compound rear tires and enclosed primary chain cases. All these add to the problems, particularly on "long tracks."
Some chain designs are unsatisfactory for speedway use no matter how well they are maintained, despite the fact that they are made by top manufacturers using top quality materials, usually because they are made to tolerance limits too small for speedway. Assuming you are using a recommended chain, here are some ways to reduce further problems.
After a race meeting, remove your primary chain and wire brush the grit from it then wash it in Varsol or other cleaning solvent until all the dirt is washed from the links. Next, soak the chain in a 50 / 50 mixture of 90W gear oil and "Mr Moly" (Canadian Tire) or other manufacturer's product containing Molybdenum disulphide or, substitute graphite powder.
An overnight soak should be sufficient. There are also chain greases on the market into which the chain is laid and then the grease is heated up to a liquid. Unfortunately this method is rather dangerous due to fire risk, splashes and spills. The hot liquid can inflict terrible burns to the skin or eyes if not handled very carefully. The best way to handle this hot grease is in a deep fryer with a thermostat, if you can pick one up at a garage sale. Gloves, long sleeves and a face shield will reduce the risk of painful burns.
After the chain has been boiled in the grease for about 20 minutes, to enable the lubricant to penetrate all of the bushings, pins, rollers, and side plates, the chain is lifted out of the grease and hung up to drip back into the container and cool down. Before it is totally cooled, it is a good idea to wipe off the surplus grease with a rag. This prevents the excess grease from being thrown all over you and the bike when it is next started up. If you are using the 90W gear oil/moly mix, this will also benefit from warming the mixture. This needs much less heat to ensure fill penetration. Again, hang up the chain to drop back into the container and wipe off the surplus.
At the track, it is better to oil or spray your chains before you go out to race, while the chains are still cool, rather than after a race when the primary chain could be at a dull red heat. This high heat will vaporize the liquid carrier in the chain spray and the dry lubricant will just stick to the outside of the chain or be thrown off. The "before race" lubricating can be done by your mechanic or helper after starting up as you leave the staging area. Make sure you start up soon enough to allow time for this operation. I find a few squirts of Castrol R will work just as well as many of the special and expensive chain sprays.
Primary chain drip feed oilers are coming back into vogue, particularly on the 1/8 mile California style mini tracks. These consist of a T piece in the oil feed hose to the engine oil pump, an adjustable valve and some small diameter tubing down to the bottom run of the primary chain. A small fuel jet between the valve and the small tube acts. as a metering device to prevent over oiling. You just need to remember to turn the drip feed on before a race and off again after it. These drip feeds are a good idea as long as the unusual requirements of tacky 1/4 mile tracks and the long, arduous workloads created by "long" tracks are taken into account.
Primary chains should be quite loose by ordinary motorcycle standards and so should rear chains unless they suffer from the common problem of tight and slack spots (usually due to off center rear sprockets). If you have the latter, make sure the chain is not too tight in its tightest position and see if you can resolve the off centre problem later. Also check that your rear sprocket lines up with the countershaft jackshaft) sprocket by sighting down from behind the rear wheel.
I recommend that no engine sprocket smaller than 16 teeth (16T) should be used, where possible. The smallest engine sprocket at 15T has so little metal between the inner hole and the outer tooth hollows that they have occasionally been known to break and cause engine damage. Also, for long track events, sprockets over 20T cause the primary chain to run at such high speeds that it is more likely to overheat and/or seize, than with a smaller sprocket. A good rule of thumb is to use the smallest engine sprocket (excluding the 15 teeth) that will give you the best gear ratio for the size of the track in question e.g. Let us say that the preferred ratio for a particular long track is 7.33 to 1. You can get this ratio or one close to it with several different combinations of sprockets. A 56T rear and a 21T engine sprocket will give you 7.33 as will 48T rear and a 18T engine sprocket. The latter would be the preferred combination from the point of view of primary chain speed.
With totally or partially enclosed primary chains, the cooling air supply reaching the chain is reduced causing even more over heating. It is a good idea to "stand-off" the primary chain cover on spacers of about 1/4 to 3/8" and so allow more cooling air to enter the chain area from behind the chaincase. Another advantage of this "stand-off " feature is that it prevents large engine sprockets from chewing into the primary chain case. The chaincase is constructed in such a way that without the "stand-off" the tapered recess for the engine sprocket come closer together, hence the chewing." Some riders fit a narrow spacer on the outside of the engine sprocket to keep the sprocket pushed further in from the chaincase. This helps a little except on the larger engine sprockets. Spacing out the chaincase permits the use of engine sprockets up to 2T on those occasions when you have no other choice.
The recommendations about the lubrication, cleaning and maintenance of primary chains made earlier in this chapter apply also to rear chains but with less frequency, due to the much lower speed of rear chains. When using very small rear sprockets on the larger "long tracks," the rear chain does travel at fairly high speeds but, due to the open air conditions under which the rear chain operates, it suffers less problems than the primary chains.
Tight or Kinked Primary Chains
The above problem is common to most primary chains and its far-reaching effects can be disastrous. Tight primary chains (or "kinked" primary chains) can cause serious damage to drive side mainshafts, bearings, housings and crankcase. The result shows up as damaged bearings, grooved shafts, broken cages (in clutch bearings) and broken crankcases. These problems may have occurred before you owned the present engine or machine. Several drive side crankcases have been TIG welded by myself and several welded by others. In some cases, the damage was so serious that the engine was only fit for parts (Jawa 2V crankcases are unobtainable)' Obviously, primary chains should not be allowed to go tight or kink. Some expensive, high quality chains are not satisfactory as they will go tight or kink in less than 4 laps. Other chains, if properly lubricated and protected, do not tend to go tight or kink although all chains will do this if not properly lubricated or protected. The problem is not caused by overloading the chain (the wheel will spin before that happens) but by overheating and/or lack of proper lubrication. Moving the primary chain guard out from the crankcase by 1/4' to 3/8" will help the chain to run cooler by allowing air to enter the back side of the drive chain. Chains should be removed and cleaned after a race meeting, then soaked in a mixture of gear oil and graphite or molybdenum disulphide (moly) then hung to drop off the surplus. They could also be boiled in any of the commercial chain greases of similar make-up (which unfortunately are extremely dangerous) and hung to drip off the surplus. Spraying chain lube on the primary chain after a race has very limited value. With the chain being hot, most of the liquid carrier evaporates and the friction reducing material intended to penetrate the rollers and pins, just simply sticks to the outside and only reduces friction between the rollers and the sprockets etc. It is far more effective to spray a primary chain before a race when the chain is cool, as the lubricant can then penetrate to the pins and rollers, where it is most needed.
Several primary chains give good performances. These are Made in England Renold 428 (no longer obtainable unless old stock). The French made Renold is useless. German Jiwis 428 chain (high cost) and Tsubaki 428HSL (low to moderate cost). There are one or two other chains which have apparently been satisfactory but, at the time of writing, their make and types are not known. Rear drive chains give very little trouble even cheap rear chains seem to stand up quite well if properly tensioned and lubricated, except on the longer tracks where the chain is much more highly stressed due to the distance and the higher speed of the chain on the shaft housing and also eliminate the necessity of putting a wrench on the nut or bolt head behind the countershaft clutch assembly when adjusting the primary chain.
As there are a variety of different chain sizes used by speedway riders, I recommend that riders stock extra chain connectors so that they can repair, extend or shorten primary and secondary chains as required.
When changing gear ratios as used on 1/8, 1/4, 1/2 mile tracks etc., there is not enough adjustment on the countershaft to permit a change from a 22T sprocket to a 15T sprocket without changing the length of the chain. As primary chain connectors are a potential source of problems, some riders make up riveted chains of different lengths to solve both these problems. Others put safety wire or clips around the spring clip or a dab of gasket cement to add an extra measure of reliability. Some riders carry extra front and rear chain links to extend or shorten their chains as required. Crank links (1/2 links, 1 1/2 links) are available to permit the rear axle to be located in the exact position preferred by the rider.
The position of the rear wheel axle in its slots is of great importance, particularly to novice riders. The general rule of thumb is:
further forward - more traction and less control,
further back - easier control but less traction.
Front wheels sliding out (washing out) going into turns indicates that the wheelbase is too short. Wheel spin coming out of turns indicates that possibly, the frame is too long, among several other causes. An experienced rider can often cope with front wheel "wash out" by getting the power on early, but, if something occurs to disrupt this, such as a balk, lack of confidence, or tiredness, the problem can result in loss of position and a possible accident. Consequently, the rear wheel axle position has to be a compromise.
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