TRM MO/So. IL 2022-March - Page 14


Final Drive Chain Maintenance
If you ’ re looking for a better way to transfer power , you may wonder if there ’ s an option to the classic roller chain . Beltdrive systems are popular with a lot of Harley ® riders , but they don ’ t seem to be an option for a lot of folks , especially in high performance or racing situations . A toothed belt ’ s power limit is directly related to its width . That might be okay for a stock 60HP ( or 90HP ) Harley ® but above that a drive belt will have to be very big to the point of widening the whole bike to make it fit . Also , unlike chains , individual belts are not adjustable . So , for the foreseeable future we ’ re stuck with our old chains .
The last big step in chain development was in the eighties with the mass introduction of the O-ring sealed chain . Those little rubber rings have solved what was the chain maker ’ s biggest headache for many years : Loss of lubricant . The load bearing pins and bushings that enable a chain to bend over a sprocket have precious little oil to keep them happy . As if that wasn ’ t enough , high centrifugal forces that occur when the chain turns around the drive sprocket throws away the oil .
Chains wear because they lose lubricants . The advent of the O-ring chain enabled the chain to keep its oil inside and stay lubricated were it counts for long periods . The lubricant in a modern O-ring chain is not ordinary oil . It contains plenty of synthetic additives that for example , help it withstand the enormous loads that develop during a first-gear burn-out . Friction-reducing additives don ’ t really help , because Friction is not the issue . A lubricant ’ s film strength is what keeps the metal from touching and wearing . The moment it is not there , wear escalates .
Tips for proper chain care . Even the cheapest chain without O-rings will last a surprising amount of time with proper care , meticulous adjustment and oiling at 350-mile intervals . Heavy gear oil applied with a brush is what many racing teams use , but this is a messy proposition and best only when the chain can be left to drip away the excess overnight . Most people spray on chain lube , which is good as long as you wait the required 20 minutes to let the solvents in the spray evaporate and leave the thicker lubricant on the chain , rather than one of the tire ’ s sidewall . Chain grease is not so efficient . It cannot get into the tight clearances between moving parts and the most good it can ever do is keep the chain ’ s side plates from rusting in the winter . Chain oil ’ s main enemy is high running temperatures . The running temperature of a chain ideally should not exceed 160 ¡ F . Above that , chain lubricant starts to thin , and the chances of it seeping out past the O-rings increase ; eventually the film strength drops .
This brings up the matter of chain adjustment or rather , chain mal-adjustment , the main culprit for “ well-done ” chains . Surprisingly an over tightened chain is a far worse than a loose one . Informed riders know that suspension movement increases chain tension , and what is a fairly tight chain at standstill becomes impossibly tight when the suspension
bottoms . These added and unnecessary tensile loads can exceed the chain ’ s capacity and the increased friction will raise the chain ’ s temperature sky-high .
A new , too-tight chain can , in no time at all , turn into history . The best way to check chain tension , the one used by many race teams , is too ask two of your biggest friends to sit on the bike and compress the rear suspension to the point where the wheel spindle , swing-arm bearing bolt and the front chain-sprocket centerline are all in line . That is the point of maximum chain tension . Or you can compress the bike ’ s rear end with a ratcheting tie down . Free up and down movement at the middle of the chain ’ s bottom run should be about half an inch ( 13 mm ) with the suspension compressed .
Of course , a loose , dragging-on-the-floor chain is not too good either . A loose chain will rub on many static parts of the bike such as the swing arm rubber buffer and frame spacers . Besides , with the chain ’ s ability to saw through anything in its path , the added friction will again raise temperatures . Also the sprockets will suffer . A loose chain will “ ride up ” into the higher and weaker areas of the sprocket teeth and slowly bend them into a wicked hooked shape . Proper tensioning as explained above is the remedy .
Also , proper tensioning means a straight and true running rear wheel . A cockeyed , sideways rear wheel will place uneven stress on the chain , making one side of it work harder than the other . That is bad . A quick check can be made by sighting the chain ’ s top run , back to front . A badly misaligned rear wheel will show as a notable kink in the chain ’ s run line . For more exact results you can pick two eight foot ( 2.5 meters ) straight-edged wood boards and place each one on either side of the bike , about 4 ” ( 100mm ) above the ground . On a properly aligned wheel , the edges should touch the rear tire sidewall and leave equal gaps on both sides of the rear tire . Adjust your chain tensioner accordingly .
Race teams mechanics don ’ t crawl on the floor with wood planks . They use a compass with two , long sharpened points to compare the distance between the swing arm bearing pivot and the rear wheel spindle . On a dirt bike , without a silencer getting in the way , a measuring tape will be just as effective .
Even after all this straightening it is worth checking that the chain runs even , centered on the rear sprocket . A missing 1mm washer somewhere may cause one side of the sprocket to make contact with the chain . If after some mileage one side of the rear sprocket gets shiny near the teeth it means that the front and rear sprockets are not properly aligned . A few shims or washers here and there can cure this .
The 500 pieces or more that make up a chain lead a very unglamorous life . On the other hand , failure of just one of them means a sidelined bike . Proper care is not too hard on body , soul or pocketbook and is definitely worth it . If your chain is misaligned and distressed you will certainly feel the difference in ride quality after a well-deserved chain care session .
Thunder Roads Magazine 12