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This month’s topic is setting up suspension, this is such an important part of riding that it still surprises me that people spend a lot of money on a new bike and then go out and ride with the suspension set up by the factory, for an ‘average’ rider. If we consider that a bike in the average mini/motocross spends 75% of its time turning or jumping and the rest of its time on bumpy straights it becomes clear how important these settings are, also if we look at the top riders in their class a large part of their success can be put down to suspension bearing in mind that keeping a 2 stroke engine reliable severely limits modifications. 

The average 85cc motocrosser has over 24 settings on its suspension accessible from outside of the bike. The KTM and KX65’s have similar; the KX60’s have rear adjustment as do the newer division 2 50’s. Although this article will mostly apply to 85’s with the exception of race sag dimensions it applies to all the above bikes, which brings us to the first subject. 

Race sag is possibly one of the most important settings on a bike, set wrong it can make a bike uncontrollable bordering on dangerous. For a large part of last year I watched a competent rider trying to ride a bike with the suspension set wrong and when jumping he was close to disaster and this was down to incorrect race sag. 

To set the race sag proceed as follows. Place the bike on a stand or milk crate so that the back wheel is off the ground, with a tape measure measure between the centre of the rear axle to a point on the rear mudguard (as near vertical as possible), this point can be marked with tape or pencil then make a note of this measurement. Take the bike off the stand and put the rider on the bike in the race position (bum off seat) and re-measure. The suspension should drop by 80 – 100mm, 80mm for hard terrain, 100m for soft mud, if this measurement is out of spec. remove the seat and adjust the preload on the rear spring by means of the adjusting nut after loosening the lock nut. This may take two or three attempts to get right but I assure you it is time well spent. With the smaller bikes consult your manual for the race sag measurement, if it is not in the manual telephone the manufacturer and ask for it. 

Next the front suspension. Firstly, in your manual should be a chart indicating spring rate to rider’s weight, ideally you should have the right springs for the rider as these springs are not adjustable. If the rider is quite heavy or very light they must be changed (the springs not the rider…. or may be that is another subject), fortunately there is a fair overlap in these springs so if the rider is the correct size and weight for the bike the standard springs are OK. The main adjustment on the front forks is by oil weight and level, if the oil level is too low the forks will bottom out, if it is too high the fork travel will be reduced. There are two ways to find out what is happening, if you have an older rider who has a bit of an idea of what is going on you can ask them, if they don’t know or the rider is younger fit an ‘o’ ring or a zip tie to one fork leg and you will see exactly how much travel you have on the front suspension, too much - add some oil or too little – remove some oil. Oil adjustment should only be made in 5mm increments, again this could take 2 or 3 attempts but the rider will thank you for it. If the oil is at the maximum level and the front suspension still bottoms out then go up to the next weight of oil or vice versa. 

Finally the last adjustment, the clickers, or compression damping and rebound damping adjustment.   These adjustments have no effects over suspension height or travel but rather the speed at which the travel occurs, some people will tell you that these adjustments have no affect over the bike’s performance, but try telling that to someone who has had head shake at over 80kph due to too soft compression damping on the rear of the bike. 

Basically there are two adjusters on the forks and two on the rear shock, a good reference point to start with is to set them all in their central position. For the front the compression damping adjustment is a screw at the bottom of the fork leg and the rebound damping adjustment is a screw at the top of the leg. These usually have 12 clicks front one end to the other so if you set them both at 6 clicks out from either end they will be in the central position. Just before leaving next to the rebound adjuster is an air bleed screw, after each moto or minicross these should be loosened with the bike on its wheels to let air out, a good tip here is to fit Shraeder valves to these, but make sure you have a tightly fitting dust cap to avoid sucking air into the fork. 

With the rear shock the compression damping adjustment is a screw on the side of the shock at the top usually next to the gas reservoir. The rebound damping adjustment screw is near the bottom of the shock. Again, as a starting point set these in their central position. Generally speaking for the front and rear, compression damping will affect tracking in corners and rider comfort. Too much damping can cause the bike to bounce on landing and not enough can cause instability at the opposite end of the bike. Rebound damping should be increased on bumpy tracks to get the wheel back on the ground as quickly as possible, on muddy tracks it can be decreased. 

When adjusting damping it is a good idea to only move the adjusters one or two clicks at a time, so as not to miss the best setting but the key here is observation (of the rider and the bike) and communication (with the rider). It is surprising how much a 10 year old can tell you about how the bike is handling and where they have a problem, sliding out on the same corner every time can be rectified with as little as 2 clicks on compression damping, but don’t be afraid to experiment. You can always put all the adjusters back to the middle setting, free riding and working-bees are ideal for this, it is also a good idea to keep a notebook and record the best settings for different tracks, if you take the bike apart for any reason you can restore the best settings (in this notebook you should also record sprockets and jetting).

Lastly, a word on modifications. Although my son rides with standard suspension I have had extremely good reports about having gold valves installed in the forks. By speaking to riders that have them they claim to have drastically improved cornering and feel to the front of the bike and I have no reason to disbelieve this. As both riders I have spoken to are doing well in club motocross and do seem to corner faster than others, these kits are available from Terry Hay and suspension specialists and would seem to be a worthwhile investment to the serious rider. 

Well that concludes this episode and once again don’t be afraid to experiment (after all it is not your neck!!!) and remember observation and communication.