SYNCRODRIVE, is an efficient design, instantaneously delivering the most power to the track, power you can feel! Requiring less horsepower than a chain from 0 to 1/3 throttle, less horsepower from 1/3 to 2/3 throttle and less horsepower from 2/3 to WFO, belt drives are the best way to maximize the power of your mx bike.
SYNCRODRIVE TECH TIPS
Tension your belt at room temperature ( 21C/72F) slightly less than the width of the red tension meter on the tensioner arm (the required belt deflection is 7/16” by pushing as hard as you can with your thumbs as in the diagram in the SYNCRODRIVE deflector)
Do not re-tension the belt in the morning after your YETI has sat outside all night at -25C or -10F. Your belt will be loose in the cold mornings compared to being inside as the gears will have slightly contracted in the cold. They will expand again as you ride.
When you start riding in the morning, your bike may be warm, but your belt is not, give it 2-3min of riding to warm up before beating on it.
Loosen the 17mm nut in the tensioner wheel as little as possible when tensioning the belt. You will notice that after you set the belt tension by adjusting the tensioner bolt, once you tighten the tensioner wheel nut, the belt will get tighter again. Get a feel for how this works.
It is better to run the belt on the tighter side than the looser side.
The belts do not stretch, only weather, the belt wearing, gear faces wearing, or the tensioner arm backing off will lose the belt.
You will get belt fibres, or dust in behind the SYNCRODRIVE clear cover, it is ok to pressure wash out the belt drive enclosure to clean it.
SYNCRODRIVE FREQUENTLY ASKED QUESTIONS
Q: How do I tension my SYNCRODRIVE belt?
A: Please scroll down for a video of how to tension the SYNCRODRIVE belt, or follow the instructions here.
Step 1: Loosen the 17mm nut in the centre of the idler wheel. Just break it free, 1/2 a turn should be plenty.
Step 2: Slide the tensioner “RED” indicator to line up with outside edge of the belt. Tension the belt with a 12mm wrench, extend the tensioner bolt to tension the belt.
Step 3: Lock down the 17mm nut and check the tension of the belt by pushing the belt towards the idler wheel with both your thumbs as hard as you can. The tension is correct when the belt deflection does not exceed the width of the “RED” tension indicator. IF the belt deflection exceeds the width of the “RED” tension indicator, repeat the process.
Step 4: Lock down the 17mm nut, and rotate the track one time to be sure the belt cogs are fully engaged in the gears, and double check the tension.
NOTE: It is better to be on the tighter side of belt tension rather than on the looser side. Loose can possibly break belts when the belt is so loose it skips teeth, whereas a tight belt cannot skip.
Q: How tight do I tighten the gear bolts?
A: You can shoot the 17mm headed bolts that hold the gears on with a 1/2” or 3/8” impact no problem. We recommend 45 ft/lbs of torque on them. The bolt is a M12 size, it is very strong. If you run the bolts too loose, they will fall out, and or strip the teeth out of the gear.
Q: I do not see an M8 nut on the tensioner bolt, why?
A: The first year we did not run a lock nut on the back of the tensioner arm. It is a M8 nut that we added as a precaution to lock down the tensioner bolt from loosening off while riding while under extreme vibration. We have seen it loosen off in a very, very few cases, and this is a simple solution to avoid the tensioner arm from doing that. To put the nut on the end of tensioner arm you will need to remove the deflector first, then install it. The nut is a basic M8 not a locker type.
The nut will not fall off the end of the tensioner bolt if you forget to tighten it, as the deflector will hold it on.
Q: What is the difference between the 21mm wide belt and the 28mm wide one?
A: The basic difference is 8mm of width, which is 33% wider, and is 33% stronger. The 21mm wide belt is rated at 3200 pounds of break force minimum spec and 4720 pounds of break force average observed, while the 28mm wide belt is rated at 4333 minimum break force and average break force of 6500 pounds force.
We have not seen any 28mm wide belts break throughout the entire winter season of riding with many riders. We also know that the 35mm wide belts we have run on our snowmobile SYNCRODRIVES for over 8 years will withstand over 400hp.
Q: What are the main causes of belt breakage?
A: #1) Belt too loose, and it skips teeth on the gear, snapping the belt instantly. #2) Snow intrusion into the belt drive area, packing full of snow, belt cannot compress wet heavy snow, causes over tension and snaps the belt (new deflector design eliminates this possibility) #3) Track is skipping/ratcheting for a while causing a shock load to the belt, belt cannot deal with the shock load and it will break #4) Getting stuck, your track buried in a hole, then holding the bike full throttle while repeatedly dropping the clutch while sitting on the bike hoping for your bike to hop out of the hole.
Q: How do I maintain my SYNCRODRIVE?
A: It is ok to pressure wash out the belt drive area with the cover off. You can also wash the clear cover with soap and warm water. Wiping out with a rag the belt dust is ok too. You will notice some belt dust in the belt drive enclosure, this is normal the belt does wear in, but does not stretch.
Q: Where can I get a replacement belt? Do the local auto parts stores carry them?
A: The belt is a Mitsuboshi 720 length x 21mm wide or by 29mm wide carbon fibre corded belt. It is not a common belt to find in an automotive shop in that size. We do highly recommend purchasing it from your YETI dealer, as they have the correct belt, and it is the one that we have spec’d and tested with Mitsuboshi engineers. The belts you will find in a common automotive shop are not usually carbon fibre corded belts, and they are rated at a much lower break force.
Gates does make a belt that works also, and is carbon corded, it is about 2x the cost of the Mitsuboshi belt, and is constructed in a different material. It is not any stronger, we have tested and run both.
Q: How long should my SYNCRODRIVE belt last?
A: The 29mm wide belt should last you around 10,000kms or 6000miles of riding when properly tensioned, or a few winter seasons of riding. The 21mm belt has the same longevity but it does not handle the same shock loads as the wider belt.