Drive System

Content Source: 2021 Timbersled SX 120 / ARO / RIOT Owner’s Manual (9931501 R01) > Maintenance Chapter

IMPORTANT

The Owner's Manual for this vehicle contains warnings, instructions and other information you must read and fully understand before safely riding or performing maintenance on this vehicle.Always follow the warnings and instructions in Owner's Manual.

Click the CONTENTS link above for the Table Of Contents, or download a full PDF of the Owner Manual in the Owner Support area of Polaris.com

Drive System

Drive Chain Tension

For long chain life and reliability, it is extremely important that you keep the drive chain adjusted properly. Always check drive chain tension before riding.

IMPORTANT

TIMBERSLED SUSPENSION STRUT (TSS) MODELS: The TSS MUST be at full extension and set to at least 200 PSI to measure and adjust drive chain tension properly. To ensure the TSS is at full extension, remove all weight from the shock by tipping the bike on its side or by using an appropriate stand to lift the bike under its engine ensuring the track is suspended off the ground. Inspecting and adjusting a chain without the suspension at full extension will indicate a loose chain and lead to over-tensioning and excessive chain stretch and wear.

NOTE

The drive chain may loosen on the first ride due to initial chain stretch and slider break-in. Re-tighten drive chain after first few rides. If problem persists, your dealer can assist.

Measuring Drive Chain Tension

To measure drive chain tension before riding:

Position your snow bike on an flat and even surface. Do not place a wheel kit under the bike. Remove all snow and debris.

Position a ruler behind or in front of the top chord of the drive chain, halfway between the counter shaft sprocket and the jack shaft sprocket (this is where drive chain displacement should be measured) . Steady the ruler so it does not move as chain displacement is measured.
Choose a single chain link pin close to the ruler to use as a reference point for measuring chain displacement. Push down on the top chord of the chain with one finger and line up the 1 inch mark on the ruler with the chosen chain pin .
Then, without moving the ruler, push up on the top chord of the chain with one finger in the same location and add up each eighth inch mark between the 1 inch mark and the new position of the chosen chain pin .
If the chain is properly tensioned, there should be between 0.75 in. and 1.250 in. between the 1 inch mark (the position of the chosen chain pin when pressed down) and the current position of the chosen chain pin (when pressed up). This is the drive chain’s displacement measurement. If the drive chain’s displacement measurement is less or more than 0.75 in. and 1.25 in. the chain needs to be adjusted (see Adjusting Drive Chain Tension).

Adjusting Drive Chain Tension

To adjust drive chain tension, follow the steps below.

If the chain requires adjustment, loosen both 15 mm frame rail slide bolts located on the right side of the Timbersled frame.
Loosen the 13 mm inner jam nut on the inner frame tension adjuster bolt .
Adjust the tension adjuster bolt in or out to achieve the correct chain tension.

Re-torque the jam nut

to specification.

TORQUE
Jam Nut 18.4 ft-lbs (25 N·m)

Re-torque the frame rail slide bolts

to specification.

TORQUE
Frame Rail Slide Bolts 36.9 ft-lbs (50 N·m)

Measure the drive chain’s displacement once again to ensure it is properly adjusted.

If the chain is too tight and the frame is difficult to compress, you may loosen the front right-hand side panel bolt and the front right-hand frame bolt to allow the frame to slide easier. Re-torque both bolts to 60 Nm prior to tensioning the chain.

Chain Case Chain Tension

It is recommended that you measure the chain case chain tension each time the chain is lubricated.

caution

Do not over-tension the chain. Improper chain tension can cause excessive wear to the chain and the tension roller bolt.

Measuring Chain Case Chain Tension

To measure the chain case chain’s tension:

Remove fasteners from chain case cover.
Position a ruler behind or in front of the right chord of the drive chain halfway between the drive shaft sprocket and the jack shaft sprocket (this is where the chain’s displacement should be measured). Position and steady the ruler so it does not move as chain displacement is measured.
Choose a single chain link pin close to the ruler to use as a reference point for measuring chain displacement. Push the chain’s right chord to the left near the chosen link pin using 1 finger. Line up the 1 inch mark on the ruler with the center of the chosen chain pin.

Then, without moving the ruler, push the chain’s right chord to the right with one finger in the same location and count the number of ⅟₈” marks between the 1 inch mark and the new position of the chosen chain pin.
If the chain is properly tensioned, there should be between ½ in and 3∕₄ in between the 1 inch mark (the position of the chosen chain pin when pressed to the left) and the current position of the chosen chain pin (when pressed to the right). This is the chain case chain’s displacement measurement . If the chain’s displacement measurement is less or more than ½” to 3∕₄”, the chain tension needs to be adjusted (see Adjusting Chain Case Chain Tension).

Adjusting Chain Case Chain Tension

To adjust the chain case chain’s tension:

Loosen the tension roller bolt .
Adjust the chain tension as needed by pushing the roller bolt towards the chain to increase tension or away from the chain to lessen tension.
Then tighten the tension roller bolt firmly once again.
Measure the chain case chain’s displacement once more to ensure proper adjustment.

Chain Inspection

IMPORTANT

Regular drive chain and chain case chain inspection is important. A broken chain can cause host bike damage.

Chains need to be regularly inspected for signs of wear, damage and stretching. A drive chain or chain case chain that has stretched 1% or more of it’s length is worn out and will need to be replaced.

NOTICE

A chain with 1000 miles or 75 hours of use will need to be replaced (see Periodic Maintenance Interval Table in the Maintenance chapter).

To measure chain stretch, perform the following procedure:

To determine whether the chain has stretched 1% or more, first ensure the chain is taut along the area you plan to measure (a screw driver is used to keep the drive chain taught in the drive chain image below).
Timbersled RIOT and ARO snow bikes are equipped with 520 drive and chain case chains which have a pitch of ⁵∕₈ in or 0.625 in. (A chain’s pitch is the length of a single link which is measured from the center of one pin to the center of the next pin ).
- Link 1
- Link 2
- Link 3
- Link 4
- Link 5

Mark out the number of links to measure (see the following table to find the number of links to measure for the chain you are inspecting). To mark this number of links, begin by marking the first pin and counting forward the same number of pins (number of pins counted should equal the number of links to measure). Finish by marking the final pin . (see image with first and last pin marked).

CHAIN TYPE	# OF LINKS TO MEASURE	EXPECTED LENGTH	EXPECTED LENGTH +1%	ACCEPTABLE LENGTH RANGE
Drive Chain	24 (mark first and last pin)	15” (24 x 0.625 = 15)	15.15” or slightly < 15 ⅟₈”	Between 15” and 15.15”
Chain Case Chain	17 (mark first and last pin)	10.625” or 10 ⁵∕₈” (17 x 0.625 = 10.625)	10.731” or slightly < 10 3∕₄”	Between 10.625” and 10.731”

Then measure the counted number of links by measuring from the center of the first pin to the center of the final pin . This measurement should equal a length somewhere within the acceptable length range (as shown in the previous table).
If the length of the counted chain links equals or exceeds the expected length plus 1% (see table) the chain is worn out and must be replaced.
If the length of the chain links is less than the expected length plus 1% (i.e. the length is within the acceptable length range), the chain does not need to be replaced at this time.