Polaris 3900 chain tensioner kit 39-120Polaris Genuine OEM 3900 Chain Tensioner Kit, 39-120 In stock$3999
Polaris 3900 chain tensioner kit 39-120
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Polaris Genuine OEM 3900 Chain Tensioner Kit, 39-120

Ask a questionMPN 39-120
$3999
In stock
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Quick overview

  • Genuine Polaris part The factory 39-120 chain tensioner kit, not an aftermarket copy.
  • For the 3900 Sport Listed for the Polaris 3900 Sport pool cleaner.
  • Keeps the drive chain tight The tensioner holds slack out of the chain that drives the wheels, which is what keeps the cleaner tracking its pattern.
  • Sold as a kit Supplied as the tensioner kit rather than as loose pieces.
  • Check it during a rebuild Chain tension is one of the first things to go on a high hour cleaner, so it is worth inspecting whenever the belly is open.
  • Look for 393-121 The product data notes 393-121 molded into the sprocket, which helps confirm the part.
Full description and specifications ↓

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Product details

This is the genuine Polaris chain tensioner kit, part number 39-120, for the 3900 Sport pool cleaner.

What the tensioner does

The 3900 drives its wheels through a chain, and the tensioner keeps the slack out of that chain. Once it wears, the chain can skip a tooth under load. The cleaner then loses drive on one side, wanders away from its pattern, or gives up on wall climbs it used to manage. Replacing the tensioner is the fix, and it is usually done at the same time as any other drive train work.

Part numbers

The kit is listed as Polaris 39-120, and the product data also notes 393-121 molded into the sprocket. Both numbers are recorded here so you can match whichever one is on the parts you took out.

Specifications
Brand Polaris
Manufacturer part number 39-120
UPC 738919066922
Type Chain tensioner kit
Fits Polaris 3900 Sport pool cleaner
Molded marking 393-121 molded into sprocket
Part type Pool cleaner part
Shipping weight 0.05 lb
Ships Parcel

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Questions and answers

What people ask about this product, answered by our pool techs.

Which cleaner is this for?
The Polaris 3900 Sport.
Is this a genuine Polaris part?
Yes. It is the Polaris OEM chain tensioner kit, part number 39-120.
Why does the part number 393-121 appear too?
The product data lists 39-120 as the part number and notes 393-121 molded into the sprocket. Both readings are carried here rather than one being dropped.
What goes wrong when the tensioner wears?
A slack chain skips or jumps under load, so the cleaner loses drive, wanders off its pattern or stops climbing walls the way it used to.
Ask your own question