Springology

The KLR650 is a dual sport motorcycle. For sure, I am not saying anything new to you with the first sentence. It was conceived in the minds of Kawasaki engineers as a motorcycle equally suitable for long distance travel on paved and unpaved road. Maybe the first generation of KLR650 back in 1987 was more into the off-road oriented side with almost zero wind protection, no faring and long suspension travel. The production of this original model was running for 21 years, until 2007, without major modifications.

1987-Kawasaki-KLR-650
1987 KLR650

2008 brought a completely re-designed KLR650. Beside many other modifications, there was shortened suspension travel  with less static sag. Together with an improved wind protection and faring the KLR650 made a step, to be a slightly more road oriented motorcycle, but keeping almost all the off-road DNA.

2014-klr-650
The re-designed KLR650 (2014 model)

In 2014 the KLR650 took one more step towards the road oriented riding. It got 40% firmer fork springs and 27% firmer rebound damping at the front, and 63% increase in spring rate and 83% increase in rebound damping at the rear.

kawasaki-klr-650-new
The “new” KLR650 (from the second half of 2014)

That’s where the dog lies buried! Depending on your riding style and/or destinations, the OEM fork springs not necessarily the ideal for you.

Let see what is a fork spring made of. In general, every spring is rated by how much force do you need to apply to compress the spring with 1 mm.

A linear spring, like the stock KLR650 fork spring, requires a linear proportional force to compress.

linear
Linear spring

A progressive spring is showing a completely different characteristic. First it is easier to compress the spring, but later it “hardens” and need more force to push it further.

progressive
Progressive spring

On your KLR650 the softer part of a progressive spring can give good damping and a smooth ride over the bumpy road, the firmer part of the spring can provide good road stability and prevent the bike bottoming out.

prog-spr
Progressive fork springs

There are many after market progressive fork springs available for your KLR650 bike. Which one should you chose? First you need to know, what is the rating of your factory fork springs. On the first generation KLR650 (1987-2007) 0.4 kg/mm. I was not able to find the the second generation (2008-2014) KLR650 front spring rates, but it can be very close to the first generation KLR650. On KLR650 motorcycles, manufactured after the second half of 2014, the front fork spring rate can be somewhere close to 0.55-0.6 kg/mm, as we know it is 40%firmer than the predecessor.

If I would shop for progressive fork springs, I would consider only those, where, at least, the spring rating is known. I would not trust in a product with no specifications but only reviews praising it.

Race-Tech has a “Spring Rate Calculator“. I did play around with this first and compared the results to the available progressive springs. Click here for the “Spring Rate Calculator”.

The Race-Tech calculator recommended a 0.6 kg/mm spring rate for me. Surprisingly I could find spring ratings on progressive fork springs only on the Happy-Trail website.

rear.jpg
Adjustable rear progressive shock for KLR650

And if you decide to replace the OEM fork springs at the front, highly recommended to replace the rear shock absorber with one matching the characteristics of your springs at the front.

Advertisements