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Stock spring on an 09KX450F

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The stock spring is rated at 5.5 kg. I have done some research in regards to my weight and style of riding on some MX Tuning websites and they are saying to go with a 5.4 kg spring. Will that different between the two make that much of a difference?

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I wouldn't go to a softer spring. At your weight of 200lb with gear you are just fine with the stockers.

How many rides do you have on it? I took about 15hrs before my bike really broke in and felt right.

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I only have about six hours on it. I just need to set the sag now and I think I will be ok. Not gonna do suspension just yet.

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Stock spring rate on a 09 KX450F is a 5.2

I was fairly certain it was 5.5

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I was fairly certain it was 5.5

I know don't hate the player,hate the game:banana:

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I know don't hate the player,hate the game:banana:

......I have rate tested three of these bikes. Each came out to about 5.5

Guess I tested wrong...

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The is straight from the RaceTech website for an '09 KX450F. Not saying they are right or wrong, just saying...

Rear Shock Spring and Spring Kits

Stock Shock Spring Rate

5.2 kg/mm

Ideal Rider Weight for the Stock Spring

185 lbs or 84 kg

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The is straight from the RaceTech website for an '09 KX450F. Not saying they are right or wrong, just saying...

Rear Shock Spring and Spring Kits

Stock Shock Spring Rate

5.2 kg/mm

Ideal Rider Weight for the Stock Spring

185 lbs or 84 kg

Let's think for a second

All according to race tech,

The 08 honda 450 comes with a 5.4 rear spring.

The 08 suzuki comes with a 5.5 stock.

The 08 kawi comes with a 5.4 stock

The 08 yami comes with a 5.5 stock.

the 09 kawi gained weight from 08. It did not see a significant change in rear leverage (longer/shorter swing arm...drastically different linkage etc..)

See a trend!?

Now maybe the three springs I tested were just oddballs...in which case I would certainly question the product control from kawi! But my personal data shows that bike at a 5.5 rear rate...and common sense would say that having gained weight from 08...kawasaki would up spring rate one fro the previous year, which coincidentally falls inline with the other manufacturers.

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......I have rate tested three of these bikes. Each came out to about 5.5

Guess I tested wrong...

Standard spring rate is 52 N. It is same as 53kg spring.

I guess that the numbers can differ between springs because production a lot.

There can be minor differences in lenghts and spring initial behaviours.

KYB have marked their spings with coloured spots and owners manual suppose to tell you how to adjust spring preload etc...

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Let's think for a second

All according to race tech,

The 08 honda 450 comes with a 5.4 rear spring.

The 08 suzuki comes with a 5.5 stock.

The 08 kawi comes with a 5.4 stock

The 08 yami comes with a 5.5 stock.

the 09 kawi gained weight from 08. It did not see a significant change in rear leverage (longer/shorter swing arm...drastically different linkage etc..)

See a trend!?

Now maybe the three springs I tested were just oddballs...in which case I would certainly question the product control from kawi! But my personal data shows that bike at a 5.5 rear rate...and common sense would say that having gained weight from 08...kawasaki would up spring rate one fro the previous year, which coincidentally falls inline with the other manufacturers.

OK,I wish I knew which is right,I didn't test any springs,but I measured the coils on a 5.4 and on the one that came off of the 09,and the 09 coils measure smaller,so I would just guess that the rate would be lower.:bonk:

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