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Discussion Starter · #1 ·
I'm hoping the collective brains trust may be able to provide some assistance....

I had installed a 25mm cartridge kit a few months ago (by a local suspension guru) & whilst it is a MASSIVE improvement over stock, I have 1 final issue that I'm stuck on.

The front end I am finding (after making MANY minute adjustments one at a time) still, to be fairly harsh, in so far as when either dropping into a hole, or hitting a raised piece of bitumen, the response from the forks is jarring my arms with the feedback through the bars.

The sag is set correctly. That was the 1st thing done.

I have the preload set to next to nothing, the compression set to nearly full soft & damping full soft.

I'm thinking the issue is being caused by the damping, as when I adjust the compression, it has no effect toward changing the characteristic that I'm referring to.

Given the damping is already at full soft, would either reducing the amount of oil in the forks, or changing the weight of the oil have any impact? The stock oil weight was 5w, it was replaced with 10w. The stock air gap was 150mm,reduced to 100mm when the install was done. Will reducing the amount of, or type of oil assist with gaining more compliance?

Hints/thoughts/tips appreciated.
 

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It sounds strange that backing off the compression doesn't change things.

Yes going from 10wt to 5wt would help. As the thinner oil flows more freely.
& increasing the air gap should help also.

I'd be concerned about the compression adjustment not working if it were me.
 

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Ok, first off the oil thickness will greatly affect the performance of the suspension. If your issue is compression damping only then you should only be concerned with one fork leg (since most cartridge kits now have compression and rebound damping in separate legs).

If it's too harsh switch to a lighter grade oil. If you are not staying with the same brand oil, refer to an oil viscosity chart (centistrokes @ 40deg) to make sure you are really using a lighter oil since the advertised weight on the bottle is often misleading.

As for the amount of oil you use, travel in the last third of fork travel will be affected. More oil will slightly make the last bit of travel more firm but I have not found this effect to be very strong on the Fz-09. I choose to use near the stock oil height of 145mm of air. I think 100mm of air is a bit too much particularly if your ride is too firm.

Ideally you should use about 80% of fork travel on a hard (spirited) ride. Hope this helps.
 

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10W oil seems excessive for a good valving upgrade. 5W for street riding should be enough, I run 7W and it perfect for the track and borderline for the road.

Your main issue is the oil level. 100mm is way to high IMO for oil level. Bring that down to 125-130mm (im at 130mm) Here's a little example of the effect of oil level... Then fire yoyr suspension guru! LOL

 

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Discussion Starter · #5 ·
Thanks to the guys that have posted up here, some very good advice.

I put this thread up on a few forums to gauge the general consensus & as a result, I will be lowering the oil weight to 5 & increasing the air gap to somewhere between 130 to 140mm. This should allow the suspension to be tuned with the settings available, not just having everything backed off to full soft (or close to it)

I'll post up the results once it's done.
 

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Did your suspension guru make sure that the residual loctite was scrubbed off of the threads of the bolts holding in the cartridges? This could clog the passages causing the harsh suspension.
 

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You need to make 2 changes before doing anything else:

1. Replace the 10W oil with 5W. The valving was optimized for 5W and anything heavier will increase damping across the board.
2. Take out some oil. 100 mm is far too little for that cartridge setup. Given the spring rate that I sent your way, start with 155 mm and add 5 ml at a time if you find that you're bottoming out.
 

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Discussion Starter · #9 ·
I've had the oil replaced & reset to the factory height. Based on the quick (time not speed) run I did, there is a vast improvement, now it'll just be a matter of dialling it in to my preferences. Failing this, there are a couple of options for reputable tuners in WA.

Thanks to all who have replied with some quality information
 
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