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Fork oil change


papac2000

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After some research, I belive the stock fork oil is an odd 3.45W. I am considering an experiment with changing to 2.5W to reduce harshness due to excessive compression damping. Any thoughts? Just dump and refill with same quantity.
2015 Matte Grey
Modded stock exhaust, modded stock screen, modded stock seat, OEM heated grips, LED indicators, FlashTuned ECU, ZX10R shock
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After some research, I belive the stock fork oil is an odd 3.45W. I am considering an experiment with changing to 2.5W to reduce harshness due to excessive compression damping. Any thoughts? Just dump and refill with same quantity.
Do you have your damping set at the highest settings, 11 clicks?

Ken, Candy Ass L.D.R. Sleeps 8 hours
(2)2005 FJR1300abs:  230,000 m
2015 FJ-09:  106,000 m (Lost compression in #2 Cyl.)

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That won't affect compression damping. It's not adjustable...only rebound
Sometimes rebound will also tweak the compression. Not sure on this models forks though.  
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2015 FJ-09, Seat Concepts seat cover and foam, Cal Sci medium screen, rim stripes, factory heated grips, Cortech Dryver tank bag ring, Modified stock exhaust, FlashTune with Graves fuel map, Cree driving lights, Aux power socket.
2012 Street Triple type R (Wifes)
2007 FJR1300 (Sold!)
 
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Changing oil weight will alter both the compression and rebound damping. A heavier oil will be more difficult to squeeze through the ports, and a lighter oil will flow more easily giving less damping effect.
 
 
This-----^
 
Increasing the fork oil level will change the compression characteristics as well.
 
You could switch to 5, 7, or 10 wt oil to I change the damping. I believe the 01 suspension oil Yamaha calls for is equivalent to around a 2.5 wt oil as you mentioned
 
HTH
-Skip.
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Changing oil weight will alter both the compression and rebound damping. A heavier oil will be more difficult to squeeze through the ports, and a lighter oil will flow more easily giving less damping effect.
I was under the impression that the left fork has the compression valving and the right fork has the rebound valve with the adjuster on top.  If this is the case then a lighter weight oil in the left fork would only effect the compression damping.  The trick will be to find a truly less viscous oil as oil weights across brands are not consistent.  Does anyone know what brand of oil is in the FJ-09 forks or who makes the forks?
2008 Street Triple G
2015 FJ-09
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My Yamaha tech called the original oil Yamaha 01. I looked it up and it is 3.45 weight as I mentioned in my first post. I am considering going to 2.5 weight.
2015 Matte Grey
Modded stock exhaust, modded stock screen, modded stock seat, OEM heated grips, LED indicators, FlashTuned ECU, ZX10R shock
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My Yamaha tech called the original oil Yamaha 01. I looked it up and it is 3.45 weight as I mentioned in my first post. I am considering going to 2.5 weight.
I am really interested in your results.  I did thicker oil in my Tiger 1050's rebound leg to good effect.  Please post the details when you do the mod. 
2008 Street Triple G
2015 FJ-09
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Well, Yes and No. Yamaha Motor USA states that 01 KYB oil is equivalent to a 2.5 weight, and the internet (including various boards, spectro oil charts, etc) says 3.45 weight. KYB is really the only one who knows what the weight is... and they don't provide that information.  
Regardless, we are splitting hairs... I think we will have to agree to disagree - on the actual weight of the 01 oil. Because we could start debates about temperature, ways of measuring, etc.
 
The point of this discussion (I think) is that you asked: will it make a difference switching to a 2.5 weight (from stock 01 weight) oil? My answer is: NO. They are too close in weight (depending on measurement, temperature, riding etc). 
 
IMHO, if you really want to experience a difference and make the change worthwhile, you need to switch to as close to a  -0- weight as you can find or go the other side of the spectrum and switch to a heavier, ie 10 weight equivalent oil.  Stick to one brand so that you are comparing weight numbers that are similar.
This will make a difference you can FEEL when you ride and won't confuse the picture if you switch fluids several times.
 
Regarding just "dumping the oil and installing the correct quantity" question? Not the right way to perform this procedure, again IMHO.  Drain the forks upside down for a set time (10 minutes is probably ok) and completely empty the inner chamber of the old oil before draining. Refill with a quantity close to specification (because the fork is now "wet" and not in a total disassembled state) and set the oil level accurately using a proper fork oil level gauge.  
 
-Skip
 
 
 
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