Fork Oil (stock damper internals)

[xlxr]

Go with Pattonme recommendations. No one has more experience. But the real trick to proper suspension set up is test riding and fine tuning based on your own experience. Using a full synthetic fluid that maintains it's viscosity over longer time periods is next important consideration especially for 2.5 W oils, but trying to find any good info on that is not easy.
 
Don't forget to get rider sag correct.
 
I weigh 270 in gear, 1.0 spring, Ohlins cartridges with compression side re-valved, Ohlins oil, I think??? 5 W, at stock levels. Next time I intend to try Amsoil 5w with additional 1/2 oz per fork to reduce fork dive a bit.

[pattonme]

put a zip tie on the right leg and once you and your front tire is warmed up, attempt your best ever stop on clean surface from say 30mph. If you can get to 12mm you're OK. If rather less, then add a little oil (say 10cc). A *rough* rule of thumb for a starting point is 25mm+travel so 137mm+25= 163. In https://fj-09.org/thread/4475/front-end-choices?page=2 I meant to type 160, not 150mm. For track use, a value toward 150 is better. 175 strikes me as a bit much and since you're using a thin oil, and the FJ is a more "relaxed" steed maybe start with 165 and see how you like it. But do the experiment first in stock guise to see where you're starting from.
 
Unless you're WAY off target (like 150mm with forks extended - don't ask me how but I've had a few people do this) then it's effects during typical street riding are overshadowed by main spring and oil flow.
 
Check your static and rider sag with the new springs. Your config is a tweener, 0.95 is a little firm, 0.925 is probably perfect, 0.9 is slightly soft.
 
 
PS. this leaving work at midnight from my day job, night after night is totally sucking. Tough to make any progress in the shop. Health seems reasonable, considering, thanks for the concern.
 

[koth442]

The Good: Was finally able to set preload with the new spring. After doing some scary hard braking (just short of stupid) with the front brakes, I got to about 15mm spare (before bottom-out). that was at one turn from fully CW. Also... the thin oil seems to have done a very, very good job at damping, especially at high speed. Going over train tracks, for example, is very smooth now. It was jarring before. Slow speed damping is also much improved, but the difference not quite as pronounced. I am very happy with my choice of spring and oil. Not a substitute for a good suspension, but will buy me time.
 
The Bad:
I have the rebound damping screw full CCW and feel that I should be able to improve the damping even more... but the rod is full out, so I believe that at 165mm my air spring is too short. I will increase that to 175mm and see if I gain usable range, and I can add a squirt in there if needed. I would like that sweet spot to be somewhere other than extreme CCW. Weather still dodgy... so now is the time.
 

The air spring length in discussion is the air gap right? If so, I'm not a suspension guru by any means, but I think rebound damping is controlled by oil viscosity, internal valving, and adjustment position. I don't see why the air spring length should matter. 
 

[pattonme]

Damping adjuster is 1-4 clicks from fully CCW... anything more than that and it becomes a bit firmer, so there's some range.

I'm going to assume you reset the needle adjuster before spinning the cap back onto the shaft. So even with thin oil (which helped with the Comp stroke) the OE rebound valving is rather too heavy. What are your sag values now?

[pattonme]

I would go back to 2 lines of preload. the reserve travel was just a hint as to suitable oil level and it shouldn't be used as a goal to alter preload and thus rider vs static sag. Right, on the XSR and I guess (some?) the FJ Yamaha elongated the coils a little bit to provide more built-in preload.

[madcat]

I followed the service manual for assembly, it calls to set the damping screw to a set position prior to assembly... and I do get the 14 clicks out of it. I had initially set the sag at 30% (2 lines in from full CCW), but then did the brake test with a zip-tie on the fork, and had to back off the adjusters. Spring feels good with just one full turn in from fully CCW. I have about 10-13mm of fork travel in 'reserve' after doing hard brake testing. Worthy note perhaps... the replacement spring is ~4mm shorter than stock. 
I started with the damping screw full CCW (one click in), and found that the bike floated a bit and wanted to go wide at speed. Went in 3 more clicks and it tightened up nicely. I've since done about 6h of moderately aggressive riding on some twisty roads (good and poor surface) and some long highway sweepers at 150kph, and the bike is behaving. I am super pleased with the outcome thus far. Riding is believing .

 
I am thinking of changing my fork springs too and would to know what you mean when you say the service manual calls for the damping screw to be set to a set position prior to assembly.