Honda ST1300 Section > Suspension ST1300

reducing st1300 fork oil level - has anyone done this

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DavidP:
Hi all,

I am trying to reduce the front end harshness and have been doing a few changes to my 2008 ST1300.

So far I have put a 2.5mm thick washer in the forks to reduce static sag (5mm more to be added, as static sag is still 42mm with a mostly empty tank), and used thinner fork oil (6.7wt - really iso20), which has made it a bit smoother.  (both Shell and Castrol use the correct iso weights for their fork oils   :thumbs )

I have read that Honda seems to have compensated for the softer springs by using quite a small air gap above the oil (62mm).  After market spring manufacturers actually recommend 120-130mm fork oil level, and that is supposed to make for a smoother ride.

I know one of the reasons the fork oil level/air gap is there to act like a progressive spring and stop bottoming.  I only use 92mm travel out of 108mm total. This was with the zip tie method and 1500km of my normal running.  I weigh 85kg and if I put in another 5mm of spacers in the forks that should drop to 87mm (giving me 21mm of travel I don't use).  7 clicks  on the rear is about the correct preload for me (38mm sag without bike gear on, I have topped up the pre-loader & replaced copper washers)

My question to others, have you reduced your fork oil level, and did that improve the front end harshness? 

Guy at (ignore the part about fork brace) http://www.st-owners.com/forums/showthread.php?25399-ST1300-Forks  reduced oil volume by 50cc per leg (so should be 3-4cm less oil in each fork), but didn't really say anything about harshness.

DavidP:
anyone?
 :popcorn :popcorn

going to try it on the weekend

DavidP:
Well, here are the results after removing 40cc of oil from each leg (amazing how dirty it is after only 1 year/15,000km  :o ), and adding an extra 5mm of spacers (now 10mm all up, forgot I had 5mm in there already).  Fuel level in tank is about the same as before I did the changes.

Static sag is now 35mm (not quite level surface, so prob closer to 40mm), max travel used is 95mm (inc. on front brakes while hitting a speed bump, and quite a few rough roads).  That leaves 13mm for even bigger bumps.
I haven't detected any bottoming, but will know more after the QLD/NSW sulk's ride 2 up this weekend.

The front suspension seems to be a bit smoother and follows the road a bit better.   :grin
Harshness is reduced and I'm tempted to try even more air gap at the next fork oil change.  40cc of oil should be around 3 1/2cm increase in air gap, so current gap should be just under 100mm.

DavidP:
Update-
After sulks rte, 700km 2up (over 200kg) on various roads (Inc lots of potholes to Lennox heads, and  hard braking on highway) used max 102mm of travel.  That leaves 6mm for REALLY bad stuff. 

Sent from my C6603 using Tapatalk

warren:
I would like to know if you managed a sweet spot for your ST!300 front fork oil level. With the springs still in and attached to your bike what is the oil level you recommend? I really only want to top up or reduce the le el I have. I am unsure of what the level should be with the spings in. Does anyone know. my ride is very harsh and the oil measurement on the bike is 62mm. Help!

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