What weight fork oil do you run?

Surprisingly, at only 45k, it looks like I've got a leaky left fork seal on my non-ABS '01 ST11 so I'm going to pull apart both forks. I think I'm going with 7.5 wt. oil but would like to hear what others are running with stock springs. I've read a lot on here but wt. info is a bit spotty. Appreciate any input and comments.

15wt, stock springs, 180 lb rider. 10wt is a good compromise between sportier feel and being too harsh, or a 10/15 weight mix if you want to go a bit stiffer. I came from the sportbike world so I like mine a bit stiffer anyway and the bike seemed to flick through the corners a bit better with 15wt.

One job I didn't do myself was bushings and seals on my 1100 Standard. Took them into a suspension specialist for the overhaul. I have Progressive springs, which I installed a few years ago. Upon picking up the forks, the guy told me to use a 10W-15 in the left fork and a 7W in the right. I put full synthetic fork oil of those grades in.

The technical reasoning behind the two weights mostly escapes me now, but each fork does a different job, as evidenced by a damping rod in only the right fork, so the different viscosities suit each fork's purpose better. The Honda manual does not make this distinction however, so I assume the functional difference is not really that viscosity sensitive.

However, I did use the different weights and I can't say it seems to make any difference.

10 wt with Progressive Suspension springs, 1991 non-ABS.

13 years and 45K miles... when's the last time you changed suspension fluid?

Wanna borrow the STOC fork seals R&R tool kit?

John

via iPhone 4S

Thanks for the info John. I've only had the bike for less than a year and put ~9k on it so far. According to the maintenance records I have, every fluid but fork oil has been changed at least once in the past 2 years. Looking at the dust seal on the leaking fork, it looks pretty old so it may have been a while since the fork oil was changed.

Yes, I would love to borrow that tool kit. Please advise. Does it come with a helper?

Stock original springs, I went with a bit more dampening, still utilizing the suspensions travel distance with 10w fork oil. The loss of damapening is mostly caused from years of oil being forced thru the dampening orfices, which over a period of time enlarges those orfices. The bit heavier oil viscosity compensates for that orfice wear. I advise NOT to mix specific vescosities together.

Thanks Brant. As I understand, the ST11 came factory with 5W oil? Is that true? Why not mix viscosities, especially when from the same manufacturer?

FWIW, in the past, I did a little experimental work with flow rates through orifices. Just breaking a sharp edge a few thousandths can make a significant difference in flow rate at a given pressure. Don't know how these orifices are designed but if there are any sharp edges in the flow path, and they get even slightly eroded, the flow rate could change significantly, making it operate like it had a lower viscosity oil in it.

With the stock springs I used 10W, with Hyperpro springs I'm on 7W; still firm but not causing sore wrists...

And I replace fork oils every 36Tkm/22,5Tmiles...

Had a short episode with Wilbers fork-springs, they suggest a 20W... feels like broom-sticks installed... tried with 10W then, no avail, suffered sore wrists... maybe nice on an absolutely flat race track, but definitely nothing for regular roads...

paulcb said:

.... Yes, I would love to borrow that tool kit. Please advise. Does it come with a helper?

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Sure, just send me a round-trip plane ticket.

To borrow any of the STOC loaner tool kits (register if you haven't already):

http://www.st-riders.net/index.php?board=15.0

John

via iPhone 4S

John OoSTerhuis said:

Sure, just send me a round-trip plane ticket.

To borrow any of the STOC loaner tool kits (register if you haven't already):

http://www.st-riders.net/index.php?board=15.0

John

via iPhone 4S

Click to expand...

Just registered. Waiting on approval. Thanks for the help John.

I have a RaceTech Gold Valve ( right fork ) & Emulator kit ( left fork - damping rod side ) with RaceTech non-progressive springs. With this kit RT recommends 15wt in the left fork & 5 wt in the right fork.

RT claims the stock springs are way too soft to compensate for harsh damping of the original OEM valving / damping piston. With the new RT parts, heavier springs can be used and you can still have a "plush, but firm " ride.

Check out the RT site for more info. on their valving & emulators. They also have a lot of good general suspension info.

Anyone have more thoughts on this? Still leaning towards 7.5wt for my stock 2001 ST11.

paulcb said:

Still leaning towards 7.5wt for my stock 2001 ST11.

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Don't know your riding terrain, style and road conditions... I think a 7W is a good compromise.

paulcb said:

Anyone have more thoughts on this? Still leaning towards 7.5wt for my stock 2001 ST11.

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If forks still have stock springs, leaning towards the 10w would be my option(Silkolene). Can see from your initial response to me, that you have a fairly good savvy of hydraulics, and flow characteristics. Remember too, that compression dampening is carried by left fork.

Brant said:

I advise NOT to mix specific vescosities together.

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Could you elaborate on your reason for giving that advice?