Fork oil height for 2001 sv650

[Patrick Mullen]

With race tech cartridge emulators and springs.

I can't find my shop manual for this bike, and along with it my notes. What is the proper fork oil height (distance from top of fork oil to top of fork tube with springs and emulators removed and forks fully compressed)?

15W oil, right? Or is it 20W?

This is for a street bike that I like to take on spirited rides but the wife rides more sedately.

Race list included because these forks went direct from the track to the street, so that setting isn't far off.

Thanks,

Patrick

[Patrick Mullen]

In reality, it doesn't matter how you measure it, as long add you're consistent. 

Patrick

On Apr 24, 2014 12:45 AM, "Jo Rhett" <jor...@fastlizardracing.com> wrote:

When I had that setup I found that I had to change back and forth between 10wt, 15wt, and 20wt depending on the weather and the ride.

I may be wrong, but I believe that measurement is fully extended not compressed. Given how often I was changing oil we learned to do it without pulling the forks, and we were using the same measurement.

--
Jo Rhett
+1 (415) 999-1798
WERA West #553

[Milktree]

On Thu, 24 Apr 2014, Patrick Mullen wrote:

> In reality, it doesn't matter how you measure it, as long add you're
> consistent.

Um... that's true, so long as you've got a sane starting point.

For example, "135mm from the top with forks compressed" is about what
I'd expect in an SV. That's about 250mm from the top with the forks
extended. "135mm from the top with forks fully extended" will be
*completely unridable*, and might not even be possible to assemble
since I expect the spring will displace enough oil to overflow the
forks. Not to mention it's a lot harder to measure, since you have to
hold the fork legs up at the same time.

Every manual I've seen, ever, says to measure the oil height with the
forks fully compresses, and the springs removed. The RaceTech
instructions say to measure with the emulators in place.

Remember, when you measure oil height, what you're *actually*
measuring is the free space above the oil, you're attempting to
approximate the amount of *air*, not the ammount of oil.

It's the air that will provide the final, highly progressive, spring
that makes the suspension not bottom. Oil height, so long as it's
above the top of the damper rod or cartridge, is completely irrelevant
to *damping*, it only matters for bottoming resistance.

If you use a heavier (actual weight, not spring rate) spring, you need
to use less oil, becase the spring takes up more space. If you use
PVC instead of steel or aluminum for a spacer, you need to use less
oil, because the PVC takes up more space.

-Will

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[Patrick Mullen]

Thanks for the measurement and the clarification on having the emulator installed during measurement.

I'll use that and adjust as necessary, but given this is a street bike, what I'm probably saying is I'll put it there and never touch it again.   :-)

Thanks,

Patrick

[Milktree]

a bunch of years ago I was curaious, and did some measurements:

PVC vs. steel/aluminum/OEM spring spacer:

http://mahonkin.com/~milktree/hawk/spacer-047-s.jpg

If you use PVC instead of a thin spacer, you should reduce the
oil height by 2.7mm for each cm of spacer.

Note that the above numbers only apply to 41mm forks (Hawks and SVs).
You have to do the math yourself for forks with a different I.D.

-Will

On Thu, 24 Apr 2014, Patrick Mullen wrote:

[Ravi Inthiran]

When Jim did my RT emulators and new springs for my 182 lb weight, I believe we used half-10wt and half 20-wt to get to 15 wt for street riding. Jim, correct?

Ravi

On Thu, Apr 24, 2014 at 7:56 AM, Milktree <milk...@mahonkin.com> wrote:

a bunch of years ago I was curaious, and did some measurements:

PVC vs. steel/aluminum/OEM spring spacer:

http://mahonkin.com/~milktree/hawk/spacer-047-s.jpg

If you use PVC instead of a thin spacer, you should reduce the oil height by 2.7mm for each cm of spacer.

Note that the above numbers only apply to 41mm forks (Hawks and SVs). You have to do the math yourself for forks with a different I.D.

        -Will

On Thu, 24 Apr 2014, Patrick Mullen wrote:

Thanks for the measurement and the clarification on having the emulator
installed during measurement.

I'll use that and adjust as necessary, but given this is a street bike,
what I'm probably saying is I'll put it there and never touch it again.
:-)

Thanks,

Patrick

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[Milktree]

On Thu, 24 Apr 2014, Ravi Inthiran wrote:

> When Jim did my RT emulators and new springs for my 182 lb weight, I
> believe we used half-10wt and half 20-wt to get to 15 wt for street riding.
> Jim, correct?

Be careful when you do this.

- oil "weight" as printed on the bottle is a terrible indicator of
actual viscosity. Different brands can have vastly different
thicknesses for the same nominal weight.

For instance, Bel-Ray HVI 5wt is 19.5 cSt, but Showa SS-15 is 20.07
cSt. (cSt is for "centistokes", a very good unit of viscosity)

Another example: PJ1 Fork Tuner 2.5 is heavier than Ohlins fork fluid
10wt)


The other lesson here is, if you're using oil weight to tune your
suspension, make sure you either stay within the same brand/product
line, or know the actual, real, measured viscosity.

Here's a chart:

http://mahonkin.com/~milktree/motorcycle/oil-weight-script/oil-weight.pl

- mixing different brands of oil can have disgusting results. I mixed
PJ1 and ... I forget what the other one was, because I was short and
needed to make up the difference. The result was this grey snot that
was a pain in the ass to clean out, and the damping was all wrong.

If you're going to mix oils, use the same brand and line.

Red Line oils are designed to be mixed, so you can tune exactly to the
weight you want. But RedLine oils are kinda spendy, and probably
overkill for a damper rod suspension.

I try to use oil with a high Viscosity Index; the higher the index,
the less it'll change viscosity as it heats up. This is a *huge*
problem with shocks, internal temperatures can get over 150F, it's a
big enough problem with cartridge forks that I make an effort to get
good stuff, and less of an issue with damper rod forks. Let price
point be your guide in that realm.

-Will

>
> On Thu, Apr 24, 2014 at 7:56 AM, Milktree <milk...@mahonkin.com> wrote:
>
>>
>>
>> a bunch of years ago I was curaious, and did some measurements:
>>
>> PVC vs. steel/aluminum/OEM spring spacer:
>>
>> http://mahonkin.com/~milktree/hawk/spacer-047-s.jpg
>>
>> If you use PVC instead of a thin spacer, you should reduce the oil height
>> by 2.7mm for each cm of spacer.
>>
>> Note that the above numbers only apply to 41mm forks (Hawks and SVs). You
>> have to do the math yourself for forks with a different I.D.
>>
>> -Will
>>
>>
>> On Thu, 24 Apr 2014, Patrick Mullen wrote:
>>
>> Thanks for the measurement and the clarification on having the emulator
>>> installed during measurement.
>>>
>>> I'll use that and adjust as necessary, but given this is a street bike,
>>> what I'm probably saying is I'll put it there and never touch it again.
>>> :-)
>>>
>>> Thanks,
>>>
>>> Patrick
>>>
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>>
>>
>>
>>
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[Ravi Inthiran]

Thanks for the good info Will. I think we did use the same brand, or perhaps we did find 15-wt oil. ... My memory really isn't that great. Jim?

...but at least now I have an excuse for the couple times I've went down, IT"S THE OIL IN MY FORKS - I BLAME JIM!! :-) (used to use cold tires as my excuse).

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[Jim Stewart]

On 4/24/2014 8:09 AM, Ravi Inthiran wrote:
> When Jim did my RT emulators and new springs for my 182 lb weight, I
> believe we used half-10wt and half 20-wt to get to 15 wt for street
> riding. Jim, correct?
>
> Ravi
>

Hi, Ravi -

Nope. We used 20 wt fork oil. Same as I use in my own forks.

-js

[Jim Stewart]

On 4/23/2014 5:14 PM, Patrick Mullen wrote:
>
> With race tech cartridge emulators and springs.
>
> I can't find my shop manual for this bike, and along with it my notes.
> What is the proper fork oil height (distance from top of fork oil to
> top of fork tube with springs and emulators removed and forks fully
> compressed)?
>
> 15W oil, right? Or is it 20W?
>

20 wt. fork oil is what Race Tech specifies, and I've always found it to
work well. SV racebikes often are set up with 30 wt, but that's too much
damping for the street. Remember, you can adjust the compression damping
with the screw in the emulator, but the only way to adjust rebound
damping is with oil viscosity.

As for the level, Will has covered it already. A few more thoughts, though:

You don't really care how much oil is there, it's the amount of trapped
air you want to adjust. But you get a comparative indication by
measuring oil level.

Level is measured with no springs or spacers, emulators in place, forks
fully compressed.

But the level depends on the springs and the spacers since they both
displace oil. I use PVC spacers and cut-down springs in my bike and most
of the installations I've done for other people's SVs. The cut down
springs displace less oil, while the PVC spacers with thick walls
displace more.

I can't suggest oil level because I don't know what springs you have.
Mine is set at 139mm, but yours will be different because I weigh more
and have stiffer springs than you probably have.

I discuss the subject at some length here:
http://www.strappe.com/suspension.html

You're going to have to test your setup yourself. Put a zip tie on the
fork tube and go do some stoppies. You want maximum fork travel short of
bottoming out.

-js