Preload Adjuster Distance

[Willsmotorcycle]

I was looking through the service manual and cannot find MM of travel for the preload, any chance some knows this or can measure: fully off/ fully on? Thank you in advance.

 

[Obo]

Assume you mean the distance the piston protrudes out to compress the rear spring?

 

[Willsmotorcycle]

I do indeed sir.

 

[Obo]

@dduelin got at least 9.7mm https://www.st-owners.com/forums/threads/st1300-pre-load-fluid-replacement.106715/post-1330528

Logic says it can't be more than 60% of the length of the preload body or it would fall out when fully extended.

Whatcha trying to accomplish? You've got stock shock and aftermarket spring correct?

 

[Obo]

This video appears to show the distance of a properly filled preload adjuster on a newly rebuild OEM shock, done by a professional. I've jumped it to the point as they are completing the computer pressure filling to bleed out the air in the unit. Sorry, no exact mm though.

 

[RaYzerman]

I don't know specifically for the ST, but typical HPA's have a stroke of 10mm. I may have an ST shock in my stash, I'll check tomorrow....

 

[Willsmotorcycle]

@Obo Thank you Jack, I just had to put in a braided line The line is exactly the same length as the OEM, but the fittings are longer, causing a repositioning on the shock side. Of course this means the line is not long enough... could use about 3". 6.1mm was all I was getting when I posted. I let it sit fully cranked for a few hours hoping for gravity bleed of air. I pulled the knob and refilled 5 or 6 more times and now have 8.1mm. For clicking reference that's no pressure for 6 clicks.

The good news was @dduelin had recommended flipping the lower shock bolt so as to not have to loosen the peg holder when servicing the shock... finally got done. Certainly wish I had done that last time. lol. Next time it will be easy peasy. As an aside, I was able to do this with the D/S tire still on, and what a great time to put on the Staintune cans, rumble rumble.

Thank you all,
Will

 

[Willsmotorcycle]

Whatcha trying to accomplish? You've got stock shock and aftermarket spring correct?

Yes, on the stock shock and aftermarket spring.

 

[Obo]

It may take a bit to bleed out the air, as you're experiencing. (Think brake bleeding....)

Is the I.D. of the new braided hose the same as the old? I'm just thinking about the volume of fluid displaced from the a reservoir & hose into the preload piston.
The piston has a fixed distance it can move but the reservoir and hose can only hold so much fluid. The braided hose *should* expand less outward, and hopefully no more in length than the OEM when pressurized. Being shorter may mean less fluid overall for the piston is all else is the same. (The old volume / pressure / area equations..)

 

[dduelin]

It can be finicky getting the last air out of the piston chamber and the hose but satisfying when preload resistance begins at 1 or 2 clicks. Key for me is to find a way to route the hose in the vertical, making it as easy as possible for air bubbles to rise all the way up and out the open end of the banjo bolt. If the shock is still in the bike (my Goldwing and BMW each use a version of the Showa preloader and I recently bled all the air in the GW's system). I have used a yard stick clamped to the bike's frame to make a vertical support for the hose. Another thing is to turn the adjuster in until resistance begins before cracking open and removing the banjo bolt/piston assembly. This pushes fluid down the hose, hopefully displacing air in the hose prior to opening the banjo. Use a syringe to fill piston chamber to spilling then tap the piston chamber repeatedly to dislodge any air up and out.