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audiowize

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On a short ride this week, I noticed a pretty serious rebound issue on my Penske 8900 shock, and ultimately found that the rebound adjuster had backed itself completely out when I had some time to stop and check it. When I attempted to adjust it back in, I ended up with no detents until it was all the way tight.

This is a shock that KFG Racing "rebuilt" last year, with less than 10,000 miles on it since, so I decided to go in a different direction to look into the issue: I enlisted the assistance of Escapefjrtist.

To get to the rebound mechanism, we started by disassembling the shock as far as you would normally go for a rebuild. We noted a fair amount of rusty crud in the shock, as well as a very worn out bushing. We ultimately discovered that the dowel pin that sits below the rebound needle/metering rod was broken in half and needed to be replaced. If you get into this pickle, here are some photos and notes to help you deal with the problem (there's nothing in the manual, and nothing on the internet that we could find until now).

20160611_122358_zpseoaapnfh.jpg


These parts will all look pretty familiar once the shock is opened up. The important points are that the spring retainer (brass disc with 3 holes) threads onto the shaft mount (brass piece at bottom of photo). One of its purposes is to limit the rotation of the rebound adjuster knob. To get the shaft mount off, loosen the jam nut first, then clamp the shaft carefully in a wood lined vise and hit it with an electric impact to back it off. Next, the knurled clear anodized rebound cap just sits on top of the red rebound adjuster knob with a tight press fit, and you can pop it off with your fingers or work it off with soft jawed pliers. With the cap off, you have access to the dowel (or what was left of it in my case) which rides against the detents of the adjustment knob and is held in place by the 150Psi of nitrogen in the reservoir.

20160611_122657_zps6v2efmm5.jpg


Bused dowel pin. George had a stroke of genius and recommended replacing this with stainless steel, which we were able to obtain fairly easily from Metal Supermarkets. We noted that on some diagrams, this O-ring isn't shown, though I do see it on the current online PDF (page 6).

20160611_145145_zpsj77dxwb4.jpg
While we were at it, I removed the metering rod and needle to clean all the rusty gunk out of there. I do not recommend removing the circlip to gain access to the jet unless you have a replacement available (it's 1/4", tiny!). Replace the seal on the needle if you have it out.

It can also be inferred from this process that the O-rings that are present around the rebound adjuster knob aren't doing a whole heck of a lot more than keeping dirt and debris out of those threads and possibly providing some extra resistance to rotation, so if you don't have replacements, that's not a huge deal breaker.

Broken dowel pin penske 8900, broken pin, broken rebound

 
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This one was interesting for sure audiowize. Although the shock was "rebuilt" last year, based on what we saw it got a oil change and maybe a fresh shaft seal.

While the investment in equipment and parts to rebuild shocks isn't cheap, knowing it's done correctly is well worth it.

--G

 
Great work, boys. That's some valuable forging into uncharted territory, right there.
thumbsup.gif


Before I sold the bike to my son, I noticed that the used Penske on my old '05 lost some of the first few detents on the adjuster, and that was also after a "rebuild" by KFG. but I was way too chicken to delve into it this far.

 
This one was interesting for sure audiowize. Although the shock was "rebuilt" last year, based on what we saw it got a oil change and maybe a fresh shaft seal.
While the investment in equipment and parts to rebuild shocks isn't cheap, knowing it's done correctly is well worth it.
Yeah, never giving GP another dollar. That bushing must've had over 40,000 miles on it, no bueno!

 
Paul and George, just wondered if a pipe wrench was involved in taking the shock apart? I hear that happens some times.
not_i.gif
And yes, right in the directions they make a point of saying not to tighten that top cap very much.

Thanks for the pictures and write up Paul.

 
This one was interesting for sure audiowize. Although the shock was "rebuilt" last year, based on what we saw it got a oil change and maybe a fresh shaft seal.
While the investment in equipment and parts to rebuild shocks isn't cheap, knowing it's done correctly is well worth it.
Yeah, never giving GP another dollar. That bushing must've had over 40,000 miles on it, no bueno!
GP Suspension and KFG are no longer the same company. I never gave KGF a dollar when it was using GP's name and reputation but would not hesitate to go back to GP now that it's original founder, Dave Hodges, is back in business.

 
This one was interesting for sure audiowize. Although the shock was "rebuilt" last year, based on what we saw it got a oil change and maybe a fresh shaft seal.

While the investment in equipment and parts to rebuild shocks isn't cheap, knowing it's done correctly is well worth it.
Yeah, never giving GP another dollar. That bushing must've had over 40,000 miles on it, no bueno!
GP Suspension and KFG are no longer the same company. I never gave KGF a dollar when it was using GP's name and reputation but would not hesitate to go back to GP now that it's original founder, Dave Hodges, is back in business.
Good to know Dave is back at it!

 
Did you contact KFG with your findings? I would be curious as to their response.
They didn't seem interested in having a second look at the shock, and after refusing to sell my a reservoir bracket (they said it woudn't fit my bike, but the one Fontaman gave me fits fine), I gave up on them.

 
Paul and George, just wondered if a pipe wrench was involved in taking the shock apart? I hear that happens some times.
not_i.gif
And yes, right in the directions they make a point of saying not to tighten that top cap very much.
Thanks for the pictures and write up Paul.
Not to worry Pops...no pipe wrenches were harmed working on audiowize's shock!

So far I've seen three variations of Penske shocks and reservoirs coming off FJRs (and a lone Tenere), probably related to age of the shock. Another order for o-rings and we'll have every possibility covered.

--G

 
I have had my Penske shock "done" by a local guy a couple of times. As far as I can tell, he only ever replaced O-rings and oil after a cleanup. The shock has around 130,000 miles on it and is leaking only a few months after it was last serviced. There really isn't anyone local where I can get this done and shipping across the border is a major hassle (and expensive).

I am thinking about have a go at this myself. Is this a bad idea for someone who is reasonably mechanically capable but inexperienced working with shocks? I was thinking that with this much mileage, it would probably be a good idea to replace O-rings, the main bushing/seal (I think is available as an assembly?) and possibly even the main shaft. (I have always used a shock-sock but there are fine scratches visible on the shaft the "might" be polished out but might not.)

Any thoughts? Anything else should be done?

What is needed in the way of specialty tools to do this? (I know I will need a zero-loss chuck and regulator to re-pressurize to 150 psi with nitrogen.)

Do you have a list of the part numbers you replaced this time?

Thanks

 
Ross - I have the list of parts that I purchased when diving into this rebuilding adventure.

Give me a couple days as I'm heading into work now and won't be home until late tonight. The big investment you're going to have is purchasing a small N2 cylinder and gauges, a couple Penske specific tools and the no-loss chuck you mentioned. The process is very simple, so yes, I would say you can tackle a shock easily.

We (the PNW gang) have rebuilt six Penske's so far. At $250-$300 each, I'll say our investment of ~$500 has paid for itself three times over already. Purchasing parts from Penske is very, very expensive. I sourced all o-rings through McMaster Carr and bushings through another party. With the miles you have on yours and based on my limited experience, you definitely need a full rebuild, not just oil and shaft seal replacement.

--G

 
Is there a description somewhere that defines what is (or should be) included in a "Full Rebuild"? I'm OK for the N2 cylinder, valve and gauge but I would need the no-loss chuck. I have seen these on-line for a pretty good price.

 
Is there a description somewhere that defines what is (or should be) included in a "Full Rebuild"? I'm OK for the N2 cylinder, valve and gauge but I would need the no-loss chuck. I have seen these on-line for a pretty good price.
If you order the rebuild kit from Penske, it should have all the parts required for a full rebuild. For whatever reason, the photo online doesn't show a bushing in the kit, but I believe that the kit Redneckj bought did have a bushing in it.

 
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