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Discussion Starter #1
So the title is a little misleading, I can't really call it an issue with the valves, but the problem stems from the valves.

In to my forks today. First time they have been down since I installed the Racetech valves a few years ago. The bike has started to feel a little loose in the front. A refresh is overdue, so I went in to replace bushings, seals and oil. First leg, no problems. Oil was pretty dark though. A little surprised by that. Second leg the oil looked even nastier. When going back together and bleeding the cartridge, I found I had no compression resistance. I can get the oil squirting out of the top for rebound, but no resistance at all when pushing back down with my finger over the rebound circuit hole. I also still get some air pulling up for the rebound circuit even after much more time bleeding than is normally needed. Bummer.


I had to leave for work, so I couldn't pull it apart again, but my thought is the o ring that seals around the valve must have deteriorated. That might also explain the nasty black oil.


I'll pull them both apart again tomorrow. Need to source some o rings. I have some, but that is probably my issue! They are hardware store o rings as I nicked the rings that came with the valves installing them. I probably need some specific type of rubber that will survive living in oil... Anyone know?
 

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What are the o-rings you used made of? You definitely want to make sure the material is correct, and there are several possible elastomers they could be -- some much better than others. I'd typically be inclined to get Viton o-rings if they can be had for that sort of application. Or check with Racetech and see what they use.

PhilB
 
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Discussion Starter #4
Yeah. Might need to order them. No idea what the rings I used are made of. They are black rubber... All I know. Probably black mush now. I got them at the renowned technical supply house of Taylor's do it center... Hey, they lasted a few years!


Viton is a safe bet. That's used for fuel systems.


I'll find the size and dig in tomorrow.


Phil! Too easy to call Racetech and ask! What the hell were you thinking???
 
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Discussion Starter #6
Busy day at work, so I haven't been back in to the forks yet, but I did dig up the o ring info.

Kidding aside, I did give Racetech a call. The guy at the extension I thought would have the best chance of answering my question gave me the verbal version of "blink blink" and promptly transferred me the guy who would know. That guy is apparently an answering machine who was happy to take my info, but has not followed up with a return call.

Anyway. Some research finds Buna N is an appropriate material for diesel fuel, fuel oil, greases, petroleum and mineral oils among others. That material is probably the most common and I was able to easily source a pack of 10 locally. Grabbed some more fork oil and I'm ready to see what's up. Could really be just as easy as some gunk causing the compression shim stack to stick open, but my money is on a failed o ring. I assume it failed because I used crappy o rings at install, but maybe I cut it pushing it in there (easy to do) and it eventually failed. The other side's compression circuit was working.

We'll see!
 

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Just Visiting Your Planet
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So, we all heading over to your house to watch you work on them? That would be a change. :D
 

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Mr Leakered
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Busy day at work, so I haven't been back in to the forks yet, but I did dig up the o ring info.

Kidding aside, I did give Racetech a call. The guy at the extension I thought would have the best chance of answering my question gave me the verbal version of "blink blink" and promptly transferred me the guy who would know. That guy is apparently an answering machine who was happy to take my info, but has not followed up with a return call.

Anyway. Some research finds Buna N is an appropriate material for diesel fuel, fuel oil, greases, petroleum and mineral oils among others. That material is probably the most common and I was able to easily source a pack of 10 locally. Grabbed some more fork oil and I'm ready to see what's up. Could really be just as easy as some gunk causing the compression shim stack to stick open, but my money is on a failed o ring. I assume it failed because I used crappy o rings at install, but maybe I cut it pushing it in there (easy to do) and it eventually failed. The other side's compression circuit was working.

We'll see!
While buna is rated for those applications, I have found that it will get soft and swell when exposed to engine oil and fuel. So IMHO, it is fine in a sealing environment, but may be problematic where parts are sliding against it, esp due to that softness aspect. Viton might be the better option. Also, flouroelastomer like FS70. They have been holding up just great at the oil cooler unions.

I've used buna o-rings for the fuel flange with no problem, other than they cannot be reused due to swelling, where the viton ones can be.

I would also think, like a lot of other stuff, not all buna o-rings are made the same. Some with a paper trail may hold up better than the ones in the buna kit from Harbor Freight. Haha!

Have a good one.
 

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Discussion Starter #9
So, we all heading over to your house to watch you work on them? That would be a change. :D
Bring sweat rags and beer!
 

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Discussion Starter #10
While buna is rated for those applications, I have found that it will get soft and swell when exposed to engine oil and fuel. So IMHO, it is fine in a sealing environment, but may be problematic where parts are sliding against it, esp due to that softness aspect. Viton might be the better option. Also, flouroelastomer like FS70. They have been holding up just great at the oil cooler unions.

I've used buna o-rings for the fuel flange with no problem, other than they cannot be reused due to swelling, where the viton ones can be.

I would also think, like a lot of other stuff, not all buna o-rings are made the same. Some with a paper trail may hold up better than the ones in the buna kit from Harbor Freight. Haha!

Have a good one.
It should be fine. Nothing here is sliding. These o rings provide a firm seal between the outer edge of the compression valve / shim stack and the inner surface of the cartridge tube. If they were to fail, the fork oil would be able to bypass the high speed shim stack short circuiting the compression valve. Swelling might be a bonus, unless it was bad enough to cause it to push out.

Generic pic, but this is a RT compression gold valve. You can see the o ring.
 

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Retired Pipe Polisher C2H6O+
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Remember that dohicky you had to drill out to get the original valve out of the damper tube? If there are any burrs left on the hole it will eat the O-ring when you put it back in. For what it's worth.
 

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Discussion Starter #12
Remember that dohicky you had to drill out to get the original valve out of the damper tube? If there are any burrs left on the hole it will eat the O-ring when you put it back in. For what it's worth.
Oh I do... That's why I ended up with crappy o rings to start with (went through a few of them)! What a PITA it is to get that part done!
 
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Mr Leakered
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Cool! It sounds like you have a handle on it.

I need to do the forks myself one of these days.

Have a good one.
 

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Discussion Starter #14
All fixed. Wish I could point to exactly what it was with certainty! O rings were perfect. Clean and still pliable. Not that I ever would, but they could have been reused. What I noticed was still a lot of black gunk in the cartridges and at the bottom of the fork tubes. When I dumped the original oil, I noticed it was pretty black. When I refresh fork oil, I use a QT of lesser quality (cheaper) fork oil as sacrificial oil and do at least two flushes with it. Normally I will use 1/2 QT per leg total. I had the flush oil coming out clear on both legs before I put the new (good) oil in.

The fork leg that was giving me the problem had a lot of gunk in the cartridge and on the compression valve. The only possibility, given the o ring was perfect, is the rebound check valve was not completely closing due to some sludge. That would let some oil through the rebound "ports" of the valve on the down stroke effectively eliminating the compression circuit. Probably would have worked itself out in one ride. In fairness to the bike, I needed to do a better job of cleaning the gunk out. There was much more of gunk than I have noticed any other time I've had forks apart. If not for the Racetech mod, I would not have been able to get it all out. OEM cartridges don't come apart without drilling the tubes like you would for the RT kit. All clean, everything works as it should.

 
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