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grayracer513

Fabricated Sub Tank setup

8 posts in this topic

Last October, JohnB posted regarding a sub tank setup he put together himself. The cool thing was that he had part source information and so on to go with everthing else. Here's the setup I built based on what I gathered from that thread.

Sub Tank

As you can see, I chose to use a single tank setup like Too Tech's. It works very well. It's the most noticeable over the smaller irregularities and up to mid stroke kinds of impacts, and it's rather like having a separate high/low speed compression adjustment on the fork. It does tend to soften the feel some even on the really big stuff, too, but perhaps not as much. The fork is much less harsh now than without the tank, and I haven't even played with the valves and clickers much yet at all. Well worth the $90 I spent, I think.

The air reservoirs are from Bimba. Look for them in the Original Line catalog under Air Reserviors. You'll need to find a distributor for them to order from. There's a list at the site.

The valves are flow control valves from Polyconn

:)

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Looks good...

I have a question tho. Why two Polyconn valves for one tank? I think by running a "Y" from the forks into one Polyconn valve should work. Then, on the other end of your tank, install the schrader valve. Yes?? - No??

With two valves, the air is being pushed into the tank and back out through the other valve. The valve would not be controlling the airflow. Maybe I got it wrong but it seems like it would be working against one another.

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Looks good...

I have a question tho. Why two Polyconn valves for one tank? I think by running a "Y" from the forks into one Polyconn valve should work. Then, on the other end of your tank, install the schrader valve. Yes?? - No??

With two valves, the air is being pushed into the tank and back out through the other valve. The valve would not be controlling the airflow. Maybe I got it wrong but it seems like it would be working against one another.

I thought about running a single valve, but the plumbing seemed like it would be messy, maybe not. I wanted the lines to have as few high and low spots in their runs as possible so that it would help the tank drain itself, as I noted. But I might try that on the 250, just for fun. I was also concerned about the flow capacity of each valve, and whether I might exceed it by using a single valve for both forks.

Each valve is going to meter air going into the tank based on the needle screw adjustment. Since both forks will be "sending" air to the tank at the same time, the volume exhausted from each should be pretty equal. Then, as they extend, the check valve within the flow control valve will allow air back to both forks freely, bypassing the needle. Again, since both forks act together, the common tank will do no more than balance pressure between the tubes. If they were independent, a single tank wouldn't work at all.

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yep looks good, but how is your oil drain? it looks like you might have a problem with your lines arc , so high. also how's your fitting holding up, no leaks?

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No leaks. I'll check for oil accumulation and see what that looks like after I get the bike cleaned up. Mud in the SoCal desert, who would have thought? :):)

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Looks good grayracer. Very clean. I'm curious, how sensitive are those Polycon valves? I made a subtank setup using Bimba valves and they are very sensitive to even small adjustments. 1/4 turn on the Bimba valves makes a very noticable change. Are the Polycon valves the same way? One other question: Did you have to tap your fork caps at an angle or were you able to drill and tap them straight? Also, did you tap them 1/8 NPT?

Here's my setup. I've been very happy with it on my 426. I'll be switching it over to my 450 one of these days.

img_4203_small.jpg

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I'm curious, how sensitive are those Polycon valves? I made a subtank setup using Bimba valves and they are very sensitive to even small adjustments. 1/4 turn on the Bimba valves makes a very noticable change. Are the Polycon valves the same way? One other question: Did you have to tap your fork caps at an angle or were you able to drill and tap them straight? Also, did you tap them 1/8 NPT?

That was one of the things that attracted me to them. When JohnB mentioned he was going to try them, I noticed in their info that the valves had a higher max flow rate, and appeared to have a longer curve of control in terms of number of turns from closed to any particular flow rate. They don't seem very touchy at this point. Another nice feature is that you can choose which direction the flow is controlled. I odered the valve reversed from standard to make it work better with my layout. That information is in the Polyconn pdf catalog on the page listing the valves.

I decided that I would need to angle the fittings slightly in order to clear the 19mm hex on the fork cap. One of them ended up tapped at very little angle but still clears. I think it's necessary to run the drill in at about 3-5 degrees, depending on the fitting you are going to use. They were tapped 1/8 NPT, yes.

Nice solution on your bracket, BTW. :)

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