PVC subtanks, 43mm kyb KX 90-94

It took me a little longer to get this posted because, well, i was embarrassed to show my previous rigging... but no more! I am proud of my work this time, and I want you all to see it so you have something to go by if you should attempt tackling this project for yourselves:thumbsup:

list of materials w/ prices to the best of my knowledge:

1" sch. 40 PVC tubing - 5ft for about $7

sch. 40 PVC end caps - $1 a piece, x4

1/4" plastic tubing - 10ft for about $3.50

1/8 npt x 1/4" tubing brass compression fittings - $2 a piece, x4

1/8 npt "tank valve" (schraeder bleed valve, like a tire fitting) - $2.50 x 2

1/8 npt female pipe coupler (female-female) - ~$8 for both

1/8 npt 1 1/2" pipe nipple (male-male) - ~$8 for both as well

1/8 npt x 1/4" tubing push-to-fit SMC 'flow valve' metered OUT - $5, x2


DeWalt drill, don't use crappy tools please... DeWalt or nothin':p

1/8 npt #27 tap - costs like $3

drill bit, i think 3/8"? maybe 7/16".. the size that corresponds with the #27 tap.

first, you need to remove the fork caps. It's no biggie just remove your bars, loosen your top clamps (but leave the bottom ones tight), and unscrew the big nut where the rebound adjusters are.

next, grab a tie-down strap and loop it through your front wheel and hook it on your lower clamp so you can sinch up your forks in a controlled manner. when you can get to the nut underneath the caps, youve gone far enough.. now get a wrench that fits onto that nut and hold it still while you loosen the cap using the first wrench.

take both caps off and get ready to get your hands dirty! This is what I did, but you can do it whichever way you so choose... usually people drill and tap the bleed off screw bigger to accept whatever fittings they use for the tanks, I beat to my own drum so I drilled a completely NEW whole opposite of the bleed screws. I'll tell you why: a 1/8npt fitting is pretty good size and if you centered with the bleed screw hole then you would blow through the outer wall where the threads screw into the forks.. NO BUENO. so you could either drill offset in that hole, yeah... right. good luck on that one.. or you could drill your own hole, that's what i did.

I drilled through the big nut and it's a close call because there are possible clearance issues if you get too close to either the center or the outer wall, so pay attention! Now just tap it with the #27, I opted to do it by hand because it's an aluminum cap and a drill could easily strip it completely. it's up to you really.

P.S. sorry i don't have any pics of the procedure! it's pretty straight forward, so don't worry it's easier done than put into words..

once they're drilled and tapped, you just need to install all your fittings! EEEAASSSSYYY.. in case you were wondering why on earth I wrote down the double male, and double female couplers it's because since you drilled so close to the wall of the nut there's no room to screw in your valve by itself, the couplers are there to raise the flow valve high enough that it will spin so you can tighten it down properly. I used a 1 1/2" pipe nipple, but in retrospect it's just way too damn long! 1" or even 3/4" would suffice..


now that you know how to drill and tap, go ahead and do it on all 4 of your PVC end caps. Then you need to cut your PVC pipe to length, I chose 5.75" because the math calculates it to around 75mL if it's a perfect cylinder, which it's not. the caps add another few mL so I was aiming for the 80mL mark and that's close enough for me! Next, just glue your caps onto your pipe using the snazzy purple glue stuff.


now, it's all about cutting your tubing and hooking it up to the various fittings, compression fittings STINK bigtime... if you can find them, opt for all push-to-fit fittings, your hands will thank you for it! The final step is just mounting them on your bike, I started out with them on my bars but it was kind of a pain and the way they were routed only one tank redrained, the other just collected oil..



I finally just ended up mounting them to my number plate on the outside of the forks, but this is also risky because of turning radius.. check for clearance! a lot of people mount them behind the #plate in between the forks, but if you have a bike like mine this is IMPOSSIBLE because of the lardass CDI back there hogging all the dang room!

I took a blade knife and sliced a small hole and threaded a hose clamp through it and i wrapped it around my fork and my tank at the top, then i zipped the bottom around just the tank and fork, i didnt go through the #plate with the bottom one.


oh btw, make sure you mount them upside-down with the tubing at the bottom, that way only oil gets sucked back up through the tubing. otherwise the oil will go in, and only air will go back into the fork... you still will have to redrain the oil completely back into the fork every now and again but it's not too bad.

The final product:





I hope that helps all of you trying to build these! please feel free to ask me whatever Q's come to mind. PM me for super specifics, I'd be happy to answer you to the best of my knowledge and resources:thumbsup::thumbsup:

And by all means post pics of your own! experiment with materials! Valves! tank sizes!

whats the benefits?

That last post got so long, I couldn't fit in my ride report..

I increased my fork oil from about 130mm to 30mm... idk if thats too much oil or not, but that's just where i started because it looked like a nice amount to add so that i could really FEEL the forks extra bottom resistance. And OH whatta increase in bottoming resistance it was!! I think it's a little too much oil because I cased it pretty bad on a 35ft camel hump-table top(not quite a 'double', just a tabletop with a cleft in the middle) and I checked the dirt line after i rode and i still had another 2.5" before a total bottomout! But even being that stiff, it never felt hard... like i wasn't bouncing off of stuff, it seemed normal except for the fact that i could hit pretty hard and not bottom them out like before.

All in all, I really liked them.. I think i spent around 80 bucks total in materials before i got the right stuff, like i started out with brass elbow needle valves but those stank. so i upgraded to the metered out SMC's because they meter flow in one direction, but freeflow back into the forks so that the air pressure is equalized and ready for the next hit.

I think I'm going to begin experiment with oil volumes and also the valve adjustments, ive only ran them full open and closed! i havn't even had the chance to run the valves partway yet..

whats the benefits?

They are so you can increase oil volume, to resist bottoming.. but maintain the same air volume on top so the initial stroke is still plush. it broadens the fork action, so it's still plush on fast, small hits, but doesnt bottomout on big jumps and hard hits.

Good job on getting some tanks on those forks.

I thought the point was to be able to run less oil for a more supple feel? I must have it backwards.

It was that or the same amount of oil with added air volume for incresed plushness.


Good job on getting some tanks on those forks.

I thought the point was to be able to run less oil for a more supple feel? I must have it backwards.

It was that or the same amount of oil with added air volume for incresed plushness.

yeah that works too, lol it's just a means of increasing either plushness or bottoming resistance without sacrificing the one for the other. there's MANY combos you could come up with! The flow valve adds another tuning capability as well, how fast you want air to flow into your tanks, while freeflowing back to the forks after the initial hit.

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