facebook1 youtube1 twitter1 instagram linkedin1 pinterest1

NOTICE:  If you are not a free registered member of the site, you will not see the photos in the forum, and you won't be able to access our premium member content. Please consider joining our community! REGISTER AND MAKE THIS BOX DISAPPEAR!

×

Pictures Posting Not Working (12 Jun 2023)

Picture uploads is again unavailable. We are working on the problem. Thanks for your patience.

Makotosun

Thermal Flow Shock Rebuild

  • tricky
  • tricky's Avatar Topic Author
  • Offline
  • Junior Member
  • Junior Member
  • Posts: 22
  • Likes received: 17

Thermal Flow Shock Rebuild was created by tricky

This is a post from another forum that I made regarding my '76 DT400 restoration, I thought maybe it could benefit some people here.

Just a disclaimer, this was my first time going through any shock, so some people more experienced then me may have some comments regarding my methods. Let me know what you think!

Thermal flow shocks, by all accounts an aggressively mediocre rear shock for the time period. But with the lower-end modern replacements upwards of 500$ for a pair, I think I'll do what I can to get these thermal flows back in order until I can afford to upgrade.

I currently own 4 pairs of thermal flows, all in different condition. I will probably go through all 8 to replace the seals and shock fluid.

So you know what I'm talking about, I got this pair of shocks off of ebay for $40 Canadian. The left one is after my first rebuild, the one on the right was the "before" condition

This image is hidden for guests.
Please log in or register to see it.



First thing is a good cleaning, I used blue scotchbrite and simple green. Then the tear down. I used zip ties to compress the spring, then its possible to remove the spring retainer from the top. Having another set of hands really helps.

This image is hidden for guests.
Please log in or register to see it.



With the spring off:

This image is hidden for guests.
Please log in or register to see it.



I simply disassembled carefully, and took note of where everything was. I used an adjustable pin spanner (for changing grinder disks I think) to unscrew the cap that holds the internals

This image is hidden for guests.
Please log in or register to see it.



More detailed cleaning, I used my ultrasonic cleaner with more simple green

This image is hidden for guests.
Please log in or register to see it.



To remove the seal from the cap, I used the same method I use for bearings. I used a sleeve anchor (3/8" maybe? Or 1/2"? I can't recall), passed through the top. Then I tightened the nut to expand the sleeve anchor to really grab the inside of the seal. Then, I used a punch to drive out the sleeve anchor with the attached seals.
Here is the seal out (still stuck to the sleeve):

This image is hidden for guests.
Please log in or register to see it.



Original seals are tricky to find. They were something like 23 mm OD, 12 mm ID and by my measure, something like 13 mm tall. Unfortunately, I worked off of incorrect info from the web and thought they were 15 mm tall. So, I ordered a pile of 23x12x7 and 23x12x8 from AVX Seals ( www.avxseals.com/ ).

So, here is me finding out the original seal is closer to 13 mm tall (the seal was slightly damaged leading to the 12.19mm)

This image is hidden for guests.
Please log in or register to see it.



My "7mm" seals measure around 6.9mm. So I decided to stack two of them to achieve something around 13.7-ish mm

This image is hidden for guests.
Please log in or register to see it.



So we are slightly over, by my measure about 0.6 mm. Not great, but hopefully it works. Unfortunately, AVX Seals only sell 7 or 8mm tall with this ID/OD combo.

With the new double seals:

This image is hidden for guests.
Please log in or register to see it.


This image is hidden for guests.
Please log in or register to see it.



Then I cleaned and painted the shock housing and spring (re-chroming the spring would be too much $$ for these shocks). I used Quick-Glo to polish the shaft. It had a couple of rough spots, but the polish helped to bring it into pretty good condition. I applied a light coat of grease. But, I think I'll have to keep an eye on the shaft to make sure it doesn't start rusting again.

And there we go, the finished product. Now, I think I will give the same treatment to my other 7 shocks.

This image is hidden for guests.
Please log in or register to see it.


This image is hidden for guests.
Please log in or register to see it.



All that's left is to fill with shock fluid (175 cc I believe) and put it on the bike and hope shock fluid doesn't spray everywhere on the first bump.
The following user(s) Liked this Post: mdscott, Dirtboy, Biker123, WAsage, NickM, Jake2020
10 Mar 2017 13:40 #1

Please Log in or Create an account to join the conversation.

  • Posts: 4575
  • Likes received: 2207

Replied by Makotosun on topic Thermal Flow Shock Rebuild

Looks like a good project. Given the cost of new shocks, and keeping the bikes as original as possible, this is a good solution.

The one that I had seen do this before machined the seal area a bit deeper in order to do exactly what you did, but if yours works . . . heh!

Thanks for documenting this!
IF it isn't one thing, it's another.
10 Mar 2017 13:44 #2

Please Log in or Create an account to join the conversation.

  • Posts: 1472
  • Likes received: 738

Replied by Scootern29 on topic Thermal Flow Shock Rebuild

Good job. I don't think you will have a problem with the slightly longer seal stack. Let us know how they work out.
Question authority, think for yourself!
10 Mar 2017 13:59 #3

Please Log in or Create an account to join the conversation.

  • Posts: 13386
  • Likes received: 9252

Replied by MarkT on topic Thermal Flow Shock Rebuild

Very nice work! Thank you for posting! :likey
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
10 Mar 2017 14:52 #4

Please Log in or Create an account to join the conversation.

  • tricky
  • tricky's Avatar Topic Author
  • Offline
  • Junior Member
  • Junior Member
  • Posts: 22
  • Likes received: 17

Replied by tricky on topic Thermal Flow Shock Rebuild

Cheers, everyone, I appreciate the kind words. I'll be sure to report back if there are any issues.

I remember reading this too, because I did a lot of research before doing this. That guy went to 24 mm diameter from 23 mm, I believe, and he said he used two 24x12x7.5 seals stacked. That's where I got the 15mm depth from, but it seems like either he was mistaken or they changed the design in some way.

I hope Scootern29 is right, and the extra little bit isn't an issue. If so, the seals are $1.62 USD each, which is a pretty sweet price. Here is the link
www.avxseals.com/ProductDetails.asp?ProductCode=TC12x23x7
The following user(s) Liked this Post: Makotosun, MarkT, RT360Fan, Steve F
10 Mar 2017 15:26 #5

Please Log in or Create an account to join the conversation.

  • Posts: 1472
  • Likes received: 738

Replied by Scootern29 on topic Thermal Flow Shock Rebuild

The only thing I can see that could be a problem would be the very top oring that seals the oil. A thicker oring would cure that though.
Question authority, think for yourself!
The following user(s) Liked this Post: tricky
10 Mar 2017 18:59 #6

Please Log in or Create an account to join the conversation.

  • Posts: 206
  • Likes received: 150

Replied by MACE6772 on topic Thermal Flow Shock Rebuild

I machined 1mm from the inside top of the cap. Then 2 AVX 23mm X 12mm X 7mm seals fit in and they sat just below the bottom edge, just like the original single seal. This allowed me to use a "stock size O ring. You can machine the I.D. of the cap to accept a 24mm O.D. seal, but I wanted to take as little metal off of the cap as possible. Also, I lightly sandblasted the springs and gave them 3 coats of black Plastidip SPRAY ( not the liquid dip) and 1 coat of clear. They look great but you have to delete the bottom black plastic sleeve as now it will not fit inside the spring. But with all that Plastidip you do not need it. Oem stock bushings- 1M1-22216-00-00 come up on Flea bay sometimes. OEM part # 275-22123-00 will work but needs to be narrowed to .782" to fit. Don't forget Part # 90106-10025-00, These are the slightly longer OEM shock bolts you will need for the top if you are installing a luggage rack.
I BUY THERMAL FLOW SHOCKS

Seal - AVX Part # TC12X23X7 www.avxseals.com/
76 Dt 125 75 Dt 175 75 Dt 250 75 Dt 400 09 FZ6R
The following user(s) Liked this Post: Makotosun, tricky, Snglsmkr, Jake2020, Le7316
Last edit: 21 Feb 2018 09:06 by MACE6772.
15 Feb 2018 10:34 #7

Please Log in or Create an account to join the conversation.

  • Posts: 169
  • Likes received: 115

Replied by Wessi on topic Thermal Flow Shock Rebuild

I like this forum, very helpful tips. Thank you for posting. Picking up this older post, I would like to add what I did to rebuild mine, so far. Not sure, if they finally will work, comments are welcome. Bought a pair of shocks on Ebay, they looked not bad on first view. At least the springs not too rusty, the rods not pitted. Disassembling them the disaster was visible. There was no oil anymore inside, just rusty crumbles. The Cylinder completely rotten, Piston worn, bottom valve on one shock is scrap. Rod was bend, no wonder looking at what´s inside the cylinder. But I didn´t want to buy another pair, to maybe face the same shit. Looking at all parts of the shocks and the chosen materials, they have not been constructed for long lifetime.




Last edit: 22 Aug 2019 12:26 by Wessi.
22 Aug 2019 12:13 #8

This message has attachments images.
Please log in or register to see it.

Please Log in or Create an account to join the conversation.

  • Posts: 169
  • Likes received: 115

Replied by Wessi on topic Thermal Flow Shock Rebuild

Also the caps of the shocks, where the sealing sits in, has a worn hole, not round anymore.
I bought a piece of Brass and machine on my Lathe a bushing to shrink in . The kind of Brass, used normally for bearings should do the job. At least better, than the soft Aluminum, used originally. For me, one oil seal is sufficient, a staple of two ones do not perform better from technical point of view.


22 Aug 2019 12:24 #9

This message has attachments images.
Please log in or register to see it.

Please Log in or Create an account to join the conversation.

  • Posts: 169
  • Likes received: 115

Replied by Wessi on topic Thermal Flow Shock Rebuild

same to the piston, which is totally worn and oval. I machined a ring of Brass, to shrink on. After, I made it to the origin diameter and re-bored the holes inside the piston, which all were totally blocked . Diameter 1.5mm


Last edit: 22 Aug 2019 12:32 by Wessi.
22 Aug 2019 12:29 #10

This message has attachments images.
Please log in or register to see it.

Please Log in or Create an account to join the conversation.

Moderators: yamadminMakotosunDEETVinnieJames Hart