SEBAC shock absorber help please

#1
I'm waiting on parts for my Hilltopper and decided to take the rear shocks off of the bike. Good thing too. They are the 60's/ 70's SEBAC coil spring type with the two sliding sleeves at the top. One shock has a hole worn in it from rubbing on the drive chain and other has both sleeves dry rot and broken.
I know the sleeves are like finding hens teeth, there just not out there.
I can hammer out the hole and fill it in with no problems.
The sleeves are another thing. I could install rubber boots?....Two pieces of PVC pipe?.... throw them out and replace the pair with something made today?
What have you done or seen done?
Please help if you can. I know how to take them apart.
shocks1.jpg

shock2.jpg

shock3.jpg
 
#2
I'm waiting on parts for my Hilltopper and decided to take the rear shocks off of the bike. Good thing too. They are the 60's/ 70's SEBAC coil spring type with the two sliding sleeves at the top. One shock has a hole worn in it from rubbing on the drive chain and other has both sleeves dry rot and broken.
I know the sleeves are like finding hens teeth, there just not out there.
I can hammer out the hole and fill it in with no problems.
The sleeves are another thing. I could install rubber boots?....Two pieces of PVC pipe?.... throw them out and replace the pair with something made today?
What have you done or seen done?
Please help if you can. I know how to take them apart.
View attachment 260127

View attachment 260128

View attachment 260129
I'd save them, the sleeves could be replaced. With a creative solution. It seemed I've seen some sleeve solutions in the past.
 
#3
It took the shocks apart which was not too bad to do. This is a desert bike so no salt water ever got to the aluminum end caps.
I used a very old pipe vice with little force to hold the tube and then headed the STEEL tubing and tapped around the threads with a 6 ounce brass hammer. Both shocks came apart with little effort. The fellow uses a step that is not needed. The nut on the shaft is 7/16" and can be reached by a 1/4" drive socket with no need to compress the spring! Both of mine unscrewed with little effort.
I then use my needle nose vice grips and pushed the dented steel tubing roughly back into shape. Then two mandrels were inserted into the damaged tubing and using a 6 ounce ball peen hammer, the dents were hammered out.
The rubber parts were placed in my heated ultra sound cleaner with a few drops of dish detergent and set to 180 degrees F. After two hours the rubber was back to normal being soft and pliable.
I then drained the US cleaner and refilled using hot water set to 200 degrees F, some soap and 6 ounces of citric acid. The acid will safely remove most of the rust. I'll let it run for several hours.
********
I'd love to find those sleeves. If anyone here knows of any,please let me know.
***********
shock5.jpg
This is a Three jaw pipe vice. With just a little force ( not enough to mar the steel ) It has one hell-of-a grip. The heated/tapped end came right off.

shock6.jpg
Needle nose vice grips pushing out the dent.
shock7.jpg
First shock apart. These sleeves are cracked as well.

shock8.jpg
This shock sat in the desert sun for decades. The plastic is so brittle you really can't touch it.

shock9.jpg
A 6 ounce ball peen hammer removed the rest of the dent and raised the surface a bit. I'll fill it in with either brazing or JB Weld.

shock10.jpg
Rubber bushings brought back to life.

shock11.jpg
Shocks sitting in heated,ultra sound acid bath to remove the light rust.
 
#7
Here's the result of three hours in the hot Citric Acid bath using my ultra sound cleaner. Every speck of rust is gone! No wire brush needed to leave scratches,no nasty cutting oils and Scotch-Bright pads. Tune the cleaner on and walk away.
This works and will not damage any part as long as you don't leave the parts in the acid bath for a week!
The black paint is now bubbled up and will wipe off with a little acetone or paint thinner. The acid reacts with the rust and leaves a nice protective coating on the surface of bare metal parts. I'll Cold Blue the steel parts and silicone coat them.

after cleaning.jpg
 
#8
I mixed up some 15 minute JB Weld and filled in the hole and the deep scuff marks and left it set up all night.
I then lathe turned the epoxy until it was almost even to the steel tubing and then used sand paper to bring it down to close to being flush.
Next was a Dremel hobby belt sander with a fine grit belt and took it down to a smooth surface.
I painted both shock bodies with a quality exterior paint.
repaired shock1.jpg Search

repaired shock2.jpg
 
#10
Yes, just citric acid. It is sold to clean automatic dishwashers. It comes bulk in a cardboard box as crystals from Amazon.
It does not hurt stainless steel. Place four ounces per gallon of water and heat to boiling or just below to keep *splatter down.
*It will leave white spots on your stove that will wipe right off.
I bought it for my hard-water spots on glassware from the dishwasher. You add a couple of table spoons full of the citric acid to the wash and it prevents any build up as well,and it really works well.
 
#11
The new Aluminum sleeves showed up today. The quality is first rate. I'm not sure if the sleeves were extruded or lathe turned, the machining marks on the inside would indicate a lathe or milling machine. They fit perfectly and were so well packed when shipped no damage could occur with normal handling.
The shocks, now repaired from the hole in the one, and removal of rust went back together in ten minutes. No big deal at all.
I threw them on the bike to see how the look,and they look good.
Here's some photo's:
Telescoping sleeves
shocksfixed1.jpg

shock fix2.jpg
Tool marks. These tubes are thin! Outstanding machining!

shock fix3.jpg
Almost back to new condition

shock fix4.jpg
The two sleeves interacting.

shock fix5.jpg
On the bike.
 
#12
Couple of questions , one on topic, another sightly off.

Do these replacement sleeves fit the Sebac shocks which are slightly smaller ie., tapered just above the bottom eye?

And is the citric acid safe to clean a carb? I'm still trying to get some of Tecumseh idle rods to rattle.
 
#13
If the spring retainers are the same, I would say yes.
Citric acid is safe on any metal for up to fours hours in a heated bath. At room temp much longer.
 

cfh

Well-Known Member
#15
on the carb question. i have an ultra sonic cleaner and i use it to clean vintage Dellorto carbs. the solution i use is "LA Totally Awesome", available at the dollar store. seems to work quite well. i would not use anything stronger on a carb.
 
#16
The new Aluminum sleeves showed up today. The quality is first rate. I'm not sure if the sleeves were extruded or lathe turned, the machining marks on the inside would indicate a lathe or milling machine. They fit perfectly and were so well packed when shipped no damage could occur with normal handling.
The shocks, now repaired from the hole in the one, and removal of rust went back together in ten minutes. No big deal at all.
I threw them on the bike to see how the look,and they look good.
Here's some photo's:
Telescoping sleeves
View attachment 260493

View attachment 260494
Tool marks. These tubes are thin! Outstanding machining!

View attachment 260495
Almost back to new condition

View attachment 260496
The two sleeves interacting.

View attachment 260498
On the bike.
well you have New shocks now, NICE ! work
 

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