This low dollar backyard vacuum pump was constructed for under $25.00 U.S. I use it to do a front fork oil change on Road King’s and Dresser models, prior to the new cartridge H-D fork’s.
I installed a regulator on the pump so I could control how fast it sucks up the fork oil in the slider drain hole. It also let’s me shut off the vacuum without disconnecting the air line when all the measured fork oil is sucked into the fork slider’s.
So to use this gizmo you first drain the fork oil. The very first thing you do is: remove the schrader valve on the right side rear strut marked “F” for front!! This relieves the air pressure on the front forks. Failure to do this before removing the fork drain screws results in one big fucking mess all over you and your work area. You won’t have enough time to put the drain screw back in fork if you forgot to do this. The fork oil will be all over everything before you know it.
First you hook up the vacuum pump to your shop air hose. You now hook up the vacuum pump to the air valve marked front. I use a screw clamp on the end of the hose to secure it to the valve.
Look in the service manual for the front fork spec’s for the correct amount of fork oil for each slider. Pour the amount needed in a ratio rite. Let’s say for discussion it’s 9.7 oz. for one fork slider. Now you’ll need a clear chunk of hose with a nipple on one end. This goes into the fork slider drain hole. The other end goes into the ratio rite with the fork oil. Put one drain screw in the slider on the other side your not working on. You need to do this for proper vacuum.
Now all you do is turn on the vacuum pump with the regulator till you see the fork oil being sucked up the slider. When all fork oil is gone pull the clear hose from the slider, vacuum is still on, this keeps the fork oil from coming back out the drain hole when you pull the hose. Now in a timely fashion, screw in the drain screw, and turn the vacuum off. One side is now done and you’re halfway there.
Now your ready for the other fork leg. You handle it the same way as the other side. Get your fork oil measured out and pour it in the ratio rite. Keeping the drain screw for the fork you just filled screwed in. You remove the drain screw you put in, at first on the empty fork slider and install the clear tubing with the nipple into that drain hole of the empty fork slider. The other end of the clear hose goes into ratio rite. Now you turn on the vacuum pump like before and suck the fork oil into the empty leg. Again in a timely fashion pull the hose with vacuum still on, screw in the drain screw, turn the vacuum off. Your almost done now.
All that remains now is to pull the hose from the vacuum pump off the air valve. Screw in the Schrader valve . Now you just pump in the desired amount of air into the system using a hand air pump.
I like to use Screamin Eagle Heavy fork oil when I do a fork service on the big bikes. This all depends on a person’s riding preference though.
I also use the vacuum pump with the coffee can/soup jar contraption to bleed brakes. The pump provides the vacuum and the coffee can/soup jar serves as a reservoir to catch the access brake fluid being sucked through the brake system.
The pump, regulator, and various air fittings etc. can all be bought from Harbor Freight Supply for under $25.00. The coffee can and soup jar need no ‘splaining. You’ll also need a couple of metal air valve’s for the soup jar lid and some rubber vacuum line hose.
Now with all that money you just saved go out and buy some Twin Cam tools for doing cam changes. You might have enough left over to get some metric ball Allens sockets you need to work on that new V-Rod.
