TELEDRAULIC TECHNICAL..........................
Associated Motor Cycles fitted their own form of tele front forks to AJS and Matchless motorcycles for over two decades. Martin Peacock puts the bounce back into his G80’s front end…
Associated Motor Cycles fitted their own form of tele front forks to AJS and Matchless motorcycles for over two decades. Martin Peacock puts the bounce back into his G80’s front end
Matchless introduced their telescopic forks quite early with the model G3L in 1941. This was considered the first front suspension innovation in 25 years and was much appreciated by dispatch riders at the time. The ‘ Teledraulic’ fork was modified over the years with changes to external elements such as the brake anchor points and drain plugs. Triple rate main springs and buffer springs were added in 1947 and the stanchion diameter increased from 11/8” to 1¼” in 1955.
Production continued with numerous detail changes until the introduction of Norton Roadholder forks for Matchless and AJS road bikes in 1964. Teledraulic forks were retained for the competition bikes, including forks from the trials model used on the G85CS to reduce weight. These and other changes over the years are described in Roy Bacon’s ‘Matchless and AJS Restoration Guide’ for post-war singles and twins. Also, consult the manual for your bike and available literature, especially an illustrated parts list. Most of the manuals, parts lists and guides include a diagram but they are of variable quality.
The Teledraulic fork has a deserved reputation for good performance and reliability, provided occasional oil changes were carried out. Even so, wearing parts such as oil seals and bushes will eventually need renewal and the forks will benefit from an overhaul. This guide is based on the later type (1961) used on my Matchless G80. Stripping and refurbishing the forks is reasonably straightforward. The main challenges can be freeing them from the yokes and separating the sliders if the years and corrosion have taken their toll. The only special tool generally needed is a draw bolt to refit the fork legs, which can also be helpful for removing them.
THINGS TO CHECK FIRST
You may be able to stop minor leakage from the seals by tightening the slider extensions. These sit on the oil seals and this may at least buy you some time. Similarly, a stiff fork action may be due to a mismatched or badly fitted mudguard bridge putting side strain on the fork legs. Check for this by loosening the bridge and checking the fork action.
Support the bike on a lift or on its centrestand with blocks under the crankcase. Attempt to move the fork legs back and forth to detect wear in the bushes. Make sure any movement is not due to play in the steering head bearings. You can check the bushes separately after removing the front wheel and mudguard, but there is no point in overhauling just one fork leg.
REMOVING THE FORKS
Clean off any accumulated road dirt and oil from the forks, wheel and mudguard. Drain the oil from each fork leg by removing the drain screws at the bottom of the sliders. You can speed this up by moving the sliders up and down. Alternatively, wait until the forks are out and simply pour the oil out. This is a good option – I have found there is always oil lurking in the fork after draining and ready to come out to make a mess exactly where you least want it.
Make sure the bike is well supported with the front wheel off the ground and then remove the wheel and mudguard. This is easier if you first move the mudguard up, clear of the studs and then rotate the sliders so the studs are pointing outward. Then lower the mudguard about half way and rotate the sliders back to pull it all the way out.
Loosen the top cap screw and then the pinch bolt on the lower yoke in turn for each fork leg. Give the top caps a sharp tap with a soft-faced hammer to free the stanchions from their tapers. If this works, breathe a small sigh of relief and unscrew the top caps completely. Unscrew the damper rods from the top caps and then pull the stanchions down, through the lower yoke.
In the likely event that a sharp tap or two fails to free the stanchions, don’t resort to more force as this will damage the threads. Unscrew each top cap fully, release the damper rods and then use a drift fitted to the stanchion’s outside diameter to allow a serious clout or two. Once the tops of the stanchions are loosened, pull them down through the bottom yoke. Corrosion can occur on the stanchion under the top covers which carry the headlamp mounting brackets. This might make it necessary to twist and pull the stanchion a little to ease it free. If necessary use the draw bolt tool, carefully, to tap out each stanchion incrementally in turn.
If the corrosion build up is severe, you may need to undo the steering head and remove the stem complete with the forks to allow removal of rust and scale from the stanchions. Make sure you collect all 56 of the 3/16” steering head ball bearings if you do this. Removing the steering stem and bottom yoke will also release the top covers and headlight which can otherwise be left in place for the fork overhaul. In either case, the rubber buffers should be checked and renewed if they are perished.
Lift off the bottom tube covers. Some early versions are secured by small screws at the bottom of the covers, accessible only from the inside. You will need a long, thin screwdriver, torch and patience to remove these.
FORK LEG STRIP DOWN
Carefully clamp the bottom of the slider in a vice with soft jaws, preferably by the bottom cap studs. Lift off the main spring, check the leather washers fitted at each end of the spring. Replace them if they are damaged. In fact, plan to replace them and similar inexpensive parts such as the stanchion rubber buffers as a matter of course.
Remove the three rubber buffers fitted over the stanchion to stop spring chatter and then undo the chromium-plated slider extension. A strap wrench (or a pipe wrench well-padded to prevent scratching) is needed for this job. If this doesn’t work, heat the area at the top of the slider where it meets the extension and try again. Once the slider extension is undone, being careful with hot parts, take the slider out of the vice and grip the stanchion horizontally at its upper end to prepare for removing the slider. Move the alloy slider smartly to the extent of its travel on the stanchion a few times. Attach the end cap and wheel spindle for more purchase if needed. This should drive the oil seal out. If it doesn’t, heat the area at the upper end of the slider with a hot air gun or by wrapping it with rags soaked in boiling water. Repeat the process until the seal comes free. At this point, you can check the damping by pouring some oil into the slider and moving the damping rod up and down. If there is little damping effect, this may be remedied by cleaning all the parts before reassembly. Remove the damper assembly by undoing the screw at the bottom of the slider as follows: Hold the slider by the front mudguard tighten the vice just enough to hold it. Do not hold the slider itself between the jaws or you could cause erious distortion. The damping unit s retained by a screw through the ase of the slider. Undo this with a ¼ Whitworth box spanner filed to fit to the limited space around the hex aded screw or possibly a slim socket. Lift the damping rod and valve embly out and set the slider to one e. Next remove the fork bushes m the stanchion. Circlips above and ow retain the hardened steel bottom h. Once this is removed, slide out the er spring, upper (plastic) bush and oil seal.
PREPARE FOR REASSEMBLY
Examine the surface of the stanchion in the region where the plastic bush and oil seal slide during use. Severe scoring, pitting or ridges in this area will need to be addressed either by hard chroming and grinding back to size or replacement of the stanchion. Minor pitting can be filled with epoxy and rubbed down to a smooth surface. Check the stanchion for straightness (rolling it on a flat plate surface will do this) and clean off any corrosion on the upper part if the stanchion is otherwise in useable condition.
The sliders should not give trouble provided the oil is changed and doesn’t leak out. You can check them after refitting the stanchions by testing for lateral movement. Also, check the springs for any obvious problems, especially if the forks have been bottoming out or are too stiff on the road.
Remove the two damper rod sleeve retaining clips then strip and clean the damper assembly parts. If the quick test described above showed there was little or no damping, test again for improved damping. These parts generally to not wear but replace any parts that are badly worn or damaged.
Review your notes and have another good look at the fork parts after cleaning. Consult the parts list and diagrams. Now you have got this far, it is worth replacing the upper bushes, oil seal and sundry washers including the leather ones. Make sure you have the correct grade of fork oil on hand. Bronze bushes are available instead of plastic and were my choice, as can be seen in the pictures.
You can also replace the chrome slider extensions if they are in poor condition but I chose to have mine re-chromed at lower cost even though it meant a few weeks’ turnaround time. The bottom bushes generally do not wear unless they have been working without oil or, worse, with water in the fork.
FORK ASSEMBLY
Thoroughly clean all the parts including the threads. Replace any damaged studs and give the sliders a good polish if you like a bit of sparkle. Smear the parts with oil as they are fitted, beginning with sliding the oil seal up the stanchion, lip downward, from the bottom. Follow that with the top bush with its shoulder against the oil seal.
Now fit the buffer spring, circlip and collar, hardened steel bush and the bottom circlip. Check that the circlips are correctly seated in
their grooves. Make sure the drain plugs and the damper rod screws have new fibre washers, then refit the damper rod assembly and tighten the anchor screws at the bottom of the slider. Screw in the drain plugs.
Insert the stanchion into the slider and tap the oil seal lightly and evenly into the slider so there are sufficient threads exposed to start the slider extension threads. Screw the slider extension down so it pushes the seal into position. Apply a light smear of jointing compound on the thread to stop any chance of oil weeping.
Slide the three-rubber spring buffers on to the stanchion so they are evenly spaced. Coat the main spring with some grease and slide it down the stanchion. Make sure the more tightly wound coils are at the top. Check the fork action by moving the stanchion in the slider.
Fit each stanchion with their leather washers and bottom tube covers into the yokes, using a draw bolt to ensure they are fully home. Tighten the pinch bolts. Use a piece of wire or magnet to retrieve the damper rods and attach them to their retaining caps, fitted with new washers.
Fill each fork leg with the correct grade and quantity of oil and screw down the caps. Then replace the front mudguard and wheel. Make sure the head races are correctly adjusted and the fork legs are parallel so they can move freely. Check the drain plugs for leakage, then if all is well, put the kettle on and bask in the glow of a job well done.