WORKSHOP: OLD FORKS

Scoop looks at old style forks and shows us how to re­fur­bish them.

Classic Motorcycle Mechanics - - CONTENTS -

Scoop tack­les both his Yammy’s gammy legs.

Be­fore Ce­ri­ani came up with the idea of plac­ing springs in­side fork tubes the shock ab­sorb­ing el­e­ment of the front sus­pen­sion sat out­side of the stan­chions. Due to the ques­tion­able aesthetics of coiled steel and its propen­sity for rust­ing, the fork leg and spring were gen­er­ally cov­ered by some form of shroud, steel tub­ing or con­certi­naed rub­ber boot be­ing the nor­mal op­tions. Post Sec­ond World War tele­scopic mo­tor­cy­cle forks be­gan to fea­ture gen­uine hy­draulic damp­ing which ne­ces­si­tated some form of seal. Al­most with­out ex­cep­tion this seal was con­tained in a stand­alone, screw on, de­vice that was known by the highly novel term ‘seal holder’. No one to­day makes bike sus­pen­sion with seal holder forks and for good rea­son – see our box­out on p81. How­ever, in our classic world seal holder forks turn up with an­noy­ing reg­u­lar­ity and es­pe­cially so if your cho­sen steeds are pre 1975. All the Ja­panese play­ers ran this set up at one time or an­other and it took the man­u­fac­tur­ers quite some time to ob­so­lete their older ma­chines and move on to what we’d see as more con­ven­tional forks. Up on the ‘Work­bench of Op­por­tu­nity’ this month; are the forks from our Yamaha CS3C street scram­bler. All signs to date in­di­cate the 200cc twin led a short but hard life and I’ve lit­tle doubt as to when the fork oil was last changed – prob­a­bly never. Not want­ing to en­trust my lat­ter years to some­one else’s po­ten­tial bodges I’m strip­ping the forks down to their ba­sic el­e­ments and re­build­ing them. The MO may be a lit­tle more con­vo­luted than many might be used to with more mod­ern

ma­chines but the prin­ci­ples are still the same: check for wear/dam­age, re­place worn parts, fit new seals and keep ev­ery­thing clean. With a ham­mer and some duct tape to hand, no se­ri­ously, we’re strip­ping down a pair of forks that haven’t been apart since the lat­ter por­tions of 1969!

11/ The gaiters sim­ply pull off the lower leg along with the spring to re­veal the lower and up­per por­tions of the fork leg. The oily rust tells us ac­tion is def­i­nitely needed.

76/ Once free, the lower fork leg is turned off the seal holder; it’s a long, fine, thread so will take some time to undo. Make notes and/or take pic­tures of how each com­po­nent fits ready for the re­build. 7/ This is the up­per fork bush and of­fi­cially a ser­vice item. It will need check­ing for wear and dam­age. For­tu­nately it’s some­thing a de­cent ma­chin­ist can knock up if you need a re­place­ment and no one can sup­ply one.

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3Closer ex­am­i­na­tion of the thin­ner tube (the fork stan­chion) shows ev­i­dence of stone/grit/ sand dam­age by way of the long scar run­ning up the chrome plat­ing. Above this there are signs of some stunt mon­key dam­age with a pipe wrench. The black plas­tic mould­ing is the lower spring seat­ing bush. 3/ It might look mad but it works! Tap­ping the seal holder hard with a plas­tic mal­let loosens up the threads in­side. If there’s rust etc. heat and/or eas­ing fluid may be needed be­fore at­tempt­ing the next stage.

5It’s not as bar­barous as it looks, hon­estly! Four or five turns of good qual­ity duct tape will pro­tect the chrome per­fectly well. A de­cent, bench mounted, vice makes what’s com­ing next so much eas­ier. 5/ In­sert­ing a suit­able lever into the wheel spin­dle mount the lower fork leg can be un­screwed from the seal holder. Man­u­als may sug­gest us­ing a chain wrench on the seal holder but I’ve found it’s not that ef­fec­tive: this way you can add some se­ri­ous lever­age if nec­es­sary.

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