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Jawa forks and gaiters

Jawa forks

This article is about Jawa forks and came about as I decided to replace the early chrome bottomed forks on a 634 combo with later alloy bottomed forks from a 632.

The first lesson is to look after your forks by checking that there are no splits in the rubber gaiters. Look very carefully - both my “new” forks looked to have perfect gaiters when in fact both were split. If water enters the gaiters then you are in for big trouble as it will not drain out. There will be rapid rusting inside the gaiter (see picture below).

The stanchion is totally covered with wet rust. Lesson 2 is to check the black coating on the fork bottoms. You can see from the picture (left) that when damaged, water gets behind the black paint and the alloy oxidises to a white/grey powder. It is possible to remove this and polish up the alloy but it is a long job and will never look pretty or smooth unless powder coated.

Lesson 3 is to check that any steel bolts and screws into the alloy do not seize. Remove them periodically and after cleaning the thread refit with a coating of copper based grease on the thread. If the bolts seize then they are likely to break off, as has happened in the lug nearest to us. Yes that broken stud can be drilled out or spark eroded but it is another difficult job needing an engineer or some serious DIY equipment. So, the fork leg shown in plate 1 was fit only for the scrap bin. I managed to save just 2 parts – a plastic spacer and a metal breather plug.

One comment on my old forks – the fork nuts still had the black plastic transit bungs in the breather holes which should have been removed when the bike was prepared for the road in 1980.

Next let’s look at the fork gaiters:

Two different gaiters both from the later alloy bottomed forks.  The top gaiter has the same size holes top and bottom and needs a plastic spacer to ensure a snug fit with the stanchion.  It had a metal breather plug.  The bottom gaiter from a 632 had the hidden split and the top hole is smaller at 36mm to fit the stanchion without the need for a spacer.  The breather hole takes a plastic breather plug.  Both gaiters will fit these alloy bottomed forks but you need the top spacer (part no 638-41-051) for the top one. The spacer or “ring” as described in the 638 parts book is not supplied with the gaiter so retain it when you chuck your old gaiter.  Whatever gaiters you fit ensure they are secured top and bottom with a circlip or even a tie wrap.  It pays to lift the gaiter periodically and check there has been no water ingress and the condition of the fork stanchion.  You can also see if the fork seal has been leaking as fork oil will be present.  With these new forks I am considering injecting some Waxoyl rust proofer or maybe spraying inside with chain lube or WD40.  I think I will probably use chain lube.

Jawa fork gaiters

To use the later 36mm forks you have to also use the later top and bottom fork yokes which are a straight swap for the old items.  That gives you the opportunity to check the head bearings and the cups and cones for any pitting, replace any suspect ball bearings, add new grease, reassemble and adjust.  Do not forget to refit the plastic shields that protect top and bottom bearings from dust etc.  

Before fitting the yokes I cleaned out the holes that the fork stanchions will slide through and used some spray grease prior to inserting the fork legs.  

I understand that only the gaiters with different sized holes are currently available as spares from Mick Berrill.  These fit the 12v CZ Model 472 350cc machine.

It makes sense to find out what new/used parts are available before you scrap any old parts.  Fork nuts for the alloy bottomed 36mm forks are also not available so if you are using your existing nuts to bash down on to remove your fork leg beware.  Damage to the thread can occur and then you are stuck.  Fork nuts for the chrome bottomed 34mm stanchions are available still and are supplied with fitted rubber O ring seal and the transit plugs in place!

By Pete Edwards

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