These bikes, particularly on the engine, employ rather soft cross-head screws and bolts which are usually very reluctant to come out after being in place for 30 years or more.

 

For a number of reasons, the cross in the head invariably strips, leaving you with a major problem to get them out.

 

The first reason for this is revealed by the tiny dot stamped on the head of the screw.

These are not standard 'Philips' cross head screws; the dot indicates that they are JIS ( which may mean Japanese Industry Standard?).

Correct JIS screwdrivers are available but you really have to hunt for them. I have not seen JIS screwdriver Bits available anywhere.

Under no circumstances should you use Posidrive screwdrivers on these screws. The Posidrive cross head is a completely different form.

You can most times use a Phillips type driver after hammering it into the screw head (but I didn't tell you that ;-) )

Only resort to an impact driver in the last extreme. Most times an impact driver will just finish the job of stripping out the cross.

 

The second reason is simply age and corrosion.

Like most things that have been firmly fixed in one place for a long time, they get stuck.  Impacting them with a hammer can usually help, sometimes some heat will free them. In some instances, the head will need to be drilled off and a stud remover used once the remainder of the screw becomes visible.

 

Replacing the OEM screws with stainless steel.

 

This is a great idea as long as the following precautions are taken.

 

The threads on all stainless steel bolts and screws are very rough. No matter what material you are screwing them into, it is imperitive that you use an anti-seize compound on the threads.

This especially applies when fitting them into alloy. It is supremely easy to ruin the threads in the alloy if you don't use a compound here.

 

The other main reason for using a compound is to keep the alloy and the stainless apart. The two dissimilar metals cause an electrolytic corrosion in the presence of water if they are unshielded and this can literally turn the threads in the alloy to dust!

 

For obvious reasons, that means a COPPER based, not an aluminium based compound.

 

Obviously the OEM torque figures will not apply to these fixings with the anti-seize on them!

 

Most mechanics will replace the crosshead screws with Allen socket heads. That's fine and a good choice unless you are doing a 100% restoration, but the combination of the anti seize compound and the extra leverage given by the Allen head socket keys means that it is very easy to strip the treads out.

Carbs and other parts that use pot metal (zinc/aluminium alloy; trade names MAZAK, ZAMAK) castings are particularly prone to losing their threads.

 

SO TAKE IT EASY WHEN USING THESE!

 

In our carburettor rebuilds, we have turned to button head socket screws since they use a smaller Allen key, thus limiting the torque somewhat, plus they look more OEM than the standard Allen socket screw.