Yamaha FZ750 Restoration - The Shock Absorber

 Originality...

The original shock on the FZ, as could be expected, was well and truly past its sell-by date. I would have loved to use the original but I also want this bike to handle as well as possible without the costs associated with Ohlins etc. 

Finding another original shock in good condition has been challenging so far but you never know what might turn up one day. So, to allow me to carry on reassembling, I again spoke to Paulo at Motogenn and bought one from a low-kilometre 2018 Ducati Monster 821. This one was chosen as it is the same length so hopefully not too many alterations needed. It's made by Sachs and should be far superior to the original anyway, not to mention lighter.

It looks absolutely mint, and now requires a slight rejig to fit the original mountings of the FZ. No easy task as the shock has rose joints to suit an M10 bolt, whereas the FZ has an 18mm pivot pin running through the lower mount. The top mount is an M12 bolt but, with spacers in the top rose joint removed, the FZ bolt is a perfect fit. It just needs some spacers to maintain its central position.

I pressed out the lower bush in the vice, and started measuring.

The bushes in the original FZ shock appear to be Teflon-coated, like fork bushes, so I made a puller to remove them for inspection. They look great so I will make a steel bush to fit the lower shock eye, fit the bushes inside and finish it off with some spacers to keep the shock central and prevent any wear occurring against the aluminium bracket that the shock is mounted to. 

This is the steel bush that will go through the bottom of the shock. The original bushes will be pressed inside. I'll probably fit a grease nipple to the pivot pin so I can grease the bearings to keep dirt outside. More on that later.

The bushes were drawn in using the puller I made earlier and worked a treat. I also made end caps to fully support the thin bush when the pivot shaft is fitted. These will also prevent any wear to the aluminium bracket.

There is the new main shock bush with Teflon bushes inside. Those are the two end caps to keep everything central.

This is how it will fit inside the monoshock bracket under the swingarm. The pivot pin slides through and has a circlip fitted for safety. The two M6 clamping bolts prevent any movement.

And finally with shock mounted. The Teflon bushes are smeared with a light Lithium grease when assembled. I was going to add a grease nipple to the end of the pivot and drill three small holes along it to grease the bearings when I wanted to, but the shaft is hardened, as expected, so I will leave it alone. 

That's the puller for removing and refitting the bushes with no damage whatsoever. Worked perfectly.

Ok, will post more when the swingarm is mounted.

KTM Superduke 990R - New Tyres and Sprocket Carrier Bearings

Four years too late...

The old Superduke of Bridgey's has been somewhat neglected lately. And when I say lately, just the last four years or so. It's still pretty clean, don't get me wrong, but legend has it Boudicea was using the same tyres on her chariots. 

Now I wouldn't have bothered putting up this post for a pair of new Pirelli Rosso II's but, what was concerning, was the state of the sprocket carrier bearings. Well, one in particular.

The Superduke has some great engineering plusses, one of which is the two bearings fitted to the sprocket carrier. Four bearings in all to let the wheel spin in the manner to which it's become accustomed. Imagine the rigidity, the ability to keep that wheel inline no matter what angles it's trying to put down the power.

As much as I like to take the piss, it's a bloody good idea.

But during a routine tyre change, it became obvious that all was not well in the bearing department, and the sprocket carrier was extremely notchy. The two spacers that go in from both sides were rusty and I wondered if the water had been held in there and got past the seals.

The two spacers on the piece of wood need to be knocked out first. Then the bearings can be hit out, one from each side taking note of the small spacer in between.

A closer look at the bearings with seals removed showed the carnage. The cage had broken up and it came to a premature end. The cause? Possibly overtightened chain at some stage.

After a good clean-up, two new bearings were fitted and everything was good again. A good reminder to always turn the bearings by hand whenever you take the wheels out, any notchiness and it's time for replacement. 

If you're very careful when removing the seals with a pick, you may be able to clean them out and regrease them, as long as they are smooth and quiet, but for the cost of new bearings, it is advisable to replace them when in doubt.

Anyway, it's certainly nice to see the old girl back out and fighting fit.