Yamaha YZF600R Thundercat (all models)

How to service the brakes

Theo, May 2005

Introduction

The brakes on the Thundercat (same as R1, R6, Bulldog, Fazer etc) are excellent when working well but easily get gummed up. When this happens they can stick, wear out your pads and disks and generally be very annoying. Servicing them is pretty easy and usually restores them to full power. If they are still lacking, they may require bleeding, new seals or new hoses. These fairly tricky jobs are not covered here, sorry.

These instructions refer to the front brakes, but the rear brake is done in exactly the same way.

Allow two or three hours on your first attempt, depending on how bad the brakes have got!

You will need

A 12mm socket
a torque wrench
an old tooth brush and some rags
a can of brake cleaner or other suitable solvent
some brake paste or copper grease (Coppaslip)
some brake assembly grease (the red stuff) or failing that a little fresh brake fluid.

Get started

Tie a bit of old rag around the brake fluid reservoir, and loosen the lid just in case it overflows.

Release one of the front brake hoses from the clamp on the mudguard, and unbolt the caliper. Slide it off the disk and away from the wheel. Do NOT unbolt the hose from the caliper.

As you work on the caliper, try not to twist or strain the brake hose, it helps if you have a box or low table to work on.

Get some hot soapy water and give the caliper a good thorough wash, pads and all. This makes the job a lot less unpleasant.

Remove the two small R-shaped pins that pass through the main pad pin, just inside the body of the caliper. You may have to rotate the pad pin around to access these.

Using something like a small allen key, push the pad pin all the way out of the caliper. Tap gently if stuck.

Remove the pad spring and slide out the pads, noting which one goes on which side. You can now see the four pistons, and probably a lot of road crap.

Give the inside of the caliper a good cleanup with your brake cleaner, toothbrush and rags.

Keeping a close eye on the pistons, gently pump the brake lever. One or more pistons will slowly extend. Once they stick out 15-20mm STOP, any further and they might fall out, which is a real pain.

If you do suspect you have extended one too far, immediately try to push it back in with your thumbs, wiggle it gently and eventually it should retract. If this happens you should also bleed the brakes in case any air has gone in.

Clean up the extended piston(s), then smear them evenly with brake assembly grease. Using your thumbs, push them all the way back in. Be patient, press hard and rock gently side to side and they will go back. Use a clamp if you absolutely must, but take care not to force them in on the skew.

Repeat this process of extend - clean - grease - retract until the piston moves smoothly and fairly easily in and out.

Now move on to the next piston. You will have to hold the clean piston(s) in place while you extend the dirty one(s), which you can do with clamps, cable ties or by wedging bits of wood in between the clean ones. The last piston is often quite stubborn and will need the most attention.

Clean the pad spring and pin with brake cleaner. If the pin is corroded, clean it up with wire wool. Coat the pin liberally with copper grease.

Now give the pads a thorough clean with brake cleaner to remove any trace of oil and grease. Carefully coat the BACK and ENDS of the pad with a thin layer of brake paste or copper grease, don't get any on the front surface.

Reinsert them into the caliper the same way they came out. Place the spring on top (there is an arrow stamped on it that should point up). Insert the pad pin with one hand while holding the pads and spring in place with the other. Ensure the pin passes through all three.

Replace the little R-pins in their holes. Slide the caliper back onto the disk, one pad each side. Try not to get grease on the disk, if you do remove it with brake cleaner.

Put a little copper grease on the caliper bolts and replace them, tightening to 40 Nm / 29 ft-lbs. Refit the hose clamp.

*** Slowly pump the brake lever until full brake pressure is felt. Failure to this before riding can be fatal!! ***

If you can't get good lever pressure, or if the lever has a lot of travel or is spongy, there may be air in the fluid, which is fixed by bleeding the brakes.(not covered here, sorry). If that doesn't work, then it's likely that the brake hoses have gone stretchy and should be replaced (ditto).

There you go, one down and one to go! Have a cup of tea then move around to the other side of the bike and do the second caliper in exactly the same way, again remember to pump the lever when you have finished.

Finally check the level of brake fluid in the reservoir, and retighten the cap.

You're finished. Give the brakes a quick test at low speed, and away you go, enjoying superior stopping power.

That's all folks

Questions and corrections very welcome. Email: cat@jeremythomson.co.uk.

All text and pictures © Jeremy Thomson 2004. No commercial reproduction allowed. You are welcome to reproduce the text and pictures for any non-for profit purpose provided you include a credit and link back to this page.

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