Front Brake Issue: Norton Commando MkIII

Reader Contribution by Keith Fellenstein
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Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Commando brakes

Q: I am stumped with a front brake issue on my 1975 Norton Commando MkIII. I have always had a slight pulsing from the front brake near the end of my stops. It has the Norton/Lockheed master cylinder and caliper. The master is sleeved, and I replaced the old rubber lines with braided stainless lines. I had an issue with the piston in the master cylinder sticking when it got hot, like from sitting in the hot sun. The master got sent back to the shop that did the sleeve. They said they got a delivery of pistons that were not made to the correct tolerances. I think, but am not sure, they replaced the piston. The owner said they bench test every master cylinder before they ship them. I am confident of the shop and what they told me.

When I put it back on the bike, I had a terrible time getting any lever pressure, but eventually prevailed — almost. I noticed I have too much travel in the lever and it feels spongy. Since starting this repair, I rebuilt the caliper, sent the master back to have it checked again (they said it checked fine) and rebuilt the caliper a second time with new stainless pistons netting the same result. The bore on the caliper appears smooth.

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