Couple of hairy moments

[alfiembra]

Got a 1977 400/4 and had a couple of close calls last night while out for a spin and was seeking some advice.

Firstly I have rebuilt my front brake master cylinder and caliper but since doing so I've never felt that comfortable with it. it has been bled several times but still feels weak and spongy at best. Had a taxi slam on the anchors in front of me last night and I struggled to stop quickly locked the back end up but didn't feel much was happening up front. Fortunately didn't come off or hit him but was a close call. So was thinking braided hoses for a start and was looking for thoughts or recommendations.

Second problem was later on was giving the bike a blast on the motorway and had been bowling along at about 75 for a good few miles with no problems whatsoever then had a white knuckle moment the bike lurched with a noticeable squealing scraping sound and what felt like a loss of power. I immediately shut off the power and coasted onto the hard shoulder the noise only lasted a couple of seconds and the bike never cut out the engine was still running as I coasted along so I lightly accelerated and sat about 50 no problem no more noises drove back the last few miles back home with no more noises or issues. My first thoughts were was it the clutch maybe slipped.

Any help and ideas welcome

Cheers

Alan

[Green1]

Braided hoses don't improve brake performance just the feel on the lever. The original hoses are actually braided under the rubber outer.
Rough up the disk and pads with course sandpaper crosshatch the disk.
If the lever is spongy and refuses to improve. I tie them to the bar overnight but you must place a 15mm spacer between the bar and lever over wise fluid can seep past the piston in the master cylinder

The squalling noise does sound like clutch slip to me.     

[hairygit]

Also check the caliper arm pivot moves freely, they seize up for fun!

Sent from my X6pro using Tapatalk

[kevski]

Drop the oil and look for particles, I would re bleed the front brake, my 350 still has original hoses and I have positive feedback from it and no spongy feelings, finally don't ride so close these do not stop like modern bikes unless you have modern brakes.

[mike the bike]

Adjust the caliper pivot so it's a gnats away from the disc.  After ensuring its free to move that is.

[Mag1]

When you rebuilt the calliper, did you replace the piston seal?. Was the piston anyway pitted or badly scored. As others have said readjust the calliper to the disc. As a precaution have you overhauled the master cylinder, maybe gummed up with dirt or seals past there best.

[alfiembra]

Thanks for all the replies.

When I rebuilt the master cylinder and caliper it was a full refurb with new seals and pistons on both, I also set the gap on the fixed pad to the face of the disc as per the manual 15 thou IIRC.

I'll check the oil for particles and report back,

Thanks again.

[hairygit]

The pad to disc clearance SHOULD be 6 thou, so at the moment you have more than twice what it should be.

Sent from my X6pro using Tapatalk

[alfiembra]

Sorry my mistake .15mm not 15 thou

[petermigreen]

Recently rebuilt a master cylinder with an aftermarket kit and brake was very spongy and could pull the lever to the bar with no problem at all could not get it to work properly despite bleeding and rebleeding. Bit the bullet and bought a genuine kit and rebuilt, brake now fine*

Peter.

*1970s fine

[totty]

On top of what has already been suggested check the pads have wear on the entire surface to see that they are bedded in. Some pads can take ages to bed in and it makes a significant difference.

[alfiembra]

Drained the engine oil and checked for particles and did have some debris there but turned out to be blobs of liquid gasket I'd used when I replaced the clutch cover gasket earlier this year. There wasn't anything gritty or solid in the oil. A mate suggested I might have got something kicked up into the chain or sprocket which I'm starting to think is a more likely possibility.