Motorcycle brake woes.

[chunkolini]

I bought a new (old) Suzuki DR350 last week, old but in great condition.
Put it through an MOT fine . first ride about 15 miles on tarmac was fine.
Today I was going to meet some mates and injure myself on the dirt. The front brake seemed to be dragging slightly but I headed off. About a mile later the motor was struggling. the brake had bound on tight. About 400 yards onto the M4.
I was able to get the caliper off, push back up the hard shoulder and gently ride back to base with just a rear brake.
The pistons seem free, push one in and other pops out. Try and push both in and it locks solid.
Any ideas? I reckon most likely the master cylinder.
is it order a caliper and master cylinder rebuild kit?
The disc is blued after getting so hot; is this a problem?

 

[addjunkie]

I have had this before, turned out to be as the system heats up due to use the pressure should vent back to the master cylinder when the lever is not pulled. I rebuild both the calliper and master cylinder. But it was the master cylinder that fixed it.

As youve overheated the disc, it may be warped. Due to the age of the bike Id mic the thickness to see if its below wear limit, and stick a clock gauge on it to see if its warped

 

[chunkolini]

Mr Fuzzy, no idea what you mean.
Fluid not being able to return to the reservoir is what it feels like.

 

[gordon stephenson]

Sometimes it is the flexible hose that has collapsed internally, And acting like a non-return valve, Keeps the pressure on causing the brake to drag, then the disc heats up and expands in width causing even more drag,

 

[Wallace]

Is there any play on the lever? The master cylinder piston might be corroded and not returning fully covering the return bleed.

 

[chunkolini]

There Goodridge hoses fitted, the braided steel ones.
All looks very clean and well cared for but is over twnty years old.
I will have a good fiddle with everything tomorrow when I am supposed to be working.

 

[dobbslc]

Time for a bit of a splurge on the bike Mr Chunkolini. If that had happened on the dirt you'd have been testing how strong your wrists are!
I would get a new seal kit for the caliper and master cylinder, a new hose and if the disc is bad enough a new one too.
I would check the caliper slides OK on its pins as they can sieze up. And check the disc is running in the centre of the caliper as it could be missing a wheel spacer or have the wrong size one in if it's ever had the wheels swapped for supermoto ones.
Lucky it's only a single disc and I think single piston caliper so not to expensive.

 

[chunkolini]

I think a brake overhaul has to be done.
Weird, it was fine the other day. I suppose it has been sat around for some time.

 

[cocker]

Try pumping the brake lever till it's rock hard then keep it squeezed while you cable tie it to the bars . Leave it over night .
Might work . ooorrrrrr take the fecker off and join that DTRA lot , front brake not allowed .

 

[chunkolini]

I reckon for peace of mind order rebuild kits. it's a not a complicated job.

 

[magicgrotto]

Ahhh but have you got any play between the leaver & the M/S ?

 

[chunkolini]

Not sure what you mean.

 

[dobbslc]

Should be a little play between the master cylinder piston and the bolt and locknut on the lever.

 

[magicgrotto]

The front brake leaver duz it move BEFORE it hits the piston in the M/S ?

 

[magicgrotto]

IF it's tight up against piston then you need to adjust it so there is a gap ! About 1/16th of a inch should do !

 

[Wallace]

The piston dust seal in the master cylinder is a good one for splitting with age and starting the dreaded alloy fur, that stuff is amazing as it grows and pushes the seals out. I stripped all the calipers on a CB900 as the dust seals were being pushed out throughout the gap between the piston and caliper locking the brakes on. Expecting to replace all the calipers I ended up fitting just seals as the pistons were perfect and the calipers cleaned up.

 

[chunkolini]

I did fit a new lever but that was pre succesful ride.

 

[magicgrotto]

I did fit a new lever but that was pre succesful ride.

But is there any play between it & the M/S?

 

[zx9]

Easy first step mate, if there is a breather hole in the reservoir cap, make sure it is clear, the aluminium ones can fur up a bit if the bike has been unused for a while.

 

[Pete.]

This is usually caused by a blocked return port. Could be the port itself is blocked, could be the lever is not allowing the piston all the way back, or it could be corrosion holding the piston in a bit.

I had a 132mph crash because of this very thing