84 XS front disc brake dragging

[SandyR]

I'm working on an 84 DOHC XS 400 that I got last weekend.
I've managed to get the engine running although I think I may need to take the carbs apart for a more thorough cleaning.

The immediate problem is that the front disc brake is dragging. It is not hard on but definitely drags when I move the bike. From what I've read it seems like I will have to take the caliper and the wheel cylinder and maybe the mc apart. I'm ok with that but I just want to check if anyone can suggest anything else I should check before I do it.

thanks,
Sandy

 

[bentwrench]

Probably not - it's not an overly complex system. I'd start with the calliper, clean and rebuild (get thee a rebuild kit with new seals). If you've never done it before, you'll need a can of brake cleaner and some fresh brake fluid, and a brake bleeder setup. I use the cheap one that crappy tire sells, and it works (but takes a long time.) There are speed bleeder setups that are much quicker (and more expensive.)

 

[SandyR]

Thanks Bent. Can anyone suggest a supplier for a rebuild kit? I'm sure I saw it somewhere on the site but now I can't find it. Canadian supplier would be good if there is one. Shipping costs have gone nuts the last couple of years.
thanks,
Sandy

 

[Scorpio1963]

You have a hard time removing the caliper piston,these things usualy get stuck and stubborn as heck to remove.Take and remove the bleeder screw use a blow gun from an air compressor if you have one and blow high pressure air through the hole.Just make sure you tie a rag or small towl around it or it will going flying.Ask me how I know LOL.Or you can undo the bleeder screw and use a grease gun to pop it out.Just make sure you clean thuroghly afterwards.

 

[XSLeo]

A lot of the problems with the brakes is that in all the yars they have never even had the fluid changed. This lets water collect in the system. Water is heavier than brake fluid and settles in the caliper. Water= rust.
The hoses also get bad fromthis water in the fluid. The rubber rots from the inside out. Leaving bits of rubber floating around in the fluyid. These bits of rubber can plug the passages in the caliper as well as migrate up and plug the M/C.
The rubber parts in the caliper and master cylinder are quite robust. Often you can reuse them with a good cleaning. In the caliper the groove the seal fits in can get a build up that pushes the seal against the piston hard enoug to bind things.
I would start by cleaning out the caliper and replace the lines. New fluid and see if it fixes the problem. If not clean out the M/C.
Rebuild kits only if needed.
Leo

 

[Scorpio1963]

I know first hand to have the front brakes drag and lockup while riding.My knees still bare the scars of what will happen if on gravel luckily not on asphault.With that being said I took my caliper off the inspect every thing looked clean and I bled the system with fresh fluid.Seem to work for a little while but back to the same.It doesnt take much corrosion to get the pistons to lock up.

 

[XSLeo]

Often just cleaning the caliper is not enough. The lines go bad and without replacing them the problem can still be there.
Start at the calipers, clean or rebuild as needed. replace the lines with new, the braided stainless is a very good upgrade. New fluid.
If this don't fix it clean or rebuild the M/C.
Another good upgrade is to replace the stock 14 mm bore M/C with an 11 mm bore M/C. This makes the brake stronger and you get better feel of what the brake is doing.
Leo

 

[bentwrench]

Our bikes use the same front caliper as the same year's XS650, so go to http://www.xs650direct.com and punch in item Part #29-0016. $18.95 Canadian.

 

[SandyR]

Thanks for all the replies. I'll wait until the weekend in the hopes the rain lets up (yeah right) and then I'll take it apart. Looks as though the parts are available.

thanks again,
Sandy

 

[bentwrench]

Wait, the rain lets up in BC? Or do you mean you're taking the bike to another province this weekend?

 

[SandyR]

It's actually in the carport but with the amount of rain we've had this week that isn't even dry.
Sandy

 

[SandyR]

Some progress. Got the caliper working and actually went for a ride around the block. Clutch, transmission and handling feel ok. Some carb issues so I guess I'll have to have another look at those.

Back to the brakes. Fluid in the m/c a bit low so I decided to top it up. Nice try. The heads on the cover screws are completely trashed. Has anyone drilled these out or is it time for a new m/c ?

thanks for the help,
Sandy

 

[bentwrench]

Ooohhh... those are really small screws. You can try drilling carefully, but it's really easy to nick the cover...

 

[16VGTIDave]

When I stripped a screw head on my master cylinder cover, I used a very pointed punch and small hammer to create a divot in the metal of the screw head, close to the edge. Then, with the point still in the divot, I tilted the punch and tapped it such as to unscrew the screw. A few smacks with the hammer and out it came. This works with any countersunk screw.

 

[SandyR]

Thanks. I'll try the punch method. If that doesn't work I'm thinking of using a Dremel to cut the top around the screws and then twist them out. I should be able to make a new top without much trouble.

Sandy

 

[bentwrench]

Just remember what Dave said when using the dremel - they're countersunk, so be careful where you grind.

 

[SandyR]

Roger that. I'm quite capable of causing considerable damage with a Dremel.

Sandy

 

[XSLeo]

You might try cutting a new slot in the screw head with a Dremmel tool. Those screw are about 3 mm as I recall. You can use a drill bit about that size to drill through the head of the screws. An 1/8 or 3/32 should work. If done carefully the head will come off the screws. You can then lift off the cover. There should be enough of the screw sticking up to get a hold of it with vise grips and turn them out.
Most any hardware store has replacements.
Once you get the cover off you may find the fluid in very poor shape. If it isn't clean you should at least flush the system out with plenty of fresh fluid.
Keep the reservoir full and bleed till clean fluid comes out at the caliper.
I would reccomend replaceing the old rubber line with new rubber or braided stainless steel. The old rubber lines rot from the inside out. As they rot bits of the rubber come loose and flot around the the fluid just looking for a place to clog the system. Bigger pieces can partly come loose and become a flap of sorts and let fluid flow past it then flip up and block the return of the fluid, this can cause excess drag or even lock the brake.
The caliper isn't hard to take apart and clean. Often the rubber seal on the piston is in veery good shape and can be reused. The outer boot mat be in bad shape. When cleaning the caliper body pay particular attention to the groove the seal sets in. Crud builds up in the groove and pushes the seal out against the piston enough to not let it return.
The M/C can be taken apart and cleaned but it needs very long nosed snap ring pliers to reach the snap ring.
Well worth the effort though.
Brakes are one thing that need to work.
Leo

 

[ken56]

I also had 1 m/c screw stripped. Can't remenber the bit size but I drilled the head off the screw. After lifting the m/c cap off there was enough of the broken screw exposed to get a hold of with pliers. Mine came out quite easily. Hopefuly yours does to. Let us know how your m/c rebuild goes. Haven't started mine yet.

 

[SandyR]

Waiting for the weekend again. I'm determined to get the top removed one way or another. I plan to try the punch method first and get progressively more violent if required. If I end having to replace the m/c I'll at least know that it is good to go.
Sandy