FZR250 stiff brakes

[Scotty595]

Hey,

I have been riding my mates bike a little bit lately and have been shocked at the brakes. They are damn near impossible to pull in, and I can barely even get the front of the bike to drop they are so weak. It has been checked out by a mechanic and they just said that Yamaha's have shit brakes and it is normal. Thing is I can brake a shitload harder on my CBR250R (single disk) where the FZR (3LN) is twin disk.

Does anyone else think this is a bit odd or is that just how the brakes are?

Any ideas on how to solve?

[Blackflagged]

Take it to another Mechanic.They should stop good.

[quickbuck]

Umm,
Honda's always have excillent (Nissin) brakes... even the single disc ones.

From memory the 3LN has Tokico brake Calipers... Thses are opposing piston, and tend to be not as good if not maintained properly.

I would start by giving the calpiers on the 3LN a bit of a service: Clean the Pucs, replace the seals etc, and replace the pads for some new ones. (This sounds most likely to be your problem).
Ensure the Discs don't have any groves either, and they are above the minimium thickness.....
Most importantly, put some new fluid in the system. The stuff only lasts a couple of years.
Inspect the lines too... These have a finite life, and I bet the lines on the 3LN are almost 20 years old!

Also, give the leaver a nd Master cylinder a bit of a service too....

As said though, it may be you are used to your super CBR Brakes.

[F5 Dave]

. . . They are damn near impossible to pull in,. . .

That right there ain't right. It would indicate several things. OK I'm assuming the wheel rotates freely enough? The lever taken off isn't munted or the wrong one bodged in place? MC isn't replaced by something odd? should be a 5/8" bore I'd expect (written on it).

These calipers do seize easily. Remove from forks one at a time & take pads out & pump the pistons out a bit. If they don't move on one piston that is bad. Preventing the other piston moving then repeating should start to move it.

Ideally you strip them completely down & carefully inspect. Esp important on old bikes.

[Scotty595]

That right there ain't right. It would indicate several things. OK I'm assuming the wheel rotates freely enough? The lever taken off isn't munted or the wrong one bodged in place? MC isn't replaced by something odd? should be a 5/8" bore I'd expect (written on it).

These calipers do seize easily. Remove from forks one at a time & take pads out & pump the pistons out a bit. If they don't move on one piston that is bad. Preventing the other piston moving then repeating should start to move it.

Ideally you strip them completely down & carefully inspect. Esp important on old bikes.

Yeah thats what i was thinking. Nothing has been fiddled with all original equipment (Yamaha MC, original lever etc). Will have to have a look on it see if the pistons are stuck. I'm just really unsure whether it is just my view on how they should be that is wrong but to me having to squeeze the lever super hard and then it only moving maybe 0.5cm and not braking much seems a bit odd. I would think surely a twin disk would be able to outbrake my single. Does anyone have a 3LN FZR that i can compare to?

[F5 Dave]

Well popping a caliper off & squeezing the lever should meet next to no resistance. If it does I'd look closely at the mc as one piston should move at least (which you will see).

[MSTRS]

Yeah thats what i was thinking. Nothing has been fiddled with all original equipment (Yamaha MC, original lever etc). Will have to have a look on it see if the pistons are stuck. I'm just really unsure whether it is just my view on how they should be that is wrong but to me having to squeeze the lever super hard and then it only moving maybe 0.5cm and not braking much seems a bit odd. I would think surely a twin disk would be able to outbrake my single. Does anyone have a 3LN FZR that i can compare to?

Piston/s are semi-seized. Or the main hose is full of gunge (technical term). Strip the lot and service.

[Blackflagged]

Brake Manufactures, tried quite a few Caliper Piston Sizes.From memory 3ln has a smaller trailing piston,and the Master / caliper ratio`s that are about the same as modern sport bikes.The same calipers were used on tzr250`s.There`s no problem with the design,there must be a fault with the Brakes.

[FROSTY]

Just to confirm here. The bike concerned has two calipers and each caliper has 2 ?? pistons--one on each side?
If so they are the exact same setupas on the XJ series (600/750/900)
Repeating the advice offered above a fair bit but there is a step by step process
1) Get a clean cloth and wipe both disks.--Is there a really thin layer grey sticky crap on em?, Look at the back of the brake calipers and see if its black and oily looking-not wet--baked on kinda oily.. -if so and the forks are not leaking then they have been in the past and both calipers need a bloody big cleanup.fork oil is on the disks and in the pads
2)Undo the bolt holding the brake lever and remove the lever. -clean up the pivot point and the bolt shaft then very lightly lube with hmp grease _not enough to seep anywhere.--reassemble.
3) remove ONE caliper --remove the brake pad slide pins --they will be rusty looking and/or covered in crud.Sand them with 400 grit sandpaper till shiney metal again. again lube the pins lightly with HMP grease.
4)Caliper wise Im seriously loath to recomend to a person of unknown mechanical experience about popping pistons out
But a really good huck out with brakeclean will make a difference.--basicly spray everything you see with brakeclean and scrub away till it looks shiney again. That also applies to the pads and disk.
put the pin/pads back in and caliper back on.--DON'Tforget the little retaining clips
-repeat the other side.
You'll know youve done it right with an older bike because the brakes feel spongey as heck-compared to what they were but stop a heap better
If what i suggested doesnt work then gimme a yell and one saturday you can come here and Ill show you how to dothe pistons

[Scotty595]

Just to confirm here. The bike concerned has two calipers and each caliper has 2 ?? pistons--one on each side?
If so they are the exact same setupas on the XJ series (600/750/900)
Repeating the advice offered above a fair bit but there is a step by step process
1) Get a clean cloth and wipe both disks.--Is there a really thin layer grey sticky crap on em?, Look at the back of the brake calipers and see if its black and oily looking-not wet--baked on kinda oily.. -if so and the forks are not leaking then they have been in the past and both calipers need a bloody big cleanup.-Ill cover that later.
2)Undo the bolt holding the brake lever and remove the lever. -clean up the pivot point and the bolt shaft then very lightly lube with hmp grease _not enough to seep anywhere.--reassemble.
3) remove ONE caliper --remove the brake pad slide pins --they will be rusty looking and/or covered in crud.Sand them with 400 grit sandpaper till shiney metal again. again lube the pins lightly with HMP grease.
4)Caliper wise Im seriously loath to recomend to a person of unknown mechanical experience about popping pistons out
But a really good huck out with brakeclean will make a difference.--basicly spray everything you see with brakeclean and scrub away till it looks shiney again. That also applies to the pads and disk.
put the pin/pads back in and caliper back on.--DON'Tforget the little retaining clips
-repeat the other side.
You'll know youve done it right with an older bike because the brakes feel spongey as heck-compared to what they were but stop a heap better
If what i suggested doesnt work then gimme a yell and one saturday you can come here and Ill show you how to dothe pistons

Thanks for that Frosty. Will have a look at doing it then give ya a yell if i need any more help.

[Blackflagged]

Late i know.But for anyone reading this later. Read the back of the brake clean can. Don`t spray any seals or rubber with brake clean.It will screw them quicker than a drunk Paris Hilton on new years eve.

[Scotty595]

Figured the Bastard out!

Had too much brake fluid in it :\ couldn't believe it... does stoppies real easy now :p

[MSTRS]

How does that work? The maximum available room for fluid is if brake pads are (hard) against the discs but with the master cylinder piston at rest.
Isn't there some sort of relief or bypass valve at the lever end to stop this happening?
Were your brakes on all the time?

[Scotty595]

How does that work? The maximum available room for fluid is if brake pads are (hard) against the discs but with the master cylinder piston at rest.
Isn't there some sort of relief or bypass valve at the lever end to stop this happening?
Were your brakes on all the time?

Nope brakes weren't on all the time. Don't ask me how it worked it just did. Its a lot smoother and easier to brake and stops a lot harder than before.

[F5 Dave]

So ddi you check the rubber cover. It mustn't be ripped.

I'm still suspicious. Is there any real clearance to the mc button with the lever out? Could be real close & happen again when hot.

[MSTRS]

Nope brakes weren't on all the time. Don't ask me how it worked it just did. Its a lot smoother and easier to brake and stops a lot harder than before.

Then I'd be worried about a problem with the master cylinder piston movement.
It is simply not possible to 'have too much fluid in the system' - at least not from the m/c piston seal all the way to the caliper pistons. The only way to get more in there is to have it under pressure, which means that the caliper pistons will be activated against the pads.

[SS90]

Er, not quite.

If (and this has been known to happen), someone was to fill the master cylinder to capacity, and the caliper pistons where all the way out (really worn/missing pads), then, the caliper pistons where pushed back (to refit the pads), then the fluid that was behind the fully extended pads would be forced back up into the master cylinder, thereby overfilling the master cylinder, and, depending on the design of the master cylinder, the lever can feel rock hard, but not apply much pressure to the caliper pistons....remember, there is a return valve in the master cylinder, and it can't operate correctly if it is over full.

That said, if the owner has any doubts, it would be wise to take it to an expert.....brakes are important!

[MSTRS]

So - too much fluid behind the m/c piston causes some sort of hydrolock?

[F5 Dave]

If for example with SS's example & the rubber was ripped/slid out of way & lid breather clogged then there could be an issue. As I said keep looking or it could happen again, for example if the the fluid gets hot it will expand with no where to go.