Front brake!

[PatM]

Hi All!
I went for the MOT today after my rebuild and failed on front brake binding and the throttle cable snagging on full-lock. One is an easy fix- but the brake is a b'strd.
I fitted new pads and yep, it does bind- but as they are running in , I left it. the non moving pad has only just got a kiss on it and the moving- I cant tell (as Ive only done about 10 illegal miles, fettling- without an MOT..)
I have had problems with 400/4 brakes in the past- trying to get a good brake on a 400 is a black-art Ive never mastered- but the only way I can reduce the bind on this is to either loosen the capiper (err, a non, no) or fit the moving old pad.
The brake is still crap, but it might just do...as the rear locks a treat!

any comments/help or jibes, feel free!

Rgds

PatM

[honda-san]

When you fitted the new pads, did you pump out the piston and clean out the groove in which the seal is fitted? Corrosion tends to "grow" behind the caliper seal and squeeze it onto the piston, preventing it from returning properly. Often not helped if the piston is just pushed back into the caliper after fitting the pads as any dirt on the piston is forced towards the seal.
Other problem area can be if the tiny bleed hole inside the master cyclinder is blocked, not allowing brake fluid an easy retrun to the master cyclinder after squeezing the lever - use a pin to clear it.

These things are pretty old now - only solution with them is to strip, thouroughly clean out the caliper (especially the seal groove) and re-build with new fluid, etc. I use rubber brake grease behind the piston seal, and DOT 5 silicon brake fluid (doesn't burn the paintwork if it spills / leaks). Old pads have often glazed, and have been known to detach from the backing plate, so would certainly fit new ones if in doubt (which of course you have). Corroded pistons, perished brake pipes should be replaced too.

Obviously new pistons, seals, pipes ets are desirable, but even with the original parts (subject to condition of course) these brakes can be made to be pretty good even if they OF COURSE are never going to compete with the latest generation 6 pot twin disc set ups!

Have fun! - Chris R.
 

[K2-K6]

Good response from Chris, covers just about everything you should be doing.

To add a bit to this about the seal and how it works: I believe the seals of this type deform in cross section as the piston drags out past them it is dragged further out at the piston contact point, when you release the brake pressure the seal elasticity? pulls the seal back to it's original shape and has the effect of taking the piston with it back into the caliper so giving a small pad to disc clearance and hence no binding.

It's vital to clean the seal area as chris says to restore the tolerances that enable this to happen. Only a small amount of muck/corrosion on the pad side of the caliper seal effectively blocks the space for the seal to operate as designed so it's critical. also I have always been able to return bike caliper pistons into the bore with two thumb pressure, it's a good measure of the piston not binding.

[Bryanj]

Main problem used to be the pivot pin siezing

[honda-san]

And of course, as Bryan suggests, make sure the caliper arm pivots freely - loosen the caliper bolts, the arm should pivot freely with the spring capable of moving it. Fitted a grease nipple to my winter hack 400/4 caliper arm so the pivot can be greased - no more seizures.

Chris

[Yoshi823]

A friend had a similar problem with his CB500K. Somebody had rebuilt the front end incorrectly & bolted the front mudguard stay between the upper caliper mount that locates the top of the pivot pin, thus misaligning the caliper mounting bracket. Once the upper mount had been placed between the fork leg & the mudguard stay the caliper bracket was realigned perfectly & the fixed pad had full contact with the disc.

Just a thought...

[PatM]

All

Thanks for the replies and advice-
You are correct in that I have replaced the pads- as the ones fitted were glazed (and the brake was crap..)
Before writing the 'Help'- I put the old 'moving' pad back in and that seemed to solve the problem-ie, the brake didnt drag- so I think a strip and re-build this w/end is in order.
The final advice regarding the mudguard- yes, Ive replaced the mudguard when I refurbished and painted the forks- Ill have a look if I can understand what you are sayong to see if Ive put something back on wrong. The pivot is obviously free- as I said, Ive stripped and re-built.

Ive had 2 400/4s and ive never had good brakes on them!

My 2001 R1 is a bit spongy know , but by golly-stops on a sixpence and my daily hack- a GS1200 Bmw has excellent stopping power- it needs to, as I do 30k a year on it!

Thanks a lot all!

PatM

[Yoshi823]

I also had a spongey front brake on my 2k R1, so I replaced the standard master cylinder with a radial Brembo one, Ferodo Supersport pads, pistons from a '01/'02 R1 front calipers & Aeroquip hoses. Now, if i'm not careful, I could be thrown over the handlebars if I were to sneeze while braking.

The R1 master cylinder went onto the Exup1000 after a clean & rebuild.

[PatM]

Thats my bike! except mines original, apart from the mirrors! Ive dinged my exhaust twice now and still managed to get a replacement- once when it was someone elses fault and the other when I dropped it- BNIB

[Yoshi823]

I have a noisey pipe but I prefer the OEM item. I heard that plod were down at the Oakdene & they did anybody with a noisey pipe, dark visor or small number plate. My R1 is very standard as I don't need the aggro.

See also www.yamahar1.co.uk

[exvalvesetdabbler]

I have to agree with honda-san, that build up of not only muck but corrosion behind the seal.  Also as the seal ages it becomes hard it's less likely to pull the piston back.  Also if you have changed the fixed pad you might need to reset the clearance to the disk to 0.15mm. Just slacken off the adjuster for the fixed pad and slip in a feeler gage and then tighten up the adjuster until it starts to grip the feeler gage  then back it off a little.


Best of luck.

[PatM]

Right chaps- I stripped and cleaned the caliper- it was clean(ish)- Ive had worse! I removed the seal and cleaned groove out with cotton-bud- washer the whole lot in hot water and fairy- blew it all dry with compressor- Now it is all back together you can see the caliper moving and no drag. But- I fited the old pads- as I think the problem is pitting on the piston causing stiction. I will re-set one the inner pad (which is new) beds in properly- as its only doing about 20% of its work judging by the marking on it. Theres just no way I can think of to bed thse pads in so they give 100% contact of the disc. So, off the the MOT place agin this week. The jobs a whole lot easier when you can legally run the bike on the road and do these tweeks!

[PatM]

MOT Passed!

Now I can enjoy!

s*it....its raining out there...maybe not..

[colin400four]

Hi Folks,

Interesting reading on the recon of a 400/4 front brake. I did mine, followed both of the manuals, advice from sites like this, used all the right components mostly new or cleaned like a new pin, Used the right grease in the right places................. Brake works a treat, BUT........ it squeels like a good en when applied, something it never did before......... any ideas please

COLIN.

[kent400]

I found using genuine Honda brake pads resolved the squeal problem. Twice the price of pattern ones of course but the front brake  seems a whole lot better now. The brake hoses are the standard ones and I'm using  silicone fluid. I know there is some questions as to the suitability of using silicone fluid in these old bikes in that in can have an adverse effect on the seals. I've been using it for at least five years now with no probems.