Honda-SOHC
Other Stuff => Tricks & Tips => Topic started by: Rozabikes Tim on November 20, 2016, 05:40:52 PM
-
Just getting my 400 up and running for pre resto check for any gremlins.
Motor running suprisingly well bar some primary chain and camchain noise. Dare not ride it far as front brake useless even by sohc standards! I know this is well covered on the forum but can't easily find relevant posts. Can someone point me to best post or just advise from experience.
Tim
-
All I can tell you is that it has a floating caliper, and mine needs adjusting every 50 miles or so due to squeeking on braking. New pads fitted about 5k ago. Not the worse bike I have ever owned for braking, that was an old 750 Bonneville. With the CB400/4 just pull the lever in on Tuesday if you want to come to a halt on Saturday at 3pm ;D ;D
-
Make sure the pads are free to move, likewise the caliper pivot. Grease the pivot with Copaslip or something similar. Bleed the brake. Fitting Stainless brake hoses makes a difference. Use PTFE tape on the bleed nipple threads so it doesn't seize.
-
Surprisingly pivot arm moving great, piston side of caliper really stiff. On stripping, pad corroded on back plate sides / ditto in front of caliper round contact area with it. Piston pitted so either replace now or clean up and see, then do proper job on resto. From what I read, new pistom from DS and genuine Hionda seal. I know copaslip can be used on pins etc on more modern and car calipers. Is a smear of this ok or a no no on sides of pad back plate?
-
All good advice here, I too wasn't too happy with the front brake performance and genuine Honda brake
pads improved performance. Keeping the disc clean with a frequent clean with brake cleaner spray also seems to help. The corrosion on the piston to caused by moisture within the brake fluid so it does need to be changed every three years or so. Alternatively change to silicone brake fluid which does not absorb moisture and before anyone says it's not compatible with the various seals after 15 years of using it following master cylinder/calliper rebuild all is fine. Still on the original hoses. Also it won't damage paint and we all know what a mess can be made when bleeding the front brake.
-
I found an old article on this ... tried to photo it as no scanner at the mo.
[attachimg=1][attachimg=2][attachimg=3][attachimg=4]
-
give both the caliper and piston a complete strip down and clean,
make sure the seal groove is clean,replace the seal ,(it should only cost about $4) as the seal and how it flexes is the
heart of how disc brakes work,
assemble carefully,ensure the pads move freely,use copa grease around the pad will (should ) cure the squealing ,
bleed,and see what happens,it should be SO much better
-
Absolutely what I was looking for chaps. Experience based advise always the best! Looks like a good article Ash, great if you could scan when available again.
What a marvelous forum!
-
If, after all the TLC outlined above you're still not happy with the brakes, I would recommend a master cylinder repair kit.
-
If time allows I will sort next weekend. Just want to be able to get it to stop this side of Xmas (if I apply the brakes now -per Julie ;D). As I say, just a pre resto shake down. If cant get it acceptable short term, recon I will go for a stainless piston and genuine seal per ebay link below. Anyone here used them?
http://www.ebay.co.uk/itm/262018047322?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
-
Went for it and bought piston and seal kit. Also silicone based fluid as suggeted. Hopefully get out to the garage at weekend. Told esssential to get rid of all residual conventional fluid. Any tips on flushing? Thinking meths then air line?
-
As I understand it generally with calipers the seal operates in a very particular way which you need to make sure it's able to do.
The groove in the caliper body has the face (back face looking into the bore) at 90 degrees to the the bore the piston travels in. The front face (the one nearest to you which you can't see) is at a small angle which is leaning outward towards you.
When the piston is at rest with no pressure on it the the seal sits square to both the piston and the back of its groove. When you use it, as the piston moves outward it drags the seal with it but the seal in the deepest part of the groove remains static. Because of the slope on the groove is in the direction of piston travel, the seal deforms in cross section to a parallelogram shape rather than a square section. Then when you let go of the brake lever it's the seal deformation that as it recovers back to its original square section that retracts the piston into the caliper. This is absolutely vital to the caliper functioning as it should.
If the piston fails to retract then the pad is always applied gently to the disc. It's this status that gently glazes the pad and makes it squeal, also reducing it's ability to generate friction and voila, crap braking is the result.
The taper in that seal groove is where corrosion builds up as it has no additional seal to protect it. The seal becomes held static by the corrosion filling up its movement space so that when you use the brake the piston is forced straight past the seal without deforming it, so no retraction takes place and it just drags all the time.
To make it all work properly, that seal groove has to be scrupulously clean, the seal needs to be of the right material/dimensions and you may want to assemble it with brake specific rubber grease.
-
K2-K6 Great info there , thanks for that.
Understanding the full function of a design really helps when restoring anything.
-
And as I have said before : treat it as a whole system, just changing or looking at one part will not help. You have to go through the lot if you want everything to work as it should.
-
Fab info chaps.
Any specific checks on flushing system for silicone fluid change?
-
I think it's a measure of how people are willing to approach things on this site that you can discuss areas like this. On some car sites it'd be met with a rider of not working on critical things like brakes and advising to only buy and replace components.
Agree with you Trigger, I was wondering after posting if I should've covered more of the system. So at the risk of boring everyone I'll make some additional points.
Quite often people assemble the caliper by using brake fluid to ease the piston past the seal but this leaves fluid on the outside of the seal which doesn't protect it. The caliper should be clean and dry, use the brake system grease to lubricate the seal and the piston should just push in with your fingers. When you then fill the completed system, the fluid is only on the correct side of the seal and helps to avoid corrosion.
The master cylinder is obviously another part critical to decent operation. The seals there have different functions which are not readily observed. When you first start to move the lever the fluid will try to go out via the easiest route from the piston chamber, this tries to exit into the reservoir. The first seal operation is to close off that route and if the part of the seal that completes that function is impaired then more of the lever stroke is used before the brake line is pressurised. The seals when they get older and less squishy just don't do that so well, they get there but the lever travel is long as the seal requires the line pressure to build up as it's closing to assist 100% closing. This results in the lever coming too close to the bars and a critical feeling of delay to the rider.
The hole into the reservoir is also an area to look at. If it's partially blocked then two affects are possible, when you release the brake after use the hole is opened to allow the reserve fluid to refill any space in the brake line that has been created by pad wear. It's this aspect that makes disc brakes essentially self adjusting (discounting the screw adjust on the Honda caliper) and resets the lever position each time to give a good lever feel. It also makes the system hard to blead as quick replenishment of the line doesn't take place with the fluid in the line just being pushed down and then pulled back again as you release the lever.
Second effect is that the hole is mostly blocked and as a bit of heat comes into the brake system during use, then the fluid can't expand anywhere so the pads are held against the disc and more heat is created (you often see this on rear disc brake systems as they are just not used at the frequency of the front) this will if not corrected end up looking the brake on.
Piston material in the caliper has an impact on longer term use as well. The corrosion of piston and bore is mostly caused by galvanic reaction ( one material electroplating from another when submerged in an electrolyte solution) in this case the electrolyte solution would be salt water. Even if you use a stainless steel piston the two materials still appear with a difference on the galvanic scale which doesn't stop the problem. There are I believe phenolic resin pistons available for these calipers which are obviously not metal so long term use of this type I think should be considered two best look after the original caliper material.
If you use them all year round and expose them to salty roads then you are probably looking at a strip down every 24months at a guess. This is alot of calipers nowadays have an additional seal outboard of the main one to keep that area as clean as possible.
I know they won't match modern systems for braking power but set up as intended they are alot better than most people indicate.
-
Great info again thanks.
Yes agree a great site and so much can be gleaned from it.
-
K2-K6 - thanks for that. I agree (and with others) the complete system is important. Not least you don't waste time/fluid addressing things separately.
As regards caliper lubrication - I intend to refurb one of my vfrs all round and will use red rubber grease. Also interested in going with silicon fluid, so flushing technique for removing the old stuff completely is welcome.
EDIT: perhaps pumping through 2*amount of new fluid is in fact the best way?
-
I think it's a measure of how people are willing to approach things on this site that you can discuss areas like this. On some car sites it'd be met with a rider of not working on critical things like brakes and advising to only buy and replace components.
Agree with you Trigger, I was wondering after posting if I should've covered more of the system. So at the risk of boring everyone I'll make some additional points.
Quite often people assemble the caliper by using brake fluid to ease the piston past the seal but this leaves fluid on the outside of the seal which doesn't protect it. The caliper should be clean and dry, use the brake system grease to lubricate the seal and the piston should just push in with your fingers. When you then fill the completed system, the fluid is only on the correct side of the seal and helps to avoid corrosion.
The master cylinder is obviously another part critical to decent operation. The seals there have different functions which are not readily observed. When you first start to move the lever the fluid will try to go out via the easiest route from the piston chamber, this tries to exit into the reservoir. The first seal operation is to close off that route and if the part of the seal that completes that function is impaired then more of the lever stroke is used before the brake line is pressurised. The seals when they get older and less squishy just don't do that so well, they get there but the lever travel is long as the seal requires the line pressure to build up as it's closing to assist 100% closing. This results in the lever coming too close to the bars and a critical feeling of delay to the rider.
The hole into the reservoir is also an area to look at. If it's partially blocked then two affects are possible, when you release the brake after use the hole is opened to allow the reserve fluid to refill any space in the brake line that has been created by pad wear. It's this aspect that makes disc brakes essentially self adjusting (discounting the screw adjust on the Honda caliper) and resets the lever position each time to give a good lever feel. It also makes the system hard to blead as quick replenishment of the line doesn't take place with the fluid in the line just being pushed down and then pulled back again as you release the lever.
Second effect is that the hole is mostly blocked and as a bit of heat comes into the brake system during use, then the fluid can't expand anywhere so the pads are held against the disc and more heat is created (you often see this on rear disc brake systems as they are just not used at the frequency of the front) this will if not corrected end up looking the brake on.
Piston material in the caliper has an impact on longer term use as well. The corrosion of piston and bore is mostly caused by galvanic reaction ( one material electroplating from another when submerged in an electrolyte solution) in this case the electrolyte solution would be salt water. Even if you use a stainless steel piston the two materials still appear with a difference on the galvanic scale which doesn't stop the problem. There are I believe phenolic resin pistons available for these calipers which are obviously not metal so long term use of this type I think should be considered two best look after the original caliper material.
If you use them all year round and expose them to salty roads then you are probably looking at a strip down every 24months at a guess. This is alot of calipers nowadays have an additional seal outboard of the main one to keep that area as clean as possible.
I know they won't match modern systems for braking power but set up as intended they are alot better than most people indicate.
You must have more time on your hands than me ;D.
Cheers for all that correct info. Saved me writing it ;)
I do get annoyed when people bring there bike to me saying, I have fitted new braided lines and still have the same problem. Honda lines are braided, you just can not see the braiding.
-
When I changed to silicone fluid I don't recall flushing the system but I had replaced the master cylinder and calliper seals. The piston was also replaced. Genuine Honda parts used. After cleaning there was certainly no fluid in the cylinder or calliper. I would imagine that any old fluid that may have been left in the system would be flushed out when the brake was bled. I think I've only bled the brake once since the change and that was because the front brake switch failed.
I would imagine that if silicone fluid has an adverse effect on the seals the fluid would become discoloured.
-
Ha ha Trigger, I suspect you're a bit more productive than me thought as you've not seen things this end. I can't even get through my list of things to do in the house without the family chief executive (known more commonly as er-in-dooors) putting things on the end of the list while I'm trying to knock things off the top ;) I was late for working today though, partly for battling with my spell checker as it insists every mention of piston should be pistol. Still some typos left in there though.
On that note; I guess the list of brake things is not complete without mentioning you've got to keep the arm pivot clean and free to move easily either.
The silicon brake fluid as far as I know will mix ok, just that by using silicon for its main attribute (it's not hygroscopic, so doesn't attract water and degrade) it will be compromised by having any old type fluid left. Think it's sufficient as stated to make sure you bleed it through the system completely, it shouldn't give any real problems.
On the subject of getting done in time for Christmas, I reckon if I get the Brussels sprouts in the pot and boiling by the end of November then they should be just about ready for Christmas day ;)
-
Should have put the sprouts on last week if you want them done properly by Xmas day 😁😁😁
-
Yaaaa bugger, another deadline missed;)
-
Should have put the sprouts on last week if you want them done properly by Xmas day 😁😁😁
oh !! you like them al dente !!!
should really be middle of april so the cook through !!!
-
Well caliper rebuilt with stainless piston / Honda seal. System fushed with meths and blown through with airline to dry out any residual meths before filling with silicone brake fluid. Caliper now very free and brake actually works. Still not brilliant but will look at other system components when resto starts.
I was amazed by the amount of oxidation etc in the seal grove. Accompanying picture shows the crap cleaned from this small area alone! (hope this works its the first time I've tried to insert an image in a post)
[attachimg=2]
Anyway was able to ride it and check gearbox etc. All seems ok so no real worries before resto starts in the new year.
Thanks again for helpful tips.
Tim
-
now you have the mechanical side working,you need to ride and use the front brake often,but gently ,just to bed the pad in,
Although I have twin discs,I only brake softly,and its taken ages to bed the pads in,
I used DSS own make pads,and they seem very hard,hardly worn at all,
-
I had to rough the DSS pads up to get them to work.But they have been fine since though.
-
It's surprising when you take them apart just how much crap builds up in the groove. All clean and reassembled properly they do last quite well with the proper grease used but longer term I think you'd have to plan reasonable maintenance into running them to keep on top of it. It's really road salt that gets them going bad so if that's avoided then they stay in good nick for longer.
Bedding any pads in should take about 50miles of light use just to get the pads lying flat to the disc and any deviations on the disc if it has any wear.
After that to really get pads working properly you've got to take them through their entire heat range and back to cool to prepare them for general use.
I do this by riding and gently dragging the brake to build heat up slowly, then as the whole caliper and disc is warm keep going with more brake pressure until the pads start to smell, and then more pressure (you may need to run it in 3rd gear to keep it moving along at this stage) until you feel the brake start to fade, ie retardation starts to go down even though you're pulling the lever hard, and the then keep going until it feels like it won't stop the bike ( yes you need to go this far) at this point release the brake but don't whatever you do stop the bike, just ride it gently until the whole system cools down back to normal. You'll they find when you use the brake normally it's the best it's ever been ( this assumes you've got all the system clean and working properly before you start). After this you'll find it gives the best friction power and linearity you can get for that system. Not many people do this properly so never get to see what their brakes will do.
-
The rear brake was non existent on the Guzzi so that's how I bed in the new pads.Now its almost unusable as it is like an on off switch at low speed.