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Honda cb400NC caliper rebuild

Scotthonda

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Joined
Jul 8, 2021
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Location
Hartlepool
Hi all, I started rebuilding my callipers last week. I ordered new piston and seal kits ( four lol ), new boots and brake pads. I also had to replace new bleed nipples because they were leaking. Any way to cut a long story short i ended ordering replacement seals again as the first lot leaked. I am attaching three photos of the pistons with seals. The first one is of the dust seal, the second two are of the oil seals, see if you can spot why they were leaking.
ATB
peter
 

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The first one is of the dust seal, the second two are of the oil seals, see if you can spot why they were leaking.
ATB
peter

Best I can tell from the photos is they aren’t sitting square, or level. One side of the seal looks higher, like it isn’t completely seated.


Tom - 1982 CM450E
 
Is the groove the seal sits in completely clean? It's a bit of a booger to get all of the corrosion out but that's critical so the seal can seat evenly in the body, once the seal is in place you should be able to rotate it in the groove to check if there are any hang up spot which if it hangs it's not clean.
 
If you look closer at the two pictures of the oil seals, there’s a huge gap around the pistons. The dust seal is a nice fit over the piston, and the oil seals should be the same lol. There’s are all brand new by the way.
yes I agree you need to make sure that the grooves are as clean as possible.
ATB
peter
 
Yes the photos aren’t that good. The gap is only about 2mm but it’s enough to make them leak. Does anyone know what TourMax piston seals are like quality wise, they seem to be a lot more money than the others.
ATB
peter
 
Does anyone know what TourMax piston seals are like quality wise, they seem to be a lot more money than the others.

I don’t, but my money is on someone here does.

I'm guessing the reason anyone here might not be aware of them (but LDR probably knows of them) might be because they're more well-known in the UK. Seems to be a Japanese brand I've not heard of until today and I found quite a few suppliers selling them but no website directly related to TourMax

tourmax.png
 
Yes the photos aren’t that good. The gap is only about 2mm but it’s enough to make them leak. Does anyone know what TourMax piston seals are like quality wise, they seem to be a lot more money than the others.
ATB
peter

2mm is enough to make them leak like crazy! When I bought mine I noticed there were two different sizes of caliper piston for the Superdream and I had to be careful which ones I bought. I can't remember the details now it was two years ago (I know, things seem to move slowly here but at the time I was a full time carer working all hours and couldn't get in the garage. Retired early now and STILL can't get in the damned garage!) I bought a matched set of pistons and seals and they were a tight fit on the piston and the bore. Fitted them with rubber grease. Can't say if they leak as I haven't filled them with fluid yet, that's for just before I ride the thing!

I think you have the twin pot per caliper brakes looking at the pictures. Mines single pot so probably cheaper to buy stainless pistons and seals (£62 plus postage)
 
I've never heard of Tour Max seals but that doesn't mean much since there's new companies and name appearing all the time.
Assuming that you've got the original caliper, most likely, you want this seal number 43209-MA3-006 which is probably still sold by Honda. Check the cross reference of the supplier to be sure what they are selling matches to this number.
 
2mm is enough to make them leak like crazy! When I bought mine I noticed there were two different sizes of caliper piston for the Superdream and I had to be careful which ones I bought. I can't remember the details now it was two years ago (I know, things seem to move slowly here but at the time I was a full time carer working all hours and couldn't get in the garage. Retired early now and STILL can't get in the damned garage!) I bought a matched set of pistons and seals and they were a tight fit on the piston and the bore. Fitted them with rubber grease. Can't say if they leak as I haven't filled them with fluid yet, that's for just before I ride the thing!

I think you have the twin pot per caliper brakes looking at the pictures. Mines single pot so probably cheaper to buy stainless pistons and seals (£62 plus postage)

Hi James, yes my super dream is the later model ( ND) and has two 27mm pistons per calliper. I bought mine from Motorcycle Products + all the Boots, £64 for all the pistons and seals. The only problem was the oil seals appeared to be to large. I had problems fitting the seals into the calliper,and pistons into the seals. All seemed to be ok till I started to get some pressure into the system,then they started to Leak. I have some new seals to try now, and will let you know how I get on.
ATB
Peter
 
I've never heard of Tour Max seals but that doesn't mean much since there's new companies and name appearing all the time.
Assuming that you've got the original caliper, most likely, you want this seal number 43209-MA3-006 which is probably still sold by Honda. Check the cross reference of the supplier to be sure what they are selling matches to this number.

Hi Jim, I tried matching the part number for the seals and found that they fit lots of different Hondas, plus Suzuki,Yamaha, and Kawasaki. The problem that I have is that the seals supplied with the 27mm pistons were to large, and started to leak.
I thought I would look to see what other companies made them. Tourmax seems to be quite popular over here in England, they are a lot more expensive than the others at £6.99 a pair. I have some on order let’s see how they fit.
ATB
peter
 
Hi James, yes my super dream is the later model ( ND) and has two 27mm pistons per calliper.

The CB400ND then Peter. That means you will have the oil pipe up the outside of the back of the engine feeding more oil up to the top end. Wish mine had that. Mind you, I'm not going to be thrashing the thing like all young hooligans used to back when they were new bikes. That's how the top end was starved of oil. I doubt very much if I'll have that problem!:)
 
The CB400ND then Peter. That means you will have the oil pipe up the outside of the back of the engine feeding more oil up to the top end. Wish mine had that. Mind you, I'm not going to be thrashing the thing like all young hooligans used to back when they were new bikes. That's how the top end was starved of oil. I doubt very much if I'll have that problem!:)

No actually this bike has the oil feed in the top of the engine, just to one side of the camshaft which makes checking the cam chain a bit difficult. I had to manually adjust the balancer chain, and found that even with a new oil pump chain it was still very slack?.
ATB
peter
 
The oil pump chain is always loose, no problem there and new or old it has zero effect on the balance chain.
Yes, sometimes the front balancer shaft is sticky and requires you to manually move it. If that's the situation then I'd suggest using some penetrating oil on it and work it back and forth until it frees up and will move with the spring. That way the chain is not too tight or loose.
If you have the early engine with out the head oil feed pipe then both sides of the cam get full lubrication delivered past the rear outside head bolts. Review the oil circuit picture in the FSM, page 2-0
If you want improved cam and rocker lubrication it's covered starting with post 16 in this thread https://www.vintagehondatwins.com/f...CM400T-Engine-Rebuild-with-some-modifications
 
Just thought that I would give you an update on the calliper seals. Well no leaks this time, the new seals were a good fit and the pistons went back in no problem. I had to fit a new master cylinder as the original one was past repair. I thought that I had bought one that was suitable for a twin calliper system, but judging by the amount of leaver travel I haven’t. Does anyone know what size piston is fitted to the cb400ND master cylinder.?

ATB
peter
 
I can't speak to the specific bike you have but I believe that most of our bikes with disc front brakes use a 14mm piston, but others will weigh in to correct me if necessary.

Be sure to post your progress regularly and include pictures if possible, so others in the community who encounter the same issues can benefit from your experiences and that way, if something happens that you didn't expect, the rest of us will be following along and may have an answer for you right away from personal experience. Sharing our experiences is what we do here, for the better of all of our favorite vintage Honda twins! (y)
 
I can't speak to the specific bike you have but I believe that most of our bikes with disc front brakes use a 14mm piston, but others will weigh in to correct me if necessary.

Be sure to post your progress regularly and include pictures if possible, so others in the community who encounter the same issues can benefit from your experiences and that way, if something happens that you didn't expect, the rest of us will be following along and may have an answer for you right away from personal experience. Sharing our experiences is what we do here, for the better of all of our favorite vintage Honda twins! (y)

Thanks I will keep you posted .
ATB
peter
 
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