Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: Nurse Julie on December 15, 2017, 04:29:33 PM
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A slight diversion from the engine building today. On a couple of occasions the front forks have bottomed out and stayed stuck down momentarily. Also the forks seemed to be very hard to me on normal riding. Therefore decided to take them apart and refurb. I know many of you are expert with front forks but this is the first time for me doing this on an old Honda, so I thought I would share.
Here they are out of the bike.
[attachimg=1]
I took the top nut off with the air wrench.
[attachimg=2]
I also used the air wrench to remove the bottom bolt. This is an Allen head bolt, so needed an Allen bit, plus a little extension bar to get in between the studs. Before using the wrench I gave the Allen bit / extension bar a couple of good whacks with the big persuader.
Trig said it is always best to use the air wrench as this can prevent the part that the bolt is attached to inside, the bottom of the under seat pipe, turning with the nut.
[attachimg=3]
The old oil seal stop was then removed
[attachimg=4]
and then the old oil seal.
[attachimg=5]
The fork pipe was pulled out from the bottom case. The fork was then turned upside down to drain all the fork oil. All the internals were then taken out. The spring, the under seat pipe, the oil lock piece and the external drain bolt.
Every part was then cleaned thoroughly in solvent and dried. Including getting a long piece of stiff wire with a rag attached right down to the bottom to make sure all the old crud had been removed. As Trig was doing some polishing at the time, he polished the bottom cases for me.
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All parts cleaned and ready for reassembly.
[attachimg=1]
The oil lock piece was dropped down inside the fork pipe, then the new seal was inserted. A little red rubber grease helped this go in but even then it was still a very tight fit.
[attachimg=4]
The under seat pipe and the spring were inserted and the socket bolt re inserted and done up with the air wrench.
The under seat pipe
[attachimg=2]
All internals back in and showing the top of the spring.
[attachimg=3]
As this was a total strip down the amount of fluid to be put in is 160 to 165 mls. I wanted them on the softer side so went for the 160 mls.
The new seal in place in the bottom case with the oil seal stop in place and the fork pipe in situ.
[attachimg=5]
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New O ring applied to the top nut and done up using a normal spanner.
All back together and standing upright for 24 hours to make sure there are no leaks. All copper washers were changed where necessary.
[attachimg=1]
A nice little job to do. I did find that I needed more than one pair of hands at times, so I got Trig to help.
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Excellent photos- no reason to understand why the forks jammed down though.
the 2nd to last looks like the spring ring is displaced?
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Excellent photos- no reason to understand why the forks jammed down though.
the 2nd to last looks like the spring ring is displaced?
I will check the spring ring Pat.
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Excellent photos- no reason to understand why the forks jammed down though.
the 2nd to last looks like the spring ring is displaced?
I have checked those springs Pat and they are sitting OK. I went round them again though and tried to push them in further but still sitting in the same place. I'm wondering if it was the angle of the photo that made it looked displaced?.
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Julie, you obviously know what you are doing, i have no doubt! As you say, the photo may have been viewed incorrectly by me- it was the 'springs' in the seals i was referring to- one seemed like it was trying to 'climb off' the seal.
Did you find anything that may have made the forks jam down?
I did my 400/4 seals ages ago due to the usual weeps/pits. Exactly the same as you- off the bike and tear-down.
I was alarmed at your engine/piston/head photos! and amazed it still ran!
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Yes, it's those springs I have checked Pat. It's strange as if you look at the pic of the seals that came out, they look like they are sitting a bit scew wiff as well.
No, didn't find a cause for jamming down, it only happened a couple of times. I couldn't really measure accurately the amount of oil that drained out but it may have been a little on the low side. Anyway, it didn't do any harm stripping and cleaning and changing the seals, at least I know they are done.
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Aaaarrrrh, Paranoia is setting in. Just checked them again and they won't seat anywhere other than where they are, so they can stay there. Paranoia moment over ;D ;D ;D
Thanks very much to the forum member that gave me the seals FOC.....you know who you are.
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I have been watching this thread and i am impressed with the work you are doing Julie, and here comes the concern, you have just done your forks and i have looked at all the pictures and i see you have re-assembled in exact reverse of dis-assembly, i rebuilt my 350f forks this year and they had never been off the bike, the difference is your seals appear upside down, this not only exposes the coiled ring to atmosphere and the possibility of rusting out but the chance of oil bypass and out of the top of the seal, i have replaced a lot of fork seals over many years and never seen them this way up, so unless this is a trick of the light or you have special seals, you need to replace the seals the right way up.
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Have to agree with the above Julie. I think the seals are in upside down....the open 'spring' side should be facing the medium its trying to seal...
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Well Kevski , thanks so much for your input and your concern and now I'm really worried. Yes, I put them back on the way they came off with the spring facing upwards. I will have to look at some pictures and speak to Trig later, to see the correct way up. I assumed they went that way, as like I said, that's the way they come out. Also, if they were supposed to be fitted 'spring' facing down, how would you know the spring was in the correct place, or even there at all and not fallen down the fork?. I will report back.
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Thanks as well James, I'm on the case :-[ :-[ :-[
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By what I have found so far, yes, it looks like I have them in upside down :'( :'( :'(
In the Shop Manual is says 'press fit the new seal, using seal driver part number blablabla' I am now thinking that if I had put the seal in the other way up and used a seal driver, which I didn't, the driver would then make contact with the 'flat' side of the seal and not the side with the recess and the spring in. No wonder I found them so tight to get in !!!
No worries, I will just have to do it again, the right way up. I will show it to Trig though before I take them apart and start again. Learning curves.......don't you just love em. Thanks to you lot for being so observant, what would I do without you.
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I suppose it's a lesson to all of us. Never assume that the old parts were fitted correctly in the first place!
Even factory original parts can be fitted wrongly. :-\
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I suppose it's a lesson to all of us. Never assume that the old parts were fitted correctly in the first place!
Even factory original parts can be fitted wrongly. :-\
Yep, bloody previous owners, they have a lot to answer for at times !!!
And I thought I was doing so well. Never mind. I wonder if that's why the forks got stuck down sometimes ?
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I suppose it's a lesson to all of us. Never assume that the old parts were fitted correctly in the first place!
Even factory original parts can be fitted wrongly. :-\
Yep, bloody previous owners, they have a lot to answer for at times !!!
And I thought I was doing so well. Never mind. I wonder if that's why the forks got stuck down sometimes ?
It may be. The stantions are straight aren't they?
Your rebuild is going really well. The fork seals are just a little hiccup. Everybody has them so no big deal.
Looking forward to the rest of the bike rebuild. 8)
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Just DON'T try re using those seals again, get new ones, a few pounds spent now will save a lot of cursing and swearing later if they leak and you have to strip them a 3rd time!
Sent from my X6pro using Tapatalk
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I suppose it's a lesson to all of us. Never assume that the old parts were fitted correctly in the first place!
Even factory original parts can be fitted wrongly. :-\
Yep, bloody previous owners, they have a lot to answer for at times !!!
And I thought I was doing so well. Never mind. I wonder if that's why the forks got stuck down sometimes ?
The air in the forks was probably being pushed out through the seals, and then a vacuum was created when the forks were going back up slowing the return to normal height and momentarily sticking from time to time, i am surprised you wern't leaking oil, in the right way up the pressure build up in the cavity makes the seal expand against the stanchion creating a tighter seal keeping even the air in, you will certainly notice the difference, better to find out now rather than finding 300ml of oil over your tyres when out riding it, doesn't bear thinking about, the coiled spring sits in a lip and i have not known one to come off yet.
We are nosey buggers, but sometimes it helps.
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Minor setback when you are otherwise doing extremely well. It is one of my pet hates in manuals is when they say assemble in reverse order of disassembly. This is no use if someone has been in there before or the part you are trying to fix has come apart in service. About 75% of the stuff I work on is already not functioning or been apart before, so if I am reaching for the manual is nice to check what should be there, and how it should be installed. About the only manual I know that shows this is the old 60s land rover one that gives exploded parts diagrams.
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I suppose it's a lesson to all of us. Never assume that the old parts were fitted correctly in the first place!
Even factory original parts can be fitted wrongly. :-\
Yep, bloody previous owners, they have a lot to answer for at times !!!
And I thought I was doing so well. Never mind. I wonder if that's why the forks got stuck down sometimes ?
It may be. The stantions are straight aren't they?
Your rebuild is going really well. The fork seals are just a little hiccup. Everybody has them so no big deal.
Looking forward to the rest of the bike rebuild. 8)
Yep, stantions are straight
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Just DON'T try re using those seals again, get new ones, a few pounds spent now will save a lot of cursing and swearing later if they leak and you have to strip them a 3rd time!
Sent from my X6pro using Tapatalk
Yes Mr Hairy, I will use new ones.
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I suppose it's a lesson to all of us. Never assume that the old parts were fitted correctly in the first place!
Even factory original parts can be fitted wrongly. :-\
Yep, bloody previous owners, they have a lot to answer for at times !!!
And I thought I was doing so well. Never mind. I wonder if that's why the forks got stuck down sometimes ?
The air in the forks was probably being pushed out through the seals, and then a vacuum was created when the forks were going back up slowing the return to normal height and momentarily sticking from time to time, i am surprised you wern't leaking oil, in the right way up the pressure build up in the cavity makes the seal expand against the stanchion creating a tighter seal keeping even the air in, you will certainly notice the difference, better to find out now rather than finding 300ml of oil over your tyres when out riding it, doesn't bear thinking about, the coiled spring sits in a lip and i have not known one to come off yet.
We are nosey buggers, but sometimes it helps.
Carry on being nosey Kevski, if it's to my benefit ;D ;D ;D. Never had an oil leak on these forks, just the sticking down at times
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Well, I was just about to take these forks apart and Trig came in. The exact words were' what the bloody hell are you doing?'
So I explained that I had put the seals in the same way I had taken them out and as a result, they are upside down. 'No they are not' he said. Anyway, I have now had a teaching session on Genuine Honda fork seals, which is what I took out and replaced them with genuine Honda ones.
This picture is showing the upper side of the seal, with the spring and the writing on the seal. The inner lip of the seal is soft and supple and the spring compresses this.
[attachimg=1]
This picture is showing the underside of the seal. The inner lip is very soft and supple. There is also a spring in the rebate which is a lot thicker and stronger than the one on the top.
[attachimg=2]
Trig says fork oil seal is always fitted with any numbers etc facing upwards or outwards.
Therefore I have fitted them correctly and do not need to strip them down again. Phew ;D ;D ;D ;D ;D
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Usually find the need to remove old fork seals etc by employing the two woodscrew and pull method..... assisted by added heat from warming the legs with hot water. So the closed side of these is uppermost....usually has the makers name and part number on this side too !
The stiction could have been from these being assembled the wrong way up?
Many like to polish the aalyy bits...I gave the fork legs the "original" brushed finish using emery to remove the corrosion and dinks then different grades of scotchbrite to get the finish.... then a coat or three of clear lacquer to protect them.
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It would be great to find out what's causing them to stick. I replaced the forks on the CG with new Chines ones and they occasionally bottom out and stick down you have to pull on the bars whilst riding to bring them back up again.
I'm sure someone at work once told me it can happen with the wrong amount of oil in them.
The fork seals in my Pegaso have springs on both sides I always assumed this was because it has upside down forks.
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There we go, learn something new every day, 350f ones were different, i on a personal note would use different ones, just don't like the coil spring on the outside, that is naturally there to help keep the top clamped to the stanchion.
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Here are both the springs side by side.
The one on the left being thicker and a lot stronger is from the underside, the one on the right the upper side one.
[attachimg=1]
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Just looked up the seals, and different for both bikes, still first time iv'e seen those seals, so special seals then.
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Just looked up the seals, and different for both bikes, still first time iv'e seen those seals, so special seals then.
Not special as such, just OEM CB400/4
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I have seen both single lip(one spring) and double lip (2 springs as described here) supplied by Honda under the same number. Both will work to stop oil leaks as it is the lower one that is supposed to keep the oil in, the top one stops secret additive (SH!T) getting to the lower lip (in theory) so the seal should last longer
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Well that sorted that one out. Well done Julie...didn't sport the writing on the seal but obviously that should site outward so good job you had them the right way in...
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It maybe linked to the old type ordinarily being used with fork gaitors, does the 350 have fork gaitors?
My 1984 Honda uses the seals in same format as Julie's, they also then have a further dust seal above that fits in the fork tube I suppose in place of the 400/4 covers that go outside the casting.
I was just looking at Mr Silver's emporium as mine are leaking so I've a similar job to do.
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Well, at least I didn't have to strip them down and start again. But, if I had of got the seals in the wrong way, I would have been quite pissed off with myself more than anything, as I used up a lot of mental energy concentrating on getting them right ;D ;D ;D ;D
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It maybe linked to the old type ordinarily being used with fork gaitors, does the 350 have fork gaitors?
My 1984 Honda uses the seals in same format as Julie's, they also then have a further dust seal above that fits in the fork tube I suppose in place of the 400/4 covers that go outside the casting.
I was just looking at Mr Silver's emporium as mine are leaking so I've a similar job to do.
350F has shrouds over the forks, but its the first time i have seen these, not even on all the other Hondas i have owned have i come across them, never had a 400/4 though.
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It maybe linked to the old type ordinarily being used with fork gaitors, does the 350 have fork gaitors?
My 1984 Honda uses the seals in same format as Julie's, they also then have a further dust seal above that fits in the fork tube I suppose in place of the 400/4 covers that go outside the casting.
I was just looking at Mr Silver's emporium as mine are leaking so I've a similar job to do.
350F has shrouds over the forks, but its the first time i have seen these, not even on all the other Hondas i have owned have i come across them, never had a 400/4 though.
400/4's are very special bikes, therefore they have very special parts fitted ;D ;D ;D
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Well, at least I didn't have to strip them down and start again. But, if I had of got the seals in the wrong way, I would have been quite pissed off with myself more than anything, as I used up a lot of mental energy concentrating on getting them right ;D ;D ;D ;D
Good news. I'm glad that you don't have to undo your good work.
Being a cheapskate I used pattern seals with a single lip on mine. ;D
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Surprised you didn't have Philpotts hard chrome them while they were apart Julie, would also have checked the stanchions are dead straight, according to their website most stanchions will be bent to some degree due to the forces exerted whilst under hard braking, they may appear straight to the eye and may even roll straight but could still be a few microns out. May not sound like much but could be contributing to the sticking your having.
The chrome is in excellent condition Ken. There is no pitting or rust in the travel areas and I never had any seepage or leaks. The stanchions were put in 'V' blocks and dial micrometer was used and they measured up perfectly. (Not that I did any of this but Trig did it for me whilst I was cooking dinner, hence no photos!!!).
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Just to confirm what already has been, I recently stripped my forks down for anodising and my new fork oil seals had a spring on both sides of the seal (CB400F). I installed mine the same orientation as Julie has done. on the first page.
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Just to confirm what already has been, I recently stripped my forks down for anodising and my new fork oil seals had a spring on both sides of the seal (CB400F). I installed mine the same orientation as Julie has done. on the first page.
Good, that's 2 of us that have got it right then ;D ;D ;D
Anyway, front end now all back in the bike after fitting the new seals. Greased up the head bearings etc and Trigger drilled out the old steering lock, which had never located properly anyway and he fitted a new one. The front disk has been skimmed, the pads were new this year anyway so the front end is all done, she will be good for the foreeable. Another job out of the way.
At least now the bike is rolling again, I can get her into the workshop sometime over the next week or two and fit the bottom end of the engine back in the frame.
[attachimg=1]
[attachimg=2]
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Aaaarrrrh, Paranoia is setting in. Just checked them again and they won't seat anywhere other than where they are, so they can stay there. Paranoia moment over ;D ;D ;D
Thanks very much to the forum member that gave me the seals FOC.....you know who you are.
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You are getting just like the other half.
Must be spending time in the same room ;D ;D ;)
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Aaaarrrrh, Paranoia is setting in. Just checked them again and they won't seat anywhere other than where they are, so they can stay there. Paranoia moment over ;D ;D ;D
Thanks very much to the forum member that gave me the seals FOC.....you know who you are.
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You are getting just like the other half.
Must be spending time in the same room ;D ;D ;)
Yes, I am learning from him but I try to stay well out of his way Paul :'( :'( :'(. To be honest, he can't stand me working in the same room as him when he's working. But, if he does need my help for something, either I'm standing in the wrong place, even though that's where he told me to stand, I do the wrong thing, even though that is what he has told me to do and as for handing him the correct tool, forget it. If he asks for a 10mm spanner, that is what I will give him but no, he didn't mean that 10mm spanner, he meant a different 10mm spanner. But we survive without killing each other somehow. (only just though ;D ;D ;D)
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;D ;D just pass him ALL the 10mm spanners
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i knew something didn't look right but thats why we are a community!
-bit like the time when I was bolting a 400/4 engine back in the frame and I put one of the LONGER bolts into the front LHS lower engine mounts- and I like things tight...so I tightened it and it went right through the crankcase and destroyed the engine....but, as Ive said on here before- parts were a plenty back in the 80's and i just brought another runner from a breakers for £50...
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Done that. Had to strip the bottom end all down and get it welded.
"Oh drat" I said.
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Yep, I did the same. Someone had fitted crash bars previously and they were rusty so I took them off and just refitted the bolts as you do when you are 19 and still living in the land of stupid!