Honda-SOHC
Other Stuff => Misc / Open => Topic started by: gary123 on September 25, 2023, 05:17:06 PM
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What is the most likely cause of a 550 not engaging 3rd gear fully. It chatters and wants to disengage all others are ok.
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One of the gears, cant remember which, is known to ocassionally shear off the locating dogs.
Drop the sump pan and see if any bits in there
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One of the gears, cant remember which, is known to ocassionally shear off the locating dogs.
Drop the sump pan and see if any bits in there
Its not mine, Im asking for a friend. Ill pass on all suggestions and probably help with any necessary repairs.
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Engine out and split job I'm afraid.
Check the primary chain etc whilst you're in there.
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oh pooh, didnt want to hear that.
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Thats to fix it, just sump off to find out then that stays off to remove lump.
Only need bottom case off if primary chain ok
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So, we removed the sump and found nothing. Removed clutch and all looks good with the mechanism.
It runs and rides great, snicks in and out of all gears just as it should and even runs in 3rd until you put some load on it. Then it slips and sounds as though the gears are hardly meshed so Im thinking a selector fork is not sliding it all the way across. Does that sound feasible? Looks like engine out :'(
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More likely dogs rounded but still engine out.
Remove sump, top breather cover and oil filter to make it easier
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It could be a combination of a worn selector fork, rounded dogs on the 3rd gear and even the corresponding gear it's engaging with.
I think the problem will be 2nd/3rd combination gear, 23431-374-000 and it's engagement gear either 23450-390-000 or 23480-390-000. All still available to buy NOS. If it's the selector fork, I suspect that's the middle one on the drum not the rods and that's hard to find new.
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I have a complete 550 gear set in my spares stash so hopefully should be able to sort something out.
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I recently replaced my 550 gear cluster that is driven by the clutch. Only one of gears was damaged so if you need anything off there it's yours for postage costs only.
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I recently replaced my 550 gear cluster that is driven by the clutch. Only one of gears was damaged so if you need anything off there it's yours for postage costs only.
Thats great, thanks. Ill bear that in mind.
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The engine is out and it looks like 3rd gear is just not sliding over enough to engage. Compared to 2nd gear it could go another 2mm at least but it just wont. The gears look ok but show evidence of slipping, the dogs are polished as is the gear it engages with.
The fork that moves it fits snug in the groove but looks well worn, do you think thats it?[attachimg=1][attachimg=2]
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Just a thought Gary, the selector drum that positions these forks when the gears are selected could also be worn and make a difference. Also the levers that rotate the drum.
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Fork looks bent sideways, only supposed to touch on either side of the two pads out at end of fork.
Looks like a half moon witness mark at base of semi circle that's been rubbing where it shouldn't. That will probably account for the error you're seeing in travel.
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Just a thought Gary, the selector drum that positions these forks when the gears are selected could also be worn and make a difference. Also the levers that rotate the drum.
There's no "slop" in the drums channel and the peg fits well but I have a spare so Ill try a swop. I discounted the levers as all other gears select well.
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Fork looks bent sideways, only supposed to touch on either side of the two pads out at end of fork.
Looks like a half moon witness mark at base of semi circle that's been rubbing where it shouldn't. That will probably account for the error you're seeing in travel.
I thought the fork might be bent, but if it is I cant discern it. Def worn at base which makes me think the pads are shot.
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I like to see pics of the gear dogs concerned, also does the gear dogs move more into the mating gear with selectors out.
2 does it look like its been apart before?
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Fork looks bent sideways, only supposed to touch on either side of the two pads out at end of fork.
Looks like a half moon witness mark at base of semi circle that's been rubbing where it shouldn't. That will probably account for the error you're seeing in travel.
I thought the fork might be bent, but if it is I cant discern it. Def worn at base which makes me think the pads are shot.
I can't see complete detail from photo as slight blurr on fork of second one, but the pad looks more worn nearer the inner edge. If the other side (not in photos) of the pad has the tips more worn, giving a "diagonal" opposed wear pattern to the pads ? Then the alignment of them is contrary to the gear slot such that it siits touching both sides from that fault.
Slightly difficult to explain, but hope that makes sense.
Also usually shows with some heat blueing from running in contact continuously on some examples. That burr around the half moon cut shows quite a bit of running contact has taken place, when it shouldn't touch there at all.
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I like to see pics of the gear dogs concerned, also does the gear dogs move more into the mating gear with selectors out.
2 does it look like its been apart before?
Yes, has def been apart before. I did it. I replaced countershaft 4th at that time cos a dog had sheared off. It looked all good then and ran great for about 200 miles.
Yes the dogs move into a better mating position with the selectors out.
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That's probably why it happened Gary. The circlips used on the gearbox are special, they are not eared like your picture, they are shouldered as well, so they fit in one direction. I seem to recall this makes them thinner than standard circlips.
Look like this.
https://www.cmsnl.com/honda-cb550f1-super-sport-550-four-1976-england_model17113/set-ring25mm_90602259010/
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Fork looks bent sideways, only supposed to touch on either side of the two pads out at end of fork.
Looks like a half moon witness mark at base of semi circle that's been rubbing where it shouldn't. That will probably account for the error you're seeing in travel.
I thought the fork might be bent, but if it is I cant discern it. Def worn at base which makes me think the pads are shot.
I can't see complete detail from photo as slight blurr on fork of second one, but the pad looks more worn nearer the inner edge. If the other side (not in photos) of the pad has the tips more worn, giving a "diagonal" opposed wear pattern to the pads ? Then the alignment of them is contrary to the gear slot such that it siits touching both sides from that fault.
Slightly difficult to explain, but hope that makes sense.
Also usually shows with some heat blueing from running in contact continuously on some examples. That burr around the half moon cut shows quite a bit of running contact has taken place, when it shouldn't touch there at all.
Yes makes sense. My thinking is it must be the fork but I cant be sure as I just dont have the experience. Dont want to put it all together and it not be right.
To be honest Im totaly baffled.
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That's probably why it happened Gary. The circlips used on the gearbox are special, they are not eared like your picture, they are shouldered as well, so they fit in one direction. I seem to recall this makes them thinner than standard circlips.
Look like this.
https://www.cmsnl.com/honda-cb550f1-super-sport-550-four-1976-england_model17113/set-ring25mm_90602259010/
When I put it together the first time I used the correct circlip the one you see in the pic is temporary to avoid stressing the correct one while Im taking it apart several times.
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You should always replace those circlips when they are removed Gary. Fairly certain I've seen a diagram by Honda on the correct orientation of them when fitting, they are flat one side but have a curved surface on the other IIRC. I can't find the diagram now I need it, typical. Maybe someone else knows where it is. Might be a bulletin, I thought it was in the workshop manual but can't find it there.
Maybe I'm thinking of something else, maybe I'm confusing them with the thrust washers.
I'm sure someone will remember better.
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OK will do, in stock at DS or maybe Julie has em.
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Think its a 750 bulletin Ken, one ting i remember is one of the gears has to be changed with its mating pair due to tooth profile
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Can't find the bulletin, but did have this:
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Not the diagram I was thinking of Seabeowner, but a good find nevertheless.
I remember the dual gear replacement bulletin Bryan. The Snap ring bulletin should also cover all the SOHC gearboxes you'd imagine Bryan, it's not like there's a massive difference between them all.
I think it's Honda bulletin SL#78 Bryan but no sign of it anywhere.
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This one Ken?
[attach=1]
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Yeah, there was a diagram as well but I can’t find it. Doesn’t matter it’s clear enough now.
Maybe check the thrust washers for wear?
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Does the mating gear run on a loose bush? If so is it top hat shaped? If so is it correct way round
Trying lateral thinking here
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They still shouldn't be touching the selector fork face with the gear or any part of it, indicating a misalignment in that fork. The gear can't do it as it runs perpendicular to it's own shaft.
The fork has to have angle on it other that 90 degree to the shaft it's sliding on to touch just at that point and give that wear mark, up near the pivot.
Something like a surface plate to hold the pads flat to, then check the fork shaft angle against vertical to see what you've got there.
It is quite normal to see forks with that wear mark if bent in most gearbox assembly.
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Does the mating gear run on a loose bush? If so is it top hat shaped? If so is it correct way round
Trying lateral thinking here
No, no bushes.
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They still shouldn't be touching the selector fork face with the gear or any part of it, indicating a misalignment in that fork. The gear can't do it as it runs perpendicular to it's own shaft.
The fork has to have angle on it other that 90 degree to the shaft it's sliding on to touch just at that point and give that wear mark, up near the pivot.
Something like a surface plate to hold the pads flat to, then check the fork shaft angle against vertical to see what you've got there.
It is quite normal to see forks with that wear mark if bent in most gearbox assembly.
This is my thinking, Ill see if I can get replacement forks, its the ones that run on the shaft, not the one on the drum.