cb 550 3rd gear

[gary123]

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.

[gary123]

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.

[Bryanj]

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?

[K2-K6]

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.

[gary123]

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.

[Oddjob]

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/

[gary123]

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.

[gary123]

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.

[Oddjob]

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.

[gary123]

OK will do, in stock at DS or maybe Julie has em.

[Bryanj]

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

[Seabeowner]

Can't find the bulletin, but did have this:

[Oddjob]

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.

[Deano400]

This one Ken?

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[Oddjob]

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?