Gearbox

[cb550k-aaron]

I'm not sure if a bottom end IS the way to go TBH, there is a lot of damage sure BUT the problem is the new bottom end isn't guaranteed to be any better unless it comes with one of course. TwoWheelSpares on E-Bay have some complete engines but no bottom ends, your never sure on what the crank shells are going to be like on another engine, his may be new but they don't transfer as we know unless your really really lucky.

Really blowing the pics up shows what I suspect has happened, just above the mainshaft 3rd gear where it is missing 2 teeth there is another tooth with just the leading edge missing, I suspect this came off, jammed between the gear teeth just below it when second was engaged, this would mean this gear cluster was sitting to the left, when the 2 teeth came off they were in close proximity to countershaft second and they jammed between the 2 gears, would explain why no teeth are missing from mainshaft second, which is puzzling as you'd expect them to be meshed but again I think maybe third was in the process of being selected. The selectors look fine, which again is puzzling as you'd expect them to be the cause of this but they clearly aren't. Maybe the PO was a bit clumsy and started the process by catching the 3rd gear tooth edge. Looking again at the pics you can see new damage just under the primary chain and again to the left of that, these were no doubt the result of all the debris getting flung out of the gearbox.

I'm not convinced the bearing spun in the casings, I've never seen them do that before even when the knock pins are squashed flat to the case as in this case, I'd like to see some pics of those bearings in detail to say for sure though, if they had I'd expect to see some damage to the knock pins and I can't see that.

I'd also think about just replacing the entire box,

 https://www.ebay.co.uk/itm/Honda-CB550-CB-550-K-F-Four-1974-1978-Gearbox-Gear-Box-Assembly/332536863177?hash=item4d6cbdd9c9:g:V5oAAOSwzRFabzr4

If you just buy a bottom end your going to need a complete set of gaskets as well, plus some time stripping both engines to see if there is any damage. However I'd also point out that the damage caused by crushing the 2 knock pins can sometimes be significant, I'd like to see pics of the sprocket area from the outside to see if the pin came through the casing and also of the clutch area for the same reason.

Oddjob, I've added two pictures of the pins where they burst the casing. These were sealed and are 100% no leaks etc. I'll take pictures of the bearings etc and upload them later on.

[cb550k-aaron]

Those both look to be recent breaks, has the engine been apart recently?

Around 2 Years ago for a full overhaul. Them pictures were taken at that stage not recently.

I added the bearing pictures etc to same link

[Trigger]

I'm not sure if a bottom end IS the way to go TBH, there is a lot of damage sure BUT the problem is the new bottom end isn't guaranteed to be any better unless it comes with one of course. TwoWheelSpares on E-Bay have some complete engines but no bottom ends, your never sure on what the crank shells are going to be like on another engine, his may be new but they don't transfer as we know unless your really really lucky.

Really blowing the pics up shows what I suspect has happened, just above the mainshaft 3rd gear where it is missing 2 teeth there is another tooth with just the leading edge missing, I suspect this came off, jammed between the gear teeth just below it when second was engaged, this would mean this gear cluster was sitting to the left, when the 2 teeth came off they were in close proximity to countershaft second and they jammed between the 2 gears, would explain why no teeth are missing from mainshaft second, which is puzzling as you'd expect them to be meshed but again I think maybe third was in the process of being selected. The selectors look fine, which again is puzzling as you'd expect them to be the cause of this but they clearly aren't. Maybe the PO was a bit clumsy and started the process by catching the 3rd gear tooth edge. Looking again at the pics you can see new damage just under the primary chain and again to the left of that, these were no doubt the result of all the debris getting flung out of the gearbox.

I'm not convinced the bearing spun in the casings, I've never seen them do that before even when the knock pins are squashed flat to the case as in this case, I'd like to see some pics of those bearings in detail to say for sure though, if they had I'd expect to see some damage to the knock pins and I can't see that.

I'd also think about just replacing the entire box,

 https://www.ebay.co.uk/itm/Honda-CB550-CB-550-K-F-Four-1974-1978-Gearbox-Gear-Box-Assembly/332536863177?hash=item4d6cbdd9c9:g:V5oAAOSwzRFabzr4

If you just buy a bottom end your going to need a complete set of gaskets as well, plus some time stripping both engines to see if there is any damage. However I'd also point out that the damage caused by crushing the 2 knock pins can sometimes be significant, I'd like to see pics of the sprocket area from the outside to see if the pin came through the casing and also of the clutch area for the same reason.

I disagree Oddjob, the pins are lower than the journal surface and I can see the marks on the journal where the bearing has turned and then gone tight and stopped as the engine heated up and the spun when it has cooled.
Seen this tooo much lately with customers engines, as they have tried to rebuild their own motor and then bring it to me saying, it is jumping out of gear.   

[cb550k-aaron]

I disagree Oddjob, the pins are lower than the journal surface and I can see the marks on the journal where the bearing has turned and then gone tight and stopped as the engine heated up and the spun when it has cooled.
Seen this tooo much lately with customers engines, as they have tried to rebuild their own motor and then bring it to me saying, it is jumping out of gear.   

In your opinion Trigger Is the spinning of the bearing the cause for the slipping and eventually the damage?

[Trigger]

Hold on I just get my crystal ball out me tool box 
The pin damage should of been repaired to make sure the bearings did not spin, before it was put together and started up. Short cuts on engine builds always bites back in a big way.

[cb550k-aaron]

Ok let me know what it says  lol.

If I go the route of repairing this casing with the pins in the correct places. Can you give any tips or would u just replace?

[Trigger]

Ok let me know what it says  lol.

If I go the route of repairing this casing with the pins in the correct places. Can you give any tips or would u just replace?

Hard to say without measuring the cases up to find how much damage has been done.

[cb550k-aaron]

Ok let me know what it says  lol.

If I go the route of repairing this casing with the pins in the correct places. Can you give any tips or would u just replace?

Hard to say without measuring the cases up to find how much damage has been done.

Are there readily available specs that it should be? Tbh it hasn't done anymore than 150miles I'd say since the Pins were damaged.

[Trigger]

Yeah your correct Trig, the new pics clearly show the damage, there wasn't enough detail on the original pics for me to be sure.

Is it enough to bin the bottom end though? I'd chance using it again TBH, so long as the pins are made to stand proud of course and a new gearbox is fitted. I'd be interested in where all the debris has gone though, is it in the sump?

The damage to the cases, were the pics taken before or after the rebuild? I'd say after as those breaks look very clean, if that's the case then whoever reassembled the cases is responsible.

I thought your eagle eye would of picked it up from the first picture 

[tom400f]

So for the curious, the gist of this damage is that gross misuse has stripped the teeth of 2nd and 3rd, locked up the free/splined cogs causing the shafts to rotate in their bearing housings and ramming the dowels down into the case where they have tried to exit. Subsequently the blind bearings are free(ish) to rotate as they want?

That's some achievement.

[Green1]

Maybe I should stop bashing mine through the box.

[Trigger]

So for the curious, the gist of this damage is that gross misuse has stripped the teeth of 2nd and 3rd, locked up the free/splined cogs causing the shafts to rotate in their bearing housings and ramming the dowels down into the case where they have tried to exit. Subsequently the blind bearings are free(ish) to rotate as they want?

That's some achievement.

Nope ! Some muppet put the crankcases together without lining up the bearing housings with the pins located. This pushed the pins through the cases, allowing the bearings to spin 

[Green1]

I shall carry on abusing mine then 

[Johnwebley]

you do as you want.
I will continue to ride like a pussycat with sore paws !!!

[Trigger]

you do as you want.
I will continue to ride like a pussycat with sore paws !!!

So will I John, I always let Julie ride like a lunatic