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Discussion Starter #1
I finally had some time to dig into the CB450 engine. The failure was in the right-hand connecting rod crank bearings. Looks like the entire inner bearing set detonated and left the big-end flopping around like a fish out of water. I'm going to look into ordering a new bearing set and finding a machine shop capable of overhauling the entire crankshaft assembly. I have a couple of spare engines floating around, so I grabbed the rotating assembly out of one that's already been broken down and after a good cleaning and lube, I slapped it into the case. So far so good. I started assembling the case halves, and everything lined up and went together amazingly well, until I got to the clutch basket and crankshaft gear. The small output gear is rubbing on the back of the clutch basket, and the inner clutch basket doesn't slide onto the shaft far enough to get the retaining ring installed. I'm not terribly worried about the gear making slight contact with the back of the clutch basket, it really is very light contact, and will self-clearance after the first run. The oil will get changed out at least twice in the first couple of miles, so I'm not even concerned about loading up the oil with the metal filings. Another option would be to mill the back of the clutch basket a couple thousandths and eliminate the issue right from the start. Since I put a different rotating assembly into the motor, I can understand where that clearance issue comes from, but I'm really scratching my head on the inner clutch basket issue. It's the same transmission set that came out of the engine, why isn't it going back together the same way? Any advice or guidance on the entire issue would be greatly appreciated, I'd like to get this bike back together and back on the road by the end of the year. -E

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Two thoughts.
Which K model was the original crank and which K model did your donor crank come from? The reason I ask is the thrust washer behind the crank primary drive gear changed from the early models to the later ones and the later ones were a bit thinner. It looks like you have the early (brass?) thrust washer on there in the first photo. Not sure if this would make a difference but it’s worth asking.
Also check the arm for the oil pump piston on the rear of the clutch basket. I believe it has an offset and there is a certain orientation for it. If installed incorrectly it can make the piston bind in the pump. Perhaps this is what is keeping you from sliding the clutch in far enough to get the retaining ring installed.
 

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^^^agree with above - and no, you shouldn't let it go that way. When the correct parts are put together for the proper year engine, these things fit correctly. Honda wasn't that sloppy. Compare the thrust washers and you may find the difference. As for the trans shaft, are you certain you have the small end bearing located on the pin in the upper case correctly? If not, and if you've already tightened the lower case bolts, you may have pushed the locating pin through the upper case. Look at the left side of the bottom end where the clutch rod goes into the mainshaft to see if the pin has punched through the upper case
 

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Discussion Starter #4
I have the brass thrust washer on the oil rotor assembly now. The thinner washer is too thin and goes so far back on the shaft that it falls off the splined area, if that makes sense. The brass thrust washer keeps everything located properly for reassembly. The pins and keepers for the transmission set were all located properly, and the engine cases went together like butter. It seriously just fell together and I didn’t have to do anything but run the bolts down. No issues there. The original engine number is CB450E-7003673. That’s the one with the trashed crank and con rod. The engine I pulled the rotating assembly from is CL450E-5018372. If I’m reading these numbers right, that would be a much earlier engine (and obviously from a scrambler, not a CB). I have the option to either turn the brass thrust washer down a few thousandths, and keep the brass in place to help locate everything. Right now I have no crankshaft end-play between the washer and circlip on the stator side. Everything feels good, just have that interference issue with the clutch basket. As for the inner basket circlip, I’m really drawing a blank. Like I said, everything is located and pinned in properly, and the case halves went together without any issue.
 

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I just compared the part numbers for the CL450K5 and the CB450K7 thrust washers and they are the same except for the last 3 digits, which usually means a different supplier IIRC or in some cases, different cosmetically, so I don't think it's that. BTW, the CL450K5 and CB450K7 use virtually all (if not exactly) the same engine parts and the CL is only 2 years older, not a significant difference. There has to be something introduced that wasn't there before or is different in some way for that much difference when assembled. Steve or Bill will need to weigh in on this one
 

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Discussion Starter #6
The entire rotating assembly wasn’t there before. ;) Seriously though, I wonder if there was a difference with the crankshafts, and the dimensions are just different enough that the new (or in this case, older but not destroyed) crankshaft is keeping the drive gear farther out. The gear actually rides in the middle now, instead of off to one side like it did when it all came apart. You can kind of see the shiny wear marks on the pictures. It would be great if it wasn’t just barely touching the clutch basket. I’m really scratching my head on the clutch basket circlip issue, though. I really hope I don’t have to break the cases apart again, but I’m wondering if that’s going to have to be what happens next.
 

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I understand what you mean about the "rotating assembly", more of a car term than vintage Honda term - the crankshafts on the 5 speeds are pretty much all the same AFAIK, so it's a mystery to me as to why you're encountering this situation - but then, I certainly haven't seen it all with these engines either, which is why I suggested that either Steve or Bill might have more insight.
 

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I think I understand and experienced what you describe with the wear on the primary gear and it riding off to one side and now you have it centered up using the brass washer. I can tell you that my K7 CB450 had the thin washer (not brass) that you mention falls off the splined area of the shaft and fits loosely until the centrifugal filter is bolted on.
In my K7 bottom end I replaced the original crank with a K2 CL450 crank and I used the brass thrust washer that came in the K2 bottom end. I can’t remember which gear I used or if I noticed any difference in thickness between the K7 or K2 gear. I do remember comparing the differences in the washers and how things fit to come up with a combination that seemed to fit best. I’ll look back through any pictures I may have for comparisons sake.
 

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I was able to go out and check my parts stash and I found this. The upper gear and (thin) washer came out of a bag labeled K6. The lower gear and (brass) washer came out of a bag labeled K3. Also of note is the part of the K6 gear where you can see the difference in color from the meshing of gears and where it was not in contact with the clutch gear.
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I was able to go out and check my parts stash and I found this. The upper gear and (thin) washer came out of a bag labeled K6. The lower gear and (brass) washer came out of a bag labeled K3. Also of note is the part of the K6 gear where you can see the difference in color from the meshing of gears and where it was not in contact with the clutch gear.
According to my parts list for K3-K5, the primary gear was the same part for all (13611-292-010). From this photo, it appears the primary was changed with the K6, and probably continued in the K7. Guessing this is the problem.
 

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Discussion Starter #13
Thanks to everyone with the help here. I’ll see if I can scare up the drive gear from the old crankshaft set. Otherwise I’ll just mill the gear down that I’ve got. Still out in the weeds with the clutch basket set. I’m happy we got the crank issue worked out, but that clutch issue is going to keep me from putting the rest of the engine back together. Any ideas would be gratefully received.
 

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If it’s true that you just have a fatter K6 or K7 gear in use with the earlier brass washer then when you either swap to the correct gear or washer then that might solve your clutch issue, correct? The other consideration is making sure the slight offset in the arm for the oil pump piston is correctly oriented.
 

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Discussion Starter #15
PBR, it’s two separate issues, it just happens that they both involve the clutch basket. The first issue seems to be solved, I think I’ll just mill down a couple thousandths off the crank gear to get the clearance I need. The other issue is that the inner clutch basket doesn’t slide back far enough to allow the circlip to seat into the shaft groove. I didn’t remove the pump shaft from the eccentric on the back of the outer clutch basket. I took the oil pump and basket off as a set. With that in mind, it would stand to reason the pump arm wouldn’t have changed orientation. There’s also no dragging on the clutch basket when you turn it over by hand. It all feels really smooth. I’m thinking it might be a worthwhile exercise to pull the pump and clutch outer basket off again and just double check everything. I’m pretty meticulous when it comes to building engines, but I suppose it’s possible I missed something.
 

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Emerikol, not doubting your skills at all. The two issues are so closely related in a physical sense that one may be affecting the other despite appearances. If it were me, I’d try and rectify the washer/gear issue and see if it fixes the other. That’s all. Good luck sorting it out and please update this thread so we know the outcome.
 

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could you have left right main bearings locating pin out? That bearing location determines the cranks end play. If it was left out it could be shifted over enough to cause this issue I suppose. You did say you didn't have any end play and that doesn't seem right to me.
 

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Discussion Starter #18
Lefty, all locating pins were accounted for and properly, well, located. :) I had end-play until I ran down the oil rotor nut on the brass thrust-washer. I think the issue is that I'm using an old-style crank with a new-style drive gear and an old-style thrust washer. I'm really making a Frankenstein's Monster engine over here, so it's not really surprising things don't want to go together exactly right. I'm going to pull the clutch basket and oil pump, then pull the crank drive gear and re-install everything without the drive gear. If I can get the clutch basket to seat far enough to put in the circlip, I'll know we've nailed down the problem. Results coming soon!
 

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Discussion Starter #19
Ok, so here's a status update. I was able to spend a few minutes in the shop last night working through this issue, and it looks like the crankshaft gear is the culprit for all the issues. I removed the oil rotor and oil pump, and slid the clutch basket and pump off. Then I removed the crank gear and re-assembled the oil pump and clutch basket assembly without the crank gear in place. I'm still every so slightly shy of getting the inner clutch basket retaining ring to seat, but it's seriously just by a whisker now. I remember it being tight to get off during engine disassembly, and it's so close that I'm confident I'll be able to seat it by lightly tapping it into the groove with a punch and mallet. So that leaves me a couple options; I can either mill the crank gear down a little bit, or mill down the brass thrust washer a little bit. I'm actually leaning towards milling the gear down since it's a heavier chunk of material, and I want as much brass in there as possible to protect the parts that rub together. I'm still going to spend some time looking for the crank gear that goes with this crankshaft, but I'm not very optimistic. This engine came to me as two case halves, and nearly everything else in an oil-soaked cardboard box. Even the crank needed some love (and a lot of oil, assembly lube and swearing) before I was comfortable using it as a replacement for the one that detonated. So that brings me to two questions I'd like to put to the group: 1)Should I have the gear milled down and clearanced, or should I take the material off of the brass thrust washer? and 2)Is there a market for overhauling these crankshafts/rotating assemblies? I have a line on a machine shop that might be interested in working with me to press the crankshafts apart, measure and repair everything as needed, and then install new bearings and put it all back together. Is there enough of a market for these 450 mills to make that a worthwhile undertaking? Thanks again for all the help with resurrecting this bike.
 

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Personally, I think it might be easier to get the gear machined but I'm not a machinist, just thinking of the part and potential ease of the process since it is larger. Plus, as long as there is enough width on the gear for proper teeth engagement - you'd have to take a lot off it for that to be an issue - there's less risk (but again, maybe the machinist would be the one to make the choice).

I think eventually there will be more need for crankshaft rebuilding as all the good used ones are gone, but I don't think we're quite there yet - there are always used cranks and spare 5 speed engines on eBay for decent prices. I have 2 spare 5 speed engines myself, with good cranks in both (I certainly hope :D ). It's quite the process requiring a serious press and proper jig to keep things in alignment. And BTW, good call 12ozPBR
 
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