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Discussion Starter · #1 ·
Well, as the title says, it doesn't rev. I haven't tuned it up yet, but I don't think that's the problem. ;)

I'm planning to source new pistons and get the cylinders bored, and will install with all other necessary new parts. What I'm unsure of though is the left side con rod. It took a beating when the valve tulip tore through the piston crown. Think I should replace it? If so, then does anyone have one for sale? If it's salvageable, then what should I check on it to make sure I can use it?

Thanks,
Camelman
 

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Wow, that's an ugly event - sorry to see it. the 450 cranks are pressed together with full-circle rods (as you may already know), so rod replacements are not simple. Most people in this position just look for a good used crankshaft. I'd start by disassembling the bottom end to inspect and assess the condition of the crank, check clearances and specs to see how it shapes up after that brutal beating, then go from there. Someone may still do repairs on them, I haven't inquired about it in a very long time.
 

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From the pictures, the top of the one rod has been hammered pretty bad, which tells me the crank is probably out of index now (pretty typical). The rod's small end is likley way out of round, big end of the rod's bearing is likely beat up, too. The crank needs rebuilt with new bearings and a good used rod, or replaced with a good used assembly that checks out for bearings being good and straightness/concentrically. The cranks are rebuildable using a good used rod and new bearings. Back in the day, we'd bring them to a motorcycle crank rebuilder, that could source the parts for us, press it apart, reassemble and straighten. The head is another story, it might be cheaper to just find another one, have a valve job done on it, and use that one as a door stop. Once they drop a valve (valve head breaks off) the tip rattles around before you can stop the engine, beating the heck out of the seat, combustion chamber, piston, valve guide. Pretty common failure that often starts with a tight valve, gets hot, stretches, breaks off, all hell breaks loose. I've had heads welded up, and the seats replaced, but the aluminum looses it's temper during welding and gets soft, and the new seats sometimes get loose later on. No one will warranty that machine work.

If it were me, before I made a decision and started buying parts, I'd pull it all the way down, make sure the cylinder is salvageable by boring oversize.

The shopping list might include so much, that you'd be better off purchasing a complete rebuildable engine, swapping parts into your case, or just using the entire thing.
 

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Discussion Starter · #5 ·
Thanks for the ideas. Looks like a replacement crank is the way to go. The affected cylinder only has minor nicks in it, and I think a half over bore will clean it up. I'll run it past my machinist first though. I also have a spare head waiting, so I'll clean it up and install it along with the new head and pistons.

I'm really looking forward to getting this moto back on the road!

Camelman
 

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Discussion Starter · #6 ·
A friend of mine asked if he could learn how to work on engines, so he's taken the lead on this 450 rebuild. There's a really good chance I'm watching EVERYTHING he does, but it sure is cool to have free help! :) Kinda slow though...

We've finally gotten into the engine and I'm ready to order a new crank. However, I'm not sure what to look for. Can you guys give me your opinions on these cranks and give me some ideas on what to ask about? Alternatively, does anyone have a crank they're willing to sell?

Honda 450 CB CB450-K5 SPORT Used Engine Crankshaft & Rods 1972 HB231 | eBay

honda cb450 cl450 450 CL CB CRANK SHAFT ASSEMBLY CRANKSHAFT 1970-1974 | eBay

72 Honda CB450K5 Super Sport CB 450 HM482B. Engine crankshaft connecting rods | eBay


Thanks,
Camelman
 

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Really, none of them look that good. the first and last ones both have small ends of the rods that don't look too savory. Missing rollers for the inner bearings might be hard to find but the rollers from your crank could be okay and if so, could be used in the second listing - but even at that, the pictures of it don't show the small ends very well at all. Only bonus in that one would be an extra alternator rotor (and possibly the starter clutch, but the metal backing looks a bit waffled-out). If it was me, I might buy the middle one if you could get better pictures of the small ends and then I might keep looking too...
 

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A friend of mine asked if he could learn how to work on engines, so he's taken the lead on this 450 rebuild.
Camelman
Wow, you screwed the pooch on this one (or got screwed by the pooch) - the head is trashed and so is the crank, most likely.
Used heads are common, but don't buy without inspecting the valve seats. Most 450 valve seats have suffered considerable damage from years of unleaded fuel now - they can be replaced (not "re-cut", but replaced), but that will cost $500-600, easily. If they're not too bad they can be re-cut, probably about $150. Plus the cost of new valves in both cases.
Used cranks?? Well, you pay your money and take your chances.

I'm not too sure a 450 engine is the best choice for your buddy to "learn how to work on engines"...........
 

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Discussion Starter · #9 ·
Mr. Ancient... I was wondering the same about the small ends of the rods. I'll keep looking, and also ask for better pics of the middle option. Thanks for the feedback on that.

Mr. Usic (assuming your first name is tbpm ;) ), I got the engine in this condition and am reviving this bike. You're dead on accurate about this being a tough engine to learn on, but I'm overseeing everything that's going on with it. I have never worked on a 450, but I've rebuilt dozens of other engines, so I'm sure I can guide my buddy through this. He's obviously overwhelmed with the engine right now, but he's learning a lot. I have a spare head already and need to go through it. Hopefully it's usable.

A little more insight on the incident. I pulled the head apart and the cam followers were almost worn away on the exhaust rocker arms. That engine was STARVED for oil! After tearing into the engine a little more I found lots of excess sealant floating around inside the cases and even some in the oil pump. It is pretty obvious that an exhaust valve was starved of oil and got stuck - allowing a piston to hit it, and I think the primary reason was due to poor oil flow to the head. That poor oil flow could have been from junk in the oil passages, which I'll investigate thoroughly when I disassemble the rest of the engine (waiting on an oil spinner nut socket to arrive). What's crazy is that the engine was supposedly gone through just prior to this happening, and considering how much junk there is in the oil strainer I doubt it was ridden more than a few hundred miles. That really sucks for the PO who bought it in "restored" condition since he bought it for $3700 and sold it to me not much later for $900 with the bad engine.
I'm considering getting some of those oil return strainers to install in the rocker box. I really want to make sure those cams and followers don't get starved for oil again.

Camelman
 

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Thinking about getting one of these for the exhaust cam. Maybe for the intake cam too. Thoughts?

Honda CB450 Cappellini #200 exhaust camshaft oil flow conveyor reduces cam wear | eBay
Not necessary for a street bike. Frequent oil changes and waiting a minute or so for the oil to reach the head are what's needed. Turn the petcock off so it doesn't fill the carbs and drain down the cylinders diluting the oil. You can't rely on the float valves. Warm it up before thrashing. Keep valve clearances adjusted. Keep revs up so spinner works better. Lots of things can cause the follower damage. I've read it's a bad pressure angle design(whatever that means) but if you follow the rules they'll last a long time and getting them welded and reground and swapping them out if need be isn't that bad with deltas prices and ancientdads guidance.
 

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Lefty's advice is all good. I would add - reinforce - that on a stock 450, the warmup at the lowest revs you can maintain for at least 2 minutes is an absolute necessity. Don't treat it like a car and just fire it up and go, you'll pay for it in a short amount of time. It takes at least a minute to a minute and a half for the oil flow to get up the cylinder studs and into the cams to lube the followers properly when the engine is cold, so be prepared to follow that regimen. Delta Camshaft does a good job for a very affordable price on follower and cam refinishing to repair damage from either oil flow loss or bad cold start behavior by the PO, I went through it with my build in part due to my missing the proper assembly of the valve in the oil filter cover on the clutch cover. If you wanted to employ an oil conveyor like the (expensive) Cappellini part you mentioned, you can save yourself some money and buy a baffle plate from an intake valve cover and make one yourself, like I did in my build thread. You can get a better and more thorough view of the design at the Team Hansen FB page, where Terry posted a picture of the one he made for his race bike. It can't hurt, though stock 450 engines survive every day without it by just being cautious on warmup and doing the proper maintenance. Lefty gives me too much credit... I'm just a survivor of the situation and have learned a few things the hard way.

http://www.hondatwins.net/forums/1-project-logs/65305-cl450-project-reboot-street-legal-time-26.html#post695345
 

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450 DOHC engine to start on? You got to start somewhere. All of the 5 speed cranks are the same. When you are looking at ebay, only buy a crank the seller will post pictures of the small ends. It is helpful to have a good picture of the wrist pin in the rod. If the rod is bad it is pretty obvious. When you get a crank make sure to clean out the oil passageways. You might consider posting in Cragslist for a 450 engine/ parts wanted. You might get lucky. I found one about 40 miles away. It needed a full rebuild.
 
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