- The number one problem with these machines is the carburetors: their as-manufactured main jets vary widely, and worse, most have been ruined by unprofessional handling (including carburetor rebuild kits)
- Taken together with these carbs' fast-wearing brass needle jets and jet needles, the result is all of these bikes run extremely rich
- The number two problem is these engines eat their starter drives and there are no replacements
- The number three problem is folks run these bikes out of oil, which trashes the top end, especially the cam followers
- Because of the engine's eccentric adjusters, cam follower damage results in the valve clearance being made impossible to adjust
- The collectability of the "Black Bomber" (1965-1967) has inflated the value of the CB450 used parts market
- These engines build up a significant amount of crankcase sludge in just a few thousand miles and only engine disassembly can remove it
- The later aluminum clutch pushrod breaks from inadequate maintenance of the clutch and final drive chain
- This pushrod and its release mechanism are rare parts now
- The engine's cam chain tension is invariably neglected
- The method of adjusting the cam chain shown on a popular YouTube channel is incorrect and ineffective
- The engine's oil filter is similarly famously overlooked and consequently is typically packed full of grime
- The original selenium rectifiers are failing and silicon replacements were not only recommended by the factory, but even in a bike in good shape they increase charge output through better efficiency
- As with many 50+ year old motorcycles, the most commonly replaced parts are scarce
- On the other hand, many of these engines are being sold piecemeal, thus used crankshafts, cams, cylinders, heads, transmissions and even crankcases are plentiful
- Honda sold a special 0.0012" feeler gauge for use in adjusting the engine's valve clearance
- No one should use this quite unreasonable clearance specification
- This engine, due its very early design, escaped Honda's soft-valve scandal that spoiled most of its 1970s bikes
- Aftermarket piston maker Wiseco still offers a 1mm-over piston that very successfully takes the place of the discontinued factory pistons
- Wiseco also has available a 3mm-over and a 4.5mm-over piston but by quantity special order only
- Dozens of aftermarket companies sold gasket kits for these engines, a few reasonable quality, but most not
- Part of the alternator stator is switched in and out of service by the headlight switch, thereby supplementing the voltage regulator in its charge control function
- Kind of a useless (if unique) system, mechanics from the very beginning have permanently wired in the switched half to increase the bike's overall battery charge
- Later, the headlight-always-on CB500T had this modification from the factory (via a pigtail inside the electrical box)
- The CB450 and CB500T transmission is surprisingly robust and durable--actually massive for a mid-displacement bike
- There are a lot of very subtle parts differences between the 450 and 500, with the result that many are interchangeable while some are not
- Possibly because certain gaskets are hard to find, the grossly inadvisable use of silicone paste is common on these engines
- An interesting characteristic of Hondas this old is their replacement left side engine covers are scarce (and priced as if made of gold) due to tipover damage
- Factory control cables are long gone, leaving owners only the comparatively poor quality aftermarket option
- Similar to the CB175 and CB350 twins, the oil drain plug on the CB450 and CB500T is a defective design that seizes to the crankcase and is impossible to remove using normal wrenches
- Expect to pay $25 to $50 for a replacement drain plug
- Because the centrifugal oil filter canister is flooded and thus pressurized before sending its oil upward in the engine through the clutch cover, its thin o-ring plays a surprisingly critical role in maintaining proper engine oil pressure
- The oil filter access plate in the clutch cover contains a transfer valve that if damaged or absent (after a clutch cover collision-related replacement) can malfunction and destroy the engine's entire top end
- Though once popular among some, the valve clearances cannot properly be adjusted with the engine running
- Honda has historically used copper-plated steel head fastener washers on its engines, but the 450 and 500 have solid (not plated) copper washers beneath two of its head nuts
- These washers are found at these spots because this engine oils its top end from the right side
- Some like it and some don't, but the CB500T revised the tuning of the 450 to give it more streetable low-rpm power
- Do your bike a favor and switch to silicone brake fluid
- Sintered all-metal disc brake pads will improve braking
- Honda's funky gas cap latch recall affected these bikes as well
- The CB500T's carburetors have added to them aircut valves that reduce afterburn and vacuum ports to aid synchronization but are otherwise identical to those on the CB450, making them useful updates
- The cylinder head casting on this engine has to be one of the most unique, most interesting, least Honda-like of anything Honda ever mass-produced--it's more 70s Italian than 70s Japanese
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