- 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 piston that very successfully takes the place of the discontinued factory pistons.
- Wiseco also has available 1mm and 3mm -over piston. And by special order a 4.5mm-over piston.
- 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 often impossible to remove using normal wrenches.
- Expect to up 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 camshafts.
- 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 the two right-side 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--including jetting--making them useful updates to the 450.
- 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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