The Bike for Long Rides: Honda CB750F

Much has been written about the Honda CB750, the motorcycle that was named “Superbike” by the Wide World of Sports announcer during the 1970 Daytona race. The original CB750s (introduced in late 1968) were powerful, sporty machines and the basis of the CR 750 race bikes campaigned in the early 1970s. They were powered by an air-cooled transverse 4-cylinder engine, with a single overhead cam. There was a disc brake in front, an electric starter and blinking turn signals. Quality-controlled machine work meant that the Honda would not leak oil. None of these items came stock on any comparable bike in 1968, and the CB caused a major uproar in the motorcycle world.

Over the next few years, the CB became more of a touring bike. The suspension got softer, the seat got plusher and the weight increased. At the same time, Honda was facing increased competition from Kawasaki, Suzuki and Yamaha in the 750cc range. While not wanting, for their own reasons, to go head to head with the Kawasaki Z1, the executives at Honda thought that they should provide their customers with a sportier offering. Enter the CB750F which debuted in 1975.

Design details

The CB750F was styled like a sport bike of the time, with a 4-into-1 exhaust, a rear disc brake and a long square-shaped tank which echoed the tank used on the 1970 CB750, that Dick Mann rode to the win at Daytona. Internal modifications included a slightly higher compression ratio achieved by new domed pistons and changes to the cam timing, made to assure compatibility with the new exhaust system. The changes raised horsepower — a Cycle period test stated that dynometer tests on prior year CB750s hovered just short of 50 horsepower, while the F version came in at 58 horsepower at 8,000rpm. The airbox was made somewhat less restrictive. The rest of the powerplant was much like previous versions of the CB750: single overhead camshaft, crankshaft riding in five plain insert bearings, a wet clutch, a 5-speed transmission (with gear ratios slightly altered) and heavy duty chain final drive. Lubrication was dry sump, and the battery and coil electrical system still featured points.

The frame featured more changes from the basic CB, known as the “K” version: the steering head was raked from 27 to 28 degrees, trail went from 3.7 inches to 4.5 inches and suspension travel was shortened from 5.6 inches to 5 inches. The dual rear shocks had more travel and more damping. One point irritated testers — you had to remove a side cover to get to the oil dipstick. Conversely, there was a lot of enthusiasm for the rear disc brake. The rear drum had been a weak point on the CB750 and the new disc was a major improvement.

Period testers found the bike needed five minutes to really warm up. Once warm, it would come off the line faster and harder than earlier CBs. There was no need to downshift when passing. The extra punch translated into somewhat worse gas mileage, but the tank on the F was larger, making for about the same distance between fill ups.

1970’s Honda 750s were known for clunky clutches, and the F was no exception. Then again, clunky clutches were pretty much the rule in the 1970s. Smooth clutching was a point to be noted and praised. Testers did like the precise and stable high-speed handling, an improvement on the K 750. They did notice a slight increase in vibration, especially when accelerating. The new exhaust system was quiet. Magazine testers concluded that the suspension changes transformed the bike “from an adequate handling machine to a really good one.” Describing it as “a bit more frivolous, but a lot more fun.”

Despite the modifications to make the CB more of a sport bike, testers noted it was a good touring machine. “The result still is a versatile bike of the same ilk as the K model even through the compromise between general use and sport/performance use now is in favor of the latter,” said Rider magazine.

Honda made the 750F in 1975 and 1976, then upped the ante in 1977 with the F2, which can be identified by its Comstar wheels and black engine. Accelerator pumps on the carburetors, larger valves and a more radical camshaft increased power. The single overhead cam version of the CB was discontinued in October 1978, and a newly designed double-overhead cam engine with four valves per cylinder took its place.

About this time, the motorcycle market began to specialize. Motorcycles were once sold as all-purpose machines that could do anything. They now came styled as cruisers, touring motorcycles, sport bikes and dual sports. It became increasingly difficult to find a bike you could ride to work, go cow trailing on, take on a 2,000 mile trip and road race, like many bikes of the Fifties and early Sixties. Yamaha was battling Honda for sales dominance, with its weapon of choice: cruiser-styled machines. Honda felt that it had to strike back against Yamaha and started to develop 4-cylinder V-engined cruisers and sport bikes. The CB 750F was discontinued in 1982, as the first cruiser-styled V-4s began to appear in showrooms.

There continued to be a market for a sturdy general purpose motorcycle, and the CB750 engine lived on in the Nighthawk, which came in cruiser and standard versions and gained a reputation as one of the most reliable motorcycles ever built. Honda finally discontinued the Nighthawk — and with it, the last iteration of the CB750 — in 2003.

Honda built a lot of CB750Fs before the model hit the end of the line — 44,000 of the CB750F1s alone. Total production of all models of the CB750 was about 400,000 units. Riders found they were reliable motorcycles that would take some abuse and keep running. Many are still daily riders and get to work machines. It is a little surprising to see motorcycles, once trumpeted as truly modern machines, appearing on vintage runs. But, despite reliable electric start, disc brakes and lack of leaks, they qualify, since most CB750s are at least 35 years old. Other people use the F to build their own personal version of the cafe racer, a fate that Neil Rodrigues wanted to rescue this bike from when he bought it.

Neil first got into motorcycles when he was 10 years old. His 12-year-old brother was given a Cushman for a Christmas present and Neil was immediately interested. As he got older, Neil found he was attracted by “anything with a motor.” He started riding off-road on a regular basis. For a while, he was involved in amateur competition. “Motorcycles have been my main interest all my life.” Several years ago, Neil was given a membership to a national classic motorcycle club, but that membership never quite worked out. Neil tried to contact that organization several times, with no success.

A web search led Neil to Don Brown and the Classic Japanese Motorcycle Club. The CJMC turned out to be a large group that had frequent rides and a yearly swap meet. It was just what Neil wanted, and he is now one of the top organizers.

As purchased, the drivetrain, chassis and bodywork were in surprisingly good shape, but, (like anything over thirty) the CB750F had a few flaws. Someone tried to do something with the carburetors. “He thought he was a carburetor guru.” Result: Broken piece off one carburetor, and a non-stock replacement. Despite the age of the bike, Neil was able to find a stock carburetor. He says that most parts for Honda CBs can be found without too much trouble. Surprisingly, despite the huge numbers of models Honda has sold over the years, Honda continues to stock many different parts for its vintage machinery. Aftermarket sources include 4-into-1 (4into1.com), which has lots of parts for 4-cylinder vintage Hondas and Dennis Kirk (denniskirk.com) who has a lot of metric motorcycle parts. Dennis Kirk had an exact replacement part for a turn signal that was damaged on a ride. Putting in a plug for his club, Neil states, “It’s also important to be part of a similar interest organization. Most members are very helpful with advice and finding the parts you need.”

Neil is an aircraft engineer by schooling and a mechanic by training. He takes maintenance seriously. Keeping this Honda in good shape is fairly straightforward. The main item is to change the oil every 1,000 miles. “That’s the old Honda standard.” Neil changed the brake fluid when he bought the bike, but hasn’t since, he keeps the bike covered and the fluid is clear. The carburetors were synched once and have stayed where Neil put them. “I checked them once, recently. They are OK.” Neil has replaced the final drive chain and installed new IRC GS-11 Retro tires, which are similar to the originals.

A common upgrade, which Neil has performed, is to replace the points with electronic ignition. Dynatec makes a reliable ignition kit, which is retailed by 4-into-1. 1970’s Showa rear shocks have a tendency to turn soft, and are not rebuildable. A period 10,000 mile test noted this problem in the report in Cycle Guide. Dennis Kirk sells replacements, which are very close to the originals.

The one item Neil has not fixed — yet — is the starter button. “The starter button went out. It sticks. I have a new button, but have not gotten around to replacing the old one yet. It kick starts really easily. I can start the Honda with my hand.” The bike runs on regular gas. “It’s a Honda.” Neil says he has tried running it on aviation gasoline and it doesn’t run any differently. There is no real trick to starting the bike: turn on the gas, choke on and kick a couple of times. “It starts right up. One time I took the 750F on a ride to Lake Tahoe and it snowed the night before. It took longer to kick start, but it still started.”

Once the bike has started and is idling smoothly, release the choke. “You can’t run with the choke on.” Neil disagrees with the period testers here — he says that there is no need for a lengthy warmup. Neil does suggest, in the interest of avoiding expensive engine wear, that you not redline the bike until completely warmed up. “Keep the rpm reasonably low.” Period motorcycle tests stated that vibration became noticeable around 5,000rpm and redline was 8,500rpm. Since testers also stated that 5,000rpm in top gear was 75mph, there is no need to over-rev the Honda in order to get someplace.

“It rides mountain roads and handles great — very smooth. I experience this bike as big, heavy and smooth. Despite the good handling, you can feel the weight. I keep this bike because it’s pretty, it runs well and is an enjoyable bike to ride. It’s the bike that gave the name to the Superbike class.” MC