Rusty Bolt Garage: 1978 HONDA CB750- Project

1978 HONDA CB750- Project

The Honda CB750 is an air-cooled transverse in-line four cylinder engine motorcycle made by Honda over several generations for year models 1969-2003 as well as 2007 with an upright or standard riding posture. It is often called the original Universal Japanese Motorcycle (UJM).

The CB750 is included in the AMA Motorcycle Hall of Fame Classic Bikes; was named in the Discovery Channel's "Greatest Motorbikes Ever;" was in The Art of the Motorcycle exhibition, and is in the UK National Motor Museum. The Society of Automotive Engineers of Japan, Inc. rates the 1969 CB750 as one of the 240 Landmarks of Japanese Automotive Technology.

The CB750 was the first motorcycle to be called a "superbike."

Honda of Japan introduced the CB750 motorcycle to the US and European markets in 1969 after experiencing success with its smaller motorcycles. In the late 1960s Honda motorcycles were, overall, the world's biggest sellers. There were the C100 Club step-through - the biggest selling motorcycle of all time - the C71, C72, C77 and CA77/8 Dreams; and the CB72/77 Super Hawks/Sports. A taste of what was ahead came with the introduction of the revolutionary CB450 DOHC twin-cylinder machine in 1966. Profits from these production bikes financed the successful racing machines of the 1960s, and lessons learned from racing were applied to the CB750. The CB750 was targeted directly at the US market after Honda officials, including founder Soichiro Honda, repeatedly met with US dealers and understood the opportunity for a larger bike.

In 1967 American Honda's service manager Bob Hansen flew to Japan and discussed with Soichiro Honda the possibility of using Grand Prix technology in bikes prepared for American motorcycle events. American racing's governing body, the AMA, had rules that allowed racing by production machines only. Honda knew that what won on the race track today, sold in the show rooms tomorrow, and a large engine capacity road machine would have to be built to compete with the Harley Davidson and Triumph twin-cylinder machines.

Hansen told Mr Honda that he should build a 'King of Motorcycles' and at the Tokyo Show of October 1968 and the Brighton Show of April 1969 the CB750 was launched. Hansen's race team's historical victory at the 1970 Daytona 200 with Dick Mann riding a tall-geared CB750 to victory saw Honda cease all motorcycle road-racing activities and the beginning of the era of the 'Superbike'.

Under development for a year, the CB750 had a transverse, straight-four engine with a single overhead camshaft (SOHC) and a front disc brake, neither of which was previously available on a mainstream, affordable, production motorcycle. Having a four cylinder engine and disc brakes, along with the introductory price of US$1,495 (US$9,614 in current money), gave the CB750 a considerable sporting performance advantage over its competition, particularly its British rivals.

Cycle magazine called the CB750, "the most sophisticated production bike ever", on the bike's introduction. Cycle World called it a masterpiece, highlighting Honda's painstaking durability testing, the bike's 120 mph (190 km/h) top speed, the fade-free braking, the comfortable ride, and excellent instrumentation.

The CB750 was the first modern four-cylinder machine from a mainstream manufacturer, and the term superbike was coined to describe it. Adding to the bike's value were its electric starter, kill switch, dual mirrors, flashing turn signals, easily maintained valves, and overall smoothness and low vibration both underway and at a standstill. Later models, from 1991, included maintenance-free hydraulic valves.

Unable to accurately gauge demand for the new bike, Honda limited its initial investment in the production dies for the CB750 by using a technique called permanent mold casting (often erroneously referred to as sandcasting) rather than diecasting for the engines – unsure of the bike's reception. The bike remained in the Honda line up for ten years, with a production total over 400,000.

*** We picked this bike up as an unfinished project from a fellow in Kansas. Along with the bike, we got a complete front end, wheels, and brakes from a 1993 Honda CBR900RR. The plans with this one are: swap out the front end, wheels, and brakes, fit a new hand shaped tank, cafe style fiberglass seat made in house, new 4-1 pipes, updating the electrics, and a house made oil tank that doubles as the inner rear fender to name a few. Overall it should be a classic looking machine with a cafe racer feel. We are shooting to get it below the 400 lbs wet mark (originally 551 lbs, getting her under 400 may be a fools dream, but we are going to give it our best shot!).

**Update March 8, 2015**

We have installed the Showa forks, triple, wheels, and braking systems from the CBR900RR and new rear shocks. The shock mounts have been relocated to raise the rear up a bit to get the stance we wanted. On the front you can also see the beginnings of a new fork brace and fender. You can also see the body work on the fuel tank is finished. We started with a tank from an earlier version of the CB750 for its narrower size and have added knee dents and smoothed out the bottom seams. A new rear hoop as been installed and a new oil tank has been fabricated. We still need to weld in the fill cap bung and finish the seams but it looks great and acts as a rear fender in the process. The tank holds an additional .5 liters and has a much larger surface area than the original, both of those things will prolong engine life by keeping temps down. We have also got the rearsets in position. The new exhaust system has been installed but we will likely be changing the muffler to a megaphone.

**Update March 11th, 2015**

While the oil tank was sent out to get the seams TIG welded, we started work on the seat. It follows the basic shape of the rear part of the fuel tank and will have a small cut out in the hump for an integrated tail light. It still needs to be smoothed out a bit but this will work as the plug for our mold. Every time we build a custom seat we always get request for more seats to be made. We will set it up so that we can make more of these seat pans and have them for sale on our eBay store.

** Update March, 21st 2015**

Got the oil tank back from the TIG welder today. This one is made of steel, but we plan to offer these in aluminum on our eBay store along with the seat. Get in touch if you are interested in getting one. Now we can finish the mounting tabs for it, and also the subframe, electronics tray, and seat.

**Update April, 22nd 2015**

Have been trying to work on this baby in between customer bikes so its been taking a while to get it ready to take apart. But the tear down process has begun! So far inside the engine everything looks great. It looks like all it will need is a little attention to the valves, new seals, and new gaskets. Then I noticed the stamp on the camshaft... R1. That means it's a cam from the 1969 CB750. It also means that it is the hottest of all the stock cams produced which gives a 8500 rpm redline and more HP than any of the later stock versions.

**Update May 5th, 2015**

Finished all the seat and electrics brackets and added steering stops so the new forks don't bash the tank. Stripped down to bare frame, wheels, swingarm, oil tank, etc., all ready to send out to be powder coated. The head got new valve seals, and we lapped the valves and seats. The bottom end got cleaned up with new seals and gaskets, a fresh coat of paint, and has a new electronic ignition installed. Just waiting on the cylinders and covers to come back from the cleaners so we can give them a polish and the engine can be reassembled. The Fireblade forks have been rebuilt with new seals, wipers, and oil. The Nissin brake calipers (4 piston up front and single piston in back) have been cleaned and had new pads installed. Pumping those will be a new 19mm Nissin Radial master cylinder. We settled on Pirelli Diablo Rosso II tires front and rear. We also reworked and finished the wiring to accept the new Reg/Rec unit, integrated rear tail light/brake light/ turn signals, integrated headlight/ turn signals up front, new control switches, and a red LED oil pressure warning light. Most of the other bits we need have been ordered including the Moto Gadget Mini Speedo that will be mounted flush in the headlight bucket. The tank and seat will get a nice coat of 'Speed Green'. By the time we get the frame back from the coaters we should be done and ready to put her back together.

**Update May 9th, 2015**

Engine is back together. Need to finish polishing the covers and the engine is done!

**Update May 29th, 2015**

Finally got the frame and other items back from the powder coater. Looking pretty slick so far! At this point its mostly bolting everything back together, finish the wiring, and paint the seat and tank. We have 3 weeks to finish this baby for the Motorado Show on Father's Day.

**Update June 2nd, 2015**

Last fitment checks before painting the tank and seat. All the electrics are done. Today we will be making custom S/S braided brake lines and prepping her for the first start.

**Update June 4th, 2015**

Fired her up yesterday. Started right up and idled smooth. We only let her run long enough to get up to temp then drained the oil and put in fresh. Brake lines are installed along with fluid, and bleeding has been done. This thing is going to stop on a dime! The seat and tank are getting painted and should be finished by early next week. Same for the seat pan upholstery. We also programmed the new speedo and transferred the mileage over so it shows the correct amount on the odometer. New custom sized throttle and clutch cables should be in early next week as well. Once we get it all back and put together we will take the first ride! Only 16 days left until the show but everything is on schedule.

**Update June 9th, 2015**