Honda C90 Super Cub - shop manuals

14th Aug 2021
Tags: manuals,  Engine

Workshop manuals

When learning how to repair my 1978 Honda Super Cub c90 one of many surprises was that the official Honda workshop manuals are still available.  Unlike the Haynes and Clymer publications that were aimed at the general public, these are the instructions used by the Honda mechanics who mended and maintained these bikes when were first introduced.    

You can view or download scanned digital copies of my workshop manuals below. They are all text searchable.

C50/C65 manuals (1964)

The original 50cc Super Cubs went on sale in 1958 and the larger 87cc version, the CM90, was released in 1964.  While working on the CM90 Honda was also researching new engine designs, aiming to improve reliability and performance. The new engine was first used in the the 63cc C65, an intermediate model positioned between the 50 and 90 also launched in 1964:

The second generation of super cubs - starting with the C65 and quickly followed by a new C50 - included a revamped body and frame design and a new engine

The brand new engine design replaced the old pushrod arrangement with an over-head cam and introduced pumped lubrication and automatic cam-chain tensioner. The resulting improvements in reliability and durability allowed Honda to offer the bike with an unprecedented 2-year warranty plan.

Shortly after the C65 was introduced the new OHC engine was adapted to the 50cc model and a few years later evolved into the 72cc C70 which, unlike the C65, was available in the UK.  The C70 was more or less identical to the 63cc bike it replaced but with an increased cylinder capacity.  Here is the manual that covers the OHC C50 and C65 models:

C50-C65 manual (printed 1971)

c90 manuals (1966)

A new 89cc model (the CM91) was released in 1966 following the same engine design pattern as the c65 but, although it looked similar, did not share any engine components with the older cub and was generally bigger and heavier, having been equipped with with a more substantial frame and other beefier components.

This 89cc motor was a very successful design and was used in all the C90s sold until the early 1980s.  A modified version continued to be used in the Japanese Mail delivery (MD90) bike and was also the basis for the CT110, both of which were made well into the 2000s.

The shop manual can be used for all the 89cc bikes made between 1966 and 1982, including the C90 Super Cubs.  The other guides are specific to the Z2 and ZZ models (made between 1978 and 1982):

Honda expected their model-specific manuals to be read in conjunction with the Honda Common Service manual, which explains the systems common to all their motorcycles. This manual is available on the excellent Vintage Honda Twins forum, as part of their document library.

The 89cc motors Honda used in the S90, CL90, CD 90, and CT90 between the late 60s and early 80s were basically identical with the only major difference being that the the C90 and CT 90 had an automatic clutch and the four speeds used on some of the models.

If you have a C90 from this period you might also find it useful to refer to the CT90, CT110 Shop Manual which covers the same engine but has better illustrations than the the earlier manual from the 1970s show above. This manual also shows the sub-transmission added to the later CTs and covers the CT 110 which succeeded the 90cc model.

Only a few minor improvements were made to the 89cc engine and gearbox during the first 20 or so years it was in production:

Cam chain tensioner changes

Three versions of cam chain tensioner were used, with the early automatic oil/spring damped version being replaced in the early 1970s with a mechanical tensioner.

the earliest tensioner is shown in the middle, the version on the right was used in some non-UK models and the one at the bottom is used in the C90-Zs

Kick start changes

the kick start mechanism was changed in the late 60s/early 70s

Transmission changes

The original transmission, gear shift drum and gear shift forks were replaced with more robust versions in the late 60s.


The final mechanical alteration of note was that  Honda changed the shift pattern from 1-0-2-3 to 0-1-2-3 when they introduced the C90-ZZ (1978-82). This engine has a different shift drum as a result.

Cosmetic changes

The main cosmetic changes came with the introduction of the Z2 model.  The Z2 was launched in the UK in 1977 and incorporated features previously only available on the special “deluxe” models sold in other markets.  This included foldable foot pegs, position light, an improved speedo with turn signal indicator and a new switch that activated the stop light when using the front brake.  The choke was also moved to below the centre of the handlebar and the main switch to the legshield.

Wiring

Note the 1971 workshop manual shows the wiring for the pre-1977 models, the wiring for the UK C90-Z (1977-82) models is included in the back of the owners manual linked above.

Later C90 models (1983)

By the early 1980s Honda determined the old C65 engine, which they had already extended to 72cc, would cope with a further capacity increase and they enlarged the cylinder once more, increasing engine capacity to 86cc.  

This decision meant that all the bikes in the cub range could now share many components, including the frame, and in 1982 Honda discontinued the old 89cc C90 model.

The relaunched C90 retained the styling of the older 89cc bikes, including round headlamps.  This model (the C90C) was only available for a couple of years and is easily recognisable because it shared the frame of the smaller bikes including the distinctive two-tone seat and enclosed fuel tank and the deleted pilot light.

86cc C90C (notice the enclosed fuel tank and lack of pilot light)

The other major change, in addition to the new/old engine, was the electrics. All the cubs from this point forward came with AC powered CDI ignition, rather than contact breaker points and battery powered ignition used on the older 89cc C90s.  This resolved two of the maintenance hassles on the older bikes which required the points to be adjusted properly and a fully charged battery to run well.  The new C90s were also lighter and had a slightly higher top speed.

From this point forward all the Super Cubs available in the UK also switched to 12v systems, but for mysterious reasons the C90D available in other locations like Australia - although still using CDI ignition - remained on 6v.

Around 1984 the C90E was released, reintroducing the electric starter last seen in the late 60s and adding the distinctive rectangular headlight and adding a handy fuel level indicator to the newly designed speedometer.  From this point forward only minor changes were made until the C90 was discontinued in the early 2000s.  Here is the 1984 manual:

Honda C90C, C90D, C90E (printed 1984)

Super Cub Glamour

It is difficult to know exactly how cool super cubs are but here are Steve McQueen, The Beach boys and Ann-Margret Olsson (accompanied by the King of rock and roll) sitting on some.

Enjoy the manuals!

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