This article contains a brief survey of the different carburettors fitted to CT90 range, and an in depth look at the the K28A installed on my CT90 K1. The K28 carb was used on the K1-K3 (1969-72) models, and is very similar to the subsequent 556a model that was used until 1977.
carburettor models
The...
This article contains a brief survey of the different carburettors fitted to CT90 range, and an in depth look at the the K28A installed on...
Honda CT90
Checking your cylinder is within the service limit involves measuring the bore with a cylinder gauge as shown in the following diagram:
What follows is what I've found out about this process from research and experimentation, but please note that I'm not an engineer and I'm just doing this...
Checking your cylinder is within the service limit involves measuring the bore with a cylinder gauge as shown in the following diagram:
What follows is...
C90 Engine
Honda invented the posi-torque system in 1967 and used it on the CT90 range of the same year. This ingenious device had the effect of providing the bike with 4 additional hillclimbing gears in addition to the standard 4 ratios for road-riding
Earlier solutions
The posi-torque system replaced the unwieldy dual rear sprocket arrangement used...
Honda invented the posi-torque system in 1967 and used it on the CT90 range of the same year. This ingenious device had the effect of...
Honda CT90
Chains tend to 'stretch' in use because material wears away from the bushings and pins, increasing the clearance between the parts and causing the chain to elongate. As a result, when Honda replaced the Super Cub push-rod engines with a new chain-driven overhead cam model they needed to incorporate a chain tensioner to...
Chains tend to 'stretch' in use because material wears away from the bushings and pins, increasing the clearance between the parts and causing...
C90 Engine
The CT90 has a simple wiring harness and making a replacement is pretty straightforward. Much of the wring on my 1969 K1 had been damaged, cut or patched so I decided to do a major overhaul, including making a brand new harness. Here are the before and after picture of the various repairs:
making a...
The CT90 has a simple wiring harness and making a replacement is pretty straightforward. Much of the wring on my 1969 K1 had been damaged,...
Honda CT90
The CT90 exhaust system, although similar in appearance to the one used on the 6v C90, has different internals with fewer baffles and the addition of a Krizman spark arrester.
Spark Arresters
Spark arresters are designed to minimise the risk of fires being started by exhaust sparks and are required in the US when using...
The CT90 exhaust system, although similar in appearance to the one used on the 6v C90, has different internals with fewer baffles and the addition...
Honda CT90
The earliest CT90s shared the same leading link suspension as the C90 Super Cubs. This is a great design, offering a comfortable ride and minimising maintenance issues by tucking the moving parts away from the elements. However, the forks were designed for road use and therefore only allowed a small amount of suspension travel; not...
The earliest CT90s shared the same leading link suspension as the C90 Super Cubs. This is a great design, offering a comfortable ride and minimising...
Honda CT90
I have just finished recommissioning a 1969 CT90 K1. The bike was originally sold in the US and was imported to the UK from California a few years ago.
One of the many repairs that needed doing was to replace the damaged wiring harness, so I colourised the wiring diagram to help with the job....
I have just finished recommissioning a 1969 CT90 K1. The bike was originally sold in the US and was imported to the UK from California...
Honda CT90
There are plenty of places that will rebuild your crankshaft for you, but it is also a job that can be done at home if you have the right equipment.
tools
You'll need a press (minimum 10 ton) to remove the pin and to reassemble the crankshaft and you’ll also need some...
There are plenty of places that will rebuild your crankshaft for you, but it is also a job that can be done at home if...
C90 Engine