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Old 01-09-2014, 06:33 PM   #1 (permalink)
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Join Date: Aug 2013
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Recumbent Honda 90

I've had a couple of requests to start a new thread, so here goes.

First a little history :-

I've been riding motorbikes since the late 60's, everything from mopeds to 1000cc 'superbikes'. It was my ambition to build a streamlined feet first motorcycle after reading an article about Craig Vetter's mileage challenge in the early eighties.

Having no fabrication or welding skills, I decided that a Honda Cub would be an ideal candidate as a 'first attempt', as the frame layout would need very little modification.

I eventually acquired a 1981 c90 in 2002 for the princely sum of 30. This sat in the shed for around 8 years until I finally found the time and motivation to get started.

The dream was to build something like Craig Vetter’s original streamliner.

I set myself a target of 70 mph and 200 mpg (uk) at 55 mph.
70 mph is easy (I’ve achieved a GPS checked 68 mph without the fairing), so I’m guessing 80 mph is possible with a slippery fairing and optimised gearing.

200 mpg is an arbitrary figure which may not be achievable without fuel injection, but it’s important to set your sights high, rather than say ‘that’ll do’.

It started like this :-

With the front footrests bolted to the fork legs (not recommended!), and a hand operated gear change.

After further development, being loaded on the recovery truck following another seizure:-

I think the 3 piston seizures were probably due to the engine over revving because of the standard gearing and reduced drag.

It was around this time I got involved with the C90 club, a great bunch of hard core Cub riders who travel all over the UK and Europe on camping trips. A top box and panniers (OK plastic boxes!) were fitted in order to carry the camping gear.

The battery has now been relocated to its original location,

The original engine was replaced with a 4 speed 125cc motor, which allows a reasonable cruising speed without overstressing the motor. I also fitted a 2 gallon tank to improve the range between fill-ups. The bike is so comfortable that 200 miles without a stop is easy.

Next stage in the evolution :-

This is where I am at the moment :-

The dustbin fairing (which needs a screen and some remedial work) is held in place temporarily while I work out clearances and fixing brackets.

Notice how well the fairing lines up with the panniers, this was not accidental, it may be possible to fill the gap between fairing and panniers at some point in the future.

I want to keep as much fairing surface area as possible to reduce drag, but I will need to get my feet down. I’m thinking of creating spring loaded flaps to achieve this, but I’m wondering whether a turned up fairing edge (to direct the airflow upwards) might be a more elegant solution.

I’ve recently rebuilt the carb with new needle and jets as the motor was running a little rich, but haven’t been able to test the results due to stormy weather. I need calm weather to set a baseline fuel consumption so that I can quantify the effects of fitting the fairing.

The bike has covered several thousand miles over the past 4 or 5 years, and is my favourite form of transport, my Harley, Pacific Coast and Shadow rarely see the light of day.

My best fuel consumption so far is 140mpg over a 300 mile motorway (freeway) run, which was with the throttle wide open and slipstreaming trucks whenever possible. Still aiming for 200 mpg.

I'm happy to share my experiences with anyone contemplating a similar build.

Last edited by Ironside; 07-26-2017 at 01:46 PM.. Reason: missing photo
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