Honda CT110 / CT90 Buyers Guide

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This guide is designed to assist people wishing to buy a Honda CT110 or CT90 'Postie Bike' Motorcycle.

A Few Facts

  • The CT110 is world's biggest selling motorcycle
  • Australia Post dispose of them to auction monthly at between 12,500 and 25,000 miles
  • The rated weight capacity is 285 lbs, but they are capable of carrying double this
  • Fuel economy is about 213 MPG Highway use, or 95 MPG City use

Frequently Asked Questions

Where can I buy a CT110? 

Answer: The best place these days, is eBay Motorcycles of course, however they can also be purchased privately via Newspaper Classifieds or from regular Auctions which are held Australia wide to dispose of old Aussie Post stock.

How fast do they go?

Answer: A Standard postie bike will cruise at 45 to 50 mph quite easily depending on the riders weight.  Assuming an average rider weight of around 187 lbs. They are not recommended for freeway or highway use. They are quite good for short trips around town.

Can I make it go faster?

Answer: Yes! There are a number of simple mods that can be done to improve performance:

Remove exhaust baffles and air intake airflow restriction and increase carburator main jet size.
Purchase a Tighe Racing Cam from Ivan Tighe Engineering in Queensland Australia.
Run engine on Shell A Racing fuel (methanol) or Aviation Fuel
Install a Pocket Bike Nitrous Oxide Injection Kit. (available on eBay)
Have the engine professionally modified and tuned.
Can I double anyone on my Postie Bike?

Answer: No. They are designed for single rider only. There are no rear footpegs or rear seat. However, for off road use these can be fitted quite easily.

Are they easy to ride?

Answer: Yes. They employ an automatic centrifugal clutch so there is no clutch lever and they have only 4 gears (all up). All the way down is neutral so there is no problem for beginners trying to find neutral in between 1st and 2nd as on a regular motorcycle.  The throttle, front brake and rear brake are all standard.  To start off you just start the engine, let it idle, click it into gear and turn the throttle to go.  No problems with it stalling as there is no manual clutch. The automatic clutch engages smoothly and prevents the engine from being stalled on take off.

Can I get spare parts?

Answer: Spares are readily available on eBay Click Here and see. You can also purchase spares and replacement parts from Honda in Australia and New Zealand.

Are there different models (Electrical Systems) available?

Answer: Yes. Pre 1986 CT110's have a points ignition and run a 6 volt electrical system. The points need to be adjusted and replaced periodically. Post 1986 models employ a CDI Ignition and 6V electrical system and are highly reliable. In around 1995 the electrical system on the Australia Post models was changed to 12V and the CDI system was simplified. These models also include a built in rev limiter which apparently prevents the frame from cracking around the engine mounts.  The Aussie Post model does not have the hi-lo range transfer case of the agricultural model. Other than that the design has been pretty much the same since the 1960's.

Mine's not registered. Can I get it registered so I can ride it on the road?

Answer: There are three answers to this question. Yes, No and maybe. Read on... 

YES - The Aussie Post models (and ex Aussie Post) have an ADR (Australian Design Rules) compliance plate so you can get them registered no problems. 

NO - The Agricultural versions (the one with the Hi/Lo range gear box) does NOT come with an ADR Compliance Plate.  So you need to be careful.  Honda have not and will not be getting these passed for ADR.  There are quite a few differences and it is not viable for Honda to have them ADR'd when they have similar sized bikes available that are designed for use on the road. (That's what Honda Australia told me anyway).

MAYBE - Check with your local authorities. I am told by some 'experts' that ADR compliance can be obtained privately by obtaining and 'Engineers certificate'. I do not know what the costs of this would be, but I have heard of people who have said they have done it via my Postiebikes forums.

Are there any common problems that they have?

Answer: They are a pretty strong machine, but they do have a couple of pitfalls to watch out for:

Detent Lever - There is a lever called the detent lever (pronounced 'detont') that controls the selection of gears and it internal on the right hand side of the engine.  When this lever bends, wears or cracks due to mistreatment, age, or general wear, it will cause the bike to find false neutrals between gears. When this happens it needs to be replaced.  It is a low cost part.

Valve Seat Wear - When they get ridden hard or flogged as some people call it, the exhaust valve will wear down in the valve seat, and the engine may no longer start easily or not at all. A loss of compression will be noticable. To fix this simply adjust the tappets. This is easy to do and manuals for CT110s are regularly sold on eBay.

Engine Won't Idle - The most common cause of this is that the rear carry rack has been removed or the air cleaner has been modified.  The CT110 is tuned to run with an airflow restricter in the rack.  If this is removed the engine will become too lean (ie not enough fuel and too much air) You may find that it will seem to run okay if the CHOKE is always left ON. The easiest way to fix this is replace the restriction. The best way to fix it is increase the size of the main jet to richen up the mixture.

Frame cracks - some of the later models suffer from cracks in the frame where the centre tube meets the main frame monocoque. These are often  hidden behind the centre tube frame cover. From my experience they pose no major problem but probably should be welded up to prevent complete frame failure. I have been told by reliable sources that the cracks occur due to harmonics at the high rev range, so the latest models include a rev limiter to prevent this. I cannot varify how true this is, but it sounds reasonable to me.

Blowing Headlight Globes - the lighting electrical system is very crude and basic.  It requires all globes (ie Tail Light, Speedo Light and High/Low Beam) to be working plus a 3 ohm resister mounted under the frame near the ignition switch to be in circuit.  These devices all need to be working otherwise there will be too much voltage going to them and one by one they will fail.

Where can I find more information?

  • Go to postiebikes dot com
  • Join the Yahoo eGroup called postiebikes (Google it)
  • or contact the author of this guide.

Submitted by: Warren Leadbeatter (eBay ID warrenlead69)

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