CT90 Rust Removal

Something you'll never be able to avoid with a CT90 project is rust! These bike are all over 40 years old and most of the "project" CT90's you find usually have been setting on the side of someones house and have seen everything mother nature could throw at it. So with rust you need to just deal with it and the two approaches I use most often are soaking in white vinegar and electrolysis. There is a third method I have used to remove rust that is also a very viable method and that is using a toilet bowl cleaner called The Works, that I touch on at the end of the article.

You can buy a variety of different commercial rust removers, but I wouldn't waste your money as both white vinegar and electrolysis are simple and very cheap approaches that will work just about as well as anything you'll buy at the store.

If you only have light rust on some of your chrome parts you might look at another post I have made on various methods people has used to address that condition.





Using White Vinegar
I mainly use white vinegar for smaller parts where I can get the parts fully immersed in a container with white vinegar.  The white vinegar has a very low acid content that given enough time will break down any rust on the part you are soaking. I usually let parts soak at least overnight, but most of the time it takes a couple of days on a well rusted part. When you pull the part out of the vinegar it may have rust on the surface, but you'll find that it easily wipes away with just your finger or a small brush. One thing you will find when on parts where you have removed all the rust is that they will flash rust very easily, so it is important to get a coat of oil on these parts right after they have been rinsed and dried off.

One application where white vinegar works well is with gas tanks. If you have a tank that is rusty on the inside just plug the two fuel line ports at the bottom of the tank and then fill it up to the brim with white vinegar and let is set for a day or two.  When you rinse out the tank at the end of the process you can add a tablespoon or two of baking soda to the tank and fill it with water and swish it around and this will help neutralize any remaining acid from the vinegar that leads to flash rust, but even after the baking soda rinse you still need to dry the tank and get a cost of oil (WD40, etc.) otherwise the bare metal will start to rust almost immediately.



Using Electrolysis
for larger parts I really like to use electrolysis as it works well and it is actually a relatively quick method compared to using white vinegar. The following website provides a great description on how the process actually works more specific details, but I will provide the readers digest version here.

What you need are as follows:

A battery charger
A bucket
Washing Soda (Baking Soda will also work if that's all you have)
A piece of steel to be an anode

You'll want to do the process outside or in a well ventilated area as it does produce gases as part of the normal process. Whenever you are hooking up the battery charger to your part or the anode in the bucket first make sure to unplug your battery charger.

You first mix in about one tablespoon of the Washing Soda for every gallon of water into your bucket so that the part you want to remove rust from can be immersed in the solution.  You next apply the negative clamp from you're battery charger to the part you want to remove rust from and place it in the solution. You then take the positive clamp (usually red) and clamp it to the piece of steel you will be using for your anode and then place that in your bucket of solution so that the anode is on the opposite side of the bucket and down in the solution, but the positive clamp is not in the solution. Next plug in your battery charger and I usually set mine to the manual mode and let the process go.  You will start to see very fine bubbles form and a rusty scum will start build on the surface over time which is all good and means the process is working.  The process will remove rust from the side of your part facing the anode, so you may have to rotate your part during the process to get rust remove from different areas of the part.

The process generally takes several hours to remove most of the rust from a part.

Here are a few pictures where I ran a seat pan through the electrolysis process:

The before picture of the seat pan.

Here is the bucket of solution and the electrodes attached to the anode and the seat pan.

Here is the battery charger I was using.

Here is a picture of the bucket after a couple of hours.

Here is a picture of the seat pan after it has gone through the process and had been rinsed off with a coat of oil applied.

The Works
The Works is a toilet bowl cleaner that is essentially a 10% Hydrogen Chloride solution that is cheap and readily available and does a good job at removing rust. The Works is much more aggressive than white vinegar so it removes rust faster but may damage your parts if you let them soak for an extended period of time.  The Works is also a lot more hazardous, so you really need to be careful (eye protection & gloves) when your using it.

Helpful Links  (Shop Manuals, Wire Diagram, Model Information, etc.)