Introduction: Built-in Tire Inflator for Motorcycle

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Tired of going into gas station for pumps? Why not install a small air compressor into your motorcycle or scooter and we can all save an unnecessary trip to gas station.

I have a small scooter which I rarely use. Both tires are still using tube and they lose about 10psi every 2 weeks sitting unused. Every time I wanted to use it it will either be too soft or have low pressure (below 15psi). I would pretty much want to pump the tires without having to go out or use the 12V compressor connected to my car.

Unlike most motorcycle, this scooter has its battery located underneath the footrest. Which means I have to install a more permanent solution rather than unscrewing the battery cover each time I want to pump. On the contrary, quite a number of bikes have their battery located inside the storage compartment which makes for easier installation.

So what you need are:
- 12V mini air compressor (or tire inflator)
- 2-pin crimp terminal connector
- Fuse
- "Ring type" crimp connectors for the battery
- Basic soldering OR crimping knowledge
- Basic tools such as wire cutter, soldering iron, pliers, color marker, screwdrivers
- (Optional) Multimeter
- (Optional) Shrinktube and lighter

This air compressor installation is completely reversible, I do not cut any wire or make a hole in any part of the body.

Step 1: Remove the Cigarette Plug and Mark the Polarity

This is the air compressor that I bought. It looks like a small tire which is quite handy and it has its own cable management system. The motor is quite small but what's surprising is that the piston is very tiny making it only suitable for small tires. It should only costs no more than $10 if you look around.

Most air compressor comes with a cigarette plug which we will remove. Unscrew the front part of the plug and you will see the wire and clamp inside. Using a colored marker, mark the polarity of the cable in the center so we know it is the positive lead.

Step 2: Storage Compartment

I want the tire inflator to be stored in the storage compartment. Luckily there is a small hole in the middle of the compartment which is only covered by a plastic clip plug.

Remove the plug using a flathead screwdriver. Place the air compressor in and reel out the wires through the hole. Do not throw the plug away, instead trim one side of the edge off so the plug can fit back in without crushing the wire (see Pic 4-5)

Step 3: Determine Where Your Battery Is Located

Most bikes have their batteries stored just underneath the storage compartment which makes for easy maintenance and modification. Not to worry here I will show you how to route your air compressor from the storage compartment all the way into the battery compartment.

[Pic 1-3]
First open the battery cover. There are two covers you will need to remove before accessing the battery and fuses.

[Pic 4-5]
There is a small hole at the compartment which allows us to route the wire from the storage compartment. To access this hole you will first need to unscrew a screw marked at [Pic 6]. Follow the cable at the [Pic 7] to see where you should route the wire from.

You should have successfully routed the wires from the storage compartment into the battery compartment.

Step 4: Battery Connection

Now you have to either crimp or solder the wires so you can connect it into the battery safely. I soldered the wires so it stays secured and I also used heat-shrink tubes.

If you have a multimeter it is always good to double-check every connection for short circuit. Here I used tube fuse because of the limited space around the battery. Any larger fuse and I can't put the battery cover back in.

Ensure the wires can reach both batteries terminal, but do not connect it yet.

Back to the storage compartment: I want the air compressor to be removable, we're going to use a 2-pin terminal connector. Mark one wire before cutting it. Either crimp or solder the female and male connectors until you're finished [Pic 9]

Finally install both positive and negative leads into the battery.

Step 5: Finished!

You're finished!

Now the most important part is to apply parking brake while pumping the rear tires.

Out of curiousity I went to check the battery voltage to ensure the battery can sustain the load from the air compressor. It turns out that my readings are as follow:

- Cold engine: 14.2V
- Warm engine: 13.9V
- Warm engine + load: 12.6V

It is clear that the charge from the alternator (or generator for older bikes) is not enough to charge the battery while pumping. Hence you should occassionally rev the engine while pumping the tires, and never use the air compressor when the engine is off to prevent excessive load to the battery. The battery shown here is a 3-amp VRLA battery.

Now I can occasionally ride this scooter with proper inflated tires anytime. Pumping a tire from 20-30psi just take less than a minute, I wouldn't worry about damaging the battery.