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Parts & Repair Pointers for Bike Bug® & Aqua Bug™ Engines

Repairing your own Engine

If it has been awhile since you ran your engine – you may need some parts – a picture and idea about the condition and how it was stored will help me – help you get the “Wind In Your Face” sooner. Most engines that have spark and have not ran in awhile will need a new fuel pump kit, foot valve, primer pump, fuel hoses and carburetor cleaning. Spark can include an ignition module, spark plug and adjustment to magneto spacing.


We are a Tanaka parts distributor specializing in Bicycle Engines. These engines were made in the 70's and are Classics. If parts are broken or lost on during attempted repairs they may be difficult to be replaced. We highly recommend you get the literature before wrenching on the engine.

We are happy to help you work on your engine. We have developed these parts by working with other owners and have sources to substitute other parts.

Enjoy the engine – they are really neat little machines.

BITW (Brothers In The Wind)
Tanaka Bicycle Engine – Spare Parts Catalogue (Standard)
For Model QBM-23 (Including Aqua Bug Model)  CLICK TO VIEW THIS CATALOG

Tanaka Bicycle Engine – Spare Parts Catalogue (Automatic)
For Model QBM-23N/NA

Repair Pointers Before Parts Arrive



The fuel lines attach to brass inlets that are heat/cold press fitted into the fuel pump housing. If you pull on the fuel lines and the brass inlets come out of the housing – they may not seal properly when reinserted. This causes bubbles in the fuel system and your engine may never run correctly again.

Fuel lines may be hardened and cracked – you can buy replacements for $6.00 (These do not cause air bubbles problems in the carburetor which will probably need cleaning to simple to do – Don’t turn adjusting bolt on bottom). You will be provided some tips in literature on doing this that will prevent a lot of headaches and repairs.


Gas Tank
What is the condition of the gas tank?  If it was drained, it would be good to flush it with a little fresh gas. If not, put some bolts & nuts in with some camping fuel (white gas) and shake them it around to knock off the old varnish and rust. If it is badly rusted, there are commercial gas tank cleaning kits other folks have used from automobile part stores that work well. I have put some of my old gas tanks in the dishwasher with dish washing power inside – very caustic and will get out rust. Might knock off paint though so you have to make a judgment call on that, not to mention what your significant other might think about that.

An electronic method that works well on some tanks is as follows:  use a power washer to remove all loose rust and sediment. Then fill the tank with water and add a tablespoon of baking soda for every gallon of water. Then get a battery charger and connect the positive (red) terminal to a piece of wire attached to a stainless electrode (such as a stainless bolt or a stainless spoon) and lower the wire and electrode into the water making sure it does not touch the bottom or sides. This is the anode. Then attach the negative terminal to the tank itself (The cathode). If your charger has a meter, be sure some current is flowing. Fine bubbles will rise from the stainless anode when cleaning is in progress. Typical cleaning time for moderately rusted objects is a few hours. Heavily rusted objects can be left over night. Then wash the inside of the tank again and dry it out with compressed air or a hair dryer.

You can also check for fire or spark on the engine by taking out the spark plug and turning the drive wheel by hand. First look for the spark and if none, try the twinkle test by holding the spark plug and turning the drive wheel. If no twinkle then remove the three bolts on the flywheel cover (where starting instructions are posted). Take a 12 or 13 mm socket mounted on a re-chargeable drill and turn the engine with it. No spark; try a electric cord drill (Be careful doing this). Don’t want to turn the engine too fast without getting everything freed up first. If you do not have electricity – you need to check for shorts – best to re-wrap all electric wires with electrical tape and test again. If no electricity you may need to clean the points (Literature package tells how). It is generally easier and simpler to install an electronic ignition $35.00. This unit replaces points and condenser (No longer made). It replaces the need to take the engine apart to clean points.

The coil lamination spacing is very important.  It should be about the width of a business card. The screws holding the coil are accessed by taking off the muffler and the carburetor/intake. Turn the engine over until the magnets are up against the coil. You can see this by taking the small flywheel cover off. A business card should be tight in the gap between the magnets and the coil lamination. If it is more loosen the screws and allow the coil to move closer to the flywheel magnets.

The literature is $25.00 + Shipping for a printed copy or view it for FREE from the link above. It will save you a lot of headaches on getting your engine running and maintaining it in running condition. There are several small parts that once lost or broken cannot be replaced. Also there were slight changes to models as these engines were manufactured, so the manuals for them contain changes. The other thing is you may have an engine that someone worked on with the literature – what they did, what they may have left out or changed out for something else can be ANYTHING that was on the shelf.

Fuel System
You are probably going to need a fuel pump kit $35.00. The rubber diaphragm gives out with time and exposure to gasoline. The drive wheel rubber may gone or in good condition. You can tell by looking at it and squeezing it. This hard firm & good shape – OK. If not a new drive wheel is $35.00.

Newer engine models were equipped with a primer pump $32.00. Engines equipped with it do start easier and the pump will last longer. Plus it gives a method to test the fuel pump is properly installed – the engine block hold downs can be busted if the engine is attempted to start with a block full of fuel.

Foot Valve & Filter - chances are the check valve is frozen in the foot valve that goes in gas tank. If you can blow through it but not suck through it - it is OK. If not we have replacements for $35.00.

Fuel Lines
Please do not attempt to pull these off the fuel pump. We will send you instructions with your parts on how to remove these and install new ones that seal better than the originals. Air leak prevention is very important to these engines running properly. We supply new Tygon lines for $6.00.

Good idea to spray Carburetor cleaner into all the passages on the Carburetor.  There is a small hole in the bolt (jet profile) located in the sump (bottom) section of the carburetor. This hole must be clear – I use a piece of bicycle brake cable to clear the hole then spray carburetor cleaner through it.  Also the O Ring that is between the two sections of the carburetor might need to be replaced – easily found at your local Hardware Store. The Work Shop manual shows how to adjust the jet needle by raising or lowering it to meet your elevation.

Mounting on Bike
If you plan to mount the engine on a newer model bike (1970 – up) the forks are 5-1/2” wide center to center, closer than bike forks were in the (1960s). You will need a mounting kit – $25.00 to spread out the frame of the engine and have the drive wheel run true.

Bench Testing Engine
Starting the engine on a work bench is so much easier than mounted on a bicycle. Plus it allows you to see potential problems and make adjustments that you can’t when seated on the bike.  Starting the engine with a rope pull is demonstrated in the Workshop Manual of the literature.  Starting the engine with an electric drill and socket is similar to the test for electricity except the replacement parts are installed and gasoline is in the gas tank – engine is ready to fire with fuel.

  • It is a good idea to secure the engine to the work bench – bungee cords work good for this.
  • Have drive wheel clear
  • Have a clean work area – because the fly wheel nut can back off and go flying away from the engine on any surface.
  • Be prepared to clean spark plug a couple of times to remove old varnish form cylinder. ·
  • Have throttle cable and lever in easy grasp.  If engine does not start – it may have flooded – clean spark plug – turn engine over with drill and clear cylinder without spark plug inserted to dry excess fuel in the engine if necessary. ·
  • Insert spark plug; attempt to start again. Increase drill speed till engine fires.