QT50 oil pump

How do I bleed the oil injection pump and how do I adjust the oil injection pump’s output?

Check the manual in the periodic inspections and adjustments chapter, section 2-4.

I’d like to eliminate the oil pump on my qt50. How do I go about doing that?

You can eliminate the oil injection system in at least two ways. First, you can just start running premixed fuel (oil & gas) in the gas tank or you could take out the oil pump and replace it with a freeze plug or with an oil pump block off plate . The block off plate or freeze plug has a cleaner look to it but I recommend just leaving the oil pump installed and running premix in the gas tank.

No matter what choice you make, make sure that you do not run straight gas through the system for any amount of time, no matter how small. Gas without any 2 stroke oil will cause major engine damage in a hurry. I made the mistake of thinking I could make it 0.3 miles home on straight gas and paid the price. I had to install a new piston and rings after honing the cylinder. You might be able to make it a block or two but why risk it?

There are a few reasons why I recommend just leaving the oil pump installed and running premix in the gas tank.

1. The oil pump is controlled by the throttle. The more throttle you give the bike, the more oil gets pumped into the carburetor. The throttle cable connects to a junction box. At the junction box, the throttle cable connects to the oil pump cable and the second half of the throttle cable which leads to the slide in the carburetor. If you remove the oil pump and the oil pump cable, your throttle cable will never be the same. In fact, it will get stuck at full throttle because the oil cable that was providing resistance is now missing. You’ll need to increase the resistance without the oil pump cable somehow if you want your throttle to function normally.

2. If you leave the oil pump and all of its components installed, you can easily switch back to using the oil injection system in the future. If you ever want to sell your Yamahopper, it is often more attractive to buyers if that system is still intact. Newbies don’t want to have to mix oil and gas. It’s just too hard for them.

3. If you leave the oil pump installed with a little bit of oil in the system, you don’t have to worry about running any straight gas through the engine. Let’s say you delete the oil pump. Most likely, you still have a little straight gas in the fuel line and/or carburetor. You add some premix to the gas tank but you still have straight gas in the fuel line. There may not be much straight gas in the system but you could be risking engine damage as a result. You are better off leaving the oil pump installed with a little oil in the system. You may run a little rich for a short period but better safe than seized.

Some recommend deleting the oil pump because it robs power from the engine. It takes so little power to run that oil pump that I doubt you notice any difference with or without it installed. Another argument for removing the oil pump is that you can use the oil tank as a reserve gas tank. Just use a fuel-T or Y and connect the oil line to the main fuel line. You may also want to install another fuel shut off. This is a nice perk and you can still do this with the oil pump installed. Just remove the oil line from the oil pump but leave the oil pump installed.