Protecting A 2 Stroke Minarelli Engine

[bull]

I recently rebuilt two 2 stroke scooter engines (Kymco Super 9 & TNG Venice LX), and I always look at why the engine failed to protect my work. Like many of you, I started the engines with premixed fuel and proceeded to bleed the oil pump and adjust its flow.

Neither scooter ever bleed out the pump, so I took a look. The Kymco pump is easy to service, and I disaasembled it, cleaned, checked the gear mating, relubed, reassembled and reinstalled. Works fine.

The TNG oil pump is behind the stator, and a little more work. Pulled the pump, and it was rotating easily, so I bleed it with a drill. Reinstalled it, but it still would not pump oil. On closer inspection, the drive gear attached to the crank was not mating with the oil pump gear. Pulled the drive gear and found a concave wear pattern on the (nylon / plastic) gear.

The wear pattern is really hard to tell even with the gear out. I would suggest if you have one of these scooters that you replace the gear as a normal maintenance item and save a lot of money from engine damage.

here is a picture of the gear:

[blueboy5000]

I just finished a Kymco DIO bbk on a zx50, so now I have officially rebuilt every kind of scooter engine currently popular.

I rebuilt the AT engine on a Yup and a Minarelli both dead from oil starvation. Every 2t I have seen with an oiler has that has died was because it was run out of oil. I have maybe seen 5 messed up oilers in the 30 years I've been building.

I'm not saying oilers don't fail, but it's usually the operator.

[bull]

maintenance failures such as not keeping the oil level up is a huge problem, but it is similar to the fact that most fail miserably when it comes to user level maintenance on anything.

I learned a valuable lesson these 2 strokes about plugs, they can refuse to start with a plug that would run fine in a 4 stroke-- if I continue to see more of these I'll start stocking a few more plugs to save time.

[scootercapecod]

I usually check my oil injection tank every other fill up and make sure I have a quart under the seat in case I need it. The other thing is I never let the tank go under 1/2 full to be safe.

[bull]

Have any of you noticed that some 2T oils specifically state "Not for use in autolube systems"?

The reason I ask is I have tried a few different oils in the premix and I find the Lucas Semi Synthetic works best and it is compatible in autolube systems, plus Summit Racing has it in gallon quantities at decent pricing vs quart pricing @ O'Reilley.

[MitchFav]

I am new to scooters, but have been having fun rebuilding a Rad2Go Milan 50 (identical to TNG Venice), but have a lifetime of experience with small 2 stroke outboard motors, and from day-one I was nervous about trusting that little oil pump and rudimentary carb to provide a reliable 50:1 mix. After struggling to get that pump out of the engine just so I could put new hoses on it (this bike is 15 years old and the oil hoses were very stiff and brittle). Got the pump back in, then tried to bleed and prime it, and it would not pump any oil. That sold me on the lesser of two evils, which is to just always run with pre-mix, and carry a small bottle of oil under the seat if I have to fill up at a gas station. So I just snipped the brand-new hoses I put on the pump short enough to keep them out of the way, and plugged both hoses with some small SS screws. I will never worry about whether I am getting the right amount of oil into the gas now.