Switching from Dino to Semi-synthetic


I have just about put 500K on my Tomos Bullet and was planning to change my gearbox fluid and at the same time switch from the Crappy Tire ('Motomaster') 2-stroke that I used to break it in to Yamalub semi-synthetic in my injector.

I would like a little advice on how to do this technically. Stupidly, I filled the injector with the Motomaster stuff so now I have to get rid of that before filling it with Yamalub. So, 2 questions:

1. Anyone have a better way to get out all of this oil than siphoning? Should I just diconnect the hose and let it drip out?

2. Do I need to 'rinse' the injector out with the new oil or can I just add the Yamalube to the small amount of dino residue that will remain?



Re: Switching from Dino to Semi-synthetic

John Joedicke /

Disconnect the line at the tank and drain, refill with the other oil and just let the remainder in the line burn through. Watch out for air bubble in line, keep it filled. Might get a wee bit messy but can be done.

Re: Switching from Dino to Semi-synthetic

i saw one page .. ( ultralight pilot? ) recommended when changing over to a different oil, the first tank of gas should be premixed as a backup and to purge all the old stuff out of the system. Seems that some oils turn to jello when mixed with others.

im still wondering how to get the oil ratio correct with a synthetic if the pump was built for low-tech stuff... are these pumps variable or no?

Re: Switching from Dino to Semi-synthetic

Jjoew has this exactly right - you do not want any amount of mixing between synthetic and petroleum oils. They can gel, congeal or even turn into a bubble-gum like stuff. Not every mix, every time, but it's not even close to being worth chancing it.

Drain the tank, as many lines as possible, and flush everything clean with gasoline. After you've refilled with synthetic, run a little premix (synthetic) in the fuel tank until you're sure that little pump is feeding the new oil. Then dump the premix (into some premix only bike) and run straight gas.

As for adjusting the oil pump.. It's typical to have a little rotary cam/washer that gives the pumprod a bump on every revolution of the engine. If you can measure the effective stroke of the pumprod, you might be able to adjust the volume by carefully reshaping the cam (taking off some height), which will decrease the stroke and volume of the pump. It would be trial-and-error, so watch the 'error' part.

Never actually tried doing this adjustment, nor have I ever felt the need. I've always just run Yamalube-2 in my oil-injected motorcycles (mainly Suzuki T-500).

Re: Switching from Dino to Semi-synthetic

John Joedicke /

This stuff he is going to use is semi synthetic so the issue of mixing is mute. Also these little Mikuni pumps don't have a means of adjusting ratios. They are fixed at 50:1

Re: Switching from Dino to Semi-synthetic

Tomos moped have a bleed screw on the oil pump to bleed the air from the lines. Open the screw and gravity does the rest. Just dont try it while the motor is running :)


Live to ride, Ride to work

Re: Switching from Dino to Semi-synthetic

Steamboat Aka J. R. Stevens /

http://www.dansmc.com/2_stroke_oilpump.htm A good read on oil injection. Jim.

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