oil injection question.. (not about removing it)

hey guys i got a 1970 ts 90 for free, but it has some problems.. one is the throttle cable was cut. it is the kind that splits into 2 and one end goes to the oil pump.. i have another throttle cable but its a single line..

so my question is, can i plug the tube that goes to the carb and pre mix, but keep the oil pump to oil the bearings?? (and pull the arm open as if it was always at WOT)

Not really.

First off, where is the pump injecting the oil? If it's just injecting into the intake track then yes ~ you can pull the pump and just use premix. However you might have to rejet as the oil will displace gas in your premix which effectively leans out the jetting.

If the injector is pushing oil into the bottom end then I would say that you can not lock the pump into a WOT posistion, it'll foul plugs.

I personally would just try to find the correct throttle cable or at least one that you could use.

the pump doesn't inject oil into the bottom end, but push's oil through the bearings to keep them lubed.

so there is a line from the oil tank into the pump, then there are 2 lines that pump oil out (one goes to the carb the other to the bearings) then another line coming from the other side of the block as a oil return line from the bearings. so basically the oil runs through the bearings then back to the pump as a cars oil pump would.. then it just has a line that feeds oil on the back of the carb, so it doesn't inject it before the jets, so i don't think it will lean out the jets, or foul the plugs..

ill try to get pics in case i cant explain it clear enough..



i forgot to mention this isnt a normal 2 stroke this is a rotary valve motor

and lol yeah im tryin to find the cable but i cant find any.. tried 3 different cables that were supposed to fit, but the lines were too long and the slide wouldn't open until about half throttle.. so im on the lookout for a parts bike.. sorry i forgot to mention that part



Excellent job on finding the diagram!

That injection system is pretty close to what Can-Am Rotax rotary valved engines used (maybe others) back in the good old oil injection days, which really did work pretty good. And those split cables are still available. Google RTRmoto.

One thing that Can-Am did oh so long ago was to use the same motor (but different rotary valve) in the MX and trail bikes (TnT's) but they also used a split cable on the TNT's. On the MX bikes instead of the split cable they locked the injection pump out at 3/4. And it actually worked great on the MX bikes as long as you didn't do any extended trail riding at low RPM ~ then they fouled plugs.

Soooo, if you can't find a cable I would consider locking it at 3/4 and see what happens. Take it easy and if it fouls a plug then you can either ride it harder or back off the pump setting.

My 2 cents.

ok ill try that, thanks! and after further inspection of the diagram the line i thought was an oil return is actually the mix line for the carb, so im curious to what the other line coming from that direction is, i know it isnt over flow cuz thats on the bottom of the carb.. maybe vacuum or something..

Looks like you've got or should have 3 lines. One feeding the left and the other feeding the right side of the crank, the third line is pushing oil into the intake side and that's what lubing the piston.

There's no vacuum operation here, the pump is pushing all of it.

Back in the day, I had my 74 TM125 converted to run pre mix. From what I can remember, they had drilled two small holes in the cases (one in each case half) approx. above where the crank bearings would be. I don't recall if the cases had to be split to do this but I did remove the engine to take it to the shop to have this done.

The bike ran great afterwards and I never had any problems with the conversion.

Hope this helps.

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