Two Stroke Oil Pumps

[Diablo007]

So the oil pump on my DT100A project leaks from one of the seals inside the cover, not the shaft seal.  I found another similar pump at the shop.  Now as I understand it, Yamaha made pump housings for the number of cylinders for which they supplied oil; 1, 2, 3...  So for my purposes, any pump for a single would work, as long as the gearing is correct.  So, as far as I can tell, there are only two gears that come into play, the worm gear and the internal gear driven by the worm gear.  I'm guessing the gear that is different is the worm gear as this the easiest to interchange.  Also, it is the only gear listed in the parts catalogue, and there are more than one listed.

Anyone out there that can confirm that I just need to make sure the worm gears are the same, or swap them if necessary?  I have to use the driven gear on the existing pump as the one I found doesn't have one.  That's one less gear to worry about.

[Arrow]

Single outlet pumps have left hand and right hand camshafts according to which outlet (on the main casting) is used/not drilled off. As long as you can get the outlet pipe to fit, it doesn't matter. But, on a single cylinder pump you can not use a camshaft that came from a  pump that uses  the top outlet and put it into a casting that uses the side outlet (or vice versa). It won't work. It would if you could spin the pump in the opposite direction.

You will need to use your original pulley, if the other one has a different ID.

You say the donar pump has no internal gear, then you will be using the gear from the original pump. You will need to make sure that the shafts are in good condition and change all the seals as a matter of course.

Does the original pump have the plastic thumb wheel on the back of the shaft? Refitting the gear on these with the spring loaded pins is a nightmare....


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[Diablo007]

So, the pumps were only similar in that they were for singles.  One turned clockwise, the other counter-clockwise.  The worm gears didn't have the same amount of turns, as well as the driven internal gears having a different amount of teeth.  I'm sure I can find the proper pump at the shop in the box of pumps, but decided I'd just rebuild this one.  Ordered the kit off fleabay today. The hardest part was getting the pump out of the body.  Years of neglect had corrosion on the exposed part of the shaft so it wouldn't push through the body.  Took quite a while of cleaning off the corrosion before I could push it through.  Next up is a visit with the ultrasonic cleaner, then a visit to the blast cabinet to hopefully make it pretty again.

Pics of the disassembly below.  Missing the pics of removing the driven internal gear.  Arrow was correct about the spring loaded pins.  I removed the gear in a clear plastic bag to make sure nothing was lost.  A trick learned from the pics of the instructions the vendor I bought the rebuild kit from posted.

[Diablo007]

The last pics.

[Arrow]

Yes, those pumps you have there are quite different to each other. One is driven directly from the center of the crank. Even though the pump outlets are in the same position the camshafts are 'timed' differently and are not interchangeable.

The condition of your original camshaft concerns me. Where the corrosion has crept along the new seal may struggle with that and have a very short life, although there is a solution to that. You can chop the back of the shaft off and use a blank plug in the back like the later pumps. You will loose the priming wheel of course. The gear is retained on the shorter shaft with just one longer pin with no spring. You can make one from the shank of a small drill. I can provide dimensions for this.

Also, look down the center of the camshaft to see what blanks it off. If you see a bright steel pin, this is good. If you see a resin plug, then check it's integrity as these are starting to fail now.

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[Arrow]

The outlet nozzle needs to come out, to clean the spring and seat. There is normally a lot of crap in there. A now roll pin (and split pin should be fitted if using the long shaft)

I prefer to press the roll pin in, first with its tapered end, but when the job is complete the pin has no tapered end, ie full diameter all the way through the hole for maximum retention.
If the roll pin comes out in use, the motor will die. Don't rely on the roll pin retainer to compromise on a poor fit here. They didn't work very well, hence two future methods, the final one being a steel screw along with steel insert top casting, not all Aluminium like the early ones.

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[Striker1423]

The outlet nozzle needs to come out, to clean the spring and seat. There is normally a lot of crap in there. A now roll pin (and split pin should be fitted if using the long shaft)

I prefer to press the roll pin in, first with its tapered end, but when the job is complete the pin has no tapered end, ie full diameter all the way through the hole for maximum retention.
If the roll pin comes out in use, the motor will die. Don't rely on the roll pin retainer to compromise on a poor fit here. They didn't work very well, hence two future methods, the final one being a steel screw along with steel insert top casting, not all Aluminium like the early ones.

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I'm fully aware of the roll-pin failures!

[Diablo007]

Thanks Arrow.  I was planning on polishing the corrosion on the pump shaft up the best I could.  I'll take the pump to the shop to see if there's another one in the box.  I didn't have it with me the first time.  Hopefully there's one in better shape.

I'm guessing the nozzle is a press fit, so heat it up a little and work it out gently?  Maybe with a heat gun or blow dryer?

[Arrow]

No heat required.
Get a good grip with a decent pair of mole grips. Turn and pull at the same time and it will come out. I bond them back in for a belt and braces job, and test them while the casting is still bare.

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[Arrow]

On those straight brass nozzles, use a small socket to bang it back in. Don't hit the small outlet stub.

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[Diablo007]

Thanks Arrow.  Rebuild kit arrived yesterday.  Going to the shop tomorrow so I'll see if I can find one in better shape.  I figure it may be a good idea to rebuild whichever goes in the motorcycle as they would both be about 50 years old.

[Diablo007]

Made it to the shop/man-cave Saturday and went through the box of oil pumps.  Found one that seemed to match up, but decided to bring the box home anyway.  Of course the one that seemed to match seems to be a perfect match.  Worm gear and drive gear match up.  I'm guessing the internal gear of the pump are the same also.  Can anyone confirm this?  I'd rather not take the pump apart as it seems brand new and as such a waste of time to do so.

[m in sc]

looks correct to me.

[Arrow]

And to me.

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[Diablo007]

Thanks guys!