Yamaha RD350 oil pump help needed


Active Member
Hi, got myself a 73 RD350 and PO had disconnected the oil pump and ran on 32:1 ratio premix. Thought of putting the pump back in service. Opened up the right cover, pump is there but the shaft that comes from the case in to the pump is missing. Wondering how much work does it involve to put one (are available on ebay for 12-16$).

Would be nice to get some help in putting this old machine on road again.
You will need to pull the clutch cover and everything is behind there. Once your there replace some o-rings and make sure all gears are in place.

Pretty simple really.
Go and look up the parts on Partzilla. You will need the shaft, nylon gear, dowel pin, worm shaft outer guide and all seals for the shaft. Run the pump and enjoy not having to mix gas and oil.
Thanks a lot,
you guys make it sound easy, will take the step and go about it. What are the thought about buying off e bay a used one?
Should I drain oil before opening up the clutch cover or just catch what drops?
Buy it and get a rebuild kit from economy cycle. Take it apart in a ziploc bag so that you do not loose any of the spring loaded parts upon disassembly. Drain the oil out of the engine unless you lay it on it's side like the racers do.
clem said:
Buy it and get a rebuild kit from economy cycle. Take it apart in a ziploc bag so that you do not loose any of the spring loaded parts upon disassembly. Drain the oil out of the engine unless you lay it on it's side like the racers do.
This is very important. If you take the front cover off (held on by 4 cross head screws) and pull the works out of the main pump case, two very tiny spring loaded pins will rocket out into orbit. It is nearly impossible to keep this from happening even if you have had many pumps apart and know exactly what you are doing. Fortunately, it is somewhat easier to put it back together, assuming you haven't lost the parts! So take out the screws, get the cover loose (it will likely be stuck with the gasket), and before going any further, put the whole thing inside a ziplock and seal it up. Then you can take it apart inside the bag and the small parts will be contained in the bag. It is worth rebuilding the pump. Actually you will simply be replacing the seals and gaskets, but they commonly weep oil, and this will fix that. Be sure to polish the shafts where the seals ride and you will be fine - the pumps are quite simple. One important thing though. Very likely the pump is fine, and only needs to have the seals refreshed, but check it first. All you need to do is connect up a supply line to it and spin the nylon gear until you see oil pump from the two discharge pipes. The pump alternates between the two, so you should see oil ooze out of one then the other. If the throttle cable is hooked up, open the throttle all the way to max out the pumped oil volume. If there is no cable (you have to have this to run the pump!), rotate the pulley to hold the pump wide open. There is a cross head screw in the outside of the pump to bleed air out. Make sure you take this out and oil runs freely from the hole to make sure oil is getting into the pump and put it back in. You should have oil pumping from the outlet pipes in 20 or so turns of the nylon gear. If not, the check valves are stuck. These are just steel balls and springs under the brass outlet pipes. Try running WD40 through the pump to get them loose, otherwise you will need to take them apart to clean them. The parts are very tiny, but simple. The brass ports are pressed into the pump body, but can be removed with a determined grip with pliers and a twisting-pulling motion. A drop of locktite stud and bearing mount will have it sealed when you put it back together, but obviously you must be really careful not to get any on the check valve parts. Lastly, if you do not have the steel worm drive shaft sticking out from the case, you also do not have the nylon drive gear (not the one on the pump). Be aware that the 250's and 350's have different parts, so be sure to get the right ones.
many thanks JP for such an informative detailed post, appreciated.

parts (shaft and gear etc) is awaited, once here, will get to doing the job. good point you brought up to replace seals of pump, will get to ebay and secure a set.

Cheers mate,
Yamaha still sells the springs and balls for the check valve setup on the discharge side. Those wear over time and the pump will free flow oil into the carbs when it sits for periods of time. Change those while you're in there.

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I am still waiting for my eBay shopping to show up to put my oil pump back in service. Meantime I filled premix of 32:1 and now it is running on left cylinder whereas right drips at the joint of muffler and header plus right muffler spits oil/gas.

Earlier it was running fine on right but left was an issue.

Removed right carb and cleaned it thoroughly, there was some cleaning required, put it back on, cleaned new plugs which were fouled and started right on but only on left.

is there a diagram showing how carbs are connected via small oil feeding tubes? I see couple of nipples on both carbs plus a joint tube (which i think is for choke).

upper nipples are connected with a tube (where originally oil pump tubes will connect. there are two nipples at the bottom which have tube connected and left open (perhaps drain) then there are two more one on each carb and nothing is connected to them?

Would appreciate any help
From your description the other 2 go to air box if you still have air jet capped, if uncapped they should be plugged with caps. I assume you capped off the oil inputs already since using premix if not will suck air in.
I think that only the RD400 had vent lines going into the air box. The 350 should have the crossover tube for the enrichener or choke circuit, bowl vents and drains, and oil injection nozzles.
Put up some pics and we can point them out.

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