My 74 DT250 is currently running pre mix as a previous owner has removed the oil pump.
I want to replace the pump and run the oil injection.
I found a used pump locally of a 77 model. Will this fit onto my 74 model or are the pumps different for these models?

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Hi,
My 1976 DT 175 is running a far later models oil pump without a problem, Having said that a friend tried to source an oil pump for his 400DT and found differences between the pump from a 250 DT and the 400,
I have just looked on Partzilla and it shows the oil pump for the 74 250 as also fitting:
This Yamaha 500-13101-01-00 OIL PUMP ASSEMBLY Not Available fits the following models and components:
Yamaha Motorcycle 1974 DT360A Oil Pump
Yamaha Motorcycle 1974 DT250A Oil Pump
Yamaha Motorcycle 1976 DT400C OIL PUMP 250B - C - 400B - C
Yamaha Motorcycle 1976 DT250C OIL PUMP 250B - C - 400B - C,

A second search for the 77 250 D oil pump gives back this result:

This Yamaha 1M2-13101-01-00 OIL PUMP ASSEMBLY Not Available fits the following models and components:
Yamaha Motorcycle 1978 DT250E Oil Pump
Yamaha Motorcycle 1977 DT250D Oil Pump
Yamaha Motorcycle 1978 DT400E Oil Pump
Yamaha Motorcycle 1977 DT400D Oil Pump

So at a guess I think there will be some differences, I think you might find the worm drive will be different, but further investigation on the individual parts via the, fits the following models and components: will probably show you what parts have changed over the model range


Hope this is of help, AJ search the Partzilla web site for the details,

Be cautious with this type of cross reference... it's very basic in that it shows the other parts lists that a part number appears on. It doesn't mean the part fits that bike... especially since Yamaha shared parts list among similar models. It can be very confusing and why you'll see things like a "magic" piston listed on ebay that fits a 250 and 400 or a 125 and 175.

The 175 is one of those great models that has far better compatibility over decades... Here in the US a 1976 DT175 shares the same exact oil pump with my 1991 RT180. The bigger bikes don't have that advantage. They seemed to change major parts on the bigger bikes every couple of years.

DEET might be able to help... or yes, if you can get a complete assembly with the worm drive shaft it's always best. There are also oil pump charts showing pump color codes and gearing for different years and models. Early bikes had the most differences.... Yamaha tried to "standardize" the pumps in the later years.

This is curiously similar to my recent oil pump situation. I needed to get my '77 pump rebuilt, but already have a pump from my '74 DT250 that I thought I might be able to install in its place. However, the ratios are different, both between the crank and the pump drive gear and the worm and worm gear. I assume the pitch on the worm gear is different, although I didn't put the two together and compare. Even if it physically bolted in place, I don't believe the worm would mesh properly. And if it meshed, it wouldn't be the correct ratio or volume.

And presumably you need the pump drive shaft also (with the worm)? Or do you have that already?

Deet rebuilt my 77 pump, which turned out to be the best decision for me, so even if you find a used pump that fits the 74, maybe consider that route.

Thanks for all your help. I dont have the worm drive shaft, I have 2 options for 2nd hand pumps that come with the shafts and drive gears. The bike currently has no pump or shaft at all. One pump is advertised as a 77 the other one is off a '70s model? I guess I will just buy one and see how I go. Might try looking up the colour code charts too.


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I went and looked at the manuals again and it does say both pumps have a 55:1 ratio on the worm gear. The crank to pump shaft ratio is different however, and the volumes don't jive. My '74 is in pieces, so if you do find a mystery pump with the shaft, post some pics and dimensions and I can compare with mine if you'd like to confirm fit for the 250A.

if it were Me, I would try to find a oil pump for a 1974-1976 DT250. might also want to make sure the oil pump driveshaft and the bushing that goes into the side cover does not fit sloppy or it will destroy that seal that is between the oil pump driveshaft, the side cover and crankshaft. otherwise it will leak two stroke oil into the transmission. it would be a great idea to get a new oil pump shaft seal in the primary cover while you are in there.

Oil pumps are designated by a paint color code put on by the factory.
This reference may be of some use and guidance. DEET may have even more data somewhere.

yamaha-enduros.com/index.php/workshop/se...oil-pump-color-codes

Follow up question...where is the "code" located on the pump? I have a DT100B, DT175C, and DT250A, I can't see anywhere there is a color coding on the pump. Maybe the paint has come off after 45 years, (of course) but where should I be looking?
Thanks

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