While researching replacement oil pump cables I just discovered Tech Bulletin M8-015C in the library which describes two different oil pumps for 250/350 twins. What's not clear to me is which one do I have in my 1975 RD250 motor. I would assume the later model but can someone confirm? Is there a way to visually check?
fyi, the 250 and 350 pumps are also different, the ring gear in there is a different tooth count between 250/350.
do you have a pic? the later ones will typically have the pin retainer tab under the nut on the end of the plunger shaft that holds the pulley on.
I think I found the answer. The Tech Bulletin in the library appears to be missing Page 1. I found the full bulletin (attached) and on Page 1 lists the engine numbers for old vs new.
Yeah, basically the difference is between A/B models and 250/350 variants.
The pdf isn't working for me.
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see if this works:
(https://www.2strokeworld.net/wp-content/uploads/2SW-BUSINESS/op1.jpg)
My engine number is 352-306071 which would mean old-style pump. Here are a few pics in case it might have been replaced with a new-style. Can anyone confirm or do I need to pull the worm gear out to verify?
Forgot to add.....oil pump cable length is 325mm outer and 575mm inner in case it helps.
looks to be the newer style pump, but im no expert.. did it ever have issues? id feel ok running it.
This is the motor I picked up at Barber VF last year so I've not yet had it running. I bench tested the pump and it seems to work. The issue I'm having is which cable do I need ... the old (longer) one or the new (shorter) one. The cable I have is frayed. I have a Wanted post out for a replacement:
http://www.2strokeworld.net/forum/index.php?topic=4174.0
Looks like the old pump to me. Interesting how it says the later 350 has a 214 part numbered wormshaft; fine with 9 threads.
The 214 shaft actually has 7 complete threads.
Never seen 9 threads on the 350.
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Pic of the worm shaft. I would guess this is the old-style (coarse). What say ye?
does it slide into the pump and turn it smoothly? to me, thats the bigger question.
Yes it slides in easy and turns the pump no problem.
Thats a 5 turn shaft. Meshes with a 40 tooth pump gear, RD250A.
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You will need a new seal for that shaft now.
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Mystery solved. Old pump it is. Thanks to all who chimed in on this. Will order appropriate cable (and a new seal)
how can you tell the diff between new and old style? tooth count only or?
Process of deduction I guess based on my engine number and what Arrow said:
" Thats a 5 turn shaft. Meshes with a 40 tooth pump gear, RD250A."
I stated it was the older pump before we saw the shaft.
The brass nozzles were the big clue. The B model had steel outlet nozzles.
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i know, just wasn't sure what visual cue you used to identify it, that makes sense. Now I know, thanks. :patriot:
So some Rd250-350 pumps can be used in YD7 & R5 motors?
As long as they are the "early" version?
you can use ds7 pumps in rd250 motors as long as the ds7 drive shaft with worm gear is used, and vice versa. same with rd350/r5. pump and shaft should match. This ive actually done before.
I have a hybrid RZ/R5 pump on my 70 r5, uses an RZ housing with R5 internal gear... rz lower shaft, and an r5 top cover, plunger shaft and pulley. :omg: theres options. I would NOT recommend tearing into oil pumps if you don't like small tiny parts and are super confident in your mechanical abilities.
Yes, I've swapped lots of pumps around when necessary. On the change over from early to later pumps, there is the issue whether to use a thrust washer on the end of the wormshaft, or not.
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So here are 2 "old" style pumps.
The one on the left out of a yd7 the one on the right from a r5.
Why is the inlet port clocked different between the two?
Quote from: BlueR32 on February 09, 2022, 08:54:44 AM
I think I found the answer. The Tech Bulletin in the library appears to be missing Page 1.
Thnks for pointing that out. :thumbs: I have fixed the files in the Tech Library to include 2 pages. Both PDF and JPEG are now posted there
Quote from: soonerbillz on February 10, 2022, 07:24:46 PM
So here are 2 "old" style pumps.
The one on the left out of a yd7 the one on the right from a r5.
Why is the inlet port clocked different between the two?
I don't know why the need for the (earlier) inlet nozzle position. Also the brass nozzles could be different here. The early one had a smaller diameter where it fits in the casting, and the valve seat is direct in the Aluminium, with no rubber valve insert.
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