Author Topic: CB750 Oil Pump Inspection (Read 18304 times)

MCRider · « **Reply #25 on:** January 15, 2009, 09:09:05 am »

I get it.

Kevin D · « **Reply #26 on:** January 15, 2009, 03:50:09 pm »

Quote

"botched oil relief valve"

My leak stopper piston was jammed open. If the bike was parked for a few days the oil would slowly drain from the tank, not too big of a deal IMHO.
I found the piston bore was out-of-round just below the adjacent dowel. When I looked at the pump body I found that the dowel didn't have the usual slip-fit into the pump body. Dunno if my pump body is one-of-a-kind flawed or not but I did note that the corresponding recess at the engine case was a little bit deeper. You can see in one of the pics that the dowel sticks up higher than the other two. If the recess was cut much deeper it would be into the plunger area.
I have a vague memory of an assembly problem there, 30 years ago, and figure that's when the thing got roughed up.
What I did to avoid trouble this time was to pre-assemble that particular dowel into the engine case, not the pump body. My leak stopper piston seems to be working well these days, whooopee-do.

Quote

How's your engine paint holding up, did you bake it?

Engine paint is doing very well, thank you. I haven't yet abused it with a power wash as I'm a fair weather rider only and no top end oil leaks to mess it up. Yes, I baked it in the oven one Sunday afternoon when nobody else was home.

HondaMan · « **Reply #27 on:** January 15, 2009, 08:27:39 pm »

Quote from: bryanj on January 15, 2009, 06:38:26 am

there are two seals shown in the gl1000 oil pump

(1) 91207-580-015----10x25x7

(2)91208-300-003----no sizes given

The second one does not even show in my very early 750 parts book that even gives individual part numbers for the carb !O! rings.

That second number modifies to
91208-MN1-771 and is 11x15x3

Fits GL up to 1800; NRX 1800; NX 650 and XR 600/650

(all that from the Motogrid link i keep giving!

It's that 11x15x3 that is not a standard size. I've been able to locate the common 11x15x3.5 version in the U.S., but that's all. I'm going to have to try the Honda suppliers to see if I can still get these from them. The old parts never had a number!

I also find it immensely interesting that the alternate part number is 91208-300-003, which IS a 750 part number series...

bryanj · « **Reply #28 on:** January 15, 2009, 08:35:21 pm »

What gets me is the original number was a 300 middle which was CB750 but its not in the 750 book and doesnt show as 750 on any comparison site---go figure. but if it fits, works and can be got its worth it

754 · « **Reply #29 on:** January 15, 2009, 10:19:14 pm »

Just a thought,

I have heard of o-ring material on a roll, you cut to size and glue!

now, this is crucial:

Most o-rings or a lot a cptive, that is there is really nowhere for it to go, and in actual assemble, leaves very minimal space around it.

So just maybe, they could be made?

HondaMan · « **Reply #30 on:** January 16, 2009, 05:23:09 am »

O-rings, yes. But this particular shaft seal, no. It's a full in-out shaft seal with a spring inside the lip, pretty fancy for being so small.

Making your own O-rings can be great, if you have a good vulcanizer. Every time I've tried, though, I have to make 3 or 4 before I get one to be nice and round.

So, I left the tool to someone more patient than I was with it.

754 · « **Reply #31 on:** January 16, 2009, 05:48:27 am »

For the seal area, you could try an end mill, or a counterbore (ground to fit if needed)

With a counterbore, you could do it accurately in a drill-press.

If the orings were made in batches, it would be easy to set up a die to cut length spot on, just use 2 razor blade..

-------------------------------------------------------------------------------

Ever wonder how they make orings?

I think they mold them, then trim them or use a mold that leaves no flash..

HondaMan · « **Reply #32 on:** January 16, 2009, 08:53:39 pm »

I contacted Hondaparts-Direct today and they said Service Honda had a batch of those seals left, so I bought some. I'll report back later on the fit-up.

MCRider · « **Reply #33 on:** January 18, 2009, 08:38:41 am »

Got the screen off today with minimal distortion, definitley reusable. Set a hairdryer in front of it for 1/2 hour to soften rubber, also used PB Blaster. More care in treating the rubber may help even more.

It was as Kevin described above. It is held in with a lip into a machined groove. But with small screwdrivers lever it off like a tire.
I've scored 2 pumps off ebay, 1 for $1.50, one for $5 (plus S&H both cases.) So I'll have a lot to inspect.

CB750F2 · « **Reply #34 on:** January 18, 2009, 02:07:20 pm »

G'Day everyone. Sorry for not getting back sooner to verify the part number for the internal oil seal. Bryan has got it right.
Old part number 91280 - 300 - 003
Nwe part number 91208 - MNI - 771
Pat

77honda · « **Reply #35 on:** January 18, 2009, 08:45:20 pm »

FYI.
I have found a guy here in Brisbane that still has a number of the OEM oil pump shaft seals available
Part number 91208-MNI-771
Web site is: http://www.bkperformance.com.au/

Price is a wopping $6.40 AUD thats around $4.30 USD

I also got all other orings from my local supplier for the oil pump for under $6.00 AUD
15 x 2.5
46 x 2

Hope this helps

Mike

77honda · « **Reply #36 on:** January 19, 2009, 01:18:53 am »

Can anyone tell me the free length of the Relief valve spring in a CB750 (Mine is a K7)

Thanks, Mike

MCRider · « **Reply #37 on:** January 21, 2009, 07:08:57 pm »

Quote from: 77honda on January 19, 2009, 01:18:53 am

Can anyone tell me the free length of the Relief valve spring in a CB750 (Mine is a K7)

Thanks, Mike

I don't know. And we might have a problem in that there is a dearth of "new" oil pumps against which to check.

HondaMan · « **Reply #38 on:** January 21, 2009, 09:21:03 pm »

Quote from: MCRider on January 21, 2009, 07:08:57 pm

Quote from: 77honda on January 19, 2009, 01:18:53 am
Can anyone tell me the free length of the Relief valve spring in a CB750 (Mine is a K7)

Thanks, Mike
I don't know. And we might have a problem in that there is a dearth of "new" oil pumps against which to check.

I think it was RXmangriff who might have scored "the last OEM pump on the planet" a while ago, or maybe he just pointed me to it, in Germany. Maybe he has one?

77honda · « **Reply #39 on:** January 21, 2009, 09:34:45 pm »

Someone scored one earlier this week on ebay $257 USD
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=300285434855&ih=020&sspagename=STRK%3AMEWA%3AIT&viewitem=

MCRider · « **Reply #40 on:** January 22, 2009, 04:58:59 am »

Quote from: 77honda on January 21, 2009, 09:34:45 pm

Someone scored one earlier this week on ebay $257 USD
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=300285434855&ih=020&sspagename=STRK%3AMEWA%3AIT&viewitem=

Plus $45 S&H from Thailand. I was looking at it (I've bought two used ones in recent weeks for less than $5 each plus $5 S&H, hoping for a gem) and got to thinking might be a little risky.

HondaMan · « **Reply #41 on:** June 07, 2009, 08:48:42 am »

An observation on replacing oil pumps:

Someone sent me an oil pump from an engine that had 8k miles on it. I replaced my 130k+ mile pump last week with it, here's the immediate differences:

1. Watching oil lamp and counting kickstart strokes until it goes out on a cold engine -
Old: 4 or 5 kicks. New: 2 kicks.
2. At idle on hot engine, oil can be heard running out on the old top end by listening to the clatter of the rockers and shafts. Old: 15-20 seconds. New: over 2 minutes.
3. I am currently using Mobil 1 15w50 diesel synthtic oil. Leaks: old - none. New: around cam cover and out of tach seal. This indicates a much deeper collection of oil in the top end.

goon 1492 · « **Reply #42 on:** June 07, 2009, 11:17:22 am »

Hondaman you just gave me a pikes peak level of confindence one more time on my old machine, my 76 750k6's oil light will turn off on the first kick when cold and using the kick starter. It's really cool to see ya'll attack and work on these old pumps, helps give alot of other people confindence to work on their machines.

I can promise this, if I ever win the lotto... A new replacable and rebuildable oil pump and wiring harness's, side covers and many other goodies that are getting harder to find will be redisigned and mass produced at a decent price from me the goon. I don't care if I eat up 100,000-200,000 in protoyping, If I had lotto money to play with that ammount wouldn't matter.

Than and I would be forever enshrined by the sohc community.

AshimotoK0 · « **Reply #43 on:** October 12, 2010, 01:49:17 pm »

If I source 0 rings do i get Nitrile or Viton. Are they 70 Shore A or harder?

Best regards

Ash

HondaMan · « **Reply #44 on:** October 13, 2010, 10:26:32 pm »

Quote from: AshimotoK0 on October 12, 2010, 01:49:17 pm

If I source 0 rings do i get Nitrile or Viton. Are they 70 Shore A or harder?

Best regards

Ash

Buna N is adequate: Viton is a step above that in durability.

Guns_Up · « **Reply #45 on:** May 23, 2012, 08:51:41 am »

I am looking to refurbish my k5 oil pump, and was wondering if anybody had a new source for the shaft seals and o-rings?

HondaMan · « **Reply #46 on:** May 23, 2012, 11:19:08 am »

Quote from: Guns_Up on May 23, 2012, 08:51:41 am

I am looking to refurbish my k5 oil pump, and was wondering if anybody had a new source for the shaft seals and o-rings?

You can get the shaft seal from Honda: it is used in the 1979-1984 Gold Wing pumps, and available. It is also used in certain Honda car engines.

The O-rings are 2.5x15mm, available almost everywhere. If you can't find them, PM me: I have about 60 of them at the moment, use them a lot on rebuilds. They also fit the oil hose fittings at the engine case and the oil filter bolt up front.

Guns_Up · « **Reply #47 on:** May 23, 2012, 07:15:19 pm »

Quote from: HondaMan on May 23, 2012, 11:19:08 am

Quote from: Guns_Up on May 23, 2012, 08:51:41 am
I am looking to refurbish my k5 oil pump, and was wondering if anybody had a new source for the shaft seals and o-rings?
You can get the shaft seal from Honda: it is used in the 1979-1984 Gold Wing pumps, and available. It is also used in certain Honda car engines.

The O-rings are 2.5x15mm, available almost everywhere. If you can't find them, PM me: I have about 60 of them at the moment, use them a lot on rebuilds. They also fit the oil hose fittings at the engine case and the oil filter bolt up front.

Thank you HM It is much appreciated

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Author Topic: CB750 Oil Pump Inspection (Read 18304 times)