Topic: The oil pump story

[tlbranth]

Got ready for a ride a couple of days ago  after the rain finally took a break. Fired up the engine and the oil light went out but came back on....and stayed on. Killed the engine and took the Goldwing. I thought it might be a bad pressure switch so I hooked up a guage yesterday. The pressure went up and then dropped like a rock.  I noticed the oil was veeeery low in my tank. It's been leaking down into the crankcase and it'd been a long while since I'd fired it up so I thought that might be the problem - no oil in the tank to pump. So I drained the sump, put that oil back in the tank and tested again. Oil pressure stayed up. After I shut the engine down, the tank emptied in about 10 minutes. That's a bit too quick so I'm resigned to pulling the pump and seeing what I can do about it. I'm pretty sure the problem is the rubber oil seal designed to keep the tank from emptying when the engine isn't running....the seal that's no longer available. So I have questions: Is there any replacement available? Has anyone used wintergreen oil and actually fixed the problem? And how long should it take for the scavenger pump to pump the oil back to the tank - it seems to take many miles for mine to do that? Any help appreciated. Bike is a 1970 CB750 K0.

[754]

 There is a chance something held the check valve open, that would alter pressure, I for sure have experienced this with a Honda twin. Not thinking your oil is dirty but could be a bit of varnish or sliver of rubber seal or gasket got in something.
 I think you can access the pump with pan off, and maybe clean it up a bit, plus see what the sump looks like.

[MCRider]

I authored a long thread on this problem, I had as well. While the seal is suspect, and not much one can do about it, seems the more common problem, as it was with mine is that something gets in the valve and holds it open. It is a piston sliding thru a cylinder that closes and opens a port (pictures available on request, or thread link.) It should be closed when the engine is stopped. Mine was wide open and would drain the tank in less than a day.

The debris in the pump was obvious.

Once i disassembled mine, removed the piston and cleaned the cylinder it slides thru, all is well. Hasn't wet sumped since, has held its oil in the tank as long as several weeks/ nearly a month I think with no loss of level in the tank, which is all you can ask.

[tlbranth]

OK, thanks fellas. I have a GL1000 in bits at the moment. As soon as it's reassembled I'll pull the 750 oil pump and take a looksee.

[Jerry Rxman Griffin aka MuthaF'er]

TL, gotta ask... did you have enough oil? Sorry, I know you're experienced and not a newby. Shouldn't you maintain the proper pressure regardless of oil being in the tank OR sump??

I got some NOS oil pump parts including the rubber stopper piece and spring from a guy in Thailand off EBay. It's been a while but he still lists a few oil pump parts but not the stopper. He has the piston and end cap at the least. Search for something similar to Coelacanth....

Here's a couple part numbers and pictures that might help

Shaft seal came from a GL1000 fiche. Notice it's a -300 part! Why don't they list it on OUR fiches!!??



Old and firm



New softer and more supple



New



Old

[HondaMan]

TL, gotta ask... did you have enough oil? Sorry, I know you're experienced and not a newby. Shouldn't you maintain the proper pressure regardless of oil being in the tank OR sump??

The short answer is "no" here...the scavenge side pumps about 60/40 to the tank/tranny, so it just slightly stays ahead of the pressure side. Only the tank side provides pressure-flow to the engine.

[grasscutter]

<<<I'm pretty sure the problem is the rubber oil seal designed to keep the tank from emptying when the engine isn't running....the seal that's no longer available. So I have questions: Is there any replacement available? Has anyone used wintergreen oil and actually fixed the problem?>>>

Anyone ever deal with Randakks?
I've got plenty of odd ball specific o-rings, misc. rubber and plastic pieces
 from him for my CX500, GL500I Silverwing, and GL1000 Goldie.

He makes better than new rubber items as the need dictates.
I'm not a CB750 owner, but theres plenty of you out there.
Send him an e-mail.
You never know!

[tlbranth]

TL, gotta ask... did you have enough oil? Sorry, I know you're experienced and not a newby. Shouldn't you maintain the proper pressure regardless of oil being in the tank OR sump??

Jerry - usually the tank has leaked slowly into the sump and after a few miles of riding it's back in the tank where it belongs. I didn't realize, 'til this episode, that it had upped its drainage speed. And oil level can't be checked 'til it's back in the tank where the dipstick is. As Hondaman pointed out, the feed to the engine pump is from the tank. Oil picked up by the scavenger pump goes back to the tank (and apparently to the transmission too) but not to the engine. I figured it worked like the old Brit dry sump engines where the return pump has a higher capacity than the supply pump and it does except on the old Brit engines only the engine was involved. The transmission and primary case had their own oil supply.
Anyway, I should be able to get the pump out in the next few days so I'll post my findings. Thanks everyone for your input.

[scottly]

When my bike has wet-sumped from sitting, I add a bit of oil to the tank to ensure a supply at start-up. I would rather suck the excess oil out with a turkey baster after the scavenge pump has caught up, than run the motor dry. BTW, it does seem to take a fair amount of time for the scavenge pump to fully catch up, in my experience.

[tlbranth]

What's the consensus on using gasket cement on Honda gaskets? It's been a while for me. I don't remember if I used some or not. Makes disassembly a lot easier if the gaskets are put on dry.

[MCRider]

What's the consensus on using gasket cement on Honda gaskets? It's been a while for me. I don't remember if I used some or not. Makes disassembly a lot easier if the gaskets are put on dry.

Consensus? We dun need no steenkin consensus! 

I put a non-hardening variety on one side only, to stick it in place for assembly. Usually on the cover side, not the engine side. For disassembly, the gasket comes of clean with the cover.

Not so much for sealing purposes.

[Henning]

This is a timely thread for me as I currently have the sump off my K1 to service the oil pump screen. I last did it 26000 km ago, so it is way overdue. No need to use gasket cement on a Honda gasket; mine has not leaked at all, even though the bolts weren't all that tight. While in there I will drop the pump to check the stop and pressure release valves, as I have experienced wet sumping. It's also a good idea to replace the three o-rings to get better oil pressure and more oil to the clutch, as per Hondaman's advice. There's also another rubber seal to replace behind the shifter cover if you want to do more for the clutch; mine gets stuck after sitting overnight.

Any consensus on reusing a Honda gasket?  Mine came off cleanly and looks good.

[tlbranth]

Got the pump out yesterday. Everything was pretty clean. Nothing holding the leak-stopper valve open. It looks like it's just hardened up. I went to Omni Seal & Packing in Seattle today and got all the o-rings for the pump but there's a tiny oil seal between the supply & scavenger pumps they don't have and in fact they say it's not listed (they have listings for all seals available in the US). The parts fiche doesn't even show it because they don't have internal pump parts. The fellow at Omni said he might be able to get it custom made but it'd cost around $300 for a couple of them because it'd be one-off.
Does anyone know where I could get one of these seals? It shows the seal in my shop manual as 11x15x3.

10 minutes later: I found the seal - it's Honda part# 91208-300-003. You can get it at
http://www.powersportsplus.com/parts/detail/honda/HP-91208-300-003.html
for $4.49. But I opted to pay $8 and order it from the local crooks.

[Jerry Rxman Griffin aka MuthaF'er]

TL,

That's why I posted up the picture for you with the Gold Wing info. It has a metal backing on it and is tricky to get out without damaging the aluminum around the shaft hole. 

[tlbranth]

TL,

That's why I posted up the picture for you with the Gold Wing info. It has a metal backing on it and is tricky to get out without damaging the aluminum around the shaft hole. 

Jeez Jerry, I zoned out there. I've got 2 bikes in pieces at the moment and juggling several other projects so not totally together.
What's the part number on that rubber stopper? I t looks like 15166-300-?00. What's the last 3 digits?

[Jerry Rxman Griffin aka MuthaF'er]

15166-300-000  OIL SEAL, LEAK STOPPER (NOT AVAILABLE) Not Available

I should've bought all the guy had but only got one. 

[tlbranth]

A belated update: Soaked the stopper in wintergreen/olive oil mix - not much change. Put the thing back together with all new seals. Doesn't seem to be leaking down much now. It's held fairly steady for several weeks. So I think McRider was correct: something was probably stuck in there. I just didn't see it.
This leads me to an interesting observation: Any crap in your tank can get into the oil pump. Mine's obviously been violated in the past 'cos there are plenty of scuff circles inside. So a clean tank might be more important than I'd figured.