Author Topic: Found this in my oil pan - cb750k1 (Read 6234 times)

Prospect · « **on:** September 12, 2011, 07:32:56 AM »

I've got the k1 to run nicely after it had been sitting for about 20 years. After a bit of city riding the oil pressure light would come on. I did a bit of research and thought that my oil pump was slowly going or perhaps the screen was getting blocked by who knows what. Well this is what I found in the pan and the pump screen. What the hell is that rubber stuff? Also there was a considerable amount of metal at the bottom of the pan. Not sure where it's coming from. Not a good sign. I'm in the process of replacing the oil pump and the 15mm x 2.5mm o-rings.

MCRider · « **Reply #1 on:** September 12, 2011, 07:51:50 AM »

YIKES! You're looking at a full engine teardown. You've wiped out the cam chain tensioner and/or primary chain tensioner. While the rest of the engine may be OK (or not) it requires these pieces to be replaced. There is a rubber roller with raised ridges, and a rubber slider.

Causes for the cam chain tensioner at least is a lack of adjustment at regular intervals which would keep the chain from whipping around and wiping out those pieces.

Could also be the primary chain tensioner roller, but that's less likely, but must be checked.

MCRider · « **Reply #2 on:** September 12, 2011, 07:54:33 AM »

Oh yeah, the sitting. I've mentioned many times here that as restorers of these machines, its no longer the mileage we have to contend with but the age. Long dormant periods allows the rubber pieces to dry out and harden. Though i have to admit I've seldom seen the internal engine pieces let go like that.

Nevertheless, even a low mileage bike is no longer attractive as the age issue is the problem.

Prospect · « **Reply #3 on:** September 12, 2011, 10:14:01 AM »

Great. Now I know why the PO parked the bike. I thought that was the cam chain tensioner but wasn't sure.

I have a spare K1 that is more and more looking like a parts bike (but running). Maybe I'll do an engine swap or maybe a rebuild. I'm halfway through a cb350f engine reubild and was gonna finish this winter but I certainly didn't want to do two this year.

WarwickE36 · « **Reply #4 on:** September 12, 2011, 10:30:38 AM »

Wow thats pretty grimm.

I was pretty surprised at how brittle my cam chain tensioner slipper was. It has hairline cracks and the ends and looked like if you picked at it pieces would come off very easily. Its great piece of mind knowing its all new rubber and "plastic" in there now. Those O-Rings have me wondering. I haven't been in a 750 before only a 550 but I wonder where they came from. Seems weird to have them in the pan. Good luck with your build. Post pictures I want to see the rest of this thing's guts.

MRieck · « **Reply #5 on:** September 12, 2011, 10:34:29 AM »

The oil pump rotors are probably toast.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #6 on:** September 12, 2011, 10:39:02 AM »

Since we really can't tell the size or the composition, would those roundish rubber pieces be the same size as the outter edges of the primary chain tensioner? Is the metal aluminum or steel?

MCRider · « **Reply #7 on:** September 12, 2011, 10:41:37 AM »

Quote from: WarwickE36 on September 12, 2011, 10:30:38 AM

Wow thats pretty grimm.

I was pretty surprised at how brittle my cam chain tensioner slipper was. It has hairline cracks and the ends and looked like if you picked at it pieces would come off very easily. Its great piece of mind knowing its all new rubber and "plastic" in there now. Those O-Rings have me wondering. I haven't been in a 750 before only a 550 but I wonder where they came from. Seems weird to have them in the pan. Good luck with your build. Post pictures I want to see the rest of this thing's guts.

I'm thinking those aren't O Rings, but large parts of the tensioner wheels.

MCRider · « **Reply #8 on:** September 12, 2011, 10:43:27 AM »

One problem with trying to freshen up the tensioners. You don't know how long the replaceent parts have been in a parts bin. They could be 20+ years old as well. Doubtful they just came off the production line any time recently. If they're in a sealed bag, that would be good.

wrenchmuch · « **Reply #9 on:** September 12, 2011, 11:27:25 AM »

It looks like parts to 2 rings . That would point to either side of the primary tesioner roller . It has raised ridges on either side . If the roller is that bad it might be hitting the cases (source of metal in the pan) .

CrankyOldGuy · « **Reply #10 on:** September 12, 2011, 05:01:41 PM »

Just happened to have the oil pan and oil pump off of my 750K1. With the oil pump removed the primary chain tensioner wheel should be visible. I have attached a pic. Sorry about the quality but it was difficult to take while laying on my back and looking up into a dark space.

Harry O.

MRieck · « **Reply #11 on:** September 12, 2011, 05:55:36 PM »

Quote from: MCRider on September 12, 2011, 10:43:27 AM

One problem with trying to freshen up the tensioners. You don't know how long the replaceent parts have been in a parts bin. They could be 20+ years old as well. Doubtful they just came off the production line any time recently. If they're in a sealed bag, that would be good.

The last few I bought were in modern bags and looked fresh

Prospect · « **Reply #12 on:** September 13, 2011, 08:09:26 AM »

I had a look up into the engine from the oil pan area to see the primary chain tensioner. It looks solid and the rubber is soft. So it's probably the cam chain tensioner. Probably the reason the oil light came on is because the oil passages throughout the engine got blocked with debris from the cam chain tensioner and pressure built up. The whole top end and bottom have to come appart and every little piece taken out. Hopefully there isn't too much damage otherwise. I think the pistons, head, and valves are still ok and only require a hone and lapping and not a bore job.

MCRider · « **Reply #13 on:** September 13, 2011, 08:16:42 AM »

Quote from: MRieck on September 12, 2011, 05:55:36 PM

Quote from: MCRider on September 12, 2011, 10:43:27 AM
One problem with trying to freshen up the tensioners. You don't know how long the replaceent parts have been in a parts bin. They could be 20+ years old as well. Doubtful they just came off the production line any time recently. If they're in a sealed bag, that would be good.
The last few I bought were in modern bags and looked fresh

That's good news. My statement was not a matter of fact, just something to be aware of.

Kevin D · « **Reply #14 on:** September 13, 2011, 08:22:23 PM »

Whats the oil filter look like?

Prospect · « **Reply #15 on:** September 18, 2011, 11:27:16 AM »

Quote from: Kevin D on September 13, 2011, 08:22:23 PM

Whats the oil filter look like?

The oil filter looks fine.

I took the engine out today and got a good picture of the primary chain tensioner. It looks not that bad so I guess it's safe to assume it was the cam chain tensioner that simply fell apart because the rubber was very brittle. Interesting to see what I'll find when I take the engine apart. I guess all the rubber restricted the flow of oil through the engine so I'll be cleaning all the passages...

Oh and I blew the engine on my xs650 this morning. Going only 65 mph on the highway. That's two engines down in less than two weeks! It's going to be an expensive winter.

754 · « **Reply #16 on:** September 18, 2011, 11:46:08 AM »

You may have caught it in time, then it wont cost too much, and you have piece of mind..
Pump rotors are generally scarred up, you may be able to use them. Did you by chance check oil pressure before teardown...?
Check the debris with a magnet to see how much is steel, aluminum and rubber tends to be less harmful..
In my opinion, the rubber wear can be oil caused.. had a buddy take his out very quickly using car oil one time..
That rubber primary roller looks fairly worn, but looks like it did not lose the lips on the side.. not like the pieces you showed.

Prospect · « **Reply #17 on:** September 18, 2011, 12:08:24 PM »

Quote from: 754 on September 18, 2011, 11:46:08 AM

You may have caught it in time, then it wont cost too much, and you have piece of mind..
Pump rotors are generally scarred up, you may be able to use them. Did you by chance check oil pressure before teardown...?
Check the debris with a magnet to see how much is steel, aluminum and rubber tends to be less harmful..
In my opinion, the rubber wear can be oil caused.. had a buddy take his out very quickly using car oil one time..
That rubber primary roller looks fairly worn, but looks like it did not lose the lips on the side.. not like the pieces you showed.

I got a new(er) oil pump already as I didn't want to rebuild this one. They're cheap and interchangeable between years. I didn't do a compression test before but I'll check the bore and hopefully just a hone will do.

Prospect · « **Reply #18 on:** September 30, 2011, 09:50:21 AM »

I took the top end off today to have a better look and prepare for a total engine rebuild. Everything looked pretty normal but there was a definite burned oil smell as I was taking the head off. I got to the cam chain tensioner and it was as MCrider predicted - hard as a rock and not much of it left. The primary tensioner looked abused as well. In the third photo there is a BIG groove on both side of where the cam chain rotates. I think this was the metal that I found in the oil pan. I haven't found any more metal but I'll probably find some when I split the cases.

CycleRanger · « **Reply #19 on:** September 30, 2011, 11:21:26 AM »

Very good pictures!

That's a lot of side to side movement!

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Author Topic: Found this in my oil pan - cb750k1 (Read 6234 times)