Topic: Brass filings in sump oil?

[BrettPPR]

Having just procured a 1973 CB750 K3, which I quickly got running, all was good until I drained the oil to reveal a "gold panners" display of brass filings in the sump oil.
I have now pulled the engine, and completely dismantled the top end to find everything OK?
Before I split the cases, does anyone have any ideas where these brass filings might be coming from?
A quick fiddle and examination of the bottom end bearings etc makes me think they are all OK as well?
Is there some brass bush somewhere (transmission?) that is prone to being chewed up?
The bike has spent some years sitting, but everything so far is free, with no signs of any internal moisture etc.
All suggestions very welcome!
 
 

[Retro Rocket]

Valve guides..?  Maybe remnants from an older fixed problem.?

[scunny]

you sure it's brass and not alloy from the cam chain whipping around shaving the "cam chain tunnel"

[Hush]

Not much brass in a SOHC4 engine, back area of the clutch basket would be one maybe?
I wouldn't have pulled the engine myself on just that evidence, draining the oil and changing the filter then running it to see if it repeated would be the way I would go but then again that's just the optimist in me.
As Retro said, it may be from a problem the PO cured but did not clean out the sump.

[Retro Rocket]

I was thinking clutch as well Hush, just wasn't too sure because i haven't seen one in a while....

[BrettPPR]

Scunny and Retro Rocket,
I originally thought it would be a cam chain related issue, and there is some signs of past shaving of the cam chain tunnel.
But the current cam chain and whole tensioner mechanism is all working as it should. All components look virginal.
And the filings are definitely brass - amazing how they actually glint in the sunshine!
If the valve guides are brass, this could be a possibility, as I have not removed the valves from the head.
I just visually inspected the valves through the ports and underside.
An open valve stem could have corroded while sitting for years, and ripped into the brass guide on re-start?
But I just went and had a scratch at the guide with a screwdriver, and I am not sure the guide is brass? Could it be steel?
A great suggestion though, and I will remove the valves tomorrow to find out more.

[BrettPPR]

Hush,
I like your optimism!
I did run the bike for a 20 minute test run on new oil, after dumping out the old original oil and it's brass filings.
I absolutely convinced myself that every extra minute I ran it was doing more damage - a psychologically tough ride.
The bike ran well, pulled like a train, spun up willingly etc.
When I dumped this new oil out, there were still some brass filings, but nothing like in the original oil.
I then dropped the belly pan and checked over the oil pump screen etc and removed every brass filing I could find.
The engine also has a head gasket oil leak, and so I removed the engine to fix this as well. On removing the head, the two small top end oil spray jets are missing? But that is another story.
The way the clutch works so well, and also looks new, you may be right, and it could be part of a previous issue that has been resolved?
I will have a close look at the clutch tomorrow as well.
Many thanks.

   

[wedoo2]

Sometimes it is good just to get the question out there.   Different perspective.  Makes you wish sometimes that there was a video for all the problems we have.  I come across so many dumb obstacles and I just post them even though it sometimes makes me feel like an idiot, but that doesn't really bother me any more.  I read the manual like it's a college final, but not everything is in a manual.

Good luck with the tear down.

[wrenchmuch]

The Oilite bushings in the transmission  look like brass . The scavenge side of the oil pump supplies oil here . The pump could be worn . There is also a o ring in the transmission bearing carrier .
http://www.cmsnl.com/honda-cb750-four-k3-usa_model481/partslist/E++19.html
The carrier is #1 and the o ring # 14  . If the ring shrinks or is omitted you won't get much pressure to the transmission . I can't think of any other source for that type of metal in the engine .
Hope this helps .
Mike

[Jerry Rxman Griffin aka MuthaF'er]

Brass/bronze in the big starter gear and inside the oil pump (shaft bearing). Not likely the pump though.

[BrettPPR]

Guys,
Thanks for all the great suggestions.
Gives me plenty to follow up today. And most I can check before having to split the cases.
 

[72500john]

i think the down and dirty here is if its making metal..tear it down and fix it before the dollar signs add up!!

[d9canada]

Might be a good time to get Hondaman's book at Lulu Publishing.  I saw the thread for this here today and got 35% off by using the code word Blizzards.

[HondaMan]

The engine also has a head gasket oil leak, and so I removed the engine to fix this as well. On removing the head, the two small top end oil spray jets are missing? But that is another story.
   

Uh-oh.
Those jets are there to limit the high-flow oil to the top end, so the crankshaft and rod bearings can get enough oil. Without those limiter jets in the top, the bottom end gets starved for oil, particularly the crank/rod bearings.

Look them over, closely.

[dave500]

maybe it has a homemade or similar bronze bush repair somewhere?

[754]

 I agree with check the starter drive bushing, pull dyno cover off CAREFULLY and see if there is bronze laying in the bottom, which would mean that is likely the source.
If it does by chance have bronze guides, you should see that in the ports...

[wrenchmuch]

The engine also has a head gasket oil leak, and so I removed the engine to fix this as well. On removing the head, the two small top end oil spray jets are missing?

   

I've found that the jets often stick to the bottom of the cam bearings on removal . Could they have fallen some where ? As stated before by Hondaman , omiting those jets will drop pressure at the crank . The transmission is fed from the scavenge pump so omitting the jets won't starve the transmission . Lack of oil at the crank will starve the bushing in the starter gear though . Do as 754 says and have a look under the alternator cover for filings . Jerry , do you have a bushing in your oil pump ? The 4 I have don't have any . I wonder if some pumps came with bronze bushings .

[Jerry Rxman Griffin aka MuthaF'er]

Wish I still had it apart! Going on memory here so i could be wrong but I believe there is a bronze bushing in there. I'm not at home or I'd take my spare apart. Here's some pictures from my rebuild.

Inner cap - this may be where I think i remembered the bushing



Outer housing with new seal installed 

 

[HondaMan]

The engine also has a head gasket oil leak, and so I removed the engine to fix this as well. On removing the head, the two small top end oil spray jets are missing?

   

I've found that the jets often stick to the bottom of the cam bearings on removal . Could they have fallen some where ? As stated before by Hondaman , omiting those jets will drop pressure at the crank . The transmission is fed from the scavenge pump so omitting the jets won't starve the transmission . Lack of oil at the crank will starve the bushing in the starter gear though . Do as 754 says and have a look under the alternator cover for filings . Jerry , do you have a bushing in your oil pump ? The 4 I have don't have any . I wonder if some pumps came with bronze bushings .

The pumps are just plain aluminum bearings. I'm in the process of "saving" a K1 pump now, by boring the seal hole bigger to fit an oversize seal in it. The hole was damaged during removal of the old seal.

[dragracer]

I hate to burst your bubble but my vote is a rod or main bearing.

Was it making any noise when you ran it last?? How about oil pressure???

I suppose i always expect the worse when i see brass color in the oil. No need to be in denial.

Good luck man.

[MRieck]

I hate to burst your bubble but my vote is a rod or main bearing.

Was it making any noise when you ran it last?? How about oil pressure???

I suppose i always expect the worse when i see brass color in the oil. No need to be in denial.

Good luck man.

I agree. I have seen the "gold sheen" in the drain pan before. It happens when the bearing delaminates.

[BrettPPR]

Guys,
Again many thanks for all the suggestions, and unfortunately I am getting as pessimistic as the later postings!
But the mystery does continue. I have still found nothing?
I have pulled the clutch, the valves, the oil pump, tranny case, stator cover  - all appear perfect.
And I have even spent a fair bit of time poking around in the sludge that fills all the nooks and crannies in these areas.
Funnily, no brass in any of these sludge pits?

But to answer some questions - YES I definitely have Hondamans book, absolute gold, and if I didn't have it, I would probably have missed those damn oil jets.
Thanks Mark, and as you can see in the pics here, I am a complete disciple, right down to the rocker gear in the egg cartons!

IMG_0092.jpg
IMG_0093.jpg

While checking everything, the good news is everything looks very low mileage, with little wear anywhere, including primary chain etc.
I figure the "not knowing" will drive me insane, so will just continue with a complete dismantle, and split the cases.
I can see that the roller on the primary tensioner is rock hard, so will at least replace that if I cannot find anything else?

It's New Years Eve here, so will be facing divorce if I don't stop playing with this motor.