Topic: Oil Light came on while riding

[754]

So here is my thought on what happened..
 Debris entered one side of pump, likely thru a passage..  you will know which one.
 It then wore the pump body, to the point that clearance and depth of cavity , wore to point of pressure falling off..
 Thus then allowed back side of gear to contact body of pump..
 One of the gear teeth looks like a small bit of something is smeared very thinly on it..

If you have a caliper,  measure depth of cavity, compare to gear width... that should give your clearance..

[jakec]

I just took a knife to some of the larger pieces and was able to break it up. So  I guess that means at least some of the debris is the blasting media. I don't have any calipers. But I think with the scoring of the oil pump body I should probably look for a new one in any case.

[Redline it]

in the oil pan, isn't there some big blobs of factory expoxy holding the splash guards? it's somewhere. it's redish i think.

[Nurse Julie]

in the oil pan, isn't there some big blobs of factory expoxy holding the splash guards? it's somewhere. it's redish i think.

The oil separation plate in the sump pan  is held in place with screws, I don't think I've ever seen blobs of epoxy anywhere.

[jakec]

Yep just screws and the pan was clean, see photos in the original post.

[PeWe]

I do not know CB400.
But if it has separate oil tank as CB750 which feed oil to pump direct without any filter.
Dirt and sand in oil tank will be chewed up by pump, then direct to filter  before lubricating the engine. Pressure sensor sit between pump and filter.

Scavange pump that pump oil from pan back to oil tank has a fine mesh (strainer) that filter the oil from particles.

[robvangulik]

The 350/400 is wet sump, and the 500/550 also.

[Tim2005]

So what's the plan now, are you going to split the bottom end and check the mains?

[jakec]

Yes, I got the engine out last night.

[minimo]

While you have the engine apart, use liberal amounts of Brākleen followed by compressed air, and blow out every single hole, and then, do it all again.


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[Kelly E]

You need to use brushes to dislodge the foreign matter, not just brake cleaner and compressed air. Unless you feel like doing it again.

[jakec]

Today after 2 years I decided I wanted to start on this project. I never took apart the bottom end of the engine until today. To summarize everything that has happened so far:

1. Full engine rebuild finished summer 2020
2. 1,500 miles since rebuild I lost oil pressure
3. Took apart oil pump to find some broken internals, scored journals, and debris
4. Oil filter also covered in lots of debris. Tested debris, not magnetic
5. Took apart top end to check piston rings, all rings are ok

That's where I stopped in 2020 and it seemed that most people thought the debris was vapor blasting media. Today here's what I found after stripping the bottom end.

https://www.youtube.com/shorts/jxR7fWXAWvk

I did not find ANY of the grey debris anywhere throughout the engine. In the video you can see that gears and bearings are all clean and there is no scoring (no more than when first assembled).

I also inspected the passages that lead to and from the oil pump and they are clean without any debris. Earlier I had found that the sump and screen were also clean. So my conclusion now is that the debris must have been aluminum from the scoring on the oil pump journal, and the loss of pressure from the clogged pump. Since there is no sign of the debris anywhere else in the engine, I can't see how it would come from any other source. I'm interested to hear others' thoughts. Right now I am leaning toward rebuilding a new/different oil pump and putting the engine back together as is.

[jakec]

Just got the bottom end back together today. I had to get a new tensioner (again). Not sure what the reason was, but the first one suffered a lot of wear from the chain and and therefore wasn't moving smoothly anymore. Other than that everything else is going back in as is, just cleaned up. I will be find another oil pump to use for parts, and using new gaskets, seals, & O rings. I will be keeping the same pistons and rings, but replacing wrist pin clips. Hopefully I'll have the transmission in the frame this week and get started on the top end some time soon.

[PeWe]

Bad copies of Honda stock cam chain tensioner can be very short lived.

[jakec]

This was actually the TTR part. Not sure what caused it, but I bought a new one and installed. I have the engine put back together now and in the frame.

I found that the old oil pump which had failed had consumed the chrome washer that goes under the main rotor, and also chewed into the recess where the washer sits. It wasn't clear until I had another nicer pump to compare with (and also had the washer included that I forgot existed). Still doesn't really tell me anything about why it happened. I took the two pumps I had and put them together to make one nice one, and installed it.

So now I just need to do a valve adjustment, timing, and put the rest of the bike back together, exhaust carbs etc, and I should be good to go.

[newday777]

Did this motor get sand blasted or vapor blasted? I don't remember all of your thread on this motor.... Just wondering if so how did you clean it out before assembly??

[bryanj]

Only reason for that tensioner wear is slack cam chain

[jakec]

Did this motor get sand blasted or vapor blasted? I don't remember all of your thread on this motor.... Just wondering if so how did you clean it out before assembly??

Yeah it was vapor blasted, and I did the normal thing which is pressure washer and air compressor to clean it. Now on second rebuild I used brake cleaner, pipe cleaners, and air compressor.

And yeah, I agree that's the cause (slack chain), but why would the chain be slack? I had adjusted it. Maybe not soon enough after initial break in (time of most stretch). I would have adjusted it most likely only once in the 1500 miles I rode.

[Tim2005]

Those chains never wear that fast when they are new. Is the tensioner slider still ok (the one on the carb side of the motor)?  If the chain is cutting into that it'll soon go slack.

[RAFster122s]

The CX500 and GL500 motors ran 8nto a batch of aftermarket tensioner slider blades that wore out in no time like described and caused massive issues for the owners who went with that tensioner rather than taking the time and expense to source a hard to find NOS original Honda tensioner blades. Sometimes the plastic of the blad would also crack/break causing damage as well.

[jakec]

Both the sliders are almost new. You can see the wear from the chain but you can't feel it running your finger over it. I figured the chain stretched very much in the first few miles similar to how a main drive chain does. and then I probably waited a few hundred miles before adjusting the chain. I never had any noise. However the tensioner wasn't able to move normally any more when I took the engine apart.

Anyways I was able to put another couple hours in tonight so almost done.

[Tracksnblades1]

“Less Abrasive Embedments” 😳

Is the advertising phrasel of vapor blasting locally.. 🤔

[bryanj]

Tensioning it the way Honda tell you does not work,
Assuming everything is free and moving properly loosen the lock nut then lock bolt, put tension on the kickstart until you can just feel the engine starting to rotate, hold this pressure and nip up the lockbolt then nut.
This puts all the "slack" into the back run where the tensioner blade is.
Thats the way i was told by a Honda UK tech support guy back in the 70's and it works for all the fours IF all the mechanism is free

[PeWe]

CB750 advice to rotate crank to 15* BTC on 1:4. Release tensioner screw and tighten it again plus lock it.

There is a Honda Service bulletin that describe it.
15*BTC when advancer spring tower has just passed case mark, rear side lined up.

My owners guide I got with my K6 describe it really wrong. Release screw at idle that only made it worse.

A risk that chain jumps a tooth or more wich I have done without damage, sheer luck.

No marks on valves nor pistons, nothing bent either.
Milled cylinder, head and thinner gaskets might increase the risk when chain is relatively longer when the entire build is 2mm lower than stock.

I usually put something in tensioner hole at rear, released screw and juse the kick and feel when tensioner shaft moved most forward.

The static adjustment at 1:4  15*BTC  reduce risk for  jumping chain to zero.

[bryanj]

Yes Pewe the book does say that But i was told be one of the traveling reps that went round all the dealsrs when there were problems