Topic: Improving top end oiling

[cbr954]

So I have been reading that the 750 top end has some oiling issues to the camshaft and valve train at lower rpms.  I have never had a problem but was wondering what people are doing to help with the problem.  Could the oil restrictors be drilled out slightly larger?  Any way to bump output of the oil pump?

[bwaller]

I know Terry tried something to improve cam/rocker oiling. Search around for that, I don't remember hearing more about it. I'd be afraid increasing flow via the oil restrictor to the top would decrease crank pressure...not good.

I'm also unclear whether there is actually a problem if the lubrication system works as it should, meaning pumps within spec, etc. Is there an issue at low rpm's except a pressure gauge might read low? I'm not sure. Adding displacement, lumpier cams, what difference does it make on lubrication except there may be more heat? When I first did the external oil line deal on a 550 I then looked at doing the same for the 750. My feeble thinking was to try to increase flow (larger pump?) and adding a tad more oil via external lines and spray down from the valve cover in four strategic points. I have to re-do my 750 one of these winters and will maybe pick it up again.

We all remember reading the stories about Honda race engineers not wanting to "over lubricate" and rob HP with increased resistance. I suppose for the factory in those days especially, winning was everything and replacing parts was a small price to pay. BUT I wonder of the 750's with burnt cams, how many were due to carelessness.

[Old Scrambler]

+++on the 'careless' oil monitoring leading to fried cam journals. I have only torn down a few motors........but the amount of dirt, grime, gobs of gasket-sealer, and nearly empty oil tanks is a high percentage.  A neglected bike is a reflection of the PO.

[MCRider]

Yeah, I'd like to see the source on your premise that the CB750 has oiling problems at any rpm. news to me.

I had a cam twist in half from one side seizing in the cam holders, so I have a little experience. I've also witnessed it on at least 3 other bikes.  But my problem along with EVERY other instance of this happening was 1. a result of sloppy rebuild usually with the hated silicone and/or 2. a result of the use of a big bump cam which flexed the cam holders, and the hold down bolts had already been compromised.

No stock engine, which had never been disassembled/reassembled that I've ever known or read of ever had an oiling problem. They are good for 100,000+ with original parts, virtually without exception.

I remember Terry tossing around the idea of an external feed, like was developed for the V4s, which did have problems.

To me, an external feed on an engine without a problem is an answer for a question that wasn't asked.

OCICBW, but i don't think so.

[cbr954]

I was asking about oiling at low rpm and idle conditions.  There was some talk about it on this forum some time ago about lack of oil at extended idling and under 2200 rpm conditions, especially with bigger cams and stiffer valve springs.  I know the external oil line was looked at but haven't heard anymore about it.  Cycle X was coming out with a new oil pump but that was almost a year ago and haven't heard anymore about that either.

[MCRider]

I was asking about oiling at low rpm and idle conditions.  There was some talk about it on this forum some time ago about lack of oil at extended idling and under 2200 rpm conditions, especially with bigger cams and stiffer valve springs.  I know the external oil line was looked at but haven't heard anymore about it.  Cycle X was coming out with a new oil pump but that was almost a year ago and haven't heard anymore about that either.

I understand what you're concerned about. My comments were meant to include low rpm. A few things. First I'll repeat I have no recollection of ever reading an instance of anyone having problems with low rpm cam oiling. If you have a link to the thread, that would be good. To further the discussion, we'd have to know what you've been reading.

Next, in ones design for an engine, I wouldn't put a big bump cam in an engine that's likely to be trapped in an extended low rpm situation, like a traffic jam. Of course this may happen. But if its a street motor, one should be looking at a milder cam with emphasis on displacement and head work to develop low rpm power.

Lastly, with as much tech know how as there is on this forum, true racers and true tourers, if oiling at any rpm were a problem, it would havee been addressed by now. HondaMan has more documented and evaluated mileage on all sorts of machines than virtually any of us. No oiling problems.

Without putting words in someone like Terry's mouth, my suspicion is that attempts at an external oiler were abandoned as being unnecessary.

Now, I'm one for not standing in the way of any development someone wants to attempt. An externa oiler would be a cool thing. But i come back to the question, is it necessary, and I'd have to say a resounding no.

[MCRider]

As to the CycleX oil pump: again a low priority item. There are people looking into replacements as you no longer can buy a new one. But as in my case plenty of good used ones around. I bot one off ebay for $75 that looks brand new, and will outlast my lifetime.

The stock pump is way overbuilt. Some people are attempting to develop rebuild kits which mainly focus on relief springs and ORings.

AS hondaMan says, if in a rebuild, you replace the pump ORings and the Oring in the trans bearing holder, you'll restore like new pressure.

I suspect a new billet oil pump is also in the future. But again its not because the original pump wasn't up to the task, but because the original pump is no longer available.

[Jerry Rxman Griffin aka MuthaF'er]

I'm heading to the local Honda shop in a few minutes to pick up a few new replacement pieces of hardware for my head. As I was looking at it after torqueing it down pondering my next move I thought it sure seems silly to have to get 4 orings for oil orifice jets when there is only 2 actual jets and holes for them. This made me wonder if anyone has experience with adding 2 more orifices in these other 2 unused "holes". Yes, I see the potential for oil pressure situations but would it in fact happen?! Now that brings up the next question - since these are "jets" as such, could someone make different sizes to not double the flow unnecessarily but just incrementally increase it and get a better more even flow into the towers? Lots of expensive work to build engines to burn up, huh 

Mikie, you out there? I know you must have been playing with a head cad program. Mark, what about you? Anyone else?

[MCRider]

AS you may know, the 2 (of the 4) ORings that go outboard of the cam holders, serve to terminate the path. That's what forces the oil out the orifices of the camholder itself onto the cam lobes.

In other words the oil comes up the 2 inboard (near the cam chain tunnel) passages, travels thru the body of the cam holders, exiting at certain points, and terminates at the outboard ORings.

Pressure being what it is, that is, equal throughout a closed system, there shouldn't be any problem of "even flow".

Messing with that system seems hugely counterproductive.

But I'm open to suggestions.   

[Jerry Rxman Griffin aka MuthaF'er]

Understand what you are saying but... the subject is improving top end oiling. That's why my thoughts were to get oil flowing under pressure from both ends into the towers. Didn't look into the supply side to see if it would be possible to get it to both ends though. Would be an interesting experiment, just don't know the actual outcome of some expensive and time consuming play. These things seem to oil fine the way they were designed. As long as there are no blocked orifices and the oil pump is working correctly we are good.

[MCRider]

Agreed, and it wasn't my intention to buzzkill the creative process, though it may have appeared that way. Something might come of it. So I've stated the challenges and will quietly withdraw and read with interest.

Merry Christmas!   

[bwaller]

Hey Ron, I've been trying to decifer the OCICBW all day.

Near as I can figure it means "old crotchety idiotic crapper brent waller" ?

Merry Merry guys

[Doctor_D]

Hey Ron, I've been trying to decifer the OCICBW all day.

Near as I can figure it means "old crotchety idiotic crapper brent waller" ?

Merry Merry guys

Of course, you could be wrong about your translation... but I like where you're going.

[754]

 If you tapped intgo the rear gallery, beside the oil lite switch......you could run lines up to top of valve cover, then thru valvecover, and spray onto the camlobes..

[TwoTired]

Pressure being what it is, that is, equal throughout a closed system, there shouldn't be any problem of "even flow".

Whoops, equal pressure in a system only occurs under static conditions (gravitational effects excluded).  If there is flow, it is not static, and requires a pressure difference between source and destination to get movement.  No pressure difference, no flow.

An old worn oil pump, can develop under pressure near idle, as can increased clearance in the crank and rod journals.  None of these are common in an SOHC4 that is within spec., and has been treated with proper oil change/ type and routine maintenance.
What IS common is the oil light coming on near idle due to faults in the sensor.  But, that is a false indication, not a symptom of actual low oil pressure.

I'm not aware of any folklore about the SOHC4 having any real oiling issues, top-end or otherwise, without some mechanic or owner based instigation.

Cheers,

[MCRider]

Pressure being what it is, that is, equal throughout a closed system, there shouldn't be any problem of "even flow".

Whoops, equal pressure in a system only occurs under static conditions (gravitational effects excluded).  If there is flow, it is not static, and requires a pressure difference between source and destination to get movement.  No pressure difference, no flow.
snip

Thanks, I had the feeling I didn't quite have that right. I was thinking of brakes, I think.

[MCRider]

Hey Ron, I've been trying to decifer the OCICBW all day.

Near as I can figure it means "old crotchety idiotic crapper brent waller" ?

Merry Merry guys

Of course, you could be wrong about your translation... but I like where you're going.

I know I wrote the explanation:
"OCICBW = of course i could be wrong"

a few days ago, but I must have missed the "post" button.

[TwoTired]

If you tapped intgo the rear gallery, beside the oil lite switch......you could run lines up to top of valve cover, then thru valvecover, and spray onto the camlobes..

Certainly, it is possible.  But, is it wise?

The oil pump doesn't put out a regulated pressure.  It only has max pressure relief valve that, as far as I know, doesn't activate at low RPM speeds.  Therefore, whatever pressure or flow is robbed at pump output for top oiling, would directly impact the main and rod journal pressure/volume, reducing both.

I wonder about the cylinder wall lubrication, too.  I'm not intimate with the CB750 internals.  Are the cylinder walls splash oiled, or squirt oiled?  I've worked on engines where the walls were squirted by a small hole in the rod big ends.  Whenever they lined up with the cross drilled oil holes in the crank, the oil pressure shot some oil onto the cylinder wall while the piston was near the top of the stroke.  (I'm probably thinking of a Chevy V8 here.)
If the SOHC4 also uses a similar arrangement, then lowering the oil pressure/volume at idle could well increase the cylinder wear, as well.
Just thinking out loud, here.

Cheers,