OK--I believe in the centrifugal oil filter now!!

jensey · Post by **jensey** » Mon Oct 15, 2012 7:06 am

Well done! All questions answered with clarity and backed up with empirical data. The only point I might argue with you Jensen (and I do so with great trepidation so maybe request further clarity is probably a better approach) is putting the medial filter on the suction side of the oil pump, if that is indeed what you did.

No, I placed it on the "pressure" side.

Since, to your point this is not a positive displacement pump, it is my understanding that as a general rule theses pumps do not suck as well as they push.

Indeed, it's a volume pump, with a relative low pressure.

So, from that I would think (best I can do at this point) that there is potential for the pump to starve or partially starve as the filter does it job and becomes more restrictive. You said in one of your replies that the media filters provide a "huge resistance in the oil flow". So one can assume that as they do their job that restriction increases until the bypass valve, if there is one, opens.

No valves, so chancing on time is what I do, that's why I added a pressure sensor, so I can see when to change it. I treid to use a filter with a valve, but the pressure of the pump is not able to open it, that's why I don't use it.

The pump should be in perfect shape, otherwise the flow back is too high.

At the moment I'm designing a pump which will have a higher pressure, and more volume, based on a trochoïde pump like the more modern fours. It's a unit design, pump, filter and sensor. It will give better flow and is more reliable.

For now I have to pump 5W/20 oil, which is too viscose on these type of bikes. If I use 10W or Honda spec 30W the pump doesn't have enough pressure to push these oil through a filter, and even worse when the engine is cold.

I know that the spinner filter isn't perfect and has it's shortcomings in certain rpm ranges, but I am a perfectionist, so I started to make it better, and I achieved a lot, but I'm not there yet. Solving much problems with the low pressure at low temperatures when cold started are time consuming. But it's fun to do so, that's why I'm doing it.

If I wasn't a perfectionist, and not a physics engineer I would never look for an alternative of the spinner filter, because when you change your oil on a regular bases, just as the specialists Bill silver and Ed Moore mention and when you use good oil (really, it isn't that important if this is a synthetic or not) you are always on the safe side.

The only particles which come easy through the spinner filter is aluminium, which is soft and not really harmful as long it doesn't block an oilway. And of course clutch particles, but like I said, when you change your oil on a regular base, you will be all right and a good rebuild engine will probably last longer then many of us ride on it.

For me it's different, I am an engineer, and when something could be made better I will do so,

Jensen

btw, it's not my intention to offend anyone, so don't feel offende, I don't either. These kind of discussions are razor sharp, because, unfortunately, like I mentioned earlier, not many people back up there theorem's with facts and measurement. I understand that not everyone is capable of doing so, and that makes it even more difficult to discuss it, the arguments are mostly based on experience which can not be "recalculated" by others.

But I do get a little itchy when people "believe" and "assume" that something is working.

Snakeoil · Post by **Snakeoil** » Mon Oct 15, 2012 10:44 am

[quote="jenseybtw, it's not my intention to offend anyone, so don't feel offende, I don't either. These kind of discussions are razor sharp, because, unfortunately, like I mentioned earlier, not many people back up there theorem's with facts and measurement. I understand that not everyone is capable of doing so, and that makes it even more difficult to discuss it, the arguments are mostly based on experience which can not be "recalculated" by others.

But I do get a little itchy when people "believe" and "assume" that something is working.[/quote]

I don't think anyone takes offense here, Jensen. I know that I tend to write in what I call "engineer-ese" which is matter of fact. Sales guys don't like it because they are always afraid I'm going to insult or otherwise offend a customer. They seem to forget that all our customers are engineers. So, when someone else writes in a similar fashion, especially when not in their native tongue, you have to always assume they are speaking with the best of intentions.

You point about changing oil regularly and using a good oil is always important to bring out in these discussions. Folks who are not deeply into technical theory and application could read these threads and think their vintage engine is a time bomb. If that were the case, we would have nothing to look at when we go to antique car and bike shows, huh?

Keep up the good work. It is these types of discussions that are what I truly enjoy about these forums.

regards,
Rob

G-Man · Post by **G-Man** » Mon Oct 15, 2012 11:31 am

Jensen

I'm curious that you say that the Honda pump is not a positive displacement device. Normally, gear pumps are regarded as exactly that and can provide 3000psi for hydraulic machines such as excavators. It's obviously impossible for any pump to 'suck' more than 14.4psi (1 atmosphere). Gear pumps share their main downside (leakage around the side plates and lobe / gear tip wear) with trochoidal pumps.

The problem with these motors is that the roller bearings do not provide any resistance to flow like a journal bearing would. Therefore whatever the pump provides, simply leaks out of the bearings, and the pressure never builds up.

If you could restrict the flow (not advisable) then the pressure would build up just like us older humans with narrowed arteries.......

It is not the pump that keeps the pressure low it is all of those leaky roller bearings.... :-)

G

jensey · Post by **jensey** » Mon Oct 15, 2012 2:28 pm

Hi G,

I'm curious that you say that the Honda pump is not a positive displacement device

I can't remember that I said that, or at least I didn't meant that. The pressure build up of this pump isn't that high. I tested a few on a rig, and the results weren't that good due to leakage. I even tried it with a NOS housing and all new gears. I can restrict the flow of the outlet by a resistance (valve), but the pressure buildup stops early, then the leakage takes over, with the result that the pump is not pumping a lot of oil. These pumps works best when there is not much resistance, the pumped volume is high because of the very high speed of the gears, as long there is not much resistance.

The volume has to be high because the oil paths in these engine are leaky, for example the spinner filter shaft with all those slits between parts. I use a tube with a restriction instead of the spinner filter construction, and I used O-rings for making it leak free.

The shape of the gears in a modern gear pump is different, more sophisticated, better machined, and result in less leakage and higher pressure build up. Compared to a modern pump, the gears of these pumps are small (diameter) and are not wide either.

Jensen

G-Man · Post by **G-Man** » Mon Oct 15, 2012 3:04 pm

Jensen

Thanks. That, perhaps, illustrates Honda pragmatism. They know it doesn't need to generate pressure so they design something nasty with loose tolerances that just stirs up the oil......

Interesting. Surprising, but interesting.

G

brewsky · Post by **brewsky** » Wed Oct 17, 2012 5:37 am

Jensen,

Great info and no intent to offend here either!

Another question that I can't remember being discussed:

The following is a quote from the shop manual……..

“Lubricating oil sumped in the crankcase is sucked by the oil pump to pass through the under crankcase and L. crankcase cover then pipeline in splitted 2-ways, one to the oil filter.” (Pg 97-99 CB72,77 Shop Manual)

This would lead me to believe the centrifugal filter is actually a bypass filter instead of a full flow filter if true.

Is this true? If so, it would make a another convincing argument for your conversion.

jensey · Post by **jensey** » Wed Oct 17, 2012 9:24 am

Hi,

Another question that I can't remember being discussed:

I mentioned it years ago, but probably you didn't realize what I meant by it, read point 1 in the following text again :

I explained the conversion elsewhere on the forum, but here the text :

In theory it's a simple conversion, practically it was a little more difficult.

The theory / wishes / engineering considerations stated in 2003 where as follows :

1. All the oil should be filtered before entering the engine, no unfiltered oil entering the engine.
2. As less as possible machining on crank cases, it’s difficult and I can’t change it back in the original state.
3. Because the oil pump is rather a volume pump than a pressure pump the oil filter should have a low flow resistance and a large surface.
4. Changing the oil filter should be really easy, without opening the engine or removing important parts.
5. Should be able to work with 10W50 full synthetic oil, and the oil filter should be easy to buy.

From a logical point of view there is only one place that meets the criteria above and that is a place before the oil pump, so I decided that the oil filter should be placed underneath the pump itself, as a part of the pump housing.

Another advantage was that the the oil is drawn down by gravity to the lowest point (oil filter) and thus the oil pump itself is not working different than in any other standard engine.

I bought several used oil pump housings to experiment, and finally I machined a three part oil pump housing where the top (part in the engine) stays the same.

I removed the centrifugal oil filter, replaced the oil filter shaft by a direct pipe with a diaphragm to regulate the flow between crank, clutch and head and dismissed the oil filter chain.

After years of optimizing and further development (I destroyed / machined at least 12 oil pump housings) I got what I wanted, I even included a pressure sensor and a temperature sensor. On top of that the engine also gained an extra horsepower due to removing the oil filter and the chain (and less noise from the engine).

I hope that this answers the question,

Jensen

btw, I see an error in the text, it's this

a place before the oil pump

and it should be :

before the oil spinner place

.

but VERY GOOD OBSERVATION and very true indeed, look at the clutch cover, here the oil way from the pump is split in two ways (actually three).

1 ) the first part of the oil goes into the oil filter and after the filter it is split again in two ways, respectively to the crank and to the head.

2) The second part of oil (this part is not filtered) is via the clutch into the transmission main shaft.

3) The third part of oil leeks out the oil filter (between shaft and spinner) and goes into the crankcase directly.

The total flow at point 3 isn't much, but I have seen worn shafts being put back into engines without any hesitation by the PO, here is a lot of flow to win if in good shape.

This is the reason why I mounted a filter directly under the pump, before the split in the clutch cover, and that's why this is the only logical place were to mount it.

BTW, pumping unfiltered oil through the transmission isn't that bad at all, because over time all the oil is filtered, but from a engineering point of view it's a mortal sin (Dutch saying).

It's also another reason to change the oil within a relative low miles interval, and use good quality oil. I cannot say that too often !

Jensen