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Discussion Starter · #1 ·
Do you think there is a way to upgrade the 350 twin's oil filter from the centrifugal type to a cartridge style like the 550 and 750 have? What type of engineering would that involve? Or for some reason do you think it would it be totally impractical and unwise to even try?
 

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Do you think there is a way to upgrade the 350 twin's oil filter from the centrifugal type to a cartridge style like the 550 and 750 have? What type of engineering would that involve? Or for some reason do you think it would it be totally impractical and unwise to even try?
I think it's a wasted effort. The factory unit is totally reliable.

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Discussion Starter · #3 · (Edited)
I think it's a wasted effort. The factory unit is totally reliable.

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Thanks for the reply. Yeah I've been trying to learn if the centrifugal type is a good design or if it's a marginally effective relic of the past. I'm somewhat new to working on these bikes. Some people seem to suggest that the centrifugal filters do not remove small particles and are only effective at removing larger debris. I haven't come to a verdict myself. I certainly seen and heard people criticizing these old twin bikes as "having no oil filter" or "not having a real oil filter". Do they have a point or are these old twin centrifugal oil filters awesome?
 

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Centrifugal filters work best when run at higher RPM's.

That said the 350's are most happy running above 5000 rpm.

So,... If you are riding your bike in it's best performance range and not like an old lady than the filter will work fine.

If Not - Well...
 

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Discussion Starter · #5 ·
Centrifugal filters work best when run at higher RPM's.

That said the 350's are most happy running above 5000 rpm.

So,... If you are riding your bike in it's best performance range and not like an old lady than the filter will work fine.

If Not - Well...
Yeah that's what common sense was telling me. Clearly there would be more centrifugal force at higher engine RPM to force particulates aside. So at idle there is very little filtering going on? It seems like such a terrible idea vs a replaceable paper element style filter. But I'm relatively new to bikes. I'm waiting/hoping for a great explanation as to why centrifugal oil filters are actually awesome.
 

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The won't be an explanation as to why they are awesome.

Centrifugal filters are simple and work.
That's all there is to them.
Sometimes simple is better.
As I posted before they work best at higher RPM's IE: While riding.

These are Air Cooled Motors they are not meant to be left running and sitting at idle.
Also the Oil Pumps are not super strong.
They need to RPM's as well to keep up the flow.
The Charging Systems don't break even until at least 3500 RPM.

Idling & low slow speeds = BAD
 

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Discussion Starter · #7 ·
The won't be an explanation as to why they are awesome.

Centrifugal filters are simple and work.
That's all there is to them.
Sometimes simple is better.
As I posted before they work best at higher RPM's IE: While riding.

These are Air Cooled Motors they are not meant to be left running and sitting at idle.
Also the Oil Pumps are not super strong.
They need to RPM's as well to keep up the flow.
The Charging Systems don't break even until at least 3500 RPM.

Idling & low slow speeds = BAD
Yes I of course wasn't suggesting to leave your bike idling unnecessarily. Was just posing the thought that there must be very little filtering going on at idle. We do all have to let our bikes idle sometimes. At red lights, etc. And we all have to ride at low speeds and low rpm ranges from time to time. I don't really see how a centrifugal oi filter is any more simple than a more modern paper element style filter. Is it because the oil pump has to be stronger for a modern filter system to work properly? Does a centrifugal oil filter system partially rely on the motors centrifugal force to not only filter the oil but to also circulate the oil?
 

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My take on it is that the cup must be completely full of oil and it exits out the center hole of the spring loaded diverter piece. I wouldn't think centrifugal force would be present at the center but maybe more pressure is created because of it? I wouldn't think it would be much because I've heard of people putting pressure guages on and seeing very low readings. Like less than 10psi iirc. It does pump sufficient volume though. And that's what matters to the design. I don't think paper filters were a big think when these were originally designed in the 60s. I'd like to hear others ideas on the subject.
 

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Discussion Starter · #9 ·
My take on it is that the cup must be completely full of oil and it exits out the center hole of the spring loaded diverter piece. I wouldn't think centrifugal force would be present at the center but maybe more pressure is created because of it? I wouldn't think it would be much because I've heard of people putting pressure guages on and seeing very low readings. Like less than 10psi iirc. It does pump sufficient volume though. And that's what matters to the design. I don't think paper filters were a big think when these were originally designed in the 60s. I'd like to hear others ideas on the subject.
I'd would like to hear others thoughts as well. The main criticism I've heard is that they do basically nothing for the filtration of the near microscopic metal pieces that wear rings, cylinder walls, camshaft, etc. I barely know what I'm talking about though.
 

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Of all the things you need to worry about with a cb350 the oil filtration is way down the list.
As far as getting out the microscopic debris you are worried about all the sludge traps I have ever cleaned out of crankshafts on Brit bikes or the trap on CB's there was an abundance of ultrafine particles. I have seen the sludge traps on Triumph Bonnevilles so packed that the sludge had to be drilled out.

The CB350 needs oil quantity so rather than chasing a filtering system that will work with 3 or 4 psi make sure the pump is good, the o rings in the trap and oil filter cover are good and use a quality oil ( 5-40 Rotella T Full Synthetic is my choice). Also make sure the contact area between the oil filter cover and the cover on the sludge trap is smooth and actually making contact between the two parts.
 

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Discussion Starter · #11 ·
Of all the things you need to worry about with a cb350 the oil filtration is way down the list.
As far as getting out the microscopic debris you are worried about all the sludge traps I have ever cleaned out of crankshafts on Brit bikes or the trap on CB's there was an abundance of ultrafine particles. I have seen the sludge traps on Triumph Bonnevilles so packed that the sludge had to be drilled out.

The CB350 needs oil quantity so rather than chasing a filtering system that will work with 3 or 4 psi make sure the pump is good, the o rings in the trap and oil filter cover are good and use a quality oil ( 5-40 Rotella T Full Synthetic is my choice). Also make sure the contact area between the oil filter cover and the cover on the sludge trap is smooth and actually making contact between the two parts.
I'm curious - what are some other things higher on the list to worry about with a CB350?
 

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I'm curious - what are some other things higher on the list to worry about with a CB350?
Well lets see....... hmmmmm

Lean air/fuel mixture, poor spark leading to poor combustion leading to fuel washing down the cylinder walls, old seals blowing out, new seals improperly installed blowing out, 45 year old cam chains, cam chain tension rollers 45 years old, oil starved camshafts, ethanol fuel, wiring and wiring connectors, dirty switches such as the Kill switch, peeling chrome, rust, faded paint, rips in seat covers ......

For the CB350 we get to do oil changes every 6 to 1000 miles. If you want filters you will have to buy a newer bike.
 

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Discussion Starter · #13 ·
Well lets see....... hmmmmm

Lean air/fuel mixture, poor spark leading to poor combustion leading to fuel washing down the cylinder walls, old seals blowing out, new seals improperly installed blowing out, 45 year old cam chains, cam chain tension rollers 45 years old, oil starved camshafts, ethanol fuel, wiring and wiring connectors, dirty switches such as the Kill switch, peeling chrome, rust, faded paint, rips in seat covers ......

For the CB350 we get to do oil changes every 6 to 1000 miles. If you want filters you will have to buy a newer bike.
Good points but eh I don't think faded paint is more of a worry than oil filtration. I find it really interesting that the CB350F has a modern style oil filter. As do all of the four cylinder CB bikes from the 70s I believe.
 

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The 350 oil pump generates low pressure, one look at the design says that. Paper oil filters are restrictive in the sense that oil has to be under pressure to be forced through the paper and this pump really isn't up to that. The 4 cylinder and later twins like the CM series use a gerator type pump which produces higher pressures.
 

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Boomer forgot the petcock.

Irving, spend as much of your time goofing around with this, and let us know when you've found the solution to a non-problem. Several members have weighed in and you continue to argue the subject. Just what is it you think isn't being filtered well enough?
Have you disassembled a 350 engine with xxxx on the clock, to find a beautiful camshaft, rockers and bearings? The slinger is really a non issue considering you could ruin your top end in 5 min if you leave the petcock on and dilute your oil, or blow your pushrod seal and dump all your oil on the highway.

Don't get me wrong, I like paper filters, and one plus about them, which you probably won't mention, is about water and running the bike good and long.
 

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Discussion Starter · #17 · (Edited)
Boomer forgot the petcock.

Irving, spend as much of your time goofing around with this, and let us know when you've found the solution to a non-problem. Several members have weighed in and you continue to argue the subject. Just what is it you think isn't being filtered well enough?
Have you disassembled a 350 engine with xxxx on the clock, to find a beautiful camshaft, rockers and bearings? The slinger is really a non issue considering you could ruin your top end in 5 min if you leave the petcock on and dilute your oil, or blow your pushrod seal and dump all your oil on the highway.

Don't get me wrong, I like paper filters, and one plus about them, which you probably won't mention, is about water and running the bike good and long.
I'm just learning man. That's all. Just pondering about the two different filtering designs. Not arguing or goofing around. I had no idea if maybe there was a mod out there for transforming the vintage centrifugal filters to a modern style filter. I'm always learning something new that people do to old bikes to modify or improve them. An oil filter conversion seemed like something that might be within the realm of possibility. I'm just doing some reading on the subject and throwing a thread or two out there to see what people have to say. I've spent maybe 10 minutes on this thread. And have already learned a ton. Time well spent I think. The internet is an amazing thing but man it's also lame when people assume you're an idiot, or are arguing or etc. I'm just contributing some thoughts and questions. You don't have to reply. I'm not hostile, or negative or a dope. Also I don't know what you mean about how I "probably won't mention water and running the bike good and long." Thanks for the thoughts man. I'm definitely aware of the dangers of float valves sticking and diluting oil with gasoline and the other issues mentioned. Although if you happened to want to explain blowing a pushrod seal I'd definitely read it. I'm unfamiliar with that. I've had my first bike for a couple years and have finally gotten the time to fully rebuild it and got it on the road. Overall running great and been a fantastic learning experience. Just got my motorcycle endorsement last week.
 

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Discussion Starter · #18 ·
The 350 oil pump generates low pressure, one look at the design says that. Paper oil filters are restrictive in the sense that oil has to be under pressure to be forced through the paper and this pump really isn't up to that. The 4 cylinder and later twins like the CM series use a gerator type pump which produces higher pressures.
That makes very good sense to me. Thank you for that. I wonder if theoretically a gerator (did you mean gyrator?) oil pump could be modified to work with an older CB twin.
 

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The fact that these almost 50 year old bikes are still on the road should tell you all you need to know about their reliability.
When's the last time you saw a Vega, Pinto, or Yugo on the road?

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