original oil filter

[Ozmadman]

Thanks Les for that detailed analysis, yes the felt filter does have a spring but I just thought that was to ensure the filter was pushed home properly and to keep it so. The principle regarding the spring acting as a release valve makes sense but I wonder whether in this instance with such a weak pumping action that enough pressure could be built up to move anything let alone quite a strong spring like this? The original filter as you see has no such advanced device and both of them just make metal to metal contact at the bottom of the tunnel(there is no seal there) so I doubt whether all the oil goes through the filter anyway. Primitive yet it's worked like that since 1960 so as you say !000 mile oil changes and a filter clean each time should be fine. At least I know my engine is clean inside so that's a good start. Interestingly, I was looking at a road test article for an old 1970 Honda CD175 that I used to own and even those wonderful Japanese oil tight high tech engines with their centrifugal oil filters needed an oil change every 1000 miles!!! and they held a gallon of oil... so I can count my chickens with only a two and a half pints each time..

Paul

[Les Howard]

I reckon the oil pump would move the filter off its base. The action would be similar to a hydraulic jack in that you have a fairly small diameter piston in the pump acting over a a large surface area of the filter which only needs to move about 1mm to allow the the oil to escape. The old gauze filter will only trap relatively large particles, but the felt one will trap smaller stuff which must be better. However, as said before roller bearings don't require a lot of oil but highly stressed engines use a bigger supply of oil for cooling. The most harmful particles are ferric such as from bore wear (carbon being softer) and much of these can be trapped on a magnet suitably placed.

Looking at the filter and depending on how much uncompressed spring length is left after tightening the end cap (easily calculated with some measuring up) it looks like a rare earth ring magnet could be fitted over the spring to hold onto most of the ferric crud...it would be easy to get at the magnet for cleaning too....

http://www.ebay.co.uk/sch/i.html?_from= ... s&_sacat=0

I'm sure one could be found in terms of ID. OD. and length.....Les

PS...I was equally impressed with the lubrication of Japanese engines. Way back in the late 60's when I and my mates owned G2 Matchlesses that seemed to have hardly any oil moving around the engine especially to the head, we were amazed when we removed the rocker cover of a 50cc step-through Honda the oil literally was gushing around, appearing to be enough to fill a cup within about 5 secs...and that was just over the rockers...yes, we were very impressed....Les

[Ozmadman]

That's an interesting concept!! I will look into that. The lightweight has two sump plugs, one to drain the internal oil tank and the other to drain any small amount that has seeped back past the pump and into the sump, this one has a magnet on it. Think now after what has been said that I will stick will the felt filter, maybe getting a spare to swop around at oil changes.

Paul

[SPRIDDLER]

I was surprised to find that my 'Grudge Special' (2014 Honda CBF125) doesn't have any sort of disposable filter, just a strainer in the sump - about half an hour's work to remove, clean and refit it every 7,500 miles. Th'engine holds only 0.9 litres (about 2 pts) oil. No magnets anywhere.

[Ozmadman]

I was surprised to find that my 'Grudge Special' (2014 Honda CBF125) doesn't have any sort of disposable filter, just a strainer in the sump - about half an hour's work to remove, clean and refit it every 7,500 miles. Th'engine holds only 0.9 litres (about 2 pts) oil. No magnets anywhere.

Blimey!!! how things have changed. Ok, can of worms time!! Done some measurements and discovered that once the oil filter cap is fully tightened the spring must be fully compressed! therefore no room for a magnet. Of more concern though is there is no room for the spring to act as a relief valve as has been mentioned? Have a look at the two pictures. The mark on the drill bit is the full length of the filter tunnel and the spring sits in a recess in a metal cap(pushed into the end of the filter) in as far as shown in the picture. As you can tell, once the large end cap(and there is a very slight recess about 1mm in that) is fully tightened the spring is squashed completely so much so the the filter comes out slightly bent. All the parts in there are the proper ones got from club spares by part number so, should I leave it as it is or shorten the or get a shorter, weaker spring so I can have the release effect should the filter become blocked?

Actually, looking at it no spring will give a release valve action as when tightened even without the spring there will be no room for movement, so why the spring in the first place?? the filter needs to be shorter... Interestingly the 250 does have a shorter filter and longer spring but the engine design is exactly the same, why? confused now?

[Les Howard]

How it strikes me:

1) Is the filter the same length as the original?..I guess it is?
2) If the new one is being squashed...why does it need a spring?
3) Seems like the new one needs to be shorter...BUT...only way to check is to access an original...does anyone have one please?
3A) Do later engines have a longer filter chamber?
4) I'm not saying deffinitely the spring acts as part of a blocked filter safety valve precaution...BUT...other makes of bikes do use this system and this is likely also to be the design.
5) Certainly use the new one as it is..it is not likely to cause a problem if regular oil changes are done.
6) You can't use your old one any way.
7) Continue the investigation.

Les

[SPRIDDLER]

Perhaps the spring is merely there to keep the mesh filter making contact both ends since the filter is a compressible mesh. Also there would be manufacturing tolerances so some would inevitably be slightly shorter/longer than others...............

[Ozmadman]

How it strikes me:

1) Is the filter the same length as the original?..I guess it is?
2) If the new one is being squashed...why does it need a spring?
3) Seems like the new one needs to be shorter...BUT...only way to check is to access an original...does anyone have one please?
3A) Do later engines have a longer filter chamber?
4) I'm not saying deffinitely the spring acts as part of a blocked filter safety valve precaution...BUT...other makes of bikes do use this system and this is likely also to be the design.
5) Certainly use the new one as it is..it is not likely to cause a problem if regular oil changes are done.
6) You can't use your old one any way.
7) Continue the investigation.

Les

1) Yes exactly the same length as the original solid mesh one
2) My thoughts exactly
3) Don't know but can't see any logic in it
4) Makes sense especially if they have bothered to include a spring in the first place
5)Will do
6) I could if I can repair the thread but it is probably not such a good filter
7) Am going to

What I can't understand is that my original fixed mesh type was standard fitment for BOTH 250 and 350 so why does the 250 now use a shorter felt filter? Anyone with a 250 that would like to comment on what kind of filter they have in their bikes? that would be useful and would there be any harm in using that in a 350 then the release valve action would become a reality..

Thanks all

Paul

[Tolly]

If the filter is put in the other way round, does the other end slide into the fixing nut. If it does the spring is there to hold the filter down to the base, if it gets blocked oil pressure will lift it against the spring therefore sliding the filter further into the fixing nut. I may be on a wild goose chase but looking at the filter you have a washer on one end and a sort of cup on the other. Just a thought.

[Ozmadman]

No the nut is almost flat on that face so no real recess. The parts are as the manual and in the correct way round. Basically, you have a cup washer with a hole in it, that goes in first then the filter, then another cup washer with no hole but a short recess to take the spring, then the nut.. That's it, so no real use for the spring except just to make sure the cup washer inside presses up tight against the hole in the crankcase. Rubbish design( if that's what you can call it) from what I can see. So, can anyone comment as to why the 250 felt filter is about an inch shorter and might I add about half the price!!

Paul