What's in your crank slingers

Hmm Piet, seems that your scale is past its cal date :P

Anyway scary stuff you guys pull out of the slingers, makes me feel better that I changed oil every 1500km in the past!

Ciao
Gerald
 
Gerald said:
Hmm Piet, seems that your scale is past its cal date :P

Anyway scary stuff you guys pull out of the slingers, makes me feel better that I changed oil every 1500km in the past!

Ciao
Gerald
Click to expand...

This begs the question - Which direction does oil flow in the engine. Does it go through the slingers before it passes through all the other sections of the engine or are the slingers at the back end of the flow and the final stage before the oil returns to the crankcase?

That is, are all the little gribbly bits of metal doing the rounds and then getting caught in the slingers or is the oil being "cleaned" prior to going through the rest of the engine?

Dave
 
I might well be wrong here, but I think the oil level should fill the slingers. If that's the case, they take the "dirty" oil from the oil-sump. Not 100% sure though, but I think that is how it works. Anyone can confirm?

 
The oil is taken trough the "filter" in the sump bottom, goes to the gallery at the cylinder base from which it is distributed to the head and crank.  The crank oil dribbles through the inner mains, surplus dribbles out the sides (hopefully) into the slingers.  These fill up to the level of the crank pin bore and overflow into the crank pin itself.  Only then are the big end bearings supplied.  The slingers filter out most of the solids floating around so the big ends recieve mainly clean oil.  Once the slingers are full of crap up to the crank pin bore, no filtering can take place, it's only a matter of time when the big end says goodbye!

The head gets crap-saturated, unfiltered oil.  Once all the parts are lubed and everything is flooded, the oil drips down in the sump and it starts its' trip all over again....  quite hit-and-miss actually, but as the oil volume is sufficient, nothing much happens.  The main bearings can stand quite a bit of punishment but the oil pump housing, big end cages, pistons and cam bearings are quickly devoured by the crap floating around.  Short oil change intervals OR a proper filter will keep the engine happier for longer. :D

piet
 
The ferrous content in the slingers also seems like a bloody good argument for magnetic sump plugs (plus other magnets in the oil system).
 
This all looks bloody scary..BUT, when was the last time a crank was known to have gone(and a rod broken, in consequence, say)because  the slingers were full? Is there any truth in the assertion that fully synth oils will loosed all the crap and send it round again? Is there a good argument here for low detergent oil not carrying stuff around, but letting it settle in the sump, to be drained out  on oil change?
My first bike (XL125) had a certifugal filter, but  sensibly designed to be cleaned out ie removeable cover. What kind of engineering thinking went into designing a system that cannot be cleaned out unless the whole shebang is taken apart, with the ultimate consequence if it is not being engine armageddon! Are these engines unique in this, or is it common to the period/even now..
Nick7 ::)
 
Quite common practice, Nick.

The old brit twins usually had their sludge traps incorporated in the crank, could only be cleaned out during total strip-down.  Very few of these had proper oil filtering systems, most had a simple felt pad through which the oil pump sucked the lubricant.

Full synthetic or oils with a high detergent volume can clean off muck and sludge that has accumulated on internal components, at least they're supposed to, but I doubt that it would shift any of the stuff in the slingers!  This has been compacted over many 1000s of km and is mostly rather solid.  It needs quite an effort to chop down and remove without taking off the slingers.  Reckon they would fill quite quick once a high detergent oil is used, the cleaned off muck will gather in the slingers.

I have been using full synthetic along with a screw-on H-D oil filter in my 3C since I re-built it 20 years ago.... when I replace the crank with my lightened one (hopefully within the next 3 weeks) I can report on effects regarding the oil.

piet

 
Really good information and pics Piet, thanks.
Look forward to more of the same when you do the post mortem on your crank. You've got me thinking !
 
Thanks for that info Piet. Am I right in assuming that the oil is pumped through the oil cooler from the oil pump to the head, or is this a separate circuit. Just wondering if it would be somehow possible to rig an external filter into one of the oil cooler lines, perhaps hide it up behind the cooler radiator.
 
Davo,

Yes, the oil goes through the cooler before it re-enters the engine, at least it's cooled down a bit before it has to take up work... the engine has only the one lube circuit, the gearbox is splash lube only.  While the 750 twins and 120s have a jet squirting oil to the primary chain, the normal triple relies on splash oil transferred through the "windows" in the gearbox wall to the primary housing.  Same goes for the starter clutch and gears.

Rob,

I'm really hoping it will be more of a periodical check-up then a post-mortem.  Crank's been working faultlessly so I'm not expecting any grave issues, just wondering how much crap has accumulated.

piet

(PS, I'm only doing this to be able to catch up with you again, left me for dead last year.... :D)
 
Piet, so with a decent oil pump fitted there should be no problem fitting an external filter unit?

Dave
 
Yep!

My 3C is fitted with an RGS type pump, copes well with the additional oil line length.  Actually, it shouldn't matter what pump is fitted, once the lines are filled it's just a matter of getting it all moving.  The larger pump will get it moving quicker, though.  I just would not fit the filter anywhere high up, the pump needs to work to overcome the height difference.  Pump efficiency is expressed how high a certain pump can transfer its' medium, I really don't like taking these sort of risks.  My filter is fitted out of sight under the swingarm pivot.  Had thoughts of bursting oil lines spewing the oil all over the rear tyre but these have since been dispersed, absolutely no issues!

OCT can supply even larger pumps with 10mm gears, just about the biggest that will fit without needing to machine the crankcase.

piet
 
Yep, thanks Piet!
But have you recently actually come across a triple which has self-destructed because the slingers are full? Yours are not, but you have had the filter. As many now do use synthetic oil, you might expect the slingers to fill up quicker and give trouble...so I wonder, do they?
Personally I find this element of the design deeply unimpressive...why could Honda foresee the need to clean out a centrifugal fliter back in the day, when Laverda could not? If of course they are not actually giving trouble, then perhaps the designers foresaw that the slingers would not fill for the reasonable projected life of the engine.....were they right? ::)
Nick7
 
sfcpiet said:
Davo,

Yes, the oil goes through the cooler before it re-enters the engine, at least it's cooled down a bit before it has to take up work... the engine has only the one lube circuit, the gearbox is splash lube only.  While the 750 twins and 120s have a jet squirting oil to the primary chain, the normal triple relies on splash oil transferred through the "windows" in the gearbox wall to the primary housing.  Same goes for the starter clutch and gears.

Rob,

I'm really hoping it will be more of a periodical check-up then a post-mortem.  Crank's been working faultlessly so I'm not expecting any grave issues, just wondering how much crap has accumulated.

piet

(PS, I'm only doing this to be able to catch up with you again, left me for dead last year.... :D)
Click to expand...

Slightly off topic Piet.
The regs for Spa, this year only, now state that 17" wheels are not allowed. I have sent an email to them asking the obvious, as I'm not prepared to take a risk with scrutineering, particularly as I didn't endear myself to the guy in the pit lane who also does the scrutineering  :-[
 
Nick,

I've actually come across quite a few engines in various states of wear that could be directly connected to the amount of crap in the slingers.  True, mostly twins, but there's been a few triples lately that were totally clapped!  Kept me busy most of the long winter!

Once the slingers fill up, the big end cages wear off their coating quickly, the next to go is the conrod, the bearing surface starts breaking up and next is the crank pin..... all fit for the skip after that.

The Lav cranks are set up for a VERY high mileage, provided the oil is frequently changed.  The gearbox is a constant source of ferrous particles, the gears constantly mesh and rub each other producing microscopic small steel chips.  Same goes for the chains, the evidence of wear can be witnessed when replacing.  Using wrong/poor quality oil or just keeping it in the engine for too long accelerates internal wear dramatically, and most of the resulting swarf gathers in the slingers.  So, if much of this crap can be removed in the course of oil changes or not be allowed to result in the first place, the engine will last longer and the longer it will take for the slingers to fill up.

When discussing crank work with a customer, the type and amount of riding to be expected is used as a guideline.  If he/she says the bike will be thrashed on a racetrack, no shortcuts.  If the bike is only occasionally taken for a Sunday morning run for a total of perhaps 2000km/year, slightly worn big ends will not give trouble for many years to come!  Usually a question of what its' worth to the owner...  In fact, most big ends in Lav engines today show differing amounts of ovality, usually not enough to cause concern, but, it's there alright!  Many big end bearings in cranks I have repaired/overhauled have been re-used, usually good for a further 50-60000km, which, to be frank, will rarely be achieved by the majority of these bikes, now being piloted by a bunch of old farts.... like myself! :D

I am quite convinced the design of Lav cranks is nigh on bullet-proof.  It's just the snapping conrod syndrome that puzzles me, doesn't really fit into the picture.  As most of the cranks with this phenomena are usually of unknown provenance, I'd suspect some sort of previous damage/neglect to be the cause.

Robjota said:
Slightly off topic Piet.
The regs for Spa, this year only, now state that 17" wheels are not allowed.   I have sent an email to them asking the obvious, as I'm not prepared to take a risk with scrutineering, particularly as I didn't endear myself to the guy in the pit lane who also does the scrutineering  :-[
Click to expand...

Rob,

Wasn't aware of that!  But then, I must admit I did not read the regs very carefully, probably oversaw that and didn't give it another thought.

It's not only in the twisties that you have a definite advantage, you blow me in the weeds in a straight line!!  THAT HAS GOT TO STOP!! >:( :D

I'll be fitting slightly larger pistons to close up a bit to you in displacement, and the head will undergo subtle surgery.....

Cheers,
piet
 
Nick, I wouldn't worry too much, I used my 3C for 90,000 miles with just regular 20/50 multigrade oil changes. I never worried about thrashing the arse out of it either. When I took it apart the small ends were getting a little bit sloppy and the big ends had no perceptible up and down movement but a bit of side movement when holding the con rods. Just a laymans test but hey 90,000 miles........dont worry about it, just use it. Regards Pat.
 
Have watched this thread (on and off) with interest. I had a Jota with a badly rebuilt crank (slingers not cleaned) that started to make a very slight tap or knock. I could not discover exactly where the noise came from (typical of early big end failing), so decided that, if it was rebuilt, maybe a modern oil would cure or kill. Well, it did kill.... I still have the conrod somewhere - it had massive amounts of it's bearing surface ground away and has metal particles impacted into it.

My advice would be that if you don't know what the state of your slingers, or if the crank has not been out/apart for a long time. DO NOT use synthetic oil.  It will start to soften the crud and feed the swarf into the motor.  Using synthetics is probably fine on squeaky clean engines. On anything else, it defeats the design.

Just a thought.......

Pete
 
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