Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board A50 (65) Primary (Drive) Side Main Bearing

Allan recons :

"If you have the inner timing case off and spin the oil pump up, even with a fresh motor you will see oil coming between the journal and the bush, same for the big ends… that’s what it’s supposed to to to lubricate the full surface.

The thrust washer does nothing to keep oil in, "

I don't suppose i made it clear enough that i was only talking about is you fit a ball bearing into a set of cases with the rebate for the trust washer as per the roller brg AND REMOVE the thrust washer .
that WILL give a void into which oil will go

spin up a crank assy with oil pumping (as you said above) into it WITHOUT the dumby "void filler" washer i am taking about and see if you get MORE flowing out the end of the TS bush ...think about it

Only theoretical and wont make a huge difference bit it will make some difference... these old scuzzers need all the help they can get

Took me a minute or two to see what you were getting at (so I hope I have it right this time).

A couple of things will happen in reality;

1: as Nick mentioned, the crank will walk and pull the bearing out of the case, mine has a needle roller in a later set of cases and I machined off the part of the casting which supports the thurst washer, mine did walk and I ended up re-fitting my outrigger plate to ensure it didn't.

2: there is always a void with or without the thrust washer in place, even if you only have 3 thou clearence against the T-Washer, the washer is still shaped with 2 grooves across to it improve oil flow between the washer and the crank thrust face.

3: oil flow is indicative of viscosity, viscosity will decrease rapidly if flow is insufficient also. So we all know that an oil is "thinner" and free'r flowing when it is hot compared to at room temperature, but if oil can't flow past a bearing (like a TS bush) then it will thin (loose viscosity until it does), if its flow isn't restricted then fresh cooler oil will be able to replace the thinner hotter oil and maintain viscosity at the bush... Likewise if you use an oil that is too viscous then not enough will flow when needed and you will get engine damage that way.

In short that oil needs to flow, keeping it flowing at a certain pump speed which is enough to exceed the losses at 3 points is the important part.

I think this is why the hole drilling is the DS rod works, its less about spraying oil up the cylinder and equally as much about keeping a fresh flow of oil to the journal.


Not trying to pick holes in what you have said, just heathy discussion.

However it is possible that I have completely got the wrong end of the stick and if so you might have to break out the pen and paper for me (not your problem, but mine).

I know what you are saying Allan. I used to get a lot of crap for saying that oil hole in the rod helped oil flow.

Oil flow can be restricted due to resistance to flow (pressure). The LH road is at the end of the line. There is definitely potential for reduced flow to the LH side due to normal losses of oil at the TS main and RH rod. Yet the internal pressure within the bearing remains the same as the other 2 bearings. But there is simply less oil available at the LH side. The hole allows a pressure drop in the LH bearing shell which induces flow.

Plain bearings need a good flow of oil. It keeps the hydrodynamic wedge alive and cools the bearing. Take away the flow of oil and things go bad quickly. Restricting the outflow of oil will also cause a failure of the bearing from lack of cooling and collapse of the wedge.

And yes, sitting static with the pump being turned independent will show a good flow of oil out of the bearings. There is no dynamics involved and the oil is free to flow.

Pleased you get where I was going with the Rich, I often lack a way with words (pretty bad considering english is a first language), im a little better with pencils and diagrams.

"Hydrodynamic wedge", exactly what I was thinking - (just not the wording, though it should have been)

I know what im TRYING to say but its to difficult.

Allan "2: there is always a void with or without the thrust washer in place, even if you only have 3 thou clearance against the T-Washer, the washer is still shaped with 2 grooves across to it improve oil flow between the washer and the crank thrust face."

so think about it ... the motors with the washer were designed so that with the 3 or so thou and grooves it gave enough to allow oil , so are you really trying to say that if you increase that 3 thou to 160 thou ( or what ever the thickness of the washer is by removing it ) it wont make any difference ...?? Really?

and regarding the hole in the LHS rod ... it is there to give better flow ... any doubts put you figure across the end of a garden hose and see how much flow you get

Hi Ignoramus,

I don’t want to sound condescending but I’m not sure how best I can say it (put this down to my poor literacy not anything else). You know at running temperature oil is really thin? Engine Oils are tested mostly for kinematic viscosity around 40c and 100c, the 40 i believe is more representative of the oil in the tank/sump and its viscosity required when being pumped. The 100c for when it is at the hottest point so around the bores and passing through the shells. Even on a multigrade the viscosity change due to temperature is pretty high. The 2 horizontal grooves in the thrust washer alone will allow a lot of oil past even if you had a 0.001” end float. The tubes used to check kinematic viscosity of oils at 100c have a tiny capillary size, probably not 0.001” but it’s not far off (I have such fine wire for doing that very job).

(Ok, I see where your going with this)

Start of looking at it the opposite way… If you were to make your own thrust washer and not have those oil release grooves put in and shim to 0.001” then you might be able to retain some oil. But, I don’t believe that removing the standard thrust washer and having an open void would allow more oil flow. And if you could kinda block it off then more oil would flow out under more pressure over the timing gears as the oils temperature would have increased due to it being blocked on one side. Clean cooler oil would replace that oil but then the same would happen to that. The speed of which the replaced oil flows would be the same in (the crazy world of Allan G ) theory.

The only real answer would be the “acid test” and to do it. But you would need an oil pressure monitor and probably an oprv which is either blocked closed or has a fixed amount of release so that a normal working one wouldn’t alter the results. You would also need the ability to see inside the motor and past the golden shower of oil.

Another thing to think of is if you are going to potentially cook the oil, then consider what oil you’re using. A 20/50 is a 20wt oil with additives. A straight 40 is just that and so on. Multigrades are Newtonian in their characteristic but only to a point (they are actually non-Newtonian because they do have a limit before PVL occurs) so if that oil has exceed it’s temporary viscosity loss limit you then end up permanent viscosity loss and your 20/50 is just a 20wt being pumped around the engine… so that ain’t going to help maintain the hydrodynamic wedge which Rich B mentioned above.

You could also test your theory (if you really wanted to) with a standard motor, one with your shimless setup and other with a restricted shim so no grooves. Same oil, same amount of engine run time and send away 4 batches of oil to an independent lab for testing (the last one being a fresh sample - all 4 from the same bottle/batch number) ask them to test for Kinematic viscosity and dynamic viscosity by HTHS method (the high temp high sheer which magneto man mentioned in another post). It would be a real ball ache and probably cost a fair few quid in testing alone.

The OPRV is another question though. If you spin the pump up with a drill. You don’t need to go fast (and you need the oprv fitted) for the oprv to open enough to blow past to the return line with a static motor. The 70psi unit opens at a higher pump speed than the 50psi unit. So…. The next question would be, would it not be worth while fitting the 70psi oprv to a bush equipped TS crank in order to promote oil flow through the 3 bearings? (This is what I did on my 823 motor). I know Nick has mentioned to me previously that the 70 psi unit could invert the oil seal on the end fed crank setups so I kept the 650 motor which is like that to 50psi oprv.

Lastly, think of a car or a (eg 4) multi cylinder bike. They have shells for everything. So each journal that it comes to is letting oil past before feeding the next journal. I can’t remember what blow off system my 400/4 has on it, (14 years since I looked at that motor) I don’t seem to recall it having one but it could be integral with the pump like the pressure switch. But I really can’t remember.

That’s a lot of typing. I’m sleepy now.

Ps. As one of the moderators I am aware that (with my help) this thread has gone somewhat off topic by a good amount. Apologies. If the thread creator wishes to express opinion on if they would prefer the thread pruning. Please let me or Jon know.

Regards

Allan

Alan: " I don’t believe that removing the standard thrust washer and having an open void would allow more oil flow. "

oil like electricity (and myself) follows the path of least resistance . If you have a "open to atmosphere " gap more oil will flow through that gap than if you have a smaller gap.

Yep its way off topic now.

Thanks Stuart - that makes a lot of sense! I wasn't aware of the different oil pump worm directions until now.

Thanks everyone; despite the topic 'evolving' I think it is all very helpful and quite relevant for my own project and for anyone else who may find this later with a similar question to myself!

Really appreciate all of the input on this.

@AllanG - upon your positive report I ordered a set of MAP rods and have to say the experience was fantastic. I ordered two items that day; one from the UK, approx. 50 miles away. The other being the MAP rods in Florida.

The rods arrived on Monday morning, still waiting for the other item! (import fees were very 'reasonable' as you suggested) - almost too nice to put inside the engine!

After reading through this thread a few times, I'm going to go with the original Ball Bearing and plain bush setup, along with a new SRM oil pump. (I'll also be looking into either an SRM OPR or one of the mods described on this forum)

Mysterious:

Glad u didnt get pissed off about "thread evolving" some of us here are obsessive ( who would have thought) . We tend to get tunnel vision on details hahahah All of it was intended to be helpful .

Sounds like some rebuild u are doing ... we will of course require stage photos so we can argue about the thickness of the washers hahhah

Love that word ORIGINAL!

I would have a look at the oprv from LF Harris, or finding a NOS one, the SRM unit I bought now resides in bits scattered between the office and my garage.

I have what was a NOS piston type 50psi oprv on my Lightning, that’s still working fine. I have a 70psi LF Harris one on my big bore/long stroke thunderbolt OIF and have also used the ball and spring item from Lyford classics, whilst that’s all stainless it works fine, the ball is larger than the bsa type and feels like a bit more spring pressure too. That used to be on the Lightning and didn’t give me any problems. I only changed as the theory was piston types were better.



Lol. That was the reason why I thought we should take a break from the subject lol. It’s one of those where you could have that discussion at the start of your first pint and by 7am the next morning your totally sloshed still discussing a subject and wondering what you started discussing in the first place.

….. I still think I’m right though

Haven't checked in here in a while as my attentions have been diverted from Brits to (lowers voice)ahem, Harley flatheads.

However this is a topic i obsessed over here a couple years ago. At the time I just thought the roller bearing looked so much more substantial so that is
what I went with. Also I rather enjoy fiddling with spacers and dial gauges.

Quick general question. Is the plain timing side bearing on the A65 a weak link if one was to race at the extremes of a drag strip or
even a land speed attempt? Assuming adequate oil flow and pressure. Any real life stories to relate?
I always wondered about the lack of faith in this part of the design considering that rods (most) operate on plain bearings at both ends.

There is nothing wrong with the bush arrangement if oil is clean and plentiful. (A filter is essential)
A roller or needle is far more tolerant of dirt in the oil.
A roller or needle roller will be more tolerant of the flexing of the crank without wear.
Many older bikes have worn oil pumps so delivery pressure can be marginal for a bush.
Swapping to a needle race immediately frees up 30-40% of the pump requirement so
often a replacement pump is not needed.
To do the job either way is quite expensive so many blokes opt for a needle race.
A bush run with a filter and regular oil changes plus a reasonable pump should do 50k miles at least.
My own one has the original bush and has done 25k, oil light still goes out on the kicker.
The bush was blamed for owners incompetence/ignorance normally.
Just my 2c.

Nick H,

I believe pushrod Tom was still using a bush setup on his LSR Hornet.

Talking out of speculation but I think good crank balance would be kinder to a bush than a motor which vibrated quite a lot?

Nick H, This will not be a definitive statement but here is my story. In 2007 I obtained a well used A-50 to use as a LSR racer. Since then it has evolved into a 650. It has run with a turbocharger and, many times, with NOS as well. It has held up well for many dyno runs and passes down the course at 150+. Inside it still has the original bush, crank and rod journals. I have had both the MAP aluminum and steel rods. SRM pump and OPR. The crank/bush has +.003 clearance which, I think, helps to give room for the crank to flex. With 50wt. racing oil (Valvoline VR1) it will maintain 50#.
I don't think this would be best for a normal use street bike but for my application it has been very reliable.

Thanks for the insights!

My racing question was an "asking for a friend" type of question.
Pushrod Tom: So I guess the concern is a flexing crank could seize on the plain bearing so you gave a bit (just a bit) more clearance?

I assembled my Lightning for regular use reliability. Had the crank balanced here:

https://www.lindskog.com/automotive-balancing

Mainly they do cars but "Mike" there knows motorcycles. And the timing side bearing was fitted by a shop after I ruined one myself.
New Hepolite pump.

It's a "right ripper" as I like to say, sounds British.

Tom:

Great that u used NITROUS ... it wouldnt work for me , here is why. Guy I know built some enormous V8 for the strip with a Nitrous button .. by the time race day came the bottle was flat ...then he had the nerve to blame me! .... man i love that stuff ahhahaha ROFLMFAO

Should have refilled it with helium… then he would have had a better reason to blame you… and you could have said in a squeaky (helium enriched) voice “it wasn’t me”

Lol

I felt HE was partially to blame ! He did provide the bottle AND the diving regulator .... me ? I was just the innocent victim playing along ROFLMFAO

all was not lost ! he had a spare bottle that his mate was going to bring to the strip on race day ,,, from memory i think he ran 6.7?

I like how you think.