The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: mrshells on 10.05. 2009 00:18

Title: wheres my little end ?
Post by: mrshells on 10.05. 2009 00:18
Been out for a ride today and she developed a knocking
almost like a tappet rattle
which got worse !
much worse !
when I got her home  I found after removing the barrels
the little end had gone on the left hand cylinder
Really gone !
As in not there!!!
like some one stole it or forgot to put one in
I know it was ther when I built the motor last year ???? *conf*

I think i may have to wash it from the sump
Title: Re: wheres my little end ?
Post by: LJ. on 10.05. 2009 09:07
OH no! thats bad news... Hope you managed to get it all sorted out soon. Sorry I did not get to the Wolds run last week, I was away at an Old Pupils reunion lunch with the Missus down near Gatwick, I hear it was a great ride.  *sad2*
Title: Re: wheres my little end ?
Post by: rocket man on 10.05. 2009 14:10
ive never heard ove a little end wearing out in such a short time
was it a pattern one or an original carnt be too carefull these days
there are a lot ove substanderd parts out there
Title: Re: wheres my little end ?
Post by: shabashow on 10.05. 2009 15:36
I just finished rebuilding mine after the right hand little end broke into a thousand pieces. That was about 350 miles after its first rebuild! Some of it was still wedged between the conrod and piston.
The oil was a fine suspension of golden flakes, and there were a few scores on the crank. They  polished out ok. Everything needed stripping and cleaning.
Should have replaced the old one at that time, but, you live and learn.
If yours broke up, there should be pieces everywhere, especially on the screen filter in the sump.
Good luck in finding it!
John
Title: Re: wheres my little end ?
Post by: A10Boy on 10.05. 2009 19:54
Oh dear, thats bad news. If it broke up, there is going to be bits of it throughout the oil system. You will obviously need to strip the motor and clean it out. Bits of it are likely to be in the oil tank, pump, sludge trap and pressure release valve too.

Good luck.
Title: Re: wheres my little end ?
Post by: mrshells on 10.05. 2009 22:51
theres bits of bearing everywhere
my No 1 concern is that the rod isnt oval
dont know how long its been in there but it was there when i bought it 1500 miles ago
will order a new bush tomorrow and start stripping for a clean up
Summer is allmost upon us and I need to be riding it not looking at a pile of bits !!!
Title: Re: wheres my little end ?
Post by: rocket man on 11.05. 2009 21:27
good luck mate
Title: Re: wheres my little end ?
Post by: a10gf on 11.05. 2009 21:31
Quote
I need to be riding it not looking at a pile of bits !!!

I know the feeling. Best wishes.
Title: Re: wheres my little end ?
Post by: RichardL on 11.05. 2009 21:34
If it were me, I'd replace both bushes while I was at it. You might also want to wait on that parts order until it's apart, you are bound to need more.

I think you need to inspect and plastigage the big-end bearings.
Title: Re: wheres my little end ?
Post by: RichardL on 11.05. 2009 22:48
OK, I'm getting that "obsessed with the issue" feeling.

Why the left side and why at all? Obviously, oil starvation. But the left side has this little hole in the hollow of the rod that, some say, squirts oil on the side wall of the cyclinder to add lubrication on the left side. However, I think the hole is there, at least mostly, for allowing oil to flow through the crankshaft journal, for both big-end bearings, without being held back by air pressure in the crank or slow flow through those bearings. So, say it squirts on the cylinder wall and is scraped into the inside of the piston where it drools onto the gudgeon pin and lubricates the small end. Other lubrication mechanisms are splash and mist. Anyway, I am not coming to a conclusion here. I just wanted to get the ball rolling, discussion-wise, to be sure there is a diagnosis, such that another occurance is not in the offing. Minimally, I think, be sure the little hole is there and it's clear.

I look forward to hearing from you and others with hypotheses as to why the left and why at all?

Richard L. 
Title: Re: wheres my little end ?
Post by: bsa-bill on 12.05. 2009 09:24
Now then Richard , if the hole was there to allow oil flow it would not matter which way the hole faced.
It is written that it should face inward to the centre of the barrels, this would make sense in as much as there were apparently problems with the left side overheating and it would surely be the centre of the barrel that overheated?.

There now let debate continue.

All the best - Bill
Title: Re: wheres my little end ?
Post by: Dynamo Regulators Mike on 12.05. 2009 09:34
Richard, funny how many threads, especially of late, relate to oil system faults or weaknesses.

One thought is that the LH cylinder, even with the hole in the rod still gets less oil than the timing side piston which benefits from inevitable leakage around the timing side bush at high pressure (if you are lucky). It has been asserted that the LH big end gets less oil than the RH as it is further from the pump. But the symmetrical feed from the sludge trap tube makes a nonsense of this.
Looking forward to other insights . . . .
Title: Re: wheres my little end ?
Post by: RichardL on 12.05. 2009 13:36
Interestingly, billet rods from MAP (also sold by SRM) do not include the little hole, as they say "don't need it." (Loosely quoted.) I couldn't live with the idea that the likes of Roland Pike probably thought the hole was needed, so I drilled my own.

Also, the billet rods do not have bronze bushes. The gudgeon rides on the aluminum.

Richard L.
Title: Re: wheres my little end ?
Post by: beezalex on 12.05. 2009 14:21
I'm thinking that the "High performance" rods (carrillo rods don't have holes either) don't have the oil hole because it creates a stress point and likely starting point for cracks.  A high-revving motor should also have enough spray to keep the DS bearing and cylinder wall properly lubricated.
Title: Re: wheres my little end ?
Post by: RichardL on 12.05. 2009 15:10
Alex,

I think that means I did the right thing in drilling the hole, as I've no intention of revving to racing speeds.

Richard L.
Title: Re: wheres my little end ?
Post by: groily on 12.05. 2009 17:46
Sounds to me like a one-off failure caused by the bush starting to rotate in the rod. Wonder what sort of fit the gudgeon pin was when it was put together? Not sure with these engines whether, per book, the pin 'should' swivel on the piston, in the eye, or both. Personally, I like them to be a close sliding fit in the little end, and a tight one in the pistons when cold (in my world, that's where a rag soaked in boiling water wrapped round the piston for a couple of mins is enough to allow the pin to move without the application of undue force). But there be varying opinions on the subject, I know.
 
Were it me, I'd just strip and clean everything - and then clean it again - with special attention to the oil tank, lines, drillings, traps etc and liberal use of compressed air, have the rods checked for ovality at the little ends, fit new bushes and ream them if necessary to get a no-play sliding fit (which takes just modest finger power to push the pin in and out). Plus check the gudgeon pin(s) very carefully for damage on any bearing surface, ditto piston. Replace as necessary, erring on the side of paranoia.
 
Reassemble and cross fingers for better luck. The which I wish you!
Title: Re: wheres my little end ?
Post by: Richard on 12.05. 2009 19:05
I notice one thing that no one has yet mentioned the timing side bush if this is worn then oil pressure will be down, resulting in less oil getting to the left side.How I was told to do a quick check my the original Mr SRM was to remove the timing side cover and see if there was any up and down movement on the crank.
Its worth checking anyway.
The hole in the left hand rod was not there on the early engines but was included later with the thought that this would splash some oil in the bore and aid lubrication
IKBA applies
Richard
Richard
Title: Re: wheres my little end ?
Post by: A10Boy on 12.05. 2009 19:49
Its enough to make yer brain hurt.....
Title: Re: wheres my little end ?
Post by: mrshells on 12.05. 2009 21:02
If it were me, I'd replace both bushes while I was at it. You might also want to wait on that parts order until it's apart, you are bound to need more.

I think you need to inspect and plastigage the big-end bearings.

Did plastigage exist in 1952 ?
rod measures up No play in the big ends OK so its 2 new little end bushes which were £6.50 each from dragonfly
the dearest bit was the reamer to get the bushes to the right size
a good flush of the oil tank pump etc
then its back on the road
Title: Re: wheres my little end ?
Post by: bsa-bill on 12.05. 2009 21:15
My crank was tested out of the bike by local machine shop and they commented they could not get equal flow to both sides - left side had less.
Wonder if it has something to do with centrafugal force combined with the sludge trap -  don't know ?
I got a nice set of reamers from RGD tools ( might be RDG even ) about nine or so in the set I think all adjustable - cost about 35 pounds or so,
I needed two gearbox bushes reamed and reckoned it would cost me around that to get it done in a shop so might as well have the set.
Do google for RDG or RGD and have a look

All the best - Bill
Title: Re: wheres my little end ?
Post by: groily on 12.05. 2009 22:09
RDG or RGD even do good stuff . . .  for the money  - I bought a couple of their boxed sets a while back and have done a fair few bushes with them since.
It wasn't until I was lent a serious (adjustable) reamer from a machine shop (for a swinging arm) that I realised how these cheap things compare with professional tooling . . . truly no comparison even though they work.
But anyway, several (gearbox) jobs done and so far, plus one little end, and no problems. Classic case of 'You get what you pay for'?
Title: Re: wheres my little end ?
Post by: RichardL on 12.05. 2009 22:20
Groily,

I know this is runnin' wild off the topic, but did you need the reamer for the swingarm because the inside bushes didn't line up after busting a blood vessel to get the silent-blocs in place. Anyway, that's why I bought one.

Richard L.
Title: Re: wheres my little end ?
Post by: mrshells on 19.05. 2009 23:41
found it !!! *smile*!!!
any one good at brazing ?
need this lot putting back together !!!! *smiley4*
Title: Re: wheres my little end ?
Post by: groily on 20.05. 2009 07:13
Blimey! Now that's a jigsaw puzzle! Good to have found (some of) it though . . . I suppose!

Re reamer Richard, it was actually for a Velo single swinging arm and was borrowed from an engineering shop - lovely thing and probably worth more than the 2 whole boxed sets I got from RDG! Touch wood haven't had to replace any BSA s/arm bushes .. . a bridge to cross in due course no doubt!
Title: Re: wheres my little end ?
Post by: rocket man on 24.05. 2009 20:20
looks like most ove it but is there eny more left in the oil passege ways
you can never be too carefull its worth stripping it down if youve removed
barrels and head why not go the whole hog then you will know for sure
Title: Re: wheres my little end ?
Post by: MikeN on 24.05. 2009 21:43
Have you measured the bore in your con-rod little-end eye yet? I hope its not been damaged by the pin rattling up and down and your new bush is a good fit.
Mike
Title: Re: wheres my little end ?
Post by: mrshells on 30.05. 2009 18:58
got her all back together now
Ive done about 50 miles and all seems ok  *smile*
Title: Re: wheres my little end ?
Post by: rocket man on 30.05. 2009 19:05
good luck did you strip down crank cases to see if
there is eany more bits left in her i would have done that just to be on the safe side
and is your little ends alright because if there is eany play there
the same thing will happen again