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#597012 - 04/28/15 11:42 am oil hole in A10 left rod to spray cylinder?  
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zoe Offline
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The stock left hand, A10 connecting rod has a small hole (about .050") to spray oil on the cylinder wall. At least one brand of aftermarket rods I've seen do not have that hole. How important is this hole? It would be pretty difficult to drill that hole accurately with home tools.

What to do?

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#597014 - 04/28/15 12:06 pm Re: oil hole in A10 left rod to spray cylinder? [Re: zoe]  
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kommando Online content
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Don't drill the hole as it will weaken the con rod, if you are worried about piston oiling then file 2 shallow and wide slots either side of the top of the big end to direct the oil coming from the big end upwards. The slots should not be deep enough so you can see the bearing back.

#597035 - 04/28/15 4:28 pm Re: oil hole in A10 left rod to spray cylinder? [Re: zoe]  
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Allan Gill Offline
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The thunder rods in my A65 don't have the oil hole ( the stock ones did) the bike see's some RPM's and the lack of an oil hole hasn't been an issue.


beerchug
#597079 - 04/29/15 2:16 am Re: oil hole in A10 left rod to spray cylinder? [Re: Allan Gill]  
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zoe Offline
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That's interesting, Allan, because I've been corresponding with Steve Campbell, of Thunder Rods, and he says they put that hole in their rods. R&R and MAP don't drill the hole for strength reasons. MAP did mention the slots or grooves Kommando discussed.

One of these guys says Norton puts a hole in both rods and I think they said Triumph uses one like BSA.

Sounds to me like it's six to one and a half dozen for the other. I guess I'll have to make up my own mind as they seem to work either way.

#597080 - 04/29/15 2:29 am Re: oil hole in A10 left rod to spray cylinder? [Re: zoe]  
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Allan Gill Offline
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I have a set of A10 rods from them waiting for my next project. Just looking at them, one rod does have a single drilling hole. I will have to consult photos of the A65 to confirm my last statement. From memory I couldn't see any at the time (they were bought about two years ago)


beerchug
#597089 - 04/29/15 5:01 am Re: oil hole in A10 left rod to spray cylinder? [Re: Allan Gill]  
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Ian Clifton Offline
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Originally Posted By Allan Gill
The thunder rods in my A65 don't have the oil hole ( the stock ones did) the bike see's some RPM's and the lack of an oil hole hasn't been an issue.


We'll test that theory on the road to Denmark!! laughing


Just a few Beezers.. ☺

#597092 - 04/29/15 5:55 am Re: oil hole in A10 left rod to spray cylinder? [Re: Allan Gill]  
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This oil holes in the conrods is interesting. BSA said that the fitting of the D/S conrod should be fitted with the hole towards the flywheel. I think later rods had an exit hole on both sides. One reason was for cylinder lubrication, another reason I read somewhere was to promote flow to the D/ S crank journal!
Now, on 750 Norton twins, the spray holes face to the outside of the engine!
I think Triumph 650's had conrod holes for a short time ( one year?) in the mid sixties for extra cylinder lubrication, but this was soon ommitted when increasing the residual oil in the crankcase ( by shortening the pickup tube ) achieved the same thing.

#597109 - 04/29/15 8:43 am Re: oil hole in A10 left rod to spray cylinder? [Re: zoe]  
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Mr Mike Offline
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Drilling holes in rods was a fairly common practice in many earlier engines...not just motorcycles. It's purpose was to oil the cylinder by providing a timed squirt when the crank drilling lnes up with the drilled hole. I have seen it described in a couple of old engine rebuild books I have. You don't see it anymore so it was either ineffective or improved lubrications systems made it unnecessary.

My A65 has two holes in both rods.

Mr Mike

#597114 - 04/29/15 9:40 am Re: oil hole in A10 left rod to spray cylinder? [Re: zoe]  
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Blown Income Offline
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The MAP rods I have in my A10 have no oil hole. I have not had an issue either without the hole.


1955 BSA Bantam D1 Plunger
1956 BSA A10RR Street and LSR Bike
1961 BSA C15S
1966 BSA spitfire
1969 Triumph T100C
1970 Triumph TR6R
1972 BSA Lightning LSR Bike
1974 Triumph T150V
#597115 - 04/29/15 9:54 am Re: oil hole in A10 left rod to spray cylinder? [Re: Blown Income]  
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photobob Offline
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Found this amongst some stuff


The text with it on another page reads "EXTRA OIL Should an engine suffer from oil starvation in the left hand cylinder, drill a 3/64 in. diameter hole, at an angle of 30degrees through the connecting rod web and into the middle of the big end bearing. The rod should then be refitted with the drillway facing the flywheel. This is a major operation,but with care, it can be done by the private owner when carrying out a strip down. Full details are given in Service Sheet No. 116, obtainable free from the service department." I have been unable to locate that service sheet anywhere. My 1963 A65 does have the hole in the left hand rod and so does my 1956 A7 both done when the bikes were new.

Last edited by photobob; 04/29/15 10:00 am.
#597125 - 04/29/15 11:53 am Re: oil hole in A10 left rod to spray cylinder? [Re: photobob]  
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Thanks to you all for the good information.

#597154 - 04/29/15 3:01 pm Re: oil hole in A10 left rod to spray cylinder? [Re: Ian Clifton]  
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Allan Gill Offline
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Originally Posted By Ian aka Frank
Originally Posted By Allan Gill
The thunder rods in my A65 don't have the oil hole ( the stock ones did) the bike see's some RPM's and the lack of an oil hole hasn't been an issue.


We'll test that theory on the road to Denmark!! laughing


There's always one, isn't there!!! grin

I can't understand the publication stating they were trying to promote lubrication, if you look at the crank cases ( in the areas which are catch fed) some have very small wells and some have none at all, noting specifically the camshaft and idler gear bushing areas.


beerchug
#597229 - 04/30/15 6:32 am Re: oil hole in A10 left rod to spray cylinder? [Re: photobob]  
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SERVICE SHEET NO. 116. Models a50/a65 engine lubrication. DATED FEBRUARY 1965.

#597230 - 04/30/15 6:34 am Re: oil hole in A10 left rod to spray cylinder? [Re: mr.moto]  
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and the first page
The fact that this is dated 1965 suggests that the first a65 models did not have the hole.

Last edited by mr.moto; 04/30/15 6:35 am.
#597265 - 04/30/15 12:07 pm Re: oil hole in A10 left rod to spray cylinder? [Re: mr.moto]  
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zoe Offline
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FWIW, the hole in my stock A10 rod is about .048", i.e. a .047" drill will go through it with a little room but an .050" drill will not. That's pretty close to 3/64".

I doubt I could drill an .047" hole in my MAP aluminum rod without breaking the drill bit off.

Last edited by zoe; 04/30/15 12:09 pm.
#597270 - 04/30/15 12:35 pm Re: oil hole in A10 left rod to spray cylinder? [Re: zoe]  
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kommando Online content
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The hole in the A65 was added to cure driveside piston seizures, however this was masking the real issue which was the 4CA ignition which was causing extra sparks from the points bouncing off the points cam more than once per rev, the 6CA cured this by increasing the dwell on the cam so no extra bounces and made the 2 sets of points independently adjustable as well. So as long as you are not still running 4CA points cam and are instead using the 6CA you do not need the hole.

#597279 - 04/30/15 1:48 pm Re: oil hole in A10 left rod to spray cylinder? [Re: kommando]  
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kommando, that is interesting. Does this suggest that tha a7/a10 got the hole for the same reason? Here is service sheet no.140 a50/a65 extended dwell ignition cam dated september 1966.
As I run an a10 with rita ignition does this mean I can do away with the oil hole?

#597282 - 04/30/15 1:56 pm Re: oil hole in A10 left rod to spray cylinder? [Re: zoe]  
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kommando Online content
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Quote:
Does this suggest that the a7/a10 got the hole for the same reason?


There is nothing to suggest the A7/A10 had an extra spark on any service bulletin, an expert on Magnetos would be better placed to know if extra sparks could be made on a magneto by the points bouncing and adding extra sparks as it can do with coil ignition.

As the hole creates a weakness and shallow slots in the sides of the con-rod achieves the extra oiling I would never add a hole to an undrilled con-rod. I would even fit an undrilled top shell bearing to a drilled con-rod as you preserve all the oil for the bearing and the slots direct the oil upwards for the piston.

#597309 - 04/30/15 6:37 pm Re: oil hole in A10 left rod to spray cylinder? [Re: zoe]  
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now that's realy strange ...pre 65 A65 didn't have the hole according to above , and yet the A10 did . They must have stopped having it for a few years very strange.

the other thing is that in the parts book the hole is shown facing the other way, so you guessed it that's how I set it in my A10 rebuild. So far so good.


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
#597316 - 04/30/15 8:05 pm Re: oil hole in A10 left rod to spray cylinder? [Re: zoe]  
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I suspect the drilled hole was likely ineffective. In theory there is only a momentary squirt of oil thru this drilling as the crankshaft drilling lines up. 99% of the oil still exits thru the edges of the bearing. IMO the lubrication system of the A50/65 was marginal at best. Poor pumps without robust volume, suspect OPRV's, and a BSA repair procedure that did not encourage align boring to fit and clearance new bearings. People have complained about low oil pressure since the sixties. You just cannot have a light weight, high compression engine making 40-50 horse power to last with low oil pressure especially when young kids are snatching the throttle after every gear change.

As far as the "maverick spark" goes, I do not deny it may have been a problem that needed to be fixed, but I find it to be unlikely that BSA had lots of catastrophic engine failures because of this spark.....it is oil pressure...or lack thereof that causes seizures and broken rods.

Mr Mike

#597324 - 04/30/15 9:13 pm Re: oil hole in A10 left rod to spray cylinder? [Re: zoe]  
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As lots of people are voicing their opinions, thought I'd do the same based on personal experience.

Over the years I have seen quite a few blown up beezer A10 and A65 engines, i have never seen a rod broken at the point where the oil hole is drilled.

What I have seen is this sort of result.
If you drain the oil out or starve the crank of a beezer or the like and ride it, it will seize the drive side piston up before it runs an end. It will then break that rod normally putting it through the case.

I have raced an a65 with the standard bearing set up as 650 and 750 and never experienced oil pressure related problems. I also did many thousand miles on an A10 with a standard bottom end with no oil pressure related problems. Both of these bike were treated with some brutal ferocity.
The oil was however, changed regularly and despite no filter being fitted they survived.

Perhaps everyone who is riding an A10 or an A65 with a standard factory bottom end should stop now and put their bikes into storage for fear of low oil pressure problems? or better still, give them to me as I don't mind riding a bike with 30psi pressure despite others opinions.
There is a lot of things that, in an ideal world could have been improved upon with beezers, but the same could be said for any bike of the period produced for a price.

Last edited by NickL; 04/30/15 9:15 pm.


#597365 - 05/01/15 6:09 am Re: oil hole in A10 left rod to spray cylinder? [Re: zoe]  
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I agree with the driveside on twins having less oil, its the same on Norton's and Triumph's. Trouble is the way to fix the problem is not to open up the driveside bearing to release more oil but to reduce the hole in the timing side big end journal the correct amount so that the oil flow to both big ends is balanced as is the bearing oil film thickness. The factory would not be aware of this solution at the time, the engineers at Glacier did exercises to sort out such problems later once computers were faster and the software was written, this software simulated the oil film thickness based on the engine design and came up with recommendations on hole sizes and also where they need to be on the journal but this was only first available in the 80's. Results were confirmed with lab tests run on samples of cranks and con rods with the various configurations.

#597381 - 05/01/15 10:02 am Re: oil hole in A10 left rod to spray cylinder? [Re: kommando]  
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If the early A65 did not have the hole drilled in the con rod then it must have been the first batch off the assembly line. My A65 is a 1963 model but it left the factory in October 1962 as shown in the dispatch records and it has the hole. I know that when I purchased the bike only the top half had ever been dismantled the bottom end had never been stripped down until I stripped it, and to this day the bike still has the original BSA standard pistons fitted and there is no stepping on the bores. Whilst I can't prove the mileage on the speedo when I bought the bike which was showing approx 10,000 miles I do have documentary evidence that shows that in it's first 10 years it only did 4,000 miles and when I stripped it down the wear in the engine was consistent with the mileage on the speedo.

#597462 - 05/01/15 8:00 pm Re: oil hole in A10 left rod to spray cylinder? [Re: photobob]  
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Way,way,way more info. than I thought I would get on this subject but I thank you all.

1. to drill or not to drill my gorgeous MAP alloy rods

2. Rod failure has occurred but not at the "3/64" hole"

3. Why create a stress riser in my new rods?

4. one instance of the D/S rod installed by the factory with the hole facing out rather than towards the flywheel.

5. Can I drill that 3/64" hole without breaking off a drill bit?????

6. can the inside of that hole be burnished or polished so as not to create a stress riser?

7. My stock rods have nicks, numbers stamped into them, the hole, etc., etc. and they are still in one piece.

I'm getting itchy to get this beast back together so I will decide soon and go with it.

#597489 - 05/01/15 9:58 pm Re: oil hole in A10 left rod to spray cylinder? [Re: zoe]  
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When I bought my 72 t'bolt I stripped it and found that neither rod had any oil holes. The bike had done less than 4k miles and had never been serviced let alone stripped down so it was like that from the factory. I have seen plenty with holes though.

Don't bother drilling the hole if fitting new rods. If they come with the hole use it don't block it off.
If you feel keen and the hole is not there, file the slots like Kommanndo says, that is a better way.



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