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Rocker Arms #775195
05/30/19 9:30 pm
05/30/19 9:30 pm
Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
V
VANDOLSON Offline OP
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VANDOLSON  Offline OP
BritBike Forum member
V

Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
After getting schooled on BSA part numbers blush
I have a question on rocker arms. My bike was running
when I bought it and tore it down. The rocker arms are
different part numbers than what is in the BSA parts
list manual and no issues with that now that I know
more about BSA part numbers.

My question on rocker arms is that my rocker arms
all have MF A4 or A3 or A2 on them after the part
number. Is that like a revision number or what?

Also I bought an intake rocker arm that was suppose
to be 68-0147 (the same number as listed in the parts
list manual for the left intake rocker arm). What I got
was a rocker arm part number 68-0150 but it had
no MF stamped after it. The left intake rocker arm
I have is stamped 68-0150 MF4. The strange thing
is the one I bought the length of the arms are
shorter by a good quarter inch??! Both are stamped
68-0150? Anyone know why they are not the same
size? Need more expert help on this. Shouldn't
both be the same size? The seller (besides saying
the rocker was a 68-0147...had a tag on it in
the picture) said it was for all A65's. Is this an earlier
A65 rocker arm and not for my 1971?

Thanks,

Van

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Re: Rocker Arms [Re: VANDOLSON] #775196
05/30/19 9:39 pm
05/30/19 9:39 pm
Joined: Aug 2001
Posts: 4,527
argyll. scotland, uk
gavin eisler Online content
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gavin eisler  Online Content
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Joined: Aug 2001
Posts: 4,527
argyll. scotland, uk
The marks on BSA motor parts are NOT "part numbers" , they are manufacturing numbers, sometimes they bear a near relation to the actual part numbers, but they seldom/ never directly cross relate .

If the part fits , use it. AFAIK all years A65 rocker arms are the same. Inlet rockers have different length arms from exhaust rockers, each inlet rocker is the mirror of the other, same for exhaust..

The number you see on a rocker arm would be for the forged part before machining and adding the pushrod button. I dont know about the MF4 variation and why its longer, might be from a unit single? Guessing., your label ?
My 71 uses the same rockers as the earlier heads. Maybe the MF4 is a tune up part for greater lift? You would need a marched pair , and check the valve tip isnt being miss hit.

I have some old rockers in the loft , next time I am up I will peer at the numbers

Last edited by gavin eisler; 05/30/19 10:03 pm.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: Rocker Arms [Re: VANDOLSON] #775209
05/30/19 11:00 pm
05/30/19 11:00 pm
Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
V
VANDOLSON Offline OP
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VANDOLSON  Offline OP
BritBike Forum member
V

Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
okay thanks. Learned some more about stamped numbers
on parts. My intake rockers are both the same length and
and match but with different MF numbers. One is an A4 and
one is an A2. On the exhaust which are both the same length
one is MF A4 and one is an A3. Dunno what that means so
reason I am asking. But strange that the one I bought has
shorter length arms than what I have. I assumed the engine
is stock although I did not check out the cam. Just put it
back in. Appreciate you checking.

Re: Rocker Arms [Re: VANDOLSON] #775219
05/31/19 1:30 am
05/31/19 1:30 am
Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
V
VANDOLSON Offline OP
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VANDOLSON  Offline OP
BritBike Forum member
V

Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
I should quit referring to the numbers that are stamped as part numbers. Old habit
from my Harley days. I learned there is no real relationship. I was more interested in
what the MF A2, A3, and A4 stamps meant and if I really have matched pairs. Your comment
about maybe they might be tune up parts for a greater cam lift got me to put my intake rocker
arms with different A numbers stamped on them side by side and really look close.

What do you know?! They are slightly different. push rod cup angles along with a slight arm
curvature difference. Found the same when comparing the exhaust rocker arms that have
different A numbers. My rocker arms are definitely not a match set. Might explain my coil
binding. I had talked to SRM Engineering about my coil binding and the service tech I talked
to was at a loss also. The bike was running so .... I went ahead and ordered SRM valve
springs from them anyway. Guess now I have to pull the cam back out to see what cam it
really is. Might not be a stock cam as I thought. I want a stock cam and correct matched
rocker arms for my 71. Guess the hunt is on for replacement rocker arms. The one I
bought which was shorter than mine might be the correct type for stock and the ones in
the bike are not stock. For sure the the ones from the bike don't match each other. Know that now.

Thanks again

Re: Rocker Arms [Re: VANDOLSON] #775220
05/31/19 1:45 am
05/31/19 1:45 am
Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
V
VANDOLSON Offline OP
BritBike Forum member
VANDOLSON  Offline OP
BritBike Forum member
V

Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
What started this was the engine was assembled and
I decided to pull the dual points out and install the
Pazon ignition. When turning the engine over to set timing
I heard a clacking noise under the rocker cover. Pulled
the cover and found that the rocker arms would not
move any further when the springs were depressed all
the way even though the tappet adjustment was set
for .008 for intake and .010 for exhaust. Also another
thought I aligned my cam timing for a stock cam. A higher
lift and/or duration might mean the cam timing might
be off a tooth or so for a different cam? Dunno. It
would be for a Harley. Jeez. Got to pull the cam
now. I just want stock.

Re: Rocker Arms [Re: VANDOLSON] #775221
05/31/19 1:51 am
05/31/19 1:51 am
Joined: Dec 2002
Posts: 459
Chelmsford MA
M
MarcB Offline
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MarcB  Offline
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M

Joined: Dec 2002
Posts: 459
Chelmsford MA
I went and looked at my exhaust rockers and have no numbers or letters on them whatsoever, casting or otherwise. I'll be happy to measure them for you if you'd like. Let me know which measurement you're looking for. Mine are from a 68 Spitfire and are likely original to the motor.

Re: Rocker Arms [Re: VANDOLSON] #775240
05/31/19 6:45 am
05/31/19 6:45 am
Joined: May 2013
Posts: 5,594
West Yorkshire
Allan Gill Online happy

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Allan Gill  Online Happy

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Joined: May 2013
Posts: 5,594
West Yorkshire
Vandolson. Take a deep breath...

Only an A65 cam will fit into an A65, providing you bought t from a reputable supplier then the timing marks on the teeth should place the cam in the correct position. There are some crank pinions which advance the cam by about a tooth and a half (the dot is almost over the key way slot). A good way of checking is the key way on the crank should be bolt upright in this position the dot should align with the idler gear and the idler gear should almost align with the cam marking... or at least would if the crank was rotated to allow this.

Before stripping the crank cases, invest in a dial gauge and timing disk for the end of the crank. This job is easier done with the head off but can be done without. Find true TDC initially. Set up a pointer and align it with zero on the disc, then set your dti on the push rod in turn, rotate the engine until the dti is showing the cam at its lowest point (follower on the base circle of the cam) then rotate the engine slowly forwards. Until you find 0.080” of lift and mark the degree position of the crank on the timing disk, keep going until you find 0.080” if lift before the base circle. Mark the value again. Do this for all 4 pushrods. You should have 8 different figures. If you do this I am happy to work out which cam you have. Or you can visit the webcamshafts website and it will do it for you.


beerchug
Re: Rocker Arms [Re: Allan Gill] #775253
05/31/19 12:25 pm
05/31/19 12:25 pm
Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
V
VANDOLSON Offline OP
BritBike Forum member
VANDOLSON  Offline OP
BritBike Forum member
V

Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
Originally Posted by Allan Gill
Vandolson. Take a deep breath...

Only an A65 cam will fit into an A65, providing you bought t from a reputable supplier then the timing marks on the teeth should place the cam in the correct position. There are some crank pinions which advance the cam by about a tooth and a half (the dot is almost over the key way slot). A good way of checking is the key way on the crank should be bolt upright in this position the dot should align with the idler gear and the idler gear should almost align with the cam marking... or at least would if the crank was rotated to allow this.

Before stripping the crank cases, invest in a dial gauge and timing disk for the end of the crank. This job is easier done with the head off but can be done without. Find true TDC initially. Set up a pointer and align it with zero on the disc, then set your dti on the push rod in turn, rotate the engine until the dti is showing the cam at its lowest point (follower on the base circle of the cam) then rotate the engine slowly forwards. Until you find 0.080” of lift and mark the degree position of the crank on the timing disk, keep going until you find 0.080” if lift before the base circle. Mark the value again. Do this for all 4 pushrods. You should have 8 different figures. If you do this I am happy to work out which cam you have. Or you can visit the webcamshafts website and it will do it for you.


Thanks! I did not replace the cam that came in the bike. I cleaned the cam up and just aligned everything IAW the BSA Workshop manual exactly has you
stated. Thank you for telling me how to check what cam I have. VERY MUCH APPRECIATED. I did not want to split the cases again. I will certainly do
as you suggested. Again, thank you so much!

Re: Rocker Arms [Re: MarcB] #775255
05/31/19 12:33 pm
05/31/19 12:33 pm
Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
V
VANDOLSON Offline OP
BritBike Forum member
VANDOLSON  Offline OP
BritBike Forum member
V

Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
Originally Posted by MarcB
I went and looked at my exhaust rockers and have no numbers or letters on them whatsoever, casting or otherwise. I'll be happy to measure them for you if you'd like. Let me know which measurement you're looking for. Mine are from a 68 Spitfire and are likely original to the motor.


Interesting. I hate to bother you with this but would appreciated it. I am looking for the length of the arms from the tip to tip. Just need you to lay an exhaust
and also an intake rocker flat and use a straight edge ruler to measure tip to tip. The one I bought is almost 1/2" shorter than the ones I have in length
tip to tip (only need ball park measurement). At work now, but after work I can send you what I have for the shorter one I bought and the ones on the
bike. Then if you can let me know if the shorter one is close to what you have, that tells me the ones in the bike are not stock rocker arms...thanks so
much for the help. As stated, first ever BSA. Been riding 49 years now with 36/37 of those years just Harleys. So all this about stamped numbers, no
stamped numbers, not being related to part numbers, etc was at first confusing. I think I got it now...don't worry about stamped numbers...

Re: Rocker Arms [Re: VANDOLSON] #775258
05/31/19 2:21 pm
05/31/19 2:21 pm
Joined: May 2013
Posts: 5,594
West Yorkshire
Allan Gill Online happy

BritBike Forum member
Allan Gill  Online Happy

BritBike Forum member

Joined: May 2013
Posts: 5,594
West Yorkshire
Originally Posted by VANDOLSON
Originally Posted by Allan Gill
Vandolson. Take a deep breath...

Only an A65 cam will fit into an A65, providing you bought t from a reputable supplier then the timing marks on the teeth should place the cam in the correct position. There are some crank pinions which advance the cam by about a tooth and a half (the dot is almost over the key way slot). A good way of checking is the key way on the crank should be bolt upright in this position the dot should align with the idler gear and the idler gear should almost align with the cam marking... or at least would if the crank was rotated to allow this.

Before stripping the crank cases, invest in a dial gauge and timing disk for the end of the crank. This job is easier done with the head off but can be done without. Find true TDC initially. Set up a pointer and align it with zero on the disc, then set your dti on the push rod in turn, rotate the engine until the dti is showing the cam at its lowest point (follower on the base circle of the cam) then rotate the engine slowly forwards. Until you find 0.080” of lift and mark the degree position of the crank on the timing disk, keep going until you find 0.080” if lift before the base circle. Mark the value again. Do this for all 4 pushrods. You should have 8 different figures. If you do this I am happy to work out which cam you have. Or you can visit the webcamshafts website and it will do it for you.


Thanks! I did not replace the cam that came in the bike. I cleaned the cam up and just aligned everything IAW the BSA Workshop manual exactly has you
stated. Thank you for telling me how to check what cam I have. VERY MUCH APPRECIATED. I did not want to split the cases again. I will certainly do
as you suggested. Again, thank you so much!



No problem, the method was written pretty quickly this morning so whilst it contain everything you may pick out something I haven't been clear on when performing the method, if this is the case just drop a message and I will elaborate further. otherwise glad to be of help.


beerchug
Re: Rocker Arms [Re: VANDOLSON] #775259
05/31/19 2:22 pm
05/31/19 2:22 pm
Joined: Dec 2002
Posts: 459
Chelmsford MA
M
MarcB Offline
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M

Joined: Dec 2002
Posts: 459
Chelmsford MA
I don't have my intake rockers on hand (head is at the machinist, and I didn't remove the intake before dropping it off) but I'll get you the exhaust measurements to start. I've never heard of A65 rockers being offered in different ratios so if you have different sets, they may be from A50. I don't know much about the smaller motors but do know the pushrods were different length so you may also want to check those as well.

I've also got an old Harley Sportster and can tell you that casting numbers on cases, cylinders, and heads are not always part numbers on those either.

Re: Rocker Arms [Re: VANDOLSON] #775262
05/31/19 3:20 pm
05/31/19 3:20 pm
Joined: Aug 2001
Posts: 4,527
argyll. scotland, uk
gavin eisler Online content
BritBike Forum member
gavin eisler  Online Content
BritBike Forum member

Joined: Aug 2001
Posts: 4,527
argyll. scotland, uk
Dug out some rockers.
The exhaust rockers are ~80 mm tip to tip across the diagonal.
The inlet rockers are ~ 64 mm tip to tip.

One ex rocker has an A2 suffix , the other an A1. All my inlet rockers are polished so no numbers.
last pic is the general arrangement..
let me know if you need any more dims before I re stash these bits.

Attached Files
IMG_1200.JPG (147 downloads)
IMG_1201.JPG (149 downloads)
A65 exhaust rocker
IMG_1202.JPG (153 downloads)
IMG_1204.JPG (160 downloads)
IMG_1208.JPG (156 downloads)

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: Rocker Arms [Re: VANDOLSON] #775354
06/01/19 12:33 pm
06/01/19 12:33 pm
Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
V
VANDOLSON Offline OP
BritBike Forum member
VANDOLSON  Offline OP
BritBike Forum member
V

Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
Perfect! Got the same length on diagonal you got on
the exhaust and intake. The intake I bought stamped
68-150 is 65mm on diagonal? Now wonder what that
is for!? Seller advertised it was for all years A65 AND
A50....Interesting. Also nice to see you have arms
also with the MF A2 stamped. Guess will never know
why what that means but doesn't matter it appears.

Probably means cam is stock now however I will check
will degree wheel and bounce degrees against what
is in the service manual just for piece of mind. It was
the coil binding cause that led me to question the
rockers and cam. I know the stem height checked
out and the valve seats were not cut/ground. Possibly
just the springs. Order new ones from SRM.

Having restored two old iron head Sportsters I agree
with what you said about possible stamps on cases
barrels and heads (and primary covers/timing/transmisson
covers). Internal parts with stamps usually match the
parts list). There are exceptions depending on year
of bike. With BSA seems to me nothing matches. LOL.
Well that is why I ask people here on the forum.

Thank you again for your time and effort. Very much
appreciated!



Re: Rocker Arms [Re: VANDOLSON] #775358
06/01/19 1:03 pm
06/01/19 1:03 pm
Joined: Aug 2001
Posts: 4,527
argyll. scotland, uk
gavin eisler Online content
BritBike Forum member
gavin eisler  Online Content
BritBike Forum member

Joined: Aug 2001
Posts: 4,527
argyll. scotland, uk
If you are getting coil bind then there are a few possibilities, most likely either the valves are too short, the wrong springs are fitted , or ( this happened to me) some one fitted oversize inlet valves which now sit further into the head leaving less room for the spring. The critical dimension for inlet valves is the stem tip to alloy spring well . This was mentioned in another recent thread , if its significantly less you will get coil bind.
Edit.
Critical dimension.
Valve tip to valve spring pocket, should be 1.730" - 1.750".

These dimensions work for my 71, not sure about earlier models.

Last edited by gavin eisler; 06/02/19 8:53 pm.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: Rocker Arms [Re: VANDOLSON] #775615
06/04/19 4:28 pm
06/04/19 4:28 pm
Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
V
VANDOLSON Offline OP
BritBike Forum member
VANDOLSON  Offline OP
BritBike Forum member
V

Joined: Sep 2017
Posts: 53
Windsor, Virginia, USA
Sorry didn't get back to you sooner. Thanks for all the
assistance. Will look at what you describe.


Moderated by  Allan Gill, Jon W. Whitley 

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