Ignition timing Again! an Irish solution????

[chaterlea25]

Hi All, having read a good few threads regarding ignition timing on the forum, there seems to be
a fair bit of differing information  out there
Attached is a copy of the BSA service sheet 216 revised 1963, which Should be the correct settings
According to this A10 RR and SR should be set at 3/8in fully advanced
When I built my SR engine I set up the degree disc with the head off and a dial gauge on the piston top
I worked out that 3/8in. (0.375) is 35.5 degrees before TDC.
I then fitted the head and again used a dial gauge fitted into the body of an old sparkplug to measure the angular distance in line with the plug hole this was 0.412in so if you only have an ordinary TDC tool this is the figure.
I have had a fair few issues with the mag since I put the bike together including 2 slipring failures
so I have had to reset the timing a few times (too many)
I found it awkward to use the dial gauge with the adaptor with the tank on, so I came up with another gizmo!!

Again an old sparkplug body I brazed a piece into the top of it then drilled and tapped the whole way down through it for a 10mmm bolt, I rounded the end of the bolt in the lathe where it meets the piston,
With a little setting up the bolt now stops the piston exactly at 0.375 before TDC,
It is held from moving with the locknut, 

I am changing the K2F magneto to a BTH that I have had rebuilt  (I have a thing for BTH's)
so I will be using my gizmo again after the weekend

Regards
John O R

[Richard]

John
When the service sheet was written we had a different grade of fuel and at 35.5 degrees pinking was not an issue, now with a lower grade of fuel a lot of, for want of a better word A10 experts recommend 5/16ths BTDC fully advanced I think this relates to about 31 or 32 degrees.
I set mine up without the head on by bolting a flat bar across the barrels raised slightly with equal spacers and a disc attached to the crank
by setting the pistons to tdc first then using a vernier set to about an inch I turned the engine back and then forward until the pistons came up to the vernier setting and noted the degrees on the disc I then turned the engine forward until the pistons went over TDC and down then turned it back until the pistons met the vernier and again noted the degree reading by dividing the total degrees between the two points x 2 this then gave me the true top dead centre mark on the disc once I had turned the engine forward so the pistons were on the up stroke and at true TDC I then set the degree disc to zero and the vernier to 5/16th turned the engine back then up to meet the vernier and set the mag so the points were just opening and fitted the drive gear wedged open  after checking by going through the engine turning again it was set and I have not had a problem with running or starting since
A friend of mine had his timing set to 35 degrees and it was pinking under load so we set it to 32 degrees to be truthfull he has noted that the bike is not pulling as well as before and is running a bit hot (which may be the 32 degree c temp we have been having here) however we are going to check it and if needed set it up again but this tim using an led gismp to indicat exactly when the points open as that is always a stumbling block when using a fag paper and having 60 year old eyes and dithery hands.
It may be that others will come back with reasons why we should set to 3/8ths and I may suggest we try that again and see if it pinks.
We will not be taking the head of but using a disc and a bought spark plug rod gismo to set for TDC
will report on the result at a later date

sorry for the book but thought it may be usefull also someone may see something I am doing wrong and correct me.
Richard

[chaterlea25]

Hi Richard,
I agree with you about the fuel quality it is very variable, I add a dollop of "valvemaster plus"
mixed with some acetone and two stroke oil, I mix it in a 100ml bottle that chainsaw 2 stroke comes in, and add half of it to a tankful.
The beauty of manual control mags is that I can give the lever a little tweak if the motor tends to pink!
My SR engine has the 357 cam, 8.5 to 1 pistons, and the head is fittted with high flow valves and a 30mm inlet
tract to which is fitted a Mikuni VM carb,
I use NGK BP7ES plugs
You went into all the detail I left out about finding true TDC, the dial gauge makes it simpler in my view
I use the buzzer/LED gadget to check the points opening
Just screw in my bolt gadget and bring the piston up to touch it, rock the mag armature on its gear backlash and the LED blinks on and off

I have found that most ATD units are now well worn and so give more advance than they were designed for!
with the wear in them it is very hard to set the timing accurately even when wedged open,
I set up a degree disc on a friends Norton twin that has an ATD and used a strobe to check the timing
it was all over the place, same story on a Guzzi T3 and an A65 !
I have yet to try electronic ignition in an A10, In my opinion the dynamo is the weakest link????
I have fitted electronic ignitions to several alternator powered bikes, the only troubles occuring when batteries were down

Regards
JOhn O R

[Richard]

John
I must agree about the auto advance unit and would prefer to have a manual one to retard it when needed then it can be set a bit more advanced, I must be honest I just cant be bothered with additives as basicaly I am to lazy to do it. I take the veiw that if it goes ok then good and when it goes wrong then good again as I enjoy repairing it nearly as much as I do when I ride it.
Some day a manual mag end will come my way and I may swap it over.
I prefer to have a mag rather than fit an Alton and coil ignition as when for any reason the battery is flat no ignition, also if the electronic unit fails, which i know is unusual or the coils go down then it is a no go situation at least with a mag usually if it is going faulty it generaly will not start when hot which means that once cold at least you can get home even with no battery power.
The plug gismo I use has graduation marks on it which saves using a dial gauge but I do have one and may set that up as well to be doubly sure.
Also I have an old plug already drilled out and your idea of setting a bolt so the piston touches it at the right point is a good one and I could set that up on the other cylinder and have it ready for next time saving the regular rigmarole.
Thanks

Richard

[olev]

JOhn O R,
I'm a big fan of Mikuni carbys and have grafted them onto all sorts of things over the years.
Can you post a picture of your setup?
What sort of adaptor did you use?
cheers

[Richard]

Well I had the bike in to my garage/workshop and the first thing i wanted to check was that I had set it to 32 degrees the first time yes it was spot on 32 degrees.
My fellow club member had contacted SRM again who confirmed once more that the timing should be 35 degrees btdc so I set it to that the same way as before but this time with the mag points set to 12 thou.
We double shecked it after several attempts to get it exact and off it went.
A later email informed me it was not pinking and was going ok but it still felt as if it was not pulling as well as when it was possibley set to far advanced (and pinking under load), all I can think is that he was used to the advanced setting and all is well. As I would not like to set it any further advanced.
The good thing about it is that I took the oportunity to check that when it is set with a plug hole gismo 5/16ths measured from the plug hole is not a true reading due to the angle. I did not have time to make a set bolt/plug gismo) as John suggested but as the owner of the bike pointed out this will not be acurate if the head has been off as the head gasket could be different or pulled down further or less than when it was set.

[RichardL]

With apologies for hyping my own ideas (if it is, even, original!), I thought you might be interested in this approach. I shared a while back. No angle issue whatsoever and, if you have domed pistons, the straw actually misses the dome and sits on the flat portion of the piston.

Richard L.

 http://www.a7a10.net/forum/index.php?topic=156.msg5969#msg5969

[chaterlea25]

Hi All,
The pistons in my SR have a raised flat crown, no matter what pistons are fitted my gizmo is "bike specific"
different machining of the head gaskets pistons etc will make a difference, maybe even left to right cylinders would be different!
If I had the head off It would be easy enough to reset the gizmo using the dialgauge in the other plughole
With the pistons I have fitted, 35 degrees is equal to 0.412in in line with the plug hole.

Olev attached are some pics of the Mikuni setup, I bought the kit from Allens in the UK, I know SRM use an adaptor plate and a standard mikuni manifold. The only thing I would like to change sometime is to a cable operated choke as I find it a bit awkward to let off the choke on the move

Also a photo of a mod I did on the oiltank, The standard setup cannot be drained properly and is a right pig to clean out, the mod consists of a stainless steel boss silver soldered to the tank, fitted with a stainless drainplug which has a magnet glued into its center, the stainless boss and plug isolates the magnet from the tank so as any ferrous bits will only stick to the magnet,
The tank now drains completely and is easy to flush out
Regards
John O R

[olev]

John OR
That setup squeezes in there nicely.
I'm a huge fan of the VM's and will definitely be fitting one to the A7, probably a 28mm job off a RD400.
btw, that filter seems to be completley clogged with sh*t.
I'm also a fan of electronic ignition. Do you have any optimum advance curves for an A10 or A7.
Orabanda was getting his bikes dyno'd but he seems to have gone quiet.
The emu export has probably rotted his socks.
cheers

[Lannis]

Again an old sparkplug body I brazed a piece into the top of it then drilled and tapped the whole way down through it for a 10mmm bolt, I rounded the end of the bolt in the lathe where it meets the piston,
With a little setting up the bolt now stops the piston exactly at 0.375 before TDC,
It is held from moving with the locknut, 

Regards
John O R

So once you've adjusted the gizmo, and then screw it back out of the head, how do you make sure it screws back into exactly the same place again without going through the whole setup?  Or is the whole point just to hold the motor from turning while you fix the gear in place .... ?

Thanks!

Lannis

[chaterlea25]

Hi Lannis,
The locknut keeps the M10 bolt from moving, the sparkplug has no washer so it all seats in the same place every time!
Olev I will have a look at the filter, it was always a black colour tho??
Cheers
John

[Lannis]

Hi Lannis,
The locknut keeps the M10 bolt from moving, the sparkplug has no washer so it all seats in the same place every time!
John

I guess it would, come to think of it, or the variation would be measured in a couple of mils, and we're looking at getting within 1/2 of 1/32" accuracy to make sure the timing is right, or about 16 mils.

I'll have to make me one of those.  I like quick, convenient, accurate ways to do timing, which is why I was interested a few months ago in "strobe timing" my A10 like I do my A65.   But all the information says that's probably not necessary ....

Lannis

[bsa-bill]

Having just put the auto a/r unit back on in the cramped second shed, the old bike seems reluctant to start ( did fire once tho ), need to check the timing, to save taking off the timing case if I don't have to does anybody know where before TDC a 61 Flash should fire when fully retarded.
Of course first move is to reverse the leads but I did set the timing with the (viewed from the rear) right hand cylinder on compresion and the points heel aproaching the lower cam on the magneto
(rear lead from magneto to right hand cylinder)

Many thanks in advance

all the best - Bill

[bsa-bill]

Just answered my own question - did a quick check and it's miles out
Ah well it's off with the timing case again

all the best - Bill

[a10 gf]

Bill wrote:

does anybody know where before TDC a 61 Flash should fire when fully retarded

I'm no expert in the autoadvance dept, but believe using this as a reference for timing could easily induce errors, due to wear, springs, and possibly more. Maybe if you trust and know your particular advance unit it could work by making some reference marks.