Hello,
Bike is a 1965 C15F.
I've rebuilt the motor and am attempting to sort the timing on it. The auto advance cam thing is on a taper and I am unsure how to position this on the shaft. I've read various service sheets but they don't really say how to position this unit as far as I can make out.
I have found a couple of old topics on here and realise that the position of this unit can be altered to adjust the timing, but I'm just struggling working out where to put it.
I've confused myself and can't get my head round it. Any help would be appreciated. Many thanks.
Hi,
Does this help at all?
You need to work backwards. Set your piston to the BTDC as described. Loosely position your points assembly on the tpaer, rotate the cam anticlock until the bob weights are fully expanded. Rotate the asssembly until your points are just opening then press more firmly onto the taper but not too hard so as as to secure tightly.
Rotate/rock the engine forwards and back over TDC to see points opening etc. If all looks ok, nip the centre bolt or adjust on taper then nip the central bolt. It should give you a good place to start. Once that's been established, set up as instructions.
It's quite straightforward but you've probably over analysed and confused yourself.
Good luck.
Thanks for your help. That page you attached was the one I'd read and, like you say, over analysed it and confused myself. There's been times I thought I made sense of it and then confused it again.
Giving it a couple of hours and seeing your reply I think I finally understand it, so thank you very much. I'll give it a go after work tomorrow and see how I get on.
Thank you for your help again.
You're more than welcome. Good luck. Just take you time and I'm sure all will be well.
I still can't get my head round this.
I don't know visually what half the terms are when I try to do this from what it says in the book of service sheet. I can't visualise what fully advanced and all the other stuff means.
I've spent nearly 2 hours trying to understand it. It's driving me barmy.
Hi,
Poor you. Have a break to clear your head and take it one step at a time. Hold your points assembly in your hand and become familiar with advancing the weights by turning the cam so that you understand the function. Once familiar place to one side.
Remove your spark plug. Make sure you're on TDC first by removing the tappet covers to ensure both valves are closed Insert a rod through the plug hole and mark it level with a fin or some reference point to indicate where TDC is. Remove the rod and make a mark 7mm lower or whatever the correct dimension for your model.
Then with the bike in gear rotate the back-wheel to get say 10 -15mm before TDC. Next set your piston to the correct distance before TDC using the rod down the spark plug hole.
Rotate the wheel until your 7mm or whatever it should be mark is visible and aligned with your reference point. You are now at the correct timing position for the piston.
Take your points assembly and using the method you learnt and perfected earlier, advance the bob weights. Hold the assembly advanced and position it on the taper. Move it around until the points are just opening with the bob weights advanced. Once achieved push and secure on the taper.
Rock the back wheel and with the weights advanced the points should just be opening. Fine tune the points backplate to achieve the opening of the points in line with your 7mm mark with the weights advance and hopefully you'll be there.
Many thanks. I've left it for a day or so and will probably end up looking at it over the weekend. Hopefully some elves will have done it by then like that book with the elf and the shoemaker - I can't remember what it's called.
For now, I understand what you're saying and reading it again you have explained it well, so thank you. With regards to the position of the points breaker, it can be positioned differently on the plate - is there a particular way that it needs to be positioned in the first instance?
Hi,
Re points on backplate, just set in the centre of its adjustment i.e. midway in the slot. It's only a starting point.
Good luck. I'm sure you'll get there and be really chuffed when you do.
I'm having another go at this today, so hopefully I will get it sorted.
Just a question, is it supposed to be difficult and fiddly to hold the weights advanced while the backplate is fitted?
How are you supposed to turn the cam to hold the weights advanced when the points plate is in the way? It seems impossible.
I'd help if I could, Courtney, but I'm just a novice. The instruction manual I got with my 1965 B40F has an "errata" sticker in it giving a measurement when fully retarded. That's what I used and it seems to start and run okay. The manual doesn't have a year written on it, and I have another - again no date - which gives a measurement for fully advanced. I'm sure someone on the forum will help you get it sorted out. Phil
Is it possible to make a small timber wedge to hold the weights in the advanced position leaving you hands free to make the adjustment. This works an A10 auto advance unit but I'm not sure of the exact layout on the C15
I've been having the same mental struggle with working out how to set/reset the timing ( on my B40F). So I'd like to know the answer as well.
One of the many references I used to confuse myself ( in this case the Haynes manual) says " revolve the cam using a pair of slim nosed pliers" " but be careful not to mark the cam"
Not keen on using pliers myself. I can twist the can by hand anticlockwise. Only moves 3 or 4 degrees though, but I can see the bob weight mechanism move out. Should it turn more than that ?
However would need 6 hands if holding cam in this position, to then rotate contact breaker plate and set at points just opening. So how's it done????
Is the cam bolt supposed to be loosened ? or not ?
I'm glad it's not just me!
Could this be why one of my booklets had an errata sticker giving a measurement to use when fully retarded? I guess not. Phil
I don't know if this is right. I also don't know what year this booklet is. I think I was given it by the previous owner when I bought my 1965 B40F. Anyway, read what it says on the "Errata" sticker, and under "Advance and Retard Mechanism." (Ignore the bit above the errata sticker - that is just regarding the C15S and C15T with the energy transfer system.)
Interesting, eh?
I set mine according to this and it starts okay and seems to run okay (not that I'm an expert by any stretch of the imagination!)
Phil.
Btw, I believe my bike had a rebore and new piston at some stage in the past. Does that affect ignition timing settings? I'm guessing not.
The 1965 B40 ignition timing should be set at 33.5 deg fully advanced which corresponds to a piston displacement of 7.14 mm before TDC.
However, using Rupert Ratio as the 'Bible', he only provides fully retarded ignition settings prior to 1965. For 1964, he gives the setting as 5 deg before TDC or 0.18 mm piston displacement. However, for 1962, he gives the fully retarded setting as 15.5 deg corresponding to a piston displacement of 1.6 mm or 1/16" (it may be this value that the above booklet is trying to amend). All this data is the same for both the C15 and the B40.
I believe the advanced setting has always been 33.5 deg - in fact, Rupert Ratio quotes this value for the 1960 models. It is the advanced setting that the engine normally runs at and you only get the fully retarded setting when you start the engine. In principle, with 15 deg auto advance mechanism range, the retarded setting should be 33.5 - 30.0 = 3.5 deg. Where the 5 deg and the 15.5 deg values come from is therefore hard to understand.
The moral of the story is to always set the ignition timing for both the C15 and B30 at 33.5 deg fully advanced!
So how did you rotate the cam anticlockwise and hold it.??(.whilst checking/adjusting the points were just opening)
& is cam rotation just 3 or 4 degrees(that being all I can get by turning cam by hand)
The distributor was changed for one with a smaller advance range during late 1962/early 1963.
To lock the AR unit find a washer with centre hole diameter just greater that the cam spindle then when you tighten the AR bolt with unit in fully advanced the washer will clamp the cam and it will be locked in advanced. This information comes from the 1965 C15/B40 owners manual.
Set the piston position, then set the points plate with fixing screw about central in the slots, position the AR unit best you can and tighten fixing bolt. You can then adjust the timing by moving the points plate.
You can find a copy of the 1965 owners manual in the members area of the BSAOC website - look for C15.
Quote from: hoogerbooger on 12 Jul, 2020, 17:12
So how did you rotate the cam anticlockwise and hold it.??(.whilst checking/adjusting the points were just opening)
& is cam rotation just 3 or 4 degrees(that being all I can get by turning cam by hand)
It's best to check that you are getting the correct amount of advance which should be stamped on the back of the points plate. Sometimes, you can get this when you pull out the bob weights manually but, because of problem with the mechanism, you might not get this when you rotate the cam. As said, it's best to set the ignition via the advanced setting of 33.5 deg or a piston displacement of 7.1 mm
Many thanks for everyone's replies. They are very helpful and makes things much clearer.
Just to clarify, with the 33.5 degree setting. Do you still need to advance the weights as well as the 33.5 setting? I take it that is the case but just want to make sure.
I'm pleased I'm not the only one with this issue. I'm new to British bikes and it's a bit of a learning curve.
Many thanks.
thank you as well.
As I have a B25 timing case on my B40 I've used a degree disc to get to 33.5 degrees before TDC. (I've put a mark on the alternator rotor as well to line up with the pointer on the case)
I've removed the cam bolt and can now see how a washer larger than the cam spindle will clamp the cam in place.
BUT turning the cam by hand anticlockwise I still only get 3-4 degrees of turn of the cam. So as 10 degrees is the likely correct fully advanced rotation for my B40 F It looks like I will need to remove the points plate to check the advance mechanism ? ( having first removed the points and condensor). Won't do this tonight, but happy to have a go.
As you will see in the photo I have marked up the current position of the points plate which is almost at it's clockwise maximum. The plate seem reluctant to move and there doesn't seem many opportunities for levering against other robust parts. Is there a trick to rotating a reluctant points place ?
( As shown in photo there are two obvious holes in the plate, so two nails in a batten of wood seems an option? being careful to ensure the nails don't project behind the plate ?)
Hi,
If the points plate will not rotate easily with the tower bolts loosened then it could be that there is a 'high spot' on the edge of the plate. Take the plate out and look for rub marks, rub them down a bit until it rotates easily.
I have just done this on an A65.
Dave.
As the cam isn't nipped up, isn't it just a case of rotating to watch it open the points at TDC, then moving the backplate until they do just open? Best way to capture the moment is with a bulb and battery or multimeter.
In addition we're not talking tenths of seconds 0-60 time. The old rod down the plug hole is I'm sure more than adequate. It takes the whole advancing thing out of the picture.
Remove spark plug. Put engine in gear on centre stand. Rotate the back wheel to find top dead centre. Make sure both valves are closed. I usually check by removing the cover above the push rod tube. If they're not shut rotate engine one revolution until they are.
Insert a rod down the plug hole and mark a refrence point that lines up with something noticeable.
Remove rod and mark a second line 7.1 mm above the first.
Insert rod, rotate wheel opposite direction until the new mark goes down into the plug hole and disappears.
Reverse the motion until the line 7.1mm line is just visible. You are now at the correct advance and the points should just be opening. Adjust backplate until they are if not.
Nip everything up.
Remove rod.
Rotate engine again to double check.
So Rick you're saying set it to 7.1mm btdc when fully retarded? Anyway it appears the 1/16" btdc I set mine to, fully retarded ( as per errata sticker)is probably wrong for my year of bike. But it starts well and seems to run not too bad. Phil
Isn't the 1/16 BTDC fully advanced? Perhaps it's because we're talking different models and eras. Sorry for any confusion.
Below from the 1965 BSA data book showing the fully advanced timing setting in inches, mm and degrees.
If it is set to 7.1mm (0.280") fully advanced, what would that be fully retarded?
7.1mm out ie 33.5 degrees. Are you sure you were fully advanced at the time?
Quote from: Phil C on 13 Jul, 2020, 23:00
If it is set to 7.1mm (0.280") fully advanced, what would that be fully retarded?
I have checked all the available data from both the user manuals for 1961 and 1965 and the data provided by Rupert Ratio and the only reliable data appears to be the fully advanced setting of 33.5 deg/ 7.1 mm. As said, it is the fully advanced setting that the engine uses most of the time it is running and therefore needs to be set accurately.
The problem is that the corresponding retarded setting depends on what the auto-advance mechanism provides. This was 15 deg prior to 1963 but was then changed to 10 deg. However, using these valves, I have found it impossible to verify any of the retarded settings given. Basically, the expected retarded settings should be either 3.5 deg (33.5 - 2 x 15) or 13.5 deg (33.5 - 2 x 10). What is provided is either 5 deg or 15.5 deg. Even more confusing, the 15.5 deg / 1/16" setting given for 1961/62 should have been 3.5 deg!
It would be nice to sort out the retarded settings but, even with the benefit of being an applied mathematician, I can't make the numbers add up. Hence, the best advice appears to be to stick with the advanced setting for the ignition.
RR does say the BSA advice on timing changed with the prevailing weather condition at Small Heath on the day. So maybe that explains why the maths doesn't work...
(It's raining here today, but not sure how that changes the settings I should use)
Remember that the settings given were based on the fuels in use at the time. Modern fuels may mean your engine runs better on a slightly different setting and you will only know that by experimentation.
I agree with the good advice given to time the engine on the fully advanced figure.
The retarded figure is too unreliable - and depends on you bike being fitted with parts to original specification.
Also 1 degree at the advance unit equals 2 degrees at the crankshaft.
The other thing to bear in mind is that the C15 and B40 are in such a mild state of tune that most people are unlikely to notice a 5 deg error in the ignition timing - they might not even notice a 10 deg error. If you are using a gauge down the plug hole to set the piston position, the accuracy you will achieve is probably going to be between 5-10 degs. It's certainly better to think in terms of removing the chaincase cover and positioning things more accurately using a timing disk attached to the alternator rotor or a dial gauge if the head is off.
In terms of using modern fuels, the advice I've seen is to back off the timing 2-3 degrees (lower octane rating) but, again, for the C15/B40 this refinement would probably make little difference.
Hi,
This is not necessarily going to solve the problem but I can remember getting C15s and B40s with distributers running and then riding along turning the 'dizzy' by hand to get the best position for performance. Not so easy with side points.
Dave.
4CA Points plate off. Only circa 5 degrees of turn of the cam when I rotate manually anti-clockwise.
The bob weights have cut-out guides between their pivot and the end of the bob that spins out. The pins through the two guides only travel to just over half way along these guides when I turn the cam anticlockwise.
So is this right ? or faulty ? Is 5 degrees of turn on the can 10 degrees of advance ? and correct ?
Also. Points plate is a very tight fit and will not turn. The plate is somewhat dished. No obvious single sticking point. so will sand down gradually until it can slide. Is it worth applying a tad of copper slip on the plate edge when I have sanded to just slide ? or leave dry.
( I don't think the picture adds anything ? looks like it should in the guides)
Forgive me if this is absolutely irrelevant, but I think that to get more adjustment I removed the cam from the taper and repositioned it slightly when putting it back on. If it's any use, the discussion started on this forum on 3 Feb 2018 on this forum, called something like "Ignition timing adjustment." Phil
The back of the advance unit will be stamped with its advance range, I think 10 degrees for B40 but they can also be found with 5 and 12 and maybe other ranges.
OK will take auto advance out....to see what it says on the back. Then I will know.
Can I check I am correct to think that when I re-seat it in the taper it doesn't matter whether the spindle has rotated from the current position.
Isn't that the same as repositioning it, as per my post above? Phil
Actually, no, I guess it's not. Maybe I marked the taper and the cam, to help me put the cam in a different position on the tape when I refitted it? Am I talking rubbish? Phil
Quote from: JulianS on 12 Jul, 2020, 17:26
The distributor was changed for one with a smaller advance range during late 1962/early 1963.
To lock the AR unit find a washer with centre hole diameter just greater that the cam spindle then when you tighten the AR bolt with unit in fully advanced the washer will clamp the cam and it will be locked in advanced. This information comes from the 1965 C15/B40 owners manual.
Set the piston position, then set the points plate with fixing screw about central in the slots, position the AR unit best you can and tighten fixing bolt. You can then adjust the timing by moving the points plate.
This is the most helpful and least confusing explanation of how to do this. I must have read and downloaded everything but this bleedin' owners manual! Many thanks.
auto advance out. It's a 10 degrees unit & whilst it doesn't look like 10 degrees of rotation to me, the bob weights do turn out to the maximum the unit will allow ( which I can now see from looking at the unit from the back.
BUT the weights do not spring all the way back. One spring in particular looks stretched and the tab it attaches to from the base plate is bent. See picci.
So I should get replacement springs (if I can find the right ones)
Before I try bending the tab back to perpendicular to the base plate. Any advice ? (seems just one spot weld attaching the tab to the base plate & if that breaks, substantial extra expense/time/electronic ignition seems an outcome.
idea so far is with narrow nosed mole pliers might be able to clamp the welded part of the tab to the base plate to reduce risk to the weld`. Sounds like, from RR, the cam is a push fit over the spindle and I shouldn't try taking the auto advance apart to make the tab easier to clamp ?
BUT a better idea might be do nothing and just put it back in with less ability to self retard ?
Mine is exactly the same as yours with the bend. It worked fine before I took it apart, so it's staying as it is. Replacement springs are available though.
Something I've noticed on mine, which I may have mentioned a long time ago: when setting the points, I rotated the cam by turning the back wheel (is that the best way?), which, as it's in gear, is a fairly jumpy revolution. Watching for the points to reach their maximum gap, whilst turning the wheel, it would be easier if I knew where on the cam the high spot was. But the cam, rather than having a distinct apex, appears to be circular with a flat on one side. Where on the circular bit the apex is is not easy to spot, so I have to focus on the points gap and guess when they are coming up to their max in what is a jumpy revolution. I guess I need to find the max points gap, and mark the cam. All comments appreciated as always.
You might also notice on the photo that I have about five or six washers on both my locking screws. Seems a bit ramshackle, but I guess it's okay. Obviously either the screws are too long or the sleeve nuts too short.
Phil.
points plate sanded so it will rotate ... auto advance cleaned and oiled ......bent spring tab gingerly straightened ..... and everyting put back in... BUT can't set the timing/do the fag paper/ light bulb test. ( bother)
I've answered a earlier question of mine... the auto advance can't be be replaced at any orientation in rotation....it needs to ensure the right part of the cam, coinciding with the points opening, is in the adjustment range of the points plate swivel... So it'll have come out again.
As I marked the spindle and replaced it in the same orientation it was, I have also answered why I was getting confused before and checked several times that I was at 33.5 BTDC and not perhaps 33.5% after ......or something else.
Oh well we all have to learn ( and thank you to all those with the patience to advise)
Phil: yes no obvious high spot on the Cam, but as far as I can see with the cam rotating anticlockwise the points are close on the lower flat-ishside of the cam, so the points open at the clockwise end of that lower flat-ish part. after that it's sparked so if it does get fractionally higher I can't see that it matters....But happy to be corrected by others ( to avoid be positioning the auto-advance wrong again !)
after a rebuilt engine on my 65 SS80 i turned my attention to thr distributor, as with just about everything on this bike ,previous owner had .ucked about with it. the screw to hold on the rotor was broken off and the shaft hammered in ! nice one (of many) drifted out roll pin and stripped down, the action plate had 2 oversize springs and bent one side. marked 10 degrees ,purchased a s/h action plate and new springs fron dragonfly cleaned ,lubed ,new point ,condenser concentrated on getting 15 thou gap then turned with a ignition lamp that lights as the points open (ebay) now how to time ? r r book does not help much it says 15 degrees advance ,mine is 10.so the head was off so found TDC with a dial guage , I think about 34 degree Btdc should do it ,backing the piston to25 degrees add 10 degrees of advance pop in dizzy turn till point just open ,lock it up.....if and .when i get it going I will let you know,
hopeing its like the morris minor trick of getting it started with a loose dizzy and adjusting to the best tick over !
probably i have not taken everything into account so will re set timing . a very confusing problem !