Hi all, can anyone tell me how many degrees a K2F auto advance unit should have? I have set up a timing disc to the drive side of the crank to check the timing with a strobe light and have found it is idling on 20 deg then advancing up to 44 deg on one side and 45 on the other. It appears my A10's A/A is advancing 24 degrees and of course over advancing the engine. Funny thing is it is not pinging. In unit BSA's I thought the A/A unit advances 12 deg so would assume the A10,s advance would be simular.
Thanks Highway, I'm thinking of timing unit motors off the crank position were we are just lining up marks on the crank not the maggy. I take it that the 12 deg at the MAGNETO is the correct advance figure then
Re: Amount of auto advance in K2F Magneto's#30159 10/13/0710:25 pm10/13/0710:25 pm
I was in the process of trial fitting a spare magneto today and after reading your post decided to check the difference between idle and full advance. On my 54 A10 with auto advance it is much the same as yours i.e 24-25 degrees. I guess that's what it is supposed to be. I agree with triton thrasher though as it doesn't really matter. The full advance is what you should aim to achieve. I would drop the 44-45 degrees back to about 34-35 even though it isn't pinging.
Graeme 1954 A10 Golden Flash
Re: Amount of auto advance in K2F Magneto's#30161 10/15/072:27 am10/15/072:27 am
Thanks for the replies 12 deg must be correct. Reset the timing with a stobe, made an adapter to mount the degree disc to the crank. Used a butchered old crank end spring nut and brazed a 1/2" bolt to one end after machining a step on the inner end to locate on a couple of the threads that hang proud of the crank nut. This screws onto the crank's end without undoing the existing spring nut or what ever it's called. Then mount the disc on it, find TDC and mount a pointer then presto a stobe light! Reset to 35deg and 33.5 on the other side (point ring's a bit out) and the bike runs great
Re: Amount of auto advance in K2F Magneto's#30162 10/15/0710:45 am10/15/0710:45 am
I was working on getting rid of my timing split on the weekend and managed to get most of it out by inserting piece of feeler gauge material between the cam ring and the housing (got this method from a previous post). I've now reduced the split from 5 deg to 3 deg and plan on a thicker piece of shim material next. You might easily get rid of your 1.5 deg the same way. Got to be better for the bike.
Graeme 1954 A10 Golden Flash
Re: Amount of auto advance in K2F Magneto's#30163 10/15/076:36 pm10/15/076:36 pm
Thanks Graeme for the tip, what size feeler did you insert? I have just had the maggy reconditioned by Peter Scott down here in Sydney but cant see any problem with what you suggest. Might leave it until I return from the Nat rally in Sth Australia. Could you send me a link to the post on adjusting the mag? Thanks.
Re: Amount of auto advance in K2F Magneto's#30164 10/16/077:42 am10/16/077:42 am
I can't recall where the link is but I'll have a look. I inserted a .004 " feeler on the side where the point gap was largest. I inserted the feeler gauge between the cam ring and the housing and gently pushed the cam ring home. I started with a thinner feeler to see how easy the cam ring pushed in and ended up with the .004" thickness. This went in without much effort which is why I think I'll increase it to try and get them firing at the same point. I will eventually replace the cam ring I think. Funny, I had my magneto repaired by Peter Scott also and it didn't have the split in it before he fitted a new/different armature. Probably slight difference in the replaced armature. cheers, Graeme
Graeme 1954 A10 Golden Flash
Re: Amount of auto advance in K2F Magneto's#30165 10/16/078:16 pm10/16/078:16 pm
He must have a batch of cam rings that are ground wrong, at $350 I would have thought that he would have tested the mag for timing split! As the job was done mid last year and the bike has covered only 700 k's (last years Nat rally and 4 day trips) one would think he'd replace the cam might give him a ring. Meanwhile will try your shim method 005" might get it spot on, the right cyl was behind on the timing so I will place the shim under the side of the cam that fires the right side. Anyone else out there fiddled with this??
Re: Amount of auto advance in K2F Magneto's#30166 10/16/079:07 pm10/16/079:07 pm
My timing was about 12 deg different between cylinders and I seized a piston before I found the problem.
I was using a K2F with a manual advance. In this case the cam ring is manually rotated by a cable to advance and retard timing and therefore shimming the cam ring to lock it in place would not work.
After a lot of measuring with a dial guage I finally established that the bearing housings on which the shaft was running were both offset and not parallel to the cam ring housing. A clue to this was that the points gap was very different on the two highest points of the two lobes of the cam ring.
Packing over (shimming) the cam ring as suggested in an earlier posting would compensate for offset bearing housings but if they are out of parallel than you will likely not cure the problem just by shimming the ring.
If they are badly out then you will have to get a machinist to recentre the bearings and cam ring housing.
If the cam ring itself is worn then you can also try correcting the opening time by carefully stoning the earlier lobe on the cam ring to delay the timing on that cylinder. But in my experience this is usually a work round for a more fundamental problem.
As a final check on competion engines I now strobe the timing on both cylinders. I have gone to the effort of engraving timing marks on the belt drive front sprocket and have a "timing cover" which I bolt on to accurately check the final result. (This sort of duplicates the set up on a Commando but I have checked it for accuracy with the barrels off) No more seized pistons for me!!! - at least not for that reason. By careful stoning and set up I get the difference to less than a degree but it is a bit of work to make all the bits to set up for the first time.
Last thing. Your experience in getting a reconditioned mag back with badly offset timing is unfortunately rather common. Often mag rebuilders fix the electical problems but ignore or even exasperate the mechanical problems!
Re: Amount of auto advance in K2F Magneto's#30167 10/17/075:15 pm10/17/075:15 pm
I read this with interest since I am restoring a A10 with an automatic advance K2F. It is not running yet , but I am wondering how much timing difference could be tolerated between the cylinders. In my case I tested the unit for 1 degree difference (on the work-bench with a timing wheel). This should then be 2 degrees on the cylinders I think. I decided to not exchange the camring for the moment. Any comments on this are welcome, thanks.
Re: Amount of auto advance in K2F Magneto's#30168 10/17/078:27 pm10/17/078:27 pm
I have no personnal experience with A10 (iron head??) but in my opinion a 2 degree differnce split between two cylinders should be fine. Especially if the bike is a modestly tuned road machine. Several authors discuss this eg Paul Dunstal in his Norton tuning notes and he recomends splitting the difference when there is one or two degree difference. He also recomends progressivly delaying the timing from (from memory) about 31 deg to 28 - 29 degree when compression is increased. These numbers are for Norton twins which have a good combustion chamber shape. Most other Brit bikes especially Triumphs carry a lot more advance than this.
I have experimented with a Norton 500 twin on the dyno and only found a drop in performance when ignition (on both cylinders) varied more than about 5 degree either away from the recomended setting. But this result should be taken as an indictor for alloy 500 Norton heads with compression about 10 to 1 with moderate domed pistons only and you should follow the manufacturors recomendation for your machine unless you get into a lot of detailed controlled testing.
Re: Amount of auto advance in K2F Magneto's#30169 10/18/078:26 am10/18/078:26 am
I'm sure that a 2 degree split is fine however, I still think that a zero degree split would be ideal. I have no doubt that the original design included an acceptable tolerance but why would you accept this if you could remove the split by simply installing a shim. My problem started with a 5 degree split which I consider unnacceptable. I now have 3 degrees and believe I have a simple way of reducing that further. Whether I achieve zero split is yet to be seen, but I will try. If I had the same split as retired-fireman, I probably wouldn't be concerned, but I would probably still try and remove it.
Graeme 1954 A10 Golden Flash
Re: Amount of auto advance in K2F Magneto's#30170 10/19/071:37 pm10/19/071:37 pm
I rang Peter Scott and explained my problem, he was surprised as he checks the mags for split when he reco's them. He told me to bring the bike to him the next day and after confirming the split of 5 degrees he fixed the problem with a dremal drill and stone. He is a very genuine bloke and was concerned that the mag was out, he has a test rig to check for split with a degree disc attached to check that the mag fires at 180deg to each cylinder. The mag is now firing at exactly 180 to each cylinder and in owning it for 27 years it has never went so good, smoother and more power.
Re: Amount of auto advance in K2F Magneto's#30171 10/20/074:35 am10/20/074:35 am
Great news. I new there would be benefit from it being spot on. Did he just grind the high side of the cam down? It is a bit far for me to take my bike to Peter although I could send the magneto back. I played with the shim yesterday and realised that I had pushed the split too far and gone past the 180 degree. I have now settled on a .002" shim although I have yet to take the primary off and fit the degree wheel. Currently I am strobing it through the filler plug using some white paint. Looks pretty good from the angle I am at but I will check later today. I had my mag back to Peter several times as it would fail after a lengthy ride. He finally replaced the armature which fixed it, but unfortunately that's when the split appeared. Before that, I had zero split. I found Peter very helpful too and would use him again. I'm glad you ended up with a good result.
Graeme 1954 A10 Golden Flash
Re: Amount of auto advance in K2F Magneto's#30172 10/20/078:17 pm10/20/078:17 pm
Graeme just ring him and have a yarn I bet he asks you to post the mag back to him and yes he machined the advanced lump on the cam back to the retarded one to correct it. BTW I made 2 tools to do the timing with a stobe, one fits on the drive side and the other on the timing side which you have to remove to adjust the mag anyway. Find an old oil pump worm drive and braze a bolt on the outer end to mount the timing disc, there is enough thread hanging out of the with existing one in situ to get the tool mounted without disturbing the oil pump or its worm drive. If you take the bike out side or put some rags on the floor you can run the motor with the timing cover off without too much mess to check the timing. The tool can be used to check you valve timing also.
Re: Amount of auto advance in K2F Magneto's#30173 10/20/079:13 pm10/20/079:13 pm
Thanks r-f. I have a modified oil end feed setup from SRM which changes the oil pump configuration. I also bought a hex head cush drive nut from them which allows the installation of a timing disk using 2 screws. I ground the cam ring down slightly yesterday after hearing that Peter does it, and now have it spot on. Sounds like were both happy with the reults. cheers, Graeme