ATD Springs SR1 magneto

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ATD Springs SR1 magneto

Postby 56G80S » Tue Aug 13, 2019 4:59 pm

Hi everyone. After using the Search facility I wonder if anyone has thoughts on this?

My ATD is not returning properly. I've done all the usual things, rinsing out with white spirit, then spraying with WD40 once loose and making sure the mag chain is in perfect adjustment.

I'd fitted the springs when the mag was returned after refurb by Tony Cooper (great job).

However, the springs had been in the "new parts tin" for ages.

On close inspection, the spring coils don't appear to separate until the ATD is at least halfway to full advance! Therefore no extension.

I don't fancy the trip down to the Jampot with the level of backfire, kickback and starting delay with a fully advanced ATD. I plan to cut off a coil and but a new "hook" on and ask Spares to have a couple of new springs that I can fit on arrival at the Jampot just in case.

Johnny B

PS re-checked the ignition timing as well - it's fine.

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Re: ATD Springs SR1 magneto

Postby Rob Harknett » Wed Aug 14, 2019 2:47 am

Springs are quite brittle and could break re making ends. Perhaps try binding 2/3 coils tight together with fine wire one end, which may shorten them.

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Re: ATD Springs SR1 magneto

Postby 56G80S » Wed Aug 14, 2019 6:51 pm

Rob

Thanks but the problem is that the spring coils do not start to separate at all until the ATD is reaching the point of being half advanced or even a bit further forward. So the spring fully closed point is reached way before the the bob weights reach full retard.

I'm surprised that the hooks haven't just slipped off the stub on the bob weights.

I do understand your point about potential breakage though so maybe hang fire until I can get some replacement springs. The thing is that as the bobweights with these springs are never going to retard, the whole thing isn't moving and then gets fixed in the advanced position. Thankfully the valve lifter is working and that helps starting so usually starts after 2 kickbacks.

Johnny B

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Re: ATD Springs SR1 magneto

Postby SPRIDDLER » Wed Aug 14, 2019 7:14 pm

56G80S wrote:Rob

Thanks but the problem is that the spring coils do not start to separate at all until the ATD is reaching the point of being half advanced or even a bit further forward. So the spring fully closed point is reached way before the bob weights reach full retard.

Maybe you already realise it but it sounds to me as if you have the wrong springs, John.
Last edited by SPRIDDLER on Wed Aug 14, 2019 7:47 pm, edited 2 times in total.
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Re: ATD Springs SR1 magneto

Postby Rob Harknett » Wed Aug 14, 2019 7:42 pm

Well it does sound like they are not just a bit short.
John you have A & R the wrong way round. The AR rests in the retard not advanced position. The springs will be just a little sloppy in this position. The AR opens to advance position when the engine has started. So you will get not kick back on starting. You only get that if the AR jams open in the advanced position. That's when it needs a clean chain tension etc. But you did mention that.

I do not understand why you have a problem going to Jampot, then getting springs you hope they will have brought to Jampot for you to collect. During the time of this topic running you could have ordered and received springs from club spares. There is still time to order and get them by this weekend. I don't know why you did not just order. Or have I missed something ?????

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Re: ATD Springs SR1 magneto

Postby SPRIDDLER » Wed Aug 14, 2019 7:53 pm

Rob Harknett wrote:John you have A & R the wrong way round. The AR rests in the retard not advanced position.

I read John's note as that he is aware that the unit should be at full retard when at rest but that the springs are in effect too long and do not pull the bobweights back sufficiently to put them in the fully retarded position when the engine is stopped.
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Re: ATD Springs SR1 magneto

Postby Rob Harknett » Wed Aug 14, 2019 8:17 pm

SPRIDDLER wrote:
Rob Harknett wrote:John you have A & R the wrong way round. The AR rests in the retard not advanced position.

I read John's note as that he is aware that the unit should be at full retard when at rest but that the springs are in effect too long and do not pull the bobweights back sufficiently to put them in the fully retarded position when the engine is stopped.

Sounds like that's the situation Nevvile. I was not thinking along the lines springs were actually that long and prevented the retard position be obtained. However, new springs could have been got by post before Jampot. I think an emergency fix years ago, would have suggested the use of Knicker elastic. Better suggest elastic bands now.

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Re: ATD Springs SR1 magneto

Postby Mick D » Thu Aug 15, 2019 6:29 am

Hi

Shortening the springs will have the desired effect of increasing their tension - unfortunately, by an undetermined level. The result could be the bob weights opening later or not fully at all.

If the bike runs OK now and it's too late to get a set of the correct replacement springs, I'd ride it to the Jampot and swap the springs there.

Regards Mick

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Re: ATD Springs SR1 magneto

Postby 56G80S » Wed Aug 21, 2019 3:44 pm

Thanks chaps.

Sprid, you had the problem spot on.

Yes, Rob, I did order but only got back today from Scotland to find the springs on the mat.

Mick, I've "adjusted" the old springs and got a full ATD movement back to retard. I'll soon find out if they do not go to full advance but expect that won't be a problem cruising maybe retard will cut in a bit early at slow speeds if so will fit the new springs at the Jampot.

Thanks for helpful suggestions.

Johnny B

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Re: ATD Springs SR1 magneto

Postby alanjennings » Wed Aug 21, 2019 3:49 pm

See you there, John- if you need a bed let me know!
Alan [Morini] Jennings

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