Forum

[ChrisD]

Hi Guys
I have a 1996 twin-plugged 535cc Bullet with twin lead coil and have long thought the advance mechanism (the second one I have tried) does not give a proper advance rate because (a) the acceleration rate is minimally changed and (b) the new downpipe is browning along fully 50cms despite the strobe-tested correct max advance (28deg) from a reduced-movement A/R mechanism (between 9-10degrees). In this regard, I have also taken advice from this message board and added stronger A/R springs and reduced the weights to ~10gms but still don’t feel it is advancing suitably.

I am considering replacing the A/R mechanism and points with a Boyer. But which one - the standard Mk4 or the Digital? The Digital one apparently gives a better advance curve for the 500cc.
Can anyone suggest what the right one is?
Thanks and compliments of the season to you all

[Mark M]

Chris, 28 deg full advance is the standard figure is it? If it is, surely your twin plug set up will require less advance? Maybe this is causing (part of) the problem?
REgards, Mark

[Alan R]

Hi guys----- and CHRIS D...A couple of "points" for you ( OH DEAR !!--just realised what I've typed !!..not very punny at all !!)........First is}--- no matter what sort of ignition system you fit on these engines they are still attached to that gear wheel drive train with all the backlash that goes with it.........Second}--- As Mark M points out, with twin plugs the full advance setting can actually be retarded a little as the combustion will be more efficient etc..........My suggestion would be to fit the Electronic system at the given figure then retard a bit at a time until the engine "feels" happy..REMEMBER that a 1 degree change on the distributor is 2 degrees at the crankshaft so it's SMALL increments only !!.Don't forget also that you'll probably have to re-set the idling speed as well......... Not the best time of the year to be doing this ????........

[PeteF]

I really wonder whether two plugs make any difference on this sort of engine.
Unless it's been very highly tuned.

[ChrisD]

Gentlemen
Thanks for the quick reasponse.

The standard advance is 10deg static plus 22degrees from the A/R (only 11 degrees measured at the A/R because it rotates at half-speed) to get the full advance of 32degrees. I reduced that by 2 because of the twin plug and another 2 because of the 8.5:1 compression. So I closed up the slot in the A/R plate with J&B Weld to 9 or 9.5 degrees A/R movement. With a slightly retarded static setting of ~0.6mm BTDC gave me a maximum advance of 28 degrees. I have tried it at a few more and less advanced with minimal effect. And there has to be a reason for that minimal effect.
The timing gear has lash, yes. But that always in the same direction at the time of the spark when the bike is running. So if the maximum advance is set using a strobe, then that's really all that matters. BUT the A/R mechanism has its own slop and this results, when using a strobe, that the thin line that is the timing mark gets wider and wider as it advances up to a centimetre or so!

Of the two distributors I have, the original one has a bush and the replacement one has bearings, and since they both have the same effect, the error cannot be slop on the shaft. I suspect it is a less-than-free A/R rotation. Yes it is quite free when hand-held and it is lightly oiled too, but maybe that free advance m ovement changes with temperature or the friction from the rotational pull or whatever.................
I'm tired of not getting anywhere when I try changing the A/R setting, so now I am game to try something else. The real question is, can the boyer setup, as sold for a single spark, handle the twin spark?

Has anyone out there actually proved, using a strobe, that the advancing mark gets no wider even at full advance?? Because if the strobe is in any way correct, that means my spark comes at different advances varying by ~10 degrees. Has anyone else seen this?
Thanks
ChrisD

[tribonnie]

Chris, you need to retard the ignition some where around 8 degrees from the standard 32 degrees fully advanced. There is no exact figure as it will depend on the state of your engine tune. The only way to find the best figure is by trial and error, Set the fully advance at 24 degrees fully advanced using a timing disc and strobe. Take the bike for a run, move the timing a degree or so and ride again. Or if you have a well tuned engine book an hour on a dyno, well worth it and not that expensive. Richard

[Phil Ashbrook]

The boyer digital kit has a advance curve at about the middle of different states of tuning , I'm not sure if the Boyer could deal with Methonal but by that stage they recomend the crank driven magneto . I wish our hosts could make one that lets you have an alternator . and a programable ignition box ..6 settings kind of thing .

[mauri]

hello,

i have the digital boyer on my bike bought from our host.
this is only as good as the play you have on the timing gears.
on my original gears i had a static play of 7°, which made the timing quiet erratic.
i solved this by buying a couple of idler pinions, and using the ones that gave me the least amount of play.
the adjustable cam spindles also ad to minimalise the play.
i now have les than 2° static play, which results in a nice steady tick over and the pinging has become very rare.

if you want to use this ignition with a second spark plug, there is part 92075 as sold by our host.

the ideal would be a heftier crank mounted system like part 92011, alas this does not charge a battery.

[Norm]

Chris,
Not sure what you are hoping to achieve, don't forget this is only an Enfield not some high tech machine that is super timing critical

[Alan R]

Norm---------- getting an Enfield started is an achievement in itself, isn't it ??