No Advance

willy mac · Aug 7, 2012

Just checking the timing after thinking I heard some "Pinking" on the last run.
Engine set at 31BTDC, Boyer ignition (Only ident for mk no is on the backplate and it's NT1a)
Rotor magnet set just before the pick up (If it's set in the CW window like the instructions say it wont fire up so I suppose it's a bit retarded)
Start up the bike and strobe all the way from Idle up to 5000. The timing mark just seems to stay put all the way through and I'm guessing around 20-25 degrees and shows no change for any RPM.
I've tried to find a thread that mentioned something about the pick up wires being reversed but cant remember if that was something to do with the advance.
The engine has the timing canister up behind the barrels so the rotor turns clockwise.
I'm wondering if this ignition problem might be one of the reasons for the Exhaust headers to start glowing when it's given stick doing the timing?
Anyone any idea's ?

L.A.B. · Aug 7, 2012

willy mac said:
I've tried to find a thread that mentioned something about the pick up wires being reversed but cant remember if that was something to do with the advance.
The engine has the timing canister up behind the barrels so the rotor turns clockwise.

Yes, if the Boyer pickup wires are reversed then the timing doesn't advance (or doesn't retard from the fully advanced setting-whichever way you wish to look at it?).

Also if I remember correctly, if the wires are reversed, then it also alters the actual timing position.

Hobot · Aug 7, 2012

Yep sounds like trigger wires reversed which shoves timing to hi advance. Might also check behind the plate in case magnets clipping terminals. Best way I found was just diddle plate adv. til slight backfire on kick off then retard till it just don't then put a light on for something to due I can objectively relate to myself or others. The trigger wires should of long ago been upgraded and the new terminal must go on as instructed not as best mechanical back up with nut behind. If not done already all bets off on any other advice. Low voltage may also do this but not if rpms over 2000-ish when charging up speed, unless of course the battery is a big drag.

willy mac · Aug 7, 2012

Cheers guys I'll try that swap over in the morning I don't think the good folks around me would appreciate a commando at 5 grand this time of night!

Matt Spencer · Aug 7, 2012

No appreciation of the acoustical properties ringing through the Lochs and hills and valleys ? Whats the world coming to . :?

willy mac · Aug 8, 2012

Matt Spencer said:
No appreciation of the acoustical properties ringing through the Lochs and hills and valleys ? Whats the world coming to . :?

A Ken, no appreciation at all ! But at 09:30 they were treated to the cacophony of the mighty twin with a working advance.
I'm not electronically minded but I can follow the basics, I thought those two wires were just for the triggers can anyone explain in " Boyer for Dummies" language how having those wires reversed causes the advance / retard not to work ?

dynodave · Aug 8, 2012

Last Saturday at our groups open house tech session, we dove into a commando rear distributor/boyer problem also. On the distributor machine the boxes (old MKIII and new MKiV) worked...advanced and made spark, so the wiring was identified and was correct. Then installed on the bike the box would both retard and go erratic with increased speed.
Tested several times it was postulated that possibly resonant chain whip affected the position or instantanious velocity affecting the voltage to the final transistor stage. The chain tension was the next step but will be posponed until we can gain better access to the bottom nut on the distributor housing.

reverse pickup wire retards the timing by 30+ degrees. Recorrecting them advances the timing by the same. The normal wiring makes a single sine wave negative going first the positive is ignored....reverse wireing makes a single sine wave, positive going first which is still ignored by the box and the negative is now always starting as the magnet goes by the post/pickup....and you get fixed /no advance

willy mac · Aug 8, 2012

dynodave said:
Last Saturday at our groups open house tech session, we dove into a commando rear distributor/boyer problem also. On the distributor machine the boxes (old MKIII and new MKiV) worked...advanced and made spark, so the wiring was identified and was correct. Then installed on the bike the box would both retard and go erratic with increased speed.
Tested several times it was postulated that possibly resonant chain whip affected the position or instantanious velocity affecting the voltage to the final transistor stage. The chain tension was the next step but will be posponed until we can gain better access to the bottom nut on the distributor housing.

reverse pickup wire retards the timing by 30+ degrees. Recorrecting them advances the timing by the same. The normal wiring makes a single sine wave negative going first the positive is ignored....reverse wireing makes a single sine wave, positive going first which is still ignored by the box and the negative is now always starting as the magnet goes by the post/pickup....and you get fixed /no advance

Thanks dynodave, I understand that explanation, you're obviously well versed in "Boyer for Dummies" language.

Hobot · Aug 8, 2012

Ms Peel and I have done all the dumb analog Boyer mechanical and electrical fault experiments. In her case w/o any cam chain tensioner left to tension chain at all, Peel was easy starting, steady idle and useable powering, up to 4900-5000 rpm, then would not rev higher, unless going down steep enough slope gravity alone increased speed, till terminal velocity reached by air resistance of huge windscreen at ~110 mph. Ie: fine with no cam chain tension but low power below 5000 and NO power above that. No rough misfiring detected but seems like too advanced so counter pressure stifled further rpm or too retarded to make much combustion pressure. I sold this Boyer off for its innate sluggish advance curve to Michael Tagileri who I think is still using it normally.

No Advance

willy mac

L.A.B.

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Hobot

willy mac

Matt Spencer

willy mac

dynodave

willy mac

Hobot

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