Timing

Skoti said:

I'm beginning to think the problem may be with the transistor box. The numbering reads:- BOX 00017 03/10/17 (maybe it's not the correct box).

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Box 00017 should be the correct one? See "KIT00053" on the BB website data sheets page: http://www.boyerbransden.com/html/data_sheets.html

Does the pickup plate have "NT 1a" on the back?

Skoti said:

I mentioned the motor runs a bit hot, do you think that might be caused by the ignition not auto advancing?

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If it isn't getting to full advance, then that would be possible.

Hi,

thanks for that bit of research, at least I know the box is correct.
I'll take a look at the pick up plate number in the morning because I'm having a beer or two right now and trying to regain my sanity!

It seems that Boyer do have a problem with units not advancing, think I'll fit a Pazon system.

Somebody else with the same problem as me:-

Amongst the bike's teething troubles was that no matter what I did about timing the ***** unit it simply would not advance or perhaps it was simply stuck on full advance. Hence a horrible lack of power.

This guy had his MK111 boyer fitted to a Triumph TR6

Hi,

after a good nights sleep I'm thinking a bit clearer about this boyer problem.

I reckon that the stator wires might be connected the wrong way round inside the transistor box, which would produce fixed timing (no advance).

When I fitted the stator plate and rotor I followed the boyer instructions regarding positioning the stator and rotor and crank etc, but no way could I get the motor to start within the stator adjustment range. I had to re-position the rotor about 30 deg before it would start.

Check out this from BritBike Forum:-

People are confused about swapping the black/yellow and black/white wires. If you cross the wires the box will change the time it fires the coil by approximately 30 degrees (60 crank degrees). With the wires crossed the bike will not start until it is retimed.

It is true, that when you cross the wires, you basically have a fixed advance ignition. There will be little, if any, change where the ignition fires the plug as the rpm's increase when the wires are crossed. It also means that you have to use the opposite timing hole (in your case instead of using the counter-clockwise rotation timing hole you would have to use the clock-wise hole).

Think I'll change the stator wires over (black/yellow to black/white) and set up the stator and rotor as per Boyer instructions. Then try and get the motor running and check for ignition advance. It's worth a try while I wait for a reply from Boyer technical dept. :idea:

Hi,

I just want to report back and say changing the stator wires across has fixed the problem and I now have ignition advance!

My conclusion is that Boyer must have assembled the transistor box with the stator wires the wrong way round.

Really annoying as I've spent a lot of time trying to figure out this fault and probably would have struggled a lot more had it not been for the advice from members of this forum.

thank you very very much indeed!

Skoti said:

My conclusion is that Boyer must have assembled the transistor box with the stator wires the wrong way round.

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Glad to hear you sorted the problem, however, before blaming Boyer 100% for incorrectly wiring the box I suggest the wires between the box and the pickup plate should be carefully checked to see if there are any extra joints somewhere along the pickup wires?

Also, the wire colours could be wrong at the pickup?

Fracture of the wires at the soldered joints on the pickup is a fairly common problem on Boyer equipped Commandos due to the amount the engine shakes around, and there should be a small cable tie that secures the two wires to the pickup board? If that tie is missing then it can accelerate the fracturing process. Also a previous owner could have re-soldered the two wires after a wire fracture, and may have soldered the wires back to the plate the wrong way around? Old stained and faded Black/White and Black/Yellow wires can look remarkably similar in poor light.

I must admit that I forgot to spell out that the timing would need reseting after the switching of the leads. Assuming you would figure this out as part of the work was my bad. You are not the first one as you say. The failure to advance was the giveaway. Be sure to clean the kill switch contacts inside on the casting if the power to the Boyer flows through there. And make sure you have all the proper grounds going to a common ground (rectifier bolt) and than a heavy wire from there to the positive battery terminal.

Hi,

I'm sure the fault is with the Boyer transitor box as I have owned this bike from new and never had problems with the stator harness, it remains original and unaltered.

This morning I double checked the wires where they join at the harness under the fuel tank and also carried out a continuity test from there to the stator plate.
It would be difficult to confuse the black/white and black/yellow cables in this case.

I have cable tied the connectors to one of the stator coils and left sufficient free play on the cable that enters the timing cover from the frame tube.

The triangle plates that connects the head steady to the frame (via the rubber mounts) I use for a common connection point for cables with eyeletted connectors running from the coils, rectifier and battery.

Never had problems with the kill switch but it's probably worth an inspection.
The high tec Morris 1000 type ignition switch has been renewed twice in 48,000 miles though!

Maybe I should run a short automotive braided type earth strap from the triangle plate to one of the head steady bolts which screw into the cylinder head as well?

My problem is that I should step back and think about problems rather than wield spanners and tear things apart indiscriminately.
Had I thought about Norbsa's advice properly about the swaping of the cables then I would have solved the problem yesterday.

Anyway thanks again for all the advice given

Skoti said:

I'm sure the fault is with the Boyer transitor box

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OK, but I still can't quite see how you can be 100% sure that it's the box wire colours that are wrong, and not the pickup wire colours reversed at the pickup plate connections?

As you look at the outside of the pickup plate where the wires connect into the board, the Black/White wire should connect to the board on the left, and the Black /Yellow on the right?

The Boyer Box should show how the wires enter the box by colour identification on the box sticker?

Again B/W on the left, B/Y on right, looking at it with the writing on the box sticker the correct way up?

o.k.

I take your point the Boyer fault could be with the transitor box wiring or the stator plate wiring. Thanks for the wiring layout info.

I'll take a look tomorrow and let you know

Hi,

I've checked the wiring at the stator plate and at the transistor box, it checks out correct.

So once again I must assume that the transisitor box has been incorrectly assembled (although it's not possible for me to dismantle it and inspect it).

I don't want to send it back to Boyer and have to wait a couple of weeks or so while they test it etc, so I'm just going to run with the wires crossed around.

Here's the reply from Boyer technical:-

Dear Sir, between idle and 3000 rpm the ignition should advance at the crankshaft by about 15 degrees, there would be a slight further advance between 3000 and 5000 rpm but this would only be in the order of 6 crankshaft degrees. If no advance is detected during strobing, check the polarity of the black/white and black/yellow stator plate wires is correct.

It's more or less the advice given by Norbsa.
But also for people who don't want to strobe ignition at 5000rpm all thats needed is to strobe at 3000rpm and set it to 24 deg, then at 5000rpm the advance should be 30 deg.

once again thanks to all for your input

Skoti said:

But also for people who don't want to strobe ignition at 5000rpm all thats needed is to strobe at 3000rpm and set it to 24 deg, then at 5000rpm the advance should be 30 deg.

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If people used a calibrated tachometer, and if Boyer ignitions all had identical advance curves, then I would be inclined to agree with that.

However, the advance curve has been known to vary considerably between individual Boyer boxes. Even if the tacho used was dead accurate there would be no guarantee that the ignition advance would be exactly right (31 deg at 5000 RPM) if timed to 24 deg. at 3000 RPM, so a check at 5000 RPM really ought be carried out as soon as the owner considers it prudent to do so if the engine has recently been rebuilt?

yes,

perhaps if you want to extract every last shred of power from your motor then maybe it's better to strobe at 5000rpm.

But I think I'll follow the lead from Boyer technical department for now and set the timing to 25 deg @ 3000rpm, assuming that a further advance of 6 deg is available at 5000rpm.

If I encounter any problems with performance I'll report back, just for the record!

L.A.B.'s advice is good the danger is being off at 5000 RPM And trying to hold 3000 and make adjustments is crazy. You should have no fear of doing the job right and revving to 5000 for the 10 seconds it takes to get the reading at 5000 when visible movement has stopped under the light of the strobe.
The next thing we will be hearing is how you stuck a valve on the carbon deposits in the head. Or that you blew up your motor doing only 3000 rpm up a slight hill. Are you reading all this break in procedure out of a manual from 1972 If so there's your problem.

So how do we know if the tacho is exactly accurate at 5000rpm then? :?

Skoti said:

So how do we know if the tacho is exactly accurate at 5000rpm then? :?

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That's easy, if the bike is on its mainstand, 5000 rpm is the point where it starts to go round in circles and the neighbours come round to complain about things falling off their shelves

The point is that at 5000 or above, the timing should be fully advanced so it doesn't matter if it's really 5000 or 5200 for example.

O.K.,

thanks for that scientific explaination!
Sort of along the same lines as Mick Hemmings advice ' give it a bit of a rev up and make sure it don't go above 30 deg'

Just be thankful you're not strobing a Lucas Rita system? As that would need checking at 6-6,500 RPM!

Yes,

I replaced my 30 year old Lucas Rita with the boyer I've just fitted, because starting and idle was getting difficult. But in the end it turned out that the coils had been shorting out because the brackets had graudally been overtightened (by me) over the years.

I've just checked the old Lucas Rita timing instructions which reads 20 deg @ 2000rpm and 28 deg @ 6500rpm. Although I never risked strobing it at 6500rpm in 30 years of riding with it fitted.

L.A.B. said:

However, the advance curve has been known to vary considerably between individual Boyer boxes. Even if the tacho used was dead accurate there would be no guarantee that the ignition advance would be exactly right (31 deg at 5000 RPM) if timed to 24 deg. at 3000 RPM, so a check at 5000 RPM really ought be carried out as soon as the owner considers it prudent to do so if the engine has recently been rebuilt?

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On my 850 with Boyer igniton the auto advance range is about 20 degrees from tickover to 5000 rpm. The result of this is that if I set the timing at 31 deg at 5000 when it drops back to tickover the timings at about about 10 to 15 deg and the bike just will not tick over smoothly and pops and bangs in the exhaust and sounds terrible.

How do you solve that problem then other than by setting the timing to about 45 deg advance at 5000 rpm when it will then be on about 25 deg at tick over and sounds sweet as a nut