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Help, 69 t100c just started backfiring on accel.
#376829 06/02/11 9:11 pm
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sbolton Offline OP
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I've put well over 400 on this bike this year, and last night on the way home from work it started to backfire real loud during acceleration and run really rough, until I pulled the clutch in then it idled fine. I got home by nursing the throttle, playing with the clutch and running low rpms in high gears. I immediately got home and checked the plugs, neither are fouled, did a quick adjustment on the valves and then hooked up the battery tender. I am assuming its a plug/ignition issue of some sort. The bike has a Boyer mark 3, typanium, and a dual fire hd coil. Any thoughts, haven't had it back out yet but looking for any more ideas?


1969 Triumph T100c chopper
1972 Triumph Tr6r chopper, N the works
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Re: Help, 69 t100c just started backfiring on accel.
sbolton #376850 06/02/11 10:54 pm
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Hi,

Originally Posted by sbolton
boyer mark 3,

What's the voltage measured across the battery (with a meter)? If it's below 12V, that'll be at least one of the problems.

If it measures above 12V, bear in mind that the battery 'surface charge' could've risen since you got it home. Imho, one of the checks you should do soon is a proper 'load test' of the battery.

I'd check all the connections between battery and ignition switch very closely, particularly around the fuse holder - if the bike stil has the standard cylindrical glass-with-metal-end-caps fuse, I'd replace it as a matter of course - the fuse wire can come loose from an end cap, which is obviously not visible. frown

Trouble is, realistically, it could be any number of things, some electrical, some not. frown If you don't find something quickly, you could be down for a lot of frustration as you try to find an intermittent problem. frown Damhik. At least you'll get a lot of suggestions here. :bigt

If you do find yourself trying to find the cause of an intermittent problem, one thing that can help is having a supply to the e.i. directly from the battery. I make up a cable and terminals long enough to reach from battery -ve (assuming standard +ve ground) to the supply connection (White wire) into the Boyer-Bransden box - as this'll be attached to the battery terminal, it'll be live so include a fuse holder and keep the fuse somewhere handy.

The idea is that, if you're out riding and the bike starts to backfire or otherwise misbehave, you stop, unplug the B-B supply from the normal wiring through the switches and connect it to the direct battery supply, install the fuse and try and restart. If the bike restarts and continues without further misbehaviour, you know the problem isn't with the e.i.; otoh, if the bike won't restart, or restarts but soon starts misbehaving again, you know that the problem is somewhere in the suck, squeeze, bang, blow bits, if not necessarily with the e.i. itself.

Hth.

Regards,

Re: Help, 69 t100c just started backfiring on accel.
sbolton #376876 06/03/11 1:07 am
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Do the battery test per the article on GABMA. It's a test the team here came up with about 7 or 8 years ago. It's not a perfect test, but it will spot about 95% of bad batteries. And best of all, it's in your price range: Free!

You might also want to read the GABMA article called Boyer Backfire.

Most spitting and sputtering is caused by low system voltage, which IME has 3 causes....
battery not accepting charge
battery not receiving charge
• Other system device dragging down the system voltage

:bigt


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA
Re: Help, 69 t100c just started backfiring on accel.
sbolton #376881 06/03/11 1:38 am
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A lot of this goes on and it seems like a lot more lately.

I have had this happen in the recent past and after getting ready to check everything and start dismantling, I just by chance traced it to a faulty fuse holder, that was semi-pulled apart, extending the spring and not allowing it to close back up so it was making an intermittent connection. It would fire up and was really strong but on acceleration and especially around 3,000 RPM it would start the drill.

Fixed that and bingo....back in action and running like a rocket. Just something to check that is most likely overlooked. Especially with a lot of those cheap glass fuse holders around.


Last edited by Jon W. Whitley; 06/03/11 1:45 am.

Jon W.


1957 6T Thunderbird 650
1968 T100R Daytona 500
1971 TR6R Tiger 650
1970 BSA A65F 650
1955 Tiger 100 - Project
1971 BSA A65 650 - Project
1972 Norton Commando 750 "Combat"


"Every time I listen to AC/DC, so do my neighbors"

Re: Help, 69 t100c just started backfiring on accel.
sbolton #376886 06/03/11 2:17 am
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Thanks for all the input, something I didn't mention, I built this chopper from the ground up, all wiring is soldered, no crimps anywhere on the bike. I use the micro auto blade type fuses. The Boyer is also soldered, and I wired everything - ground when I assembled it. I am guessing the battery may be the culprit, but not sure yet. I will do the testing this weekend, I am also running the ngk iridium plugs. She starts beautifully on the first kick every time, I am also going to go ahead and change the plug wires, something I've been meaning to do anyway for awhile now. But nothing electrical on this bike is stock, heck the motor and the rear hub are the only close to stock parts on this chopper.


1969 Triumph T100c chopper
1972 Triumph Tr6r chopper, N the works
Re: Help, 69 t100c just started backfiring on accel.
sbolton #376893 06/03/11 3:29 am
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Unless you are very good at low power solder, solder is not the best for bikes. You heat the wire too hot, and the vibration will work harden it, and it will break.

We've covered that in the past.

I think the problem with back fire is the battery. But you should have it properly load tested, if you have an EI. The beauty of the GAMBS test, not withstanding.

Make sure your regulator is still sound. Test the AC current across the battery terminals.


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
Re: Help, 69 t100c just started backfiring on accel.
sbolton #376916 06/03/11 6:52 am
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How can you overheat copper wire?


Amateur Loctite enthusiast.
Re: Help, 69 t100c just started backfiring on accel.
triton thrasher #376925 06/03/11 7:56 am
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Originally Posted by triton thrasher
How can you overheat copper wire?


Bt would not have a clue but what he is parroting is stress concentration when solder soaks out along the cable core from the connecting point to where the wire is subject to vibration, the copper core them work hardens and can fracture.

Crimped terminations have a plastic sleeve outboard to prevent this.

Sounds like a voltage problem to the Boyer or a crook Boyer box, is it aircooled ?

I am also running the ngk iridium plugs.

Bought a pair of BR8E1X today, damn that hurt but they are good plugs, did you torque them down to 25nm + when first installed ?

Last edited by Tiger; 06/03/11 8:13 am.

1969 TR6R
7.62 x 51 is not a maths puzzle.
Re: Help, 69 t100c just started backfiring on accel.
sbolton #376926 06/03/11 8:48 am
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Been soldering everything from circuit boards on gaming units to wiring for autos/bike for 20+ years now with no issues. I just did a test on my battery, I got home last night and put the battery tender on it. Well the starting voltage was only 12.54, when the headlight, taillight-which is LED so not too much draw, and turn signals were on it dropped very quickly down to 11.63v. So, I guess its time to put out another 30 bucks on a battery, wish I could find a good sealed or Gel for this thing....


1969 Triumph T100c chopper
1972 Triumph Tr6r chopper, N the works
Re: Help, 69 t100c just started backfiring on accel.
sbolton #376936 06/03/11 10:34 am
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battery is obviously buggered as you diagnose, try Radio Shack or similar for a suitable AGM.

You could fit an Odyssey PC-310, damn good battery but not inexpensive.

Last edited by Tiger; 06/03/11 10:35 am.

1969 TR6R
7.62 x 51 is not a maths puzzle.
Re: Help, 69 t100c just started backfiring on accel.
sbolton #376944 06/03/11 11:10 am
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Btour,please tell us about the "AC"current test accross the battery?? Dick

Re: Help, 69 t100c just started backfiring on accel.
sbolton #376965 06/03/11 2:20 pm
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Sbolton, Batterystuff.com is where you need to go for a AGM battery for your bike. At the end of the list of bikes, there is "show all batteries",it will then show all the batteries, but more importantly,they give all the specs.and dimensions so on a modified bike you can get one that best fits your bike. Also I've found that the dimensions are exact. The prices are good and shipping is included. They even have the "new" lithium batteries. Jack

Re: Help, 69 t100c just started backfiring on accel.
Dick Harris #377000 06/03/11 5:02 pm
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Originally Posted by Dick Harris
Btour,please tell us about the "AC"current test accross the battery?? Dick


G'day Dick,

Happy to do so. I discovered this as a result of my rectifier failing, which is partial failing had been blowing my headlight bulbs. And btw thanks for the new holder.

The test is to see if the regulator/rectifier is doing its job of converting AC from alternator to DC which can be stored in the battery, and which the advance of EI needs to do its job. Thus when My rectifier finally failed altogether my bike back fired something awful and would even stall. I got stuck about nine miles from greenfield where the problem started. Headlights still functioned just fine.

One simply uses a voltmeter which is set to AC mode, touching its leads one to battery positive and one to battery negative. The reading should be only fractional. If more than one or more of the diodes are failing. I assume even regulators have diodes which can fail.

If the regulator has failed completely the battery will not charge, and the EI will fail with weird symptoms. With some EI's, AC can cause permanent damage to the advance in the box!


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
Re: Help, 69 t100c just started backfiring on accel.
Tiger #377005 06/03/11 5:10 pm
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Hi,

Originally Posted by Tiger
stress concentration
Crimped terminations have a plastic sleeve outboard to prevent this.

confused Crimped terminations? Been crimping terminals for nearly thirty years, only "plastic sleeve" I've ever fitted is the corresponding insulation.

Originally Posted by Tiger
ngk iridium plugs.
Bought a pair of BR8E1X today, damn that hurt

From a recent thread over on the BSA Board, I discovered B8EV and B8EVX are still available in GB as well as BR8EIX, but not in the US. confused Unless you specifically need the resistor, you might want to check if EV's and EVX's are available in Oz?

Hth.

Regards,

Re: Help, 69 t100c just started backfiring on accel.
Tiger #377007 06/03/11 5:28 pm
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My Dear Tiger,

I do not know why you feel the need to do this:

Originally Posted by Tiger
Originally Posted by triton thrasher
How can you overheat copper wire?


Bt would not have a clue but what he is parroting


Parroting has quite a nasty connotation. I do repeat, what I have read here in an effort to help people. Most people do not read a lot of these threads. They come with a problem. Get it solved and pretty much that is it.

Do I have incomplete knowledge? Yes. Guilty. I know only from my limited experience and what I have read from research. I do make quite an effort to research and understand. And I have freely stated my limitations in the past.

I make an effort to credit the knowledge to those who have it. Not as an effort to appeal to authority, but to give credit.

Do I parrot? NO! Do I repeat? Yes! Absolutely I do. The people with the real knowledge do not have infinite time, so I proffer there knowledge as best I can, in an effort to help.

But I have been thinking, that this is quite a waste of time, as the effort does not seem to be appreciated. And then have to put up with your derogatory remarks to boot.

If it were not for a few people, like Steverat, or Dvarney, who have made an effort to thank me, I would certainly have given this up by now.

I am not trying to win any contests or prove anything to anyone. Nor promote my own business nor fame. I am simply trying to do my best to help. If I have any selfish interest, it is just that by keeping myself immersed in these discussions, and commenting, I can help myself understand more clearly, and most importantly remember. And I can admit to feeling of warmth when a comment of mine actually helps someone.

As to the original statement. I have witnessed myself a solder connection I made a long time ago with a high heat solder gun. The wire broke more than an eighth inch from any visible solder. The copper wire were it broke was an off color. To give credit, John has warned us of solder connections. Certainly if one is adapt at low power, and uses shrink wrap or something of the sort, it is certainly a fine way to do motorcycle connections. Else the crimp is better way to go.

I have no way of knowing at the time, the knowledge of soldering that the poster had. Certainly, I did not know at one time. Until I had read the discussions here. Then I learn. And yes I repeat. How else does human kind learn and pass on knowledge?


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
Re: Help, 69 t100c just started backfiring on accel.
sbolton #377141 06/04/11 11:35 am
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Thanks Btour,interesting,never heard of that test before. Dick

Re: Help, 69 t100c just started backfiring on accel.
sbolton #377155 06/04/11 2:06 pm
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Checking for AC leaking from a rectifier has been test recommended by Boyer for as long as I have been associated with the product. This is most often seen with the original Lucas rectifiers, but the problem can happen with modern equivalents.

The home workshop test was to disconnect the output from the rectifier and run the engine. As Bob mentioned you can also use an AC voltmeter, if you have one, across the battery for a quicker test.

The leaking AC signal will trigger the box and cause it to fire in sequence to the false trigger signal, or not at all. It is not unlike the false signal that can happen when the black/white and black/yellow wires pick up stray Radio Frequency (RF) signals from the alternator wires.

It just happens that a few of the very, very early Boyer MKIV units trigger circuit was quite sensitive to this. Typically when you have an AC leak, when you fix it the box returns to its normal operation. With a few of the early MKIV boxes the AC signal would damage the unit. This problem was caught with some prototype units and corrected before the unit was put into mass production.

Re: Help, 69 t100c just started backfiring on accel.
sbolton #379813 06/20/11 3:06 am
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Ok, battery is now new and in excellent order, timing checked, valves checked. Went for a ride today with 2 new ngk br8eix in it and after 9 miles the backfiring started back up. I have since put the old b8's back in, but haven't had a chance for a long enough run to test it. Could the new iridium plugs have been an issue with the Boyer? Due to the resistor?

Last edited by sbolton; 06/20/11 3:07 am.

1969 Triumph T100c chopper
1972 Triumph Tr6r chopper, N the works
Re: Help, 69 t100c just started backfiring on accel.
sbolton #379829 06/20/11 7:52 am
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Sbolton

I had a similar problem a couple of years ago and also initially suspected and then replaced the battery to no effect. The bike would start up fine then as it got hot would start misfiring badly. I was at a loss as I could not find anything wrong with the wiring.

After much testing and head shaking (including having the EI box tested by tricor) it turned out that the EI stator was going open circuit intermittently. One of the hairline wire to the coils had severed but most of the time the broken ends were still touching. Tricor sent me a free replacement.

Not saying this is your problem but surely worth a close look.

Cheers Paul



1969 T100S
1955 Tiger Cub
Re: Help, 69 t100c just started backfiring on accel.
paulberry #379894 06/20/11 3:59 pm
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When you say the ei stator, are you referring to the plate under the points cover? If so I do have a spare since my first Boyer died after my coil cracked years back.


1969 Triumph T100c chopper
1972 Triumph Tr6r chopper, N the works
Re: Help, 69 t100c just started backfiring on accel.
sbolton #379896 06/20/11 4:25 pm
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Sbolton

Yes.
The stator is the plate that sits in front of the magnets.
It should have two coils on a twin to ensure firing every stroke.

I have a sparx unit and the static impedance through my stator coils is approx 120 Ohms. Somebody may correct me but I would suspect the Boyer to be similar.

Paul

Last edited by paulberry; 06/20/11 5:01 pm. Reason: correction

1969 T100S
1955 Tiger Cub
Re: Help, 69 t100c just started backfiring on accel.
paulberry #379944 06/20/11 8:08 pm
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What I thought, I will switch the plates out and see if it helps.


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1972 Triumph Tr6r chopper, N the works
Re: Help, 69 t100c just started backfiring on accel.
sbolton #380420 06/23/11 5:02 am
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I've decided 2 boyers in 10 years is enough, granted the first died because the coil cracked and shortest it out. Tri Spark is ordered, simple, easy and cleaner. The Boyer worked good but failed twice too often.


1969 Triumph T100c chopper
1972 Triumph Tr6r chopper, N the works
Re: Help, 69 t100c just started backfiring on accel.
sbolton #381015 06/26/11 10:19 pm
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btour>
Once again Tiger was way out of line.
Personally I dont think being directly rude on this forum should be accepted, but hell... I´m no moderator.
After all, the goal is not to scare people away, but help people to a better understanding.
Several people has been deeply insulted by Tiger and for no obvious reasons.
Apparently he´s a grumpy old fart and should be ignored for his comments unless of technical interest or relevance.


*******************
Run `em...
*******************
1969 T120
Re: Help, 69 t100c just started backfiring on accel.
sbolton #381047 06/27/11 2:04 am
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Problem has been solved, thanks for all of the input. After installing the nifty new tri spark the problem persisted. I eventually traced the coil power wire back about a foot from the coil where it was zip stripped to the frame. I grabbed the wire and it snapped under the zip tie. Good thing I have another project the Boyer can go on, or it might also get a tri-spark, it is nice how compact they are. Thanks again for all of your input.

Shawn


1969 Triumph T100c chopper
1972 Triumph Tr6r chopper, N the works

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