Boyer MkIII Timing Curve

Parker · Jul 4, 2006

74 850 Roadster
Has anyone had experience of the Boyer analogue advance curve getting out of spec? My bike runs fine when timing set to 31 deg at high rpm, but bike doesn't want to idle smoothly. Checking out & tuning Amal Mk1's won't fix it so adjusting timing by giving more advance at idle makes a huge improvement - but now bike pings under load a cruise, ie too much advance at top end. Saw on a site that Boyers advance can vary by up to 10 deg at low end, (due to manufacuring tolerances?). Does anyone have experience of this? I'm tempted to buy a digital unit, but some say they are no better.

norbsa48503 · Jul 4, 2006

You need to skip past the digital and move on to the micro power Or use the Pazon who developed the system for Boyer. Pazon also does mark three's if your bugeting.

79x100 · Jul 4, 2006

My old Boyer has started doing a similar thing. Could it be fuel quality related ? After years of setting it at 31° I now find myself setting at 34° in order to obtain an even tickover.

I found this out by accident after it ticked over nicely when statically set but got worse after strobing.

My low comp (at least I think they all are) 850 Mk111 running super unleaded doesn't have a pre-ignition problem at those settings.

When I put on my spare Boyer as a control, it retarded instead of advancing (yes, I did check the wiring, though I'm not sure that should cause it !) The response from Boyer was the usual "nothing wrong with it" I have to admit that I haven't tried it since but I am very seriously considering the Pazon route.

concours · May 6, 2012

Re:

79x100 said:
My old Boyer has started doing a similar thing. Could it be fuel quality related ? After years of setting it at 31° I now find myself setting at 34° in order to obtain an even tickover.

I found this out by accident after it ticked over nicely when statically set but got worse after strobing.

My low comp (at least I think they all are) 850 Mk111 running super unleaded doesn't have a pre-ignition problem at those settings.

When I put on my spare Boyer as a control, it retarded instead of advancing (yes, I did check the wiring, though I'm not sure that should cause it !) The response from Boyer was the usual "nothing wrong with it" I have to admit that I haven't tried it since but I am very seriously considering the Pazon route.

EXACTLY what I observed today. Static set up ran PERFECTLY... ran it 120 miles. Today I put the strobe on it, it was at 45 degrees, so brought it bck to 31. The bike now backfires under light throttle, idle is poor. I was thinking of advancing it, but not sure what the pump gas will tolerate.

72Combat · May 6, 2012

Got the same problem with an analogue on my BMW racer, set to correct max advance, won't idle very well, advance for smooth idle and its too far advanced at the top end. the Pazon site has a good read on the differences between the two.
Turns out the analogue just keeps on advancing...... and I think its voltage dependent and advances too much on starting. I have one on my Combat and if the battery is not fully charged it kicks back. I'm planning on ditching it later in they year for a Pazon.
I am fitting a programmable Ignitech one to my BMW, so I can set the limits, curve and even a limiter.

ranmar850 · May 6, 2012

...and this is where the Tri-Spark comes in. Idle stabilisation feature seems to work wonders. So much easier to get a reliable idle , twin Amals still fitted. You find you will get out of the habit of blipping the throttle at the lights, just to make sure it keeps going. Just sits there happily idling , just like those bikes with single Mikuni's fitted. And they reckon it's all the Amals' fault...

bmwbob · May 7, 2012

Parker said:
74 850 Roadster
Has anyone had experience of the Boyer analogue advance curve getting out of spec? My bike runs fine when timing set to 31 deg at high rpm, but bike doesn't want to idle smoothly. Checking out & tuning Amal Mk1's won't fix it so adjusting timing by giving more advance at idle makes a huge improvement - but now bike pings under load a cruise, ie too much advance at top end. Saw on a site that Boyers advance can vary by up to 10 deg at low end, (due to manufacuring tolerances?). Does anyone have experience of this? I'm tempted to buy a digital unit, but some say they are no better.

See my previous post!

rpatton · May 7, 2012

Check out Dave's comparisons of the various Boyer timing curves. I read someplace that Boyer can alter the stock curve on the Micro Digital or the Micro Power to anything you want. I've never heard of anyone taking them up on it.

http://atlanticgreen.com/norton.htm

Boyer Exposed
Boyer Evolved

pommie john · May 7, 2012

In my experience, most problems with Boyer Mk3s are down to poor voltage either from a bad battery or poor connections somewhere along the way. Either bad switches, corroded connections and the like.

Check the wiring and battery.

72Combat · May 7, 2012

My friends boyer on his Triumph was not working, and it had been running a bit intermittent. spent about an hour checking it and found the cable from the pickups to the ignition looked to be open circuit. We ran a temp pair for testing and it fired into life, I then soldered up the connections and it ran fine for the following weekends racing. They do stress you need good earthing too. But the advance issue is probably a design thing.
I found this when I was trying to work out why more advance would improve the idle ( BMW) but give too much advance.....the explanation I found here matched my findings. Can't comment on the Pazon but I might spring for one for the Combat as they are made 'down the road' from me. My Combat idles fine...I assumed it was because PO had fitted brass sleeves to the slides.

http://www.pazon.com/files/PDF/info1/PAZONvBOYER3.pdf

JimC · May 7, 2012

Soldering those leads to the pickup coils is what caused the Boyer to fail in the first place. Doing the same thing will get the same results. I know of no bike or auto manufacture that uses solder, unless the connection is potted.

rpatton · May 7, 2012

Those leads often break right at the point where they are zip-tied to the board. It's brought on by the fact that people tie the cable that houses the wires to the frame near the engine. The engine vibrates quite a bite relative to the frame, so the wires get tugged at. There should be a rubber sleeve in the timing cover, 061093 that will help buffer that movement some. You can modify the pickups in a number of ways to eliminate the problem.

JimC · May 7, 2012

The problem is the solder, not the zip tie. The solder turns the wire from a stranded flexible wire into a solid wire when the solder wicks up the wire some inch or so from the connection point. Then our old friend vibration takes over. Flex that solid wire a few 100,000 times and it breaks, whereas a stranded wire is not susceptible to break from vibration.

rpatton · May 7, 2012

pommie john said:
In my experience, most problems with Boyer Mk3s are down to poor voltage either from a bad battery or poor connections somewhere along the way. Either bad switches, corroded connections and the like.

Check the wiring and battery.

If there was ever a situation that was asking for a relay, then the power supply to the ignition is it. Everything from the ignition switch to the many bayonet connectors, to the kill button are great places for a voltage drop to a unit that is sensitive to that very issue. With a relay you don't eliminate those circuits, you reroute the power to switch the relay on and off. The relay switches unadulterated fused power directly from the battery. Tony Foale explains it well.

http://www.tonyfoale.com/Articles/Ignition/Sidebar.htm

rpatton · May 7, 2012

JimC said:
The problem is the solder, not the zip tie. The solder turns the wire from a stranded flexible wire into a solid wire when the solder wicks up the wire some inch or so from the connection point. Then our old friend vibration takes over. Flex that solid wire a few 100,000 times and it breaks, whereas a stranded wire is not susceptible to break from vibration.

I can only talk about the way it happened on my bike. The wire strands broke right at the ziptie. The insulation was intact but a little wiggle would show the fault in the continuity. It seemed to be more likely to show itself when the engine was warmed up and the insulation softened up some.

bmwbob · May 7, 2012

rpatton said:
Those leads often break right at the point where they are zip-tied to the board. It's brought on by the fact that people tie the cable that houses the wires to the frame near the engine. The engine vibrates quite a bite relative to the frame, so the wires get tugged at. There should be a rubber sleeve in the timing cover, 061093 that will help buffer that movement some. You can modify the pickups in a number of ways to eliminate the problem.

I just put a hunk of old rag over leads to absorb vibration. No more broken leads!

JimC · May 7, 2012

That's exactly right. Where is the zip tie in relation to the soldered connection? Did you happen to strip the insulation from the broken wire? No doubt, if you did, you have found solder at the break in the wire. I'm not doubting your experience or expertise, I'm just telling you what caused the wire to break. It's the solder coupled with the vibration. You have to eliminate one. Looking at the photo of the Boyer board you posted, it looks like you or someone have done the best fix.

concours · May 13, 2012

screw it, going back to my roots, timing by ear. Advanced it back plenty to where the static timing mark was, I'll listen for pinking, feel for kick back, advance until I get some, then come back. The 31 degrees at 5000 was, as we say in Boston, "wicked retahdid!" and it was doggy as hell.

Boyer MkIII Timing Curve

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