boyer timing

Having fitted the Boyer micro digital to my 84 mk11a, its running fine, tick over rock steady.
I checked the plugs after a run and now its running lean,( very white ). The plugs were perfect before I fitted the boyer.
I have strobed the Boyer and checked it with my rev counter as the instructions say. If my rev counter is out- as its not an original one but an after market replacement supplied by Norvil-could the ignition timing be the fault?

If the timing doesn't effect plug colour then do I need to go up a size in jets or down?
I never take it above 5000rpm and mainly 4000rpm which is 75 mph. Would this only be on the needle jets or main?
Thanks for any replies.
chris r

I've read electronic ignitions in britbikes can be timed for a little more advance than the 28 degrees BTDC recommended in the manual due to better control of the advance curve than can be established with points and bobweights on springs.

If there is no air leakage (leakdown test) and considereing how well it starts and runs, I would richen things up somehow, maybe raise the floats a shade. Or the jet needles a notch. I don't think it's too far advanced if you're sitting at 28 now and the engine can tolerate 32 (with proper fuel, of course).

blacklav said:

I checked the plugs after a run and now its running lean,( very white ).

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Checking plugs "after a run" probably doesn't tell you much.

blacklav said:

I have strobed the Boyer and checked it with my rev counter as the instructions say. If my rev counter is out- as its not an original one but an after market replacement supplied by Norvil-could the ignition timing be the fault?

Click to expand...

The actual revs aren't important as long as you rev it past the point where the ignition basically stops advancing.

blacklav said:

If the timing doesn't effect plug colour then do I need to go up a size in jets or down?

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Up, but I don't think you have yet established there is a problem.

blacklav said:

I never take it above 5000rpm and mainly 4000rpm which is 75 mph. Would this only be on the needle jets or main?

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Jetting is about throttle position, not RPM. At a constant 75 MPH the carbs are probably still running on their throttle cut-aways most of the time.



http://amalcarb.co.uk/downloadfiles/ama ... _guide.pdf

Danno said:

I've read electronic ignitions in britbikes can be timed for a little more advance than the 28 degrees BTDC recommended in the manual due to better control of the advance curve than can be established with points and bobweights on springs.

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The Boyer Micro-Digital recommended setting is 31 degrees BTDC (same as Micro MkIII & IV).

http://www.boyerbransden.com/pdf/KIT00084.pdf

One of the tricks with Boyer timing is to ignore your rev counter, just time it on your chosen full advance point when the Boyer has stopped advancing. You can see this with the strobe.
Boyer's can vary from unit to unit as to at what revs they reach full advance and Rev counters can be inaccurate.

Forget static timing on the microdigital, because at low revs, the spark stabilization feature means that the ignition curve is V shaped not linear.

Hope this helps

Charles

The old , if its peaky and lumpy ( responce )your advanced , if its dull 7 sluggish , you retarded ( or is that the Ignition ) .

Runnig 31 Deg. on a 750 with POINTS Ign , ( in good order ) One monitered the plugs for the center electrode rounding off ,
Being a sign of over advancement .

NEVEr Going over 5-000 , and if you expect it to pull from Zero , loaded and touring , around the 28 marks what your looking for .

If smoking it at the lights & baiting hondas , the 31's more appropriate .

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One could always set it at one & then the other , scribing a LINE at Each . Then mark of equal segments at 27 to 31 , and try Each .
Without having to re strobe it- then you could hustle what suits your riding , etc .

Whether you are running on the mains or the needle jets depends on throttle position, the revs are irrelevant. If the throttle is wide open, you are on the mains. If it is closed more than a quarter, you are on the needle jets. If you have increase the degrees BTDC with the ignition system and have not changed anything else, the motor will probably run leaner. You have a choice - either get the timing right with a strobe light and degree disc, or jet the carbs to suit the new timing by increasing the size of the needle jets, or lifting the needles a notch or two. I'd use the strobe light, especially if you get pinking.

Thanks for the replies guys, but if I strobe it to 32 degrees at 5000rpm it is almost impossible to start due to it kicking back, so I back it off a bit to 28 degrees which helps but it still needs full choke for starting even hot. I originally thought the unit was faulty but after returning it for testing and replacement 4 times it must be ok.
Ive altered the needle valves to there highest setting of the three, i.e. the lowest ring on the needle. It hasn't made any difference to the plug colour except the outer ring is black but the inner porcelain is still white.
Ill take it out for a long run soon and hope it settles down and the plugs colour up a bit, else book it into a garage and let the experts sort it.
chris r

Chris,
FWIW when I finally got around to checking TDC with a stop block I found my timing indicator located in the primary was off by 3 degrees. If you have a similar condition you could be at more than 32 degrees. Timing will show itself on the back strap of the plug. You should see a line of discoloration at the bend of the strap, if it's too close to the threads that will mean too much advance, too close to the open end would be retarded.

Pete

blacklav said:

Thanks for the replies guys, but if I strobe it to 32 degrees at 5000rpm it is almost impossible to start due to it kicking back, so I back it off a bit to 28 degrees which helps but it still needs full choke for starting even hot. I originally thought the unit was faulty but after returning it for testing and replacement 4 times it must be ok.
Ive altered the needle valves to there highest setting of the three, i.e. the lowest ring on the needle. It hasn't made any difference to the plug colour except the outer ring is black but the inner porcelain is still white.
Ill take it out for a long run soon and hope it settles down and the plugs colour up a bit, else book it into a garage and let the experts sort it.
chris r

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I have a boyer red box microdigital ignition. I don't use the enrichment levers to start the bike ever... I see them as just one more moving part to break. Because of that, my bike will kickback too if I don't follow a well learned procedure when starting it. My bike runs fine once it's started with the timing set at 31 degrees.

My starting procedure is to bleed the carbs until they puke fuel, Then lift the slides 1/4 turn while kicking the bike. Lifting the slides when you kick it, makes sure the engine gets a big gulp of fuel which keeps it from kicking back. My bike has a stock cam, but it is higher than stock compression. As I've said before, you wouldn't be able to kick it over without stradling the bike because of that higher compression. So, if there isn't enough fuel when you kick it over, the kick lever is coming back at you pretty forcefully.... I don't think of this as a flaw. It's a characteristic of a bike that has higher compression and inoperable choke slides.

I've messed with combinations of ignition timing, carb jetting, and a range of spark plugs. I tried running bigger mains to keep from being lean at WOT, but it turned out that the bigger main jet actually made the bike bog down above 80mph. After all my frankenstein experimenting, I concluded that the known suggested stock carb settings worked the best so I use the suggested needles, jets and recommended positions. I'm convinced that they are best.

As far as ignition timing goes, if you're really dead set on finding out exactly where you are, then you need to use a degree wheel to check the accuracy of the mark on your rotor. If you do that then you'll know for certain where your spark is falling when you strobe your timing. If you just retard your spark a few degrees to be safe, it probably isn't a big deal either in the performance of a street bike that never revs over 5000 rpm... My bike really comes alive at about 4000, and by 5000 it's pulling strongly. At 6000, I'm starting to think how much it will cost if I blow it up, and I just assume it will blow up above 7000 so I don't go there....

HTH...