Four Stroke / Tractor

Joined
May 27, 2006
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54
Running my 750 Roadster the last couple of trips it just hasn't felt quite right. Difficult to put finger on, but at in town speeds & throttles it sounds a bit like it's missing - something like model aircraft engines when they 'four stroke'.
Out of town when you open up it comes together - no shortage of power & whisks up to 90 no prob, but rough again when back in town.
I've checked the timing - correct to the marks, which may mean about 1deg over advanced ( scale checked to degree wheel).
Plugs look ok - a bit sooty on the outer metal rim when I stop, but the ceramic is pretty clean.
The only other change is that on kickstarting it seems keener than usual to have a go at wrecking my ankle by blowing back, but perhaps that just means I'm weakening!
The ignition is old style Boyer
Would appreciate any pointers at to where to look, or if I'm missing something obvious :oops:
chris
 
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Apr 7, 2004
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Check the kill switch and the key switch first for voltage drops. Then check the engine ground to the head to see if that bundle broke at the terminal. If you run a wire from the hot side of the battery to the power in on the Boyer just as a test and that fixes the problem it's one of the switches. Don't forget to check all the grounds I add a few but the boyer to battery ground and the engine are most important. The rest depends on what coils ,plugs and wires you run. You have to make sure that the trigger wires from the Boyer plate have not broke inside as well. Kind of a list of most often found to be a problem.
 
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Apr 5, 2006
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Hi

I had a similar problem last year. Turned out to be a knackered battery (the zener diode was allowing it to overcharge it & it buckled the plates but thats another story). Basically, when running at low revs (ie around town) the alternator does'nt provide enough charge and the battery takes over - if the battery is iffy and does'nt give the Boyer enough volts, the Boyer will retard the ignition giving you erratic running (also a sore leg when kicking over!). Once on the open road and the revs are higher the alternator takes over, and the ignition advances properly and all is sweet again!

Hope this helps.
Alan
 
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May 19, 2006
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Classic symptoms for Boyer-equipped bikes. It certainly sounds as if the unit is not seeing 12v plus.

As the others have said, it could be battery, connections or wiring. How old are yours ? If you think they're a bit iffy then it might be best to re-do it from scratch because the voltage drop is often cumulative and finding one problem and rectifying it doesn't mean that there aren't others lurking, waiting their turn !
 

L.A.B.

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Alan W said:
if the battery is iffy and does'nt give the Boyer enough volts, the Boyer will retard the ignition giving you erratic running (also a sore leg when kicking over!).

As far as I am aware, low voltage causes the Boyer to over-advance, and not retard, -hence the sore leg when kicking over!
 
Joined
May 27, 2006
Messages
54
Many thanks! - Good suggestions, and the weather forcast for the weekend is good, so I should be able to work through the ignition wiring & volts. I'll report back later :D
 
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Apr 5, 2006
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Alan W wrote:
if the battery is iffy and does'nt give the Boyer enough volts, the Boyer will retard the ignition giving you erratic running (also a sore leg when kicking over!).

LAB wrote:
As far as I am aware, low voltage causes the Boyer to over-advance, and not retard, -hence the sore leg when kicking over![/color][/size]

Les, yep I think you are right again. My mistake, I scibbled the note down a bit too quick!
 
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