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Bigsieuk
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VBMWMO #8791
Joined: 02/27/2012
Posts: 106

Hello all,

I have a 1939 R51 with Bing 1/22/61-62's from the R51/2.

It keeps sooting both plugs up though after a very short while (minutes). I've checked the points gap (0.4mm) changed the coil, condenser and plugs. I've tried reducing the jet sizes but this hasn't helped.

The only things I haven't changed are the HT leads and the points. One plug sooting up could indicate a problem with a single carb but both makes me think is a spark issue?

If it makes a difference both carbs have the schutzschraube.

Any ideas?

Thanks

John

Twocams
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VBMWMO #8750
Joined: 03/16/2014
Posts: 707
I have never owned anything

I have never owned anything that old & I was built in 1949. But let me give it a try. Where I live there is snow on the ground, in other words cold. So if I was to run an engine for a few minutes it would soot up too. Have you tried to get the engine up to operating temp? And see if it will burn the soot off. Also the heads and pistons could have soot build up. And when you start the engine it blows soot onto the plugs?
So that's just my .02

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Twocams
69 R69S
92 R100RT
2004 Aprilia Atlantic 500cc Scooter

Bigsieuk
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VBMWMO #8791
Joined: 02/27/2012
Posts: 106
sooted up when hot

The problem started on a run home. After about 5 miles its started spluttering and won't even get up to operating temperature. I'm inclined to think this is a spark issue.

I've replaced coil, condenser and plugs. Next to check is points, rotor and leads - hopefully this weekend.

Regards,

John

Twocams
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VBMWMO #8750
Joined: 03/16/2014
Posts: 707
I only lived in England for 5

I only lived in England for 5 yrs. But how is your petrol your using. Its newish, clean, no water in the tank. Nice blue spark from the plugs is always better than a weak Orange spark. You have checked the timing & its good? Im just throwing some stuff out there.

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Twocams
69 R69S
92 R100RT
2004 Aprilia Atlantic 500cc Scooter

Bigsieuk
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VBMWMO #8791
Joined: 02/27/2012
Posts: 106
Update

New petrol this weekend didn't help unfortunately.

New plugs this weekend too, it idled but the engine was missing when on throttle and sooted the plugs up within minutes.

I dropped the needles a notch which seemed to make a difference and it idled a lot better. I ran out of time (British weather) and didn't get a chance to ride it out on the road. I'll double check resistance through the leads and cap this weekend to see if I have a rotor/cap/lead related issue.

Regards,

Bigsieuk
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VBMWMO #8791
Joined: 02/27/2012
Posts: 106
Update - Resolved

Thanks to Peter Ardron, he found that it was an intermittent ignition board problem that was interrupting power to the ignition system causing a no-spark condition.

Regards

John

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