Running in,- should I worry?

[alanjennings]

Unleaded fuel tends to leave a sooty deposit round the top edge of the plug, but the electrodes should be clean.

[Ib-Denmark]

Unleaded fuel tends to leave a sooty deposit round the top edge of the plug, but the electrodes should be clean.

The electrodes look ok and I have no starting problems at all.
Regards Ib

[pkr87]

Pinking will not cause the engine to tighten up but if ignored could eventually burn the piston. After the re-bore did you set the piston ring gap correctly? If the gap is too small the rings could be too tight in the bore which can cause the engine to tighten up when hot without actually seizing. At the time of the re-bore did you replace any valves or valve guides?

[Ib-Denmark]

Pinking will not cause the engine to tighten up but if ignored could eventually burn the piston. After the re-bore did you set the piston ring gap correctly? If the gap is too small the rings could be too tight in the bore which can cause the engine to tighten up when hot without actually seizing. At the time of the re-bore did you replace any valves or valve guides?

The ring gap was checked and I had the valves ground but not replaced.

After checking the carb I saw that I had a 410 jet and the needle is in slot 3 (Which is not what I remembered )
When the weather is getting colder (Today we expect up to 30 dgr C) I will test with a richer mixture. (450 and slot4)
Ib

[Ib-Denmark]

Pinking will not cause the engine to tighten up but if ignored could eventually burn the piston. After the re-bore did you set the piston ring gap correctly? If the gap is too small the rings could be too tight in the bore which can cause the engine to tighten up when hot without actually seizing. At the time of the re-bore did you replace any valves or valve guides?

The ring gap was checked and I had the valves ground but not replaced.

After checking the carb I saw that I had a 410 jet and the needle is in slot 3 (Which is not what I remembered )
When the weather is getting colder (Today we expect up to 30 dgr C) I will test with a richer mixture. (450 and slot4)
Ib

Thinking it over the engine might not slow down by itself??
Maybe it is me closing the throttle in panic as soon as I hear the sound? - Must try to analyze what happens if there will be a next time.

[teebee67]

Did you fit GPM pistons (I believe these are what the club spares dept. sell). I am told these pistons need a bigger clearance when reboring (0.005").

[pkr87]

teebee may I pinch your comment ? as I am only old on the outside except for the aching bits inside

[Ib-Denmark]

This might be difficould to explain, but I dont get much sleep these days.

I had a rebore of my G12 1965 with 8,5 pistons.

After 900 miles I can still experience this:
When hot (like after 5 miles at a speed of 50mph) the bike might loose power and there is a sound like klicking or rattling (it is not stuck ) and I then grib the clutch and thereafter I can start the engine again by releasing the clutch, still while the bike is running and has not stopped.
This happens maybe every 100 km.
The first ore second time I saw this I dismantled the bike , but I saw no damage in the pistons or the barrels.

Should I worry? Ib-Denmark

I GIVE UP
Looking at Rob and Groilys story of 2000 miles before the nipping stopped I have decided to give it a try and go on with the bike as it is now.(Unless I get
another advice
Still nipping app. each second hour) (Loosing power for a short moment and is then free again emmediately)
p.s. The rebore-workshop ("Iversens") is highly recommended and has done more AMC twins.
Just resume:
389 carb., Main jet 450, Needle position 5 (bottom slot), Plug: NGK B8ES, Ignition (Pazon) timing: 35 dgr. before TDC, Piston clearence as the vendor (GPM) recommends, Piston ring gap checked, Petrol oktane 100,Oil (20-50) temp. 50-60 dgr.C, Got air filter, but the filter insert i a modern one with no resistance

[Ib-Denmark]

This might be difficould to explain, but I dont get much sleep these days.

I had a rebore of my G12 1965 with 8,5 pistons.

After 900 miles I can still experience this:
When hot (like after 5 miles at a speed of 50mph) the bike might loose power and there is a sound like klicking or rattling (it is not stuck ) and I then grib the clutch and thereafter I can start the engine again by releasing the clutch, still while the bike is running and has not stopped.
This happens maybe every 100 km.
The first ore second time I saw this I dismantled the bike , but I saw no damage in the pistons or the barrels.

Should I worry? Ib-Denmark

I GIVE UP
Looking at Rob and Groilys story of 2000 miles before the nipping stopped I have decided to give it a try and go on with the bike as it is now.(Unless I get
another advice
Still nipping app. each second hour) (Loosing power for a short moment and is then free again emmediately)
p.s. The rebore-workshop ("Iversens") is highly recommended and has done more AMC twins.
Just resume:
389 carb., Main jet 450, Needle position 5 (bottom slot), Plug: NGK B8ES, Ignition (Pazon) timing: 35 dgr. before TDC, Piston clearence as the vendor (GPM) recommends, Piston ring gap checked, Petrol oktane 100,Oil (20-50) temp. 50-60 dgr.C, Got air filter, but the filter insert i a modern one with no resistance

Just couldnot leave it
Here is a picture of my left piston.
I have an appointment with the workshop monday morning.
Ib

left piston.jpg

[Rob Harknett]

Opps does not look good Ib. A piston starts off oval and when it warms up goes round. Looks like when warmed up, your piston has expanded too much in one place causing high spot. Are you going to lap it and hope that works OK? It would have taken miles of careful running in to avoid that happening.