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Over size piston
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Bola
Swindon
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July 9, 2019 - 11:46 am
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Throwing a question out there...

150cc D3 with a +0.6 piston. Would i need to change the jet size from standard?

 

Bike now running OK on tick over however stutters with higher revs. 1st I thought it was the HT earthing out but i have now added heat shrink to the coil to try and insulate it, not 100% sure its fixed. 

Earthing.JPG

 

Maybe its not getting enough fuel at higher revs?

 

Also dies when hot! currently in the process of elimination (Again) thoughts welcome.

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steve morrison
Co.Durham
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July 11, 2019 - 10:07 am
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Would not expect +0.6 would make any difference in fact was not aware you could get this size as normal rebore would be +20 and this would not req a jet size increase maybe put needle up 1 grove and try this out.

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Bola
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July 11, 2019 - 1:16 pm
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Woops! +60 not 0.6 rofl(couldn't get +40 piston so had to jump up 1 more)

More fuel, not tried this yet so worth a go!

Tried to cover HT lead to give some insulation too. Points still opening just before optimal piston poison but i have no more movement on the contact breaker housing ( 1/16 in. before top dead centre on D3 i believe).

Stator.JPG

 

Many Thanks

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steve morrison
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July 12, 2019 - 7:30 pm
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Sounds like fueling issue more than timing issue make sure no air leakage where carb fixed and air way clear via choke ie :choke fully opening.

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cocorico
Central France
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July 12, 2019 - 8:59 pm
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Bola said
... Points still opening just before optimal piston poison but i have no more movement on the contact breaker housing ( 1/16 in. before top dead centre on D3 i believe).

Points should be opening at 4mm before top dead centre, so you are set somewhat retarded.

1956 D3 running, lights to sort. 7 other bikes in the Barn, including a Morini 250 now running nicely, almost road worthy.

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Bola
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July 14, 2019 - 4:36 pm
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Looks like i have movement on the points holder.

Is this common and will it affect the points gap while running?? 

 

If so so how can it be fixed?

674594BA-521A-45AD-B66B-8AE61BA57463.jpeg

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