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D7 running rich.
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Geoffrey25
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March 23, 2019 - 10:05 pm
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Hi all I have a d7 1966 with d10 barrel and a 185 piston from Rex caunt Racing it has a nearly new 626 concentric carb with pancake air filter with new element fitted I seem to be having problems getting to run well it starts 1st or 2nd kick it has 118 psi compression it idles quite well but stick in 1st and pull away and it just bogs down.I have points gap at 12 thou  it doesn't like it at 15 thou timing set main needle set in second groove it has a 170 main jet I have tried 180 ,190 I do have a 160 jet which I have not tried yet I am not sure what to try next any ideas would be much appreciated many thanks joe.

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SpacedMarine
Up north
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March 23, 2019 - 11:43 pm
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What is your mixture screw set at?What about the idle screw?

Procedure is  get engine warm turn idle up and adjust mixture to the point where it doesn't run away with itself then back the idle out so that it just ticks over.The book says 1 1/4 turn for my model(d14) but it prefers just 1/2 a turn.The pilot and cutaway control idle-about 1/4 throttle then your on the needle so unless your doing full throttle starts I'd get that set 1st.Unless you already have and then its something else 🤣.I'd say the big bore would have some effect on the carburation you'd think it would need more fuel but not always the case!Best getting a good base then you can start messing with needles and jets.

What's 7/16 in mm again?

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Sponge
Lancashire (A chip shop somewhere near Preston)
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March 28, 2019 - 8:43 am
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HI Geoffrey29, 

A bike that starts OK but dies above tick over would indicate incorrect timing and / or a blocked / incorrectly set up carburettor.  

Suggest as a first measure that you obtain a carb from a working bike and try it  after that ......

Due to the changes you are in the badlands with this bike but if you start at the beginning you will be able to get some light at the end of the tunnel. 

Check that the exhaust is not blocked/bunged up

Set the timing for a D10 and get it as accurate as you can. 

New fuel mixture.

Check your 626 carburrettor is actually a 2-stroke carb with all the right bits (correct length needle, correct jets, float hight etc etc) 

Check that you have a D10 cylinder head on it  - if not then suggest you get a D10/D14/B175 head as the D7 one will be too low compression ratio and will also overheat. 

Suggest start with 160 main jet and see what happens then.  If all is well it should be running reasonably at that point.     

Sponge

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