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ignition coil
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Geoffrey25
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June 17, 2019 - 9:00 pm
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Hi all my 1966 D7 is still causing me some issues after half throttle on a run out I have set the carb and the timing changed the spark plug ,I have altered needle positions on carb changed jets and rechecked timing several times but still doesn't go above 35 mph even at full throttle.I was thinking is it possible that the ignition coil within rotor be causing high speed running issues it tends to get worse after about 20 mins riding it also gets hot quite quickly ,I have changed the condenser and the 6volt ht coil under the seat.I do a spark plug check and all seems fine with a nice tan brown colour so I'm just wondering if the small ignition coil within the magneto could be the trouble or am I barking up the wrong tree ihave never ridden another d7 to compare them so I don't know how they should perform any help with this matter would greatly appreciated many thanks Joe.

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sunny
Norfolk
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June 18, 2019 - 9:47 am
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is  this  a  2switch  D7  with all the  crect  parts  to the  geny    dont  think  you  said        a  broun  plug  me  thinks  NOT  enuf   petrol     but  ive   a  feeling  the  crankshaft  &  oilit  BUSH    need to  be  chect             or  a  H/T  coil  fited  to  a  single  S/W  LOOM   or  all 3   

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Mags 1
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June 18, 2019 - 11:36 am
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You don't have two ignition coils on any Bantam, on D7s there's an external one under the seat, nothing inside the stator, that's a magneto set up for earlier bikes. Top coil is for battery charging on the D7 bikes and other two inside stator are lighting coils.

I generally get somewhere near 50 top speed on most of my past D7 bikes, are your crankshaft oil seals in good order? Do you have an air leak at carb. joint? These are the sort of things you need to be looking at.

Four now on the road and at least several in bits.

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sunny
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June 18, 2019 - 1:13 pm
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well   Mags  iv come   across at  lest   3  singal  swich  bantams   that  have  had   ht coils  fited  under  the  seat  and  the  ht mag  coil  discarded   ,,  this   makes  charing   much   harder

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Geoffrey25
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June 18, 2019 - 8:53 pm
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Hi all thanks for the replies my d7 is the twin switch one I must of got a bit confused about the two coil thing the bike starts easily enough but just seems to be holding back somewhere, Sunny reckons a brown plug shows it needs more fuel so I will raise the needle in the carb up a notch and see how it runs. I have had this bike for a good few years now and I don't think it has ever performed as it should I have tried so many different things to get it to run better I can get to about 40 mph on a good day but that's on about 3/4 throttle I have noticed that the bottom half of the contact points are slightly offset could something like this cause slower running I have got them set at 12 thou 15 thou doesn't seem to good.The carb is only 2 years old with hardly any mileage on it I have set the timing with the cigarette paper method the condenser is two months old the coil under the seat is almost new ,the exhaust is clean and I am using ngk b6hs plug  so I am running out of ideas so any info would be great many thanks Joe.

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Mags 1
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June 18, 2019 - 9:36 pm
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Have you got the correct grey faced speedo with the orange needle? Wrong speedo could be simply showing wrong speed. Also is the speedo gearbox the correct ratio?

Four now on the road and at least several in bits.

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stubaker58
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June 18, 2019 - 10:45 pm
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You can get a speedo app for your phone so as to check your actual speed ... trouble is that it showed my speedo was a tad optimistic! The most I’ve seen on my D7 Is 53mph but it’s much happier at 40/45 and gets there pretty quickly .. for a Bantam.

D7/14 hybrid (4 speed with D7 crank etc.) on the road, D10 Bushman awaiting rebuilding.

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sunny
Norfolk
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June 19, 2019 - 11:36 am
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the  monobloc   carbs   needle   seting  is   4  th   from  the TOP    ,,NOT   2nd   as  stayed  in  most  books

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Geoffrey25
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June 19, 2019 - 7:57 pm
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Hi all took my D7 out for a run this afternoon starts out ok doing about 30 mph then 3 miles on starts to bog down to about 20mph then after 5 miles or starts to slowly pick up a bit to about 35-40 mph but no more this is on 3/4 throttle when you give full throttle it just makes high revs but no speed increase.So in all done 7 miles or so when I got home I quickly removed plug which was sort of tan /grey colour but carb was quite hot to touch ,its a1966 d7 with a d10 barrel and head with a 626 concentric carb with all the correct 2 stroke stuff inside with a 170 main jet and needle notch no2.Iam beginning to think this isn't carb related but might be timing trouble even though I have set it by using cigarete paper method ,am I right in saying if it was crank seals it would be hard to start with quite a lot of white smoke.Well it starts really well ,hardly smokes at all and idles nicely so I am on the brink of giving up as to what to do next ,I wonder if any one has had a similar problem with their bantam any one got any clues as to what to try next many thanks Joe.

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Geoffrey25
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June 19, 2019 - 9:09 pm
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Hi all just wondering if anyone has had a d7 with a d10 barrel and head like mine and if so what was the best way to set the timing because the piston is a ts185 type which I got from rex caunt racing it has good compression of around 117psi when I measured it 2 weeks ago thanks Joe.

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Mick W
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June 19, 2019 - 10:40 pm
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Comment incorrect so deleted I missed that you had a 626 carb fitted

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stubaker58
Sunny Felixstowe
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June 20, 2019 - 8:30 am
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Hi,

my D7 does indeed have a D10 Barrel and head (and D14 crankcases to get the four speed box!). I timed it as per the D7 and it starts and runs well although is no faster than an unmodified D7. Mines running positive earth, on original Wipac points and condenser, with the generator wired for maximum output and regulated/rectified to six volts.

its running a concentric which, if memory serves, is straight off the D10 engine, I didn’t change any jets.

once I got it running I’ve pretty much left it alone although I did have the barrel off to cure a leak at the base gasket caused by a small ding in the mating faces, three bond sorted it.

maybe worth taking the head off to get an accurate TDC measurement, cleaning and gapping the points and going through the timing procedure again.  If the revs rise but the speed doesn’t it suggests some clutch slip so maybe check the primary side too?

regards.

D7/14 hybrid (4 speed with D7 crank etc.) on the road, D10 Bushman awaiting rebuilding.

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Mags 1
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June 20, 2019 - 10:59 am
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Geoffrey25 said
Hi all took my D7 out for a run this afternoon starts out ok doing about 30 mph then 3 miles on starts to bog down to about 20mph then after 5 miles or starts to slowly pick up a bit to about 35-40 mph but no more this is on 3/4 throttle when you give full throttle it just makes high revs but no speed increase.

Are you sure your clutch isn't slipping badly?

Four now on the road and at least several in bits.

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johnsullivan
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June 20, 2019 - 12:29 pm
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sounds like clutch slip as the bike gains power,but fuel flow problem as well .Remove the carb fuel banjo and see if there is a good  steady flow,and check the base filter.

67 D10. and a D7    2007 Honda Hornet FA. Honda CD200 81 93 Yamaha TTR 250 Raid, Sinnis SC 125.   75 Montesa Cota 247 an electric scooter of Famous make.

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Geoffrey25
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June 23, 2019 - 10:51 am
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Hi john the clutch is fine and carb is good I did find that the condenser wire  was broken so I repaired it the bike starts ok pulls away good I rechecked timing and points gap of 12 thou that's still ok ,while points casing was off I started bike and when warmed up I graduly reved it to full throttle and it revs well just not when on road in third gear under load. I checked the points whilst it reving and sparks from the contact points were a bit eratic is this normal it sounded ok I'm abit concerned about the timing I moved timing plate a touch to the right just till it starts to kick back and it seems to run a bit better on the road to about 40mph at 3/4 throttle but that's it.I was wondering how much the back plate should be moved to make a difference to the timing I'm sure I have used the whole range  of movement over time I like to keep it original but am now thinking should I be looking at electronic ignition as I have run out of ideas many thanks Joe.

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Geoffrey25
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June 23, 2019 - 11:57 am
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Hi all one more thing I will try ,if a bantam starts ok and runs slightly eratic to 35 mph could the condenser be at fault if so can anyone recommend where to purchase a good quality condenser many thanks Joe.

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johnsullivan
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June 23, 2019 - 5:46 pm
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Electronic ignition will not cure underlying faults.I do not understand when you say it  'makes high revs but no speed increase'  if the engine speed increases then the road speed  will unless the clutch is slipping ..or the dogs are shot on third gear.

67 D10. and a D7    2007 Honda Hornet FA. Honda CD200 81 93 Yamaha TTR 250 Raid, Sinnis SC 125.   75 Montesa Cota 247 an electric scooter of Famous make.

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Geoffrey25
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June 23, 2019 - 7:38 pm
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Hi John the clutch is fine it was all over hauld 2 years ago after the gear selector spring broke and while it was apart I replaced thrust washer new clutch plates and gear box components were in good order , I have experienced clutch slip on many bikes over the years and this does not feel like it. Iam quite sure it is timing ,points or condenser related which is why I would like to know of any good quality condensers available please many thanks Joe.

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cocorico
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June 23, 2019 - 8:49 pm
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1956 D3 running, lights to sort. 7 other bikes in the Barn, including a Morini 250 now insured and on road testing.

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sunny
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June 24, 2019 - 8:45 am
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has  the  crankshaft  been  cheched out  proly   on a  laeth   ,,, is the  shaft  bent  or  the   magnet  rotor  out  of   TRUE   &  scaping   on  the  coil  sator  legs       

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