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Post by rooster on Apr 19, 2015 13:02:17 GMT
Can anyone explain why when starting my 250NB, only 1 plug fires and after several seconds no2 fires. I have checked Earth on the coil all seems ok. Any ideas please.
Alan
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Post by jonnyboy on Apr 19, 2015 13:28:05 GMT
Carbs balanced properly? choke working correctly?
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Post by rooster on Apr 19, 2015 14:03:56 GMT
The carbs have just been fitted after a clean and new float valves etc. Balance has been checked and found to be ok. New plugs have also been fitted.
Alan
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stevegbr
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Post by stevegbr on Apr 19, 2015 14:11:42 GMT
have you any air leaks, between the airbox or manifold?
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Post by jonnyboy on Apr 19, 2015 14:18:15 GMT
Only thing i can think of is to check the coils, earthing etc, have you ridden it at all and got it nice and hot?
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Post by rooster on Apr 19, 2015 14:42:55 GMT
Is there any test laid down for coil or the CDI unit. I don,t have a manual yet.
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Post by stevegbr on Apr 19, 2015 14:45:48 GMT
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Post by rooster on Apr 19, 2015 15:26:24 GMT
Cheers Steve.
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Post by mikef on Apr 21, 2015 20:28:38 GMT
Hi Alan. My SD 400 used to fire only on the right hand cylinder when first starting from cold. I also had another issue a bit long winded to explain now. The fault turned out to be the height of the floats. I notice that your SD is an NB, if that has adjustable floats then I think that would be a good check to make. Adjust as per the manual or if that is not clear then I could try to explain how I adjusted mine, it seemed to do the trick. Good luck. Mike.
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Post by rooster on Apr 23, 2015 8:11:36 GMT
Hi Mike, the floats in my VB30B carbs are fixed plastic type. I have been told to check the CDI unit connections which is in hand. Thanks for your comment. Alan
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Post by dolomite1850 on Apr 28, 2015 18:40:43 GMT
I wouldn't worry about it too much if it runs O.K. after a few seconds. Mine coughs and splutters for a bit every time if it's been left for a while.
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Post by rooster on Apr 30, 2015 14:37:52 GMT
I have fuel pouring from the right hand overflow now!!
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stevegbr
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Post by stevegbr on Apr 30, 2015 14:53:57 GMT
does sound like the shut off valve is not seating, a couple of taps should work to stop the flow of fuel.
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Post by mikef on Apr 30, 2015 19:55:51 GMT
Hi Alan. This seems like a common problem with these Kehin carbs, especially if they haven't had fuel in them for a while. I have nicknamed it "the curse of the Kehin carb". As suggested a few taps on the float bowl can stop it. If it is a recurring fault then a new float needle may sort it out. In my case I could not stop fuel leaking out of the overflow, I checked that the float was not leaking and replaced the float needle, I even fitted a separate fuel filter and still they leaked. I remembered reading somewhere that the seating for the float needle could oxidise and prevent a good seal of the float needle. The answer was to polish the needle seating in the body of the carb with metal polish. I used a cotton bud soaked in Brasso to polish the seat for the float needle and have not had a problem since. Could be worth a try if all else fails. Good luck. Mike.
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Post by rooster on May 1, 2015 7:52:32 GMT
Thanks Mike. Like you, I fitted a new valve without success. Now where are the cotton buds kept!!
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