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Hello All!! I just registered here to hopefully get some imput on an old Honda Twin that I am currently working on...yes, I know that there is a HondaTwin Forum, but they are having login issue's....
So the bike is a 1978 Hondamatic CB400A and I just recently changed the base and head gasket's as the base gasket was leaking a bit of oil, and possibly pulling air. I put it all back together, timing marks all line up, valves in spec etc. yet when I start it, let it warm up and twist the throttle, it lags, coughs and sputter's....so I put a timing light on it after re-checking timing marks and valves and the light flashes on this 'FN' mark between the 'T' and 'F' marks on the rotor instead of on the 'F' mark.
Can anyone tell me what this FN-mark is all about? The way it is running seems like timing is a tooth off yet timing mark's line up. I am slightly miffed at this situation! LOL
Any insight is Greatly Appreciated!
Thanks in advance!
 

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This is several years late, but I thought I'd chime in so if anyone else sees this, there's an answer. The FN is the timing marks while the bike is in Neutral. (Fire Neutral) then when put in gear, it fires on the slightly advanced F mark. The T is top dead center for the piston, and the 2 marks to the left on the picture are the advanced timing marks. When you give it throttle, those should line up with the mark on the case to let you know your timing is advanced forward. If it doesn't, she'll run like ****. :)
 

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Yeah, I do hope the OP got his running long ago but thanks for this info. Maybe the next person can see this and not have to wait so long. Well ... that's provided they use the search tool in the first place. (y) :)rolleyes:
 
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