Honda CB 250 G Unstable Idle and Left Cylinder Troubleshoot


New Member
Hello everyone . After being around on these scenarios for quite awhile , I've decided to come over to ask for some help to the local Doctors because I feel on a dead end at the moment .
I will tell , to the best of my knowledge , whats going on .
She was under a restoration ! Lot's of new stock parts from DSS UK .
I disassembly the carbs fully to polish them . Reassembly following photos that I've took it during disassembly . New carbs kit was installed , not from stock .
Engine has new standard pistons and rings , new cam chain , new head cam sprocket , main tensioner , all from stock and full engine gasket third party .
Follow all the rules ( I think , maybe not ) that I have learned over here for a quite long time . Still , I am not an expert .

1 - Cam chain adjusted after 90 degrees ( anticlockwise ) of LF compression stroke .
2 - Tappets are under specs , free at LT comp sroke ( 0.08 mm exhaust and 0.05 mm intake ) . Same applies to F at comp stroke. ( 0.003 inch and 0.002 inch )
3 - Timing points was followed by HerrDeacon procedure .

Unstable Idle :
She starts very well , choke on , for less than a min soon I feel that I need to put on off position. Engine will rev higher , up to 2000 rpm and some times more .
The throttle cable its not even set and the screw that commands both plates is on a non action position ( not even touching the middle mechanism ) .
If I pressure the middle mechanism , opposite direction of normal movement , revs will decrease to almost normal idle . It moves just a little .

Left Cylinder Troubleshoot :
Left cylinder is the real headache . He never gets hot comparing with the right ( very hot ) . If I switch spark plugs still the same happen . ( Both spark plugs look dark and a bit wet of fuel ) . If I unplug the coil lead on the left , engine runs on the same level . If I do on the opposite side ( right ) , engine stops . I swap coils and points leads and what happen is the opposite , unplugging the right lead engine stops .
The old left coil ( nippon denso ) had a failure on the secondary circuit and was replaced by a new original TEC ( FL802 12V ) . It shows 4.9 ohms on primary and 14.58 Kohms on the secondary .

I appreciate the time that you have spend to read all this description and some eventual tips regarding this issues .

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