You need to look down inside the plug where the insulator meets the body of the plug...........what color is it down in there? If I remember this correctly;the motor can be lean on the main but rich at idle......read white with black............also to get a proper plug read you need to do a plug chop (new plug flat in top gear cut motor check plug).

As for the hard start is the enricher going full on or is one of them sticking..........this will make it hard starting. You pull the choke/enricher and they don't extend all the way..........this is not uncommon on Hitachi SU.

As a rough guide you can fatten it up 1/4 turn at time, just mark the original position. Use the hillbilly dyno to test results. Find a section of road with slight uphill grade, find two stationary objects and accelerate between them in top gear.............note the rpm's or speed, richen it up or lean it out see where you end up. Note that it may give better acceleration when it is ever so slightly lean (may start pinging) so best to run a touch rich......just a touch.


The proper approach would be to get an air fuel ratio meter on it and see for sure.


Tom

there is no problem with my motor, except a little hard to start in cold morning. just want opinions why the insulator is white yet the ring is black.

L series indeed. with twin SU.

I'm guessing that you have an L16, the correct plug should be BP6ES. But what I see is a lot of black around the edges, indicates to me that you re running rich, leaning out the fuel system might be more helpful.

what should i do? add fuel? or go 1 heat range colder? BP5ES on my 1600