What color spark plug are people getting on their Beta 4t?  I have a 2016 300 with standard muffler.  With 115 main, 20 pilot, mid needed (white plastic space below) and idle mixture 1 turn out, plug is powdery looking black.  Riding at sea level at 60 to 90 degrees F, it runs OK but it seems the plug is way too dark yet jetting is lean compared to what I see others are running.    

Yes often it is black - trials 4T bikes tend to run a rich first range of carburettor tuning to help with idling through without stalling and a snappy pickup.

Typically Beta ships the bikes to pass emissions, I would suggest try lifting the needle (drop the clip) one or two notches and see what the mid-range does (typically it will be stronger). 

My bike has the idle mix tuned for the day/weather but 2 turns out is not unusual.

Also....call the importer and get his advise as he will know what is a good combination

Edited November 21, 20196 yr by nzralphy

I have the same problem in the UK with my 2012 300 4T

120 Main

Mine came with 27.5 but tried 22.5 to get the mixture leaner ended up with 17.5.

Needle currently in top groove,

plug still just as black, it uses no oil so it is not likely to be that.

I wondered if it was really rich or if the plug was not hot enough to self clean so put in a harder plug 6 in place of 7 that read a bit leaner

used to have a lot of back firing with all the jets but got round that by putting a lighter spring in the overrun enrichment valve. Not sure if it had the right spring in but it seemed very strong.

 

Nige

Are you doing a plug chop or just riding about and then when you stop pulling the plug and viewing. The latter will not give you a true reading. 

No not a plug chop but they take no time to go black, the hotter plug stays a better colour. It seems modern fuels dont really go the old fashioned brown colour.

Richer runs cooler, but build up of carbon leads to other concerns later on.