Wow I got a ton more information/replies than I expected, thanks all!
Because of all the info I will explain below exactly what I have done and then hopefully I can be given advice on what step to take next.
A family member bought the bike for super cheap from a friend, it was stood for approx 3 years without any use, old fuel still in the bike. He doesn't know much about bikes and only rides so I was doing all the work for him.
- Emptied tank
- Put straight fuel in and washed it out making sure tank is clear
- Cleaned the carb with carb cleaning, including jets ect
- Fresh plug (BR9)
- Fresh mixture, 40:1 putoline oil
After all of the above it still spluttered so I did a lot of researching and did the below:
- Another fresh plug
- Checked reeds
- Leak down test on the inlet with carb cleaner
- Checked for any obvious sign of damage to electrics
- Tried a different muffler
I also purchased a few jets both bigger and smaller pilot and main ready to try.
The splutter was extremely bad, right through the range too and the bike smoked a lot (blue smoke though)
I was reading the manual and noticed it recommends 50:1 so I tried that with a different type of plug (br8) and it seemed to do the trick, the bike is hitting powerband in every gear, zno spluttering at all.
I don't get to ride the bike until Sunday but my plan is to run it and see how it rides, check the plug after some more riding. If the plug is lean what steps should I take to make it more rich?