T5 main jet

ive got a T5 classic standard set up,ive just put a sip performance
pipe on its great in 1st 2nd 3rd but dies in fourth any suggestions
what size main jet to put on?


I always use a B9.

tried a 113 good in 1st 2nd 3rd 60 mph in 4th put on a 115 and got 70 mph in 4th,any ideas about what plug to use?

yes a b9 sounds good, nice and cold. but i think the 115 is a tad on the large side for just a pipe and a standard t5 lump, they are a 110 standard,and u usually go up 2 main jet sizes and a colder plug, the plug will make a big difference, JUST KEEP A CLOSE EYE ON THE COLOUR OF THE PLUG. nice chocolate brown

My suggestion is, get a Scorpion

112/ 114 main,2.5 turns out on mix screw, just keep an eye on the plug, o go up a grde or two on your plug as well, ie colder