T5 running a bit rough

I have a standard T5 classic engine with a PM exhaust and a 112 main jet.

It seems to have a spluttery spot that lasts about 2 or 3 seconds near top revs that it has to try and get through before reaching the powerband in 2nd and 3rd.

What could be the problem? Do you think it’s worth going a size in main jet or should I be looking at changing some of the other jets (stadard carb).


Thanks for the advice so far,

I will try this and let you know how I get along

it could be the pick up or generating coil in the stator plate or back to the fuel it could be somthing as simple as a slight blockage in your fuel pipe which i have had similar problems with before. so you could try changeing that


It seems that the problem may be a bit worse than just a jetting problem.

I just took the scooter off for a reasonable ride (10 miles or so) and it started to develop a flat spot in the lower rev range, directly after changing gears, then backfiring before the revs would pick up again. It seemed to get worse as the engine warmed up.

The engine cutout completely on a few occasions as well. It is starting to look like an electrical problem, but I have just put a brand new coil on the scooter, so it can’t be that.

What else could be worth looking at (electrics wise)


yes it could be also an electrical problem, but a „spluttery spot“
it is difficul to say what it is if not having the scooter.
So try with the jet and if the problem is still there we go to the electric.


yes my t5 had the same flat spots with a scorpion and then the back firing started , so i changed the plug ,it went ok then i stopped,to chat, went to start the bike, it fired died out went to kick again , solid , siezed…, sorry

I’m going to try the bigger main jet and see if that cures the problem. If that fails, I’ll see if the pick-up behind the flywheel is worn.

Thae way that it started dying on me after it had warmed up is indicating an air leak possibly though.

Looks like I’ve got a busy weekend ahead of me. Determined to get it working.

Here’s my scooter, the one that is giving me grief if anyone is interested:



it seams the point where the transition between mixer tube and main jet is more evident.
if it is from 3/4 of trottle to WOT it is worth trying a 114 main jet.
So take mixer tube out (should be a BE4) clean it put a 114 main, see how it goes and if the problem still there then we try something else.


i would go for the cdi in your plate. i posted not that long ago the same problem after i had sorted it.lucky enough i had a spare one here to try.my prob was that my light circuit went. the spare i had also had a blown light circuit so i borrowed one off a mate. who had it lyin in his garage.all systems go again, all lights, speedo rev counter etc working again ,but once test driven exactly the same symptoms as u!tried my old plate and the spare one i had and no probs, (except no electrics)