Tzr not Banding

[Teazer125]

Hi all, ive come across a stumper. I have a derestricted TZR125 2RK. Ive cleaned the carbs, replaced the ypvs unit, got a new coil for it, new spark plug. Problem is whilst riding it destricted it absolutely refuses to powerband, it just sputters and wont increase the revs at all. Disclosure here, it does come with a ypvs servo, but it was in a right mess when i got it, so now its on a custom circuit so its either fully restricted or fully derestricted by button select. i know it works fine, engine pitch changes. The only things that are not standard is the air filter, which is a much smaller one, amazon jobby, and the exhaust, which im pretty sure isnt actually a tzr one.
Ive owned 2 different tzrs back in the day, bith never had an issue with hitting the band. any ideas? TIA, Mike

[jamietzr250r]

Could be air flow, you admit you have an Amazon 'smaller' filter. Try running it with the standard air box and see if that works.... elimination is the key here, even the exhaust could be the problem but stick to the easy things first....

[AndyYam]

Hi all, ive come across a stumper. I have a derestricted TZR125 2RK. Ive cleaned the carbs, replaced the ypvs unit, got a new coil for it, new spark plug. Problem is whilst riding it destricted it absolutely refuses to powerband, it just sputters and wont increase the revs at all. Disclosure here, it does come with a ypvs servo, but it was in a right mess when i got it, so now its on a custom circuit so its either fully restricted or fully derestricted by button select. i know it works fine, engine pitch changes. The only things that are not standard is the air filter, which is a much smaller one, amazon jobby, and the exhaust, which im pretty sure isnt actually a tzr one.
Ive owned 2 different tzrs back in the day, bith never had an issue with hitting the band. any ideas? TIA, Mike

A few questions here:

1. When you say it "refuses to powerband", what exactly do you mean? It won't rev beyond 6krpm?
2. You say the YPVS servo is on a custom circuit and is "either fully restricted or fully derestricted by button select". I don't understand what you mean by this. Do you mean the exhaust valve is either full open/full closed? Fully de-restricted would be where the valve opens gradually as the revs increase.
3. Reagrding the airfilter being a small amazon jobby. Is this replacing the whole airbox, so it's like a pod filter?
4. You think the exhaust is not one from a TZR? That would probably play a massive factor, the shape of the pipe will determine where the power is in the rev range so if you're running a pipe not built for that engine then that will likely mess up alot!

Get some photos up of the bike, might help to diagnose.