MBK Nitro problems.

[SiLvEr-NiTrO]

Hi,

I have an MBK Nitro 50 and recently it's been playing up.
It all started when i fitted a Technigas Next-R exhaust and rollers that came with it. The first ride with the new exhaust was not that bad it had more power than before but pulling off was slower (which i expected anyway with the valve stopper removed from the pipe) But after a few rides i noticed a power loss around 35-40mph, and then it kicked in again and was sweet all the way up to 55/60. It got worse and worse untill i could not go over 40mph.

I thought the rollers must be too heavy so i bought some 5.5g roller weights which are the standard ones i had in it before i had the exhaust. After fitting the standard rollers i took it out for a rode test and it was even worse. Pulling off became even slower and the only power it had was between 10 and 20mph.

Now, (one week later) it's even worse and it won't go over 25mph.
You can imagine how embarrissing this is getting beeped at on the rode and laughed at. if i try to go up the slightest bit of hill i'm Fu**ed, i'm talking 10mph job and that's on a good day.

Please help.

Sorry about the long post.
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02 Yamaha YZ250F
03 MBK Ovetto (stolen)
04 MBK Nitro (New ped)