Top end sip pipe disappointment

Yes its that old chesnut,what jetting on a standard t5 with sip pipe!Looking back on old posts it seems a little playing about with jets is needed which I have done but I still can’t seem to get that power out!At the moment i’m on a 112 main jet and performance1st to 3rd is great,loads of zip nice powerband great!My problems start in 4th,ie theres nothing there!its especialy bad uphill,the motor just bogs,the revs disappear and I end up having to drop down to 3rd to get the power back.I’m running a cosa clutch 20 tooth and was wondering if that would make much of a difference but apart from that its just standard.My mates millenium flys off into the distace uphill and its pissing me off!!!Any ideas??? [:angry:] [:angry:] [:angry:] [:shock1:] [:shock1:]

I think youll find that the sip pipe performs best with a kit , i used to have a pm pipe on a standard barrel and it had exactly the same probs as yours, Is your cosa clutch deffinately a 20 tooth and not a 21 tooth ? this could make a big difference .

No its definatley a 20 from my old px engine,I may try a pollini kit didnt think much of the mallossi I had ,rattled like buggery it did.

quality expansion pipes like the sip/scorpion need a lot of output from an engine for them to perform as they should thats why they are designed for high output engines i.e kits.a standard engine just cant fill the chambers to make them work,they dont push out enough power.ive built a standard but refined rally 200 that kicks out 14hp but even that isnt really enough for the sip pipe.210 here we go.if the only modification is the pipe i wouldnt increase jet size by more than the next size up i.e 116 to a 118