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Hello, hoping for some experience with exhaust, got A perfectly running Yamaha dt125r, 1989, comepletly stock, very lo mileage, engine, piston ect. in good condition, (factory unrestricted 30 HP model), purchased and fitted new giannelli complete exhaust system on the bike, fits perfectly, and sounds great, but bike lost at lot of midrange power,(YPVS adjustement correct), engine revs higher thoug, topspeed is I belive also a bit higher, but when swithing back to stock exhaust, bike pulls A lot better, no signs of poor jetting, bogging or anything else, just low midrange power. Anyone tried similar issues ? Or is gianelli just not good enough?
Regards Torben.
 

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I guess the Giannelli pipe shifted the power band higher, thus you felt that the bike had lower power at a certain RPM. (EG: standard belly, the power starting at 6k RPM and ending at 10k, with Giannelli power starting at 7k and ending at 11k). also, the YPVS timing may need to adjust to suit the shifted powerband. you can get the adjustable version from Zeeltronic or you can get other YPVS controller that may have a different valve timing operation (not sure what is compatible).

overall you decide what you want for the bike, wider and torquey at low to mid rpm or a crotch rocket that only have power at high rpm.

what I can say about old Yamaha engine, they tend to have wider and tamed powerband. its quite hard from stock parts to make the bike into a crotch rocket.
 
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