Yamaha Jog R problems!?

[Timbo is here]

It is normal to have to make adjustments to the jetting when the exhaust is changed and restricted so I would say he is spot on correct.
If not done it could even cause damage if it runs too lean - melting piston and spark plug for example

 

[Dan]

Hi! I have a 53 plate (air cooled) yamaha jog r. I'll get straight to the point - i have recently put a technigas sports exhaust on it, had the washer taken out of the variator and had heavier rollers put in. Unfortunatley I'm still only doing 30-35mph...what do you reckon is wrong with it? i took it to a mechanic and he reckons i need to have my carb jetted? ideas needed!