I have an old 73 el tigre 440 free air quad plug and for some reason the right cylinder is running way cooler then the other and after i have rode it for a while it starts to bog down in low speeds until it gets goin again. I pulled all the plugs and the plugs in the right cylinder( the cooler one) are all oily and black, but the ones on the left cylinder( the good warm on) are a nice golden brown. i am thinking that the reason it starts to bog is because it starts to run on one cylinder but at the start of my run it runs great. I have no clue what happened because it used to be fine. if anyone knows anything i could try or if anyone knows may be happening it would be greatly appreciated. Thanks.