Rough running at speed.

[sail121j]

I have a restored 1966 superhawk 305 and it starts perfectly, idles forever and accelerates and revs up in first and second gears just fine. Above 5,000 rpm in third, it burbles when opening the throttle and won't recover until you reduce the throttle somewhat - basically it won't accelerate. In fourth gear, the symptoms are worse. It will maintain speed at constant throttle, but won't accelerate very well (if at all) and can't seem to climb even modest grades without stumbling. <br /> I have taken the carbs apart and cleaned and set the main jets at the second slot (from the pointy end), they were originally in the third slot. After I changed to the second slot, the bike seemed to work perfectly. The next time I took it out, it had reverted to the 'no power' when accelerating in 3rd and 4th gear or trying to maintain speed on a grade.<br /> Any clues? I am at a loss as it works fine in 1st and 2nd gear, start and idles just fine but bogs down baddly in the higher gears.

[kustommusic]

Sail, Sure sounds like its starving for fuel. have you looked into the petcock? It has a filter screen in it. Also the fuel lines could be rotted and collapsed(not likley unless they were changed out to rubber lines). Or, the fuel tank could be rusty or otherwise contaminated. Let us know what you find,Good luck! Steve Greer

[sail121j]

Thanks for the hints - never thought to look at the petcock filter or fuel lines. Both carb bowls seem to fill with fuel ok with the bowls off and the floats all the way down. Is there a way to check if the floats are maintaining the right fuel level easily in the bowls?

[kustommusic]

Sail, There is but it involves a clear plastic tube and an adapter fitting to the bowl drain hole. Kinda alot of fooling around but might be the thing for diagnosing. Steve Greer

[sail121j]

What a clever way to check the level... I can do the clear tube trick tomorrow and let you know how all of your ideas turned out. Many thanks.<br /><br />Jack

[sail121j]

Well I couldn't do the clear tube method because both drain screws were impossible to get out. I did check that fuel was getting to the carbs ok, no problem with filter or hoses. I adjusted the floats by eye a couple of times and the final adjustment made it work just fine. Not sure if it was a problem with one or both of the floats -did both. Lots of power in all gears and no hesitation. I had to put the main jets back to the middle position (3) because in 4th gear cruise, it was running too rich and not running smooth unless you were accelerating or decelerating. Works perfect now with the floats adjusted and the needle back in the middle postion. Thanks for all the suggestions. Hard to believe that a fairly minor float adjustment would make that much difference - but there you go.<br /><br />Jack

[kustommusic]

All Right !! that is good news! Steve