Throttle response boggy in top gear between 4500 and 5000 rpm

[Guest]

I got a new petcock as mine had messed up internals.
I took the old girl out for a hard test drive after installing it today and found I still had a bogging at 4500 to 5000 rpm rolling on top gear. It was as if it was lugging but the bike should be able to take a roll on at 90 kmph in top gear as it sure used to no problema

It oddly seems to happen worse when rolling up a hill. I was thinking float height but how could that be if it idles and works great esp. when pushed WFO in all 6 gears.

The bogging is not as bad as it was before I replaced the petcock. Have a new fuel line and vacuum line and will install it tomorrow if I can find time. I also sprang for some soft and supple new airbox boots so it may not require removal of the battery box to get to the fuel inlet and vacuum ports.

If carbs were dirty why would the bike work so well in all but this engine rpm? Its perverse.

[Billy Ricks]

You probably aren't at much more than one quarter throttle when just cruising at that speed. Have you had the carbs apart and if so did you get the hardware on the needles in the right order? You wouldn't be anywhere near just being on the main at that point. If the hardware on the needles is in the right order you might want to try shimming them a tiny bit and see if it helps.

[JEEPRUSTY]

All internals are in a stock state. I suppose I could just flog it for a while with a bot of techron in the tank. I may be letting it lug I guess that is an issue measured in engine vacuum.

[JEEPRUSTY]

So golly gee just back after whipping that thing.
What a sweet lithe and powerful bike.
Still has the queer 6th gear roll on issue more pronounced going uphill than down.

my wretched front tire is cracking damn Bridgestones.......now another 120 into a 500 dollar motorcycle.

[mmattockx]

I took the old girl out for a hard test drive after installing it today and found I still had a bogging at 4500 to 5000 rpm rolling on top gear. It was as if it was lugging but the bike should be able to take a roll on at 90 kmph in top gear as it sure used to no problema

It has pretty much nothing to do with road speed and RPM, it is what throttle opening you have at the start of the roll on and how you are rolling on the throttle. As Billy Ricks says, you will be at a small throttle opening when cruising in top gear at 90kmh so it will most likely be the needle that is the issue here. Second part is how are you opening the throttle? Are you whacking it open suddenly or smoothly opening it to WFO?

Put some tape on your throttle and mark each 1/4 throttle opening (even better if you do 1/8's) so you know where you are running in the carb circuits then repeat your test to see where your throttle is at for the start of the roll on. If you can manage it, hit the choke a bit as you roll into the bog and see what happens. If it gets worse then you are rich, if it gets better then you are lean. That will let you know which way to go when you start adjusting things.


Mark