Bike sputtering - why?
 

Motor was running fine… in 6th gear then bike started to lose power like I'd run out of gas… but I hadn't. Kept riding - every time I opened the throttle it would sputter. Got home thinking dead battery because I had been having a start up problem: 1 out of 10 times I'd take my finger off the starter and it wouldn't turn over - it would stop and when I would push again it would have lost the trip setting / time. Checked battery - it is fine. What else should I check? It has a new spark plug. Checked vent hose for fuel tank - fine. Checked boots for carb - no air leak.

Where is the battery grounded on the bike?

More Info
 

I also just installed a 351 and did the vales and was running a 90/100 watt h4 headlight but pulled it out after the lose of power and replaced with 55/100.
Did I do sum thing wrong in this proses?
I have about 150 miles on the bike sins doing this work.
It dose fire right up and in neutral I can rev it up just fine.
but under a lode it will just bog and sputter.

Thanks for your thoughts:confused:

Sounds like your main jet is clogged but as for the electrical no idea, but it has happened to me before

Another possibility is that the slide in the carb is not moving when you rev it up. Easy way to see if that is a problem is to remove the boot from the air box to the carb and rev the engine. You should see the slide moving up when you rev it-if it doesn't then there is a problem with the rubber diaphragm on the top of the slide.
Get your electrical problem sorted first-that will cause all kinds of running issues.

Yep, that's where I would start. Good Call Frampton. ;)

Ok I will pull the carb and let you know who was right.I will check slide first then main jet and report back. hope one of you gets a thums up! Thanks for your respons.

Pulled the gas tank thinking I was just going to pull the carb and check main jet, then remembered GBAUTO slide idea. pulled the boot on the air box and twisted the throttle without bike started I did not see the rubber slide move. Do I need the bike running? I am going out so I will get to it later today. Thanks again you all are very helpful and I would not be doing any of this stuff without you. ie 351 valves carb thanks again

The slide on stock carb is vacuum actuated. It won't move unless the motor is running. Opening the throttle opens a butterfly valve on the motor side of the slider, which in turn when the motor is running increases vacuum on the air box side. This vacuum is transferred to the top of the carb, upper side of the diaphragm, which causes the slider to rise.

Just put the tank back on and checked the slide it was working. So on to the main jet. If there are other ideas out there bring them on.

When the bike is running and in first gear I noticed it seems fine until about 3000 rpm then the sputtering begins if more throttle is applied it just lurches and sputters.Would the floats have an affect in this situation? Sorry for the lack of basic understanding.Just learning.

Jets are clear. Put carb back on and now have fuel coming out right side vent tube and bottom drain tube.:eek::confused::o

Float problem

Checked float hight seams to be in spec.

Ensure that the float valve is not sticking. I had a problem with mine sticking on occasion - I'd be riding then it would sputter like it was running out of gas, I'd tap the float bowl lightly with a wrench and then it would start up again and ride for a while, then do it again. I took the carb out and cleaned it, problem re-occurred, but less often, so I took the carb out again and cleaned it again, and only had the problem once when I was going flat out (130KPH) for several KM straight, but it only sputtered a little until I let off the gas, then I could go full throttle again for a while.

I think it was just that the float was not getting filled quickly enough when at WOT for an extended period of time with no breaks.

Could be a little flake of sand or grit in the needle/seat.

Any luck finding out what the problem was? Im trying to get rid of a similar issue with my bike, loses power at 6000rpm. Cleaned the carb, fresh gas, new plug, raised the needle a notch... no luck. I am 3 turns out on the fuel mix screw, it idles fine... but doesnt go!

If you figured out the problem, it would be awesome to hear about it.

Can you ride it with the choke on? And by that I mean run it through the gears while it revs like crazy? You'll end up going around 30-35mph IIRC, DAMHIK. If so, something is still in the carb.
At 3 turns out you might need to up a size to get rid of the lean bog. Up what I'm not sure, no carb guru here, but plenty of info to be had here on the carb.
And once you fix it, add some insurance, get a fuel filter.
I installed an inline fuel filter and have never had a carb problem since, other than flooding the carb during a dirt nap(not really a carb problem, more of a pilot problem).

sounds like main jet at that rpm use helthy amount of carb cleaner and a good air compreser.

I did get the bike running well with a very thorough carb cleaning.

Hmm, I did clean it out, no improvement after, maybe I missed something. I think ill clean it again, might have left something behind. Been searching the forum like crazy and have taken the carb out way too much lately, hopefully this does it. I have also been using an in line filter, no idea whats up... ill post here later after cleaning it out today.

Thanks for the reply

If the carb is clean anther thing; it may be a long shot but I had a problem which sounds a little similar. I had a fuel line which has a tight bend radius. The cold everything was fine. Once the engine got hot the heat would soften the fuel line and it would pinch off at the tight bend radius. To find it I finally unbolted the petcock and let it hang to straighten the fuel line and get home. Take a close look at the fuel line routing

New fuel line and I added a 90 degree filter to aid with that bend. It was weird and not very intuitive to find, but I had about 40 miles of lonesome desert to figure it out.

Here is my story:
At about 23,000 miles my klx would occasionally have the clock and tripmeters reset to zero and zero time. Kind of a pain. About 2 weeks later after a good ride, it would not start, no click no lights, no instruments. I push started it and I am on my way. But the engine only works well up to about 4,000 rpm, at that rpm the engine would be "missing", studdering, back fireing and pretty muck acting like like some serious carb problems. Below 4000, fine, above 4000 crap, in any gear. Got home, measured the battery voltage and it was 1 or 2 volts, with the battery disconnected.
New battery, end of problem.
The resetting of the clock and tripmeters was the heads up clue that I ignored.
Just saying!

Figured it out yesterday. The carb was not seated properly at the intake manifold, the loss of power was a vacuum leak! The screws on the hose clamps had been starting to strip and I didnt tighten them enough, allowing the carb to work itself out during a ride.

Something I overlooked like a dummy, but at least its not a big deal.