Engine Acting Weird - Randomly Cutting to Low Performance

[Maddawg]

A couple weeks ago, I was riding and for just a portion of a second, the bike would feel like it lost most of its power. Since then, it has progressively become worse and worse. At first, whenever I was on the highway, it would lose a large portion of its power, have a low rumble, and I would have to nearly completely open the throttle to go. If I stop and turn off the bike, it goes back to normal. Occasionally, if I rev it, it will restore to full power.

Also the bike will die even when it is acting normal. After driving on the highway for 30 minutes, I stopped, and it died. It used to never do that. It stays at low RPMs and continues to drop down until it dies (often, but a lot of the time it is normal).

Now it is also doing this at low speeds anywhere I go. I felt like it was probably the carbs, but a few months ago I had my bike apart and the carbs looked clean. Any ideas of what is going on?

[alex.s]

maybe a vacuum leak

[sonny4472]

Coils? Plugs?

[DaBlue1]

Check these things first...

Poor fuel flow- Make sure any fuel filters are clean, fuel lines are plumbed properly and not pinched or too long.

Check your float valves- carbs that do not fill properly don't get enough gas for operation

Make sure you have good fuel level in the tank- low fuel levels can also affect performance. Performance can drop off after more than 1/4 throttle if fuel is too low

Make sure your tank vents properly- A gas cap that doe not vent properly can prevent proper fuel flow. make sure the cap gas is venting properly by checking for noise due to expanding gas vapors.

Also make sure you idle speed is set properly (1350 +/- 50 rpm) when the bike is fully warmed

When was the last valve adjustment, spark plug change, and air filter replacement?

[Brian]

It may just be simpler than you think. My bike acts sluggish the first 10-15 minutes of riding from a cold start, but usually kicks into more power once I start moving up the gears more(at least I feel like it does), after that.

[warlord]

I think the mandatory first mod on this bike should be installing a real fuel filter. You need to clean the fuel filter screen but I would just replace it with an inline fuel filter. you're probably bogging down after some time because your fuel filter is partially occluded and is not able to give your carburetor enough fuel at high speed.

[cuong-nutz]

Follow Blue's suggestions as well as check the vacuum lines for cracks or loose connections as pointed out by Alex.

There's a stock fuel filter that fits into the fuel inlet pipe for the carb and may get stuck in the hose when you pull it off. Make sure it's clear of debris.

You could try leaving the gas cap cracked open to see if the tank is venting properly.

[mgentz]

Originally Posted by DaBlue1

Check these things first...

Poor fuel flow- Make sure any fuel filters are clean, fuel lines are plumbed properly and not pinched or too long.

Check your float valves- carbs that do not fill properly don't get enough gas for operation

Make sure you have good fuel level in the tank- low fuel levels can also affect performance. Performance can drop off after more than 1/4 throttle if fuel is too low

Make sure your tank vents properly- A gas cap that doe not vent properly can prevent proper fuel flow. make sure the cap gas is venting properly by checking for noise due to expanding gas vapors.

Also make sure you idle speed is set properly (1350 +/- 50 rpm) when the bike is fully warmed

When was the last valve adjustment, spark plug change, and air filter replacement?

Do this, then pray. I had an issue very similar to this and it was the coil leads (read:small incoming wires) gone bad. I had to solder on new ends.

Could also be just the coil or ECU.

[Maddawg]

Thanks for the replies. Sorry I am so late for getting back. Here is the status:

Here is what I installed today:
1/4" LDR Clear Fuel Line
Oregon 07-064 In-Line Fuel Filter (for fuel injected vehicles)
K&N KA-2508 Kawasaki High Performance Replacement Air Filter
2 NGK CR8EIX Iridium IX Spark Plugs
Wix 24941 Cartridge Metal Canister Lube Filter
Rotella (550019921) T6 5W-40 Full Synthetic
And I have half a tank, and does it on a full tank
Does it with the gas cap vented open as well
Set the idle speed correctly
Checked for vacuum line cracks and loose connections

It is running better, but it still does it to some extent. It definitely isn't because it is running at high speeds, because I just ran it down the highway, and it didn't do it until I got off the highway on had to stop at some lights. It does it sometimes at high speeds, but if I rev it high enough, it will go back to normal. Additionally, it does it after I have been driving for a long time or a short time.

I haven't had time to:
Check the float valves
Adjust the valves (I checked them at 10,000 miles or so and they were pretty close, but I just ordered a shim kit)
Check the coils
Check the ECU

Additional questions:
Will the cracks in the vacuum lines be obvious for me to find?
How do I check the ECU (I assume that is the acronym for the fuel injection system)?