Acceleration problems

[t.c.mitchell]

ok, i'm not really sure this will make any sense but i'll try my best. in first gear when i give it some wrist and it hits 6K or 7K rpms it acts like it hits a wall and the rpms drop to almost nothing then once i back off the throttle it picks up again. i just had the fuel filter changed and it still does. the spark plugs have been changed about 4 or 5 months ago. any help would be great!

Trevor

[Staerke]

ok, i'm not really sure this will make any sense but i'll try my best. in first gear when i give it some wrist and it hits 6K or 7K rpms it acts like it hits a wall and the rpms drop to almost nothing then once i back off the throttle it picks up again. i just had the fuel filter changed and it still does. the spark plugs have been changed about 4 or 5 months ago. any help would be great!

Trevor

You say this happens when in first gear, I'm assuming it happens in other gears as well?
And have you cleaned the carbs?

[kevin2502000]

Make sure your fuel filter isn't running uphill, it sounds like your running out of fuel. If that looks okay, run it on pri and see if it still does it.

[Stinger02]

dude we need to get together because my bike does the EXACT same thing. Ive cleaned my carb myself with no improvement, Im gonna start throwing parts at it next, lol. air filter and fuel filter here i come!

[paul.miner]

Yeah, sounds like a fuel supply problem. Things to check include petcock, fuel line routing, fuel line pinched, fuel filter, and the carb float/bowls.

I made a useful little rig for this situation and others. You can take an empty oil bottle (the plastic used should resist gasoline well) mount fittings on it to turn it into a small fuel tank that's easy to hang up high. I mounted the fuel outlet in the cap and put a small air vent in the bottom of the bottle (which can be plugged with a machine screw while filling the bottle). This eliminates any fuel hose/filter and petcock problems, and acts like a petcock set to PRI.

If you still have problems when using this alternate fuel supply, the problem is likely in the carbs.

dude we need to get together because my bike does the EXACT same thing. Ive cleaned my carb myself with no improvement, Im gonna start throwing parts at it next, lol. air filter and fuel filter here i come!

Although the carbs may be clean, float height can give these symptoms. You can check float height by attaching clear tubing to a bowl drain and keeping the open end above the carbs, and seeing where the fuel level settles.

[Stinger02]

hope im not hijacking your thread and sorry if I am

So Paul, u attach the tube to the bottom and then hold the open end up, how do you know where it should settle, Should they all be equal or something? Im not near my bike so i cant try this right now

[rice_rocket]

I had a similar problem.. found out that the stupid ring inside my air filter fell out... haha

[t.c.mitchell]

You say this happens when in first gear, I'm assuming it happens in other gears as well?
And have you cleaned the carbs?

yeah it has done it in second but since i don't ride that fast or hard i seldom get the rpm's up that high except in first or second.

[Rangerx52]

I think you may have a bad A/F mix.


Last week i pulled my bike apart because it was running rich, and afterfiring.
my AF screws were set to 2.5 turns out (which is unacceptable) my bike is not modded.

I found that my airbox drain hose had fallen off, leaving an unobstructed 1/2" hole in the bottom, increasing airflow in an undesired way. i plugged the hole with a plastic caplug

I set my AF screws to 1.75 turns out, and reassembled. The bike sounded different- almost more aggressive than it should. no afterfiring though.

I got 1km away from my work (which is where i did this), until i realized that at 3k rpm
the power just vanished and the bike would shudder and choke until i fell below 3k again.

I have not fixed the problem or had the time to attempt it recently, but i encountered that problem just from altering those 2 variables on a bike that normally runs well.

[paul.miner]

So Paul, u attach the tube to the bottom and then hold the open end up, how do you know where it should settle, Should they all be equal or something? Im not near my bike so i cant try this right now

I think they should all be about even with the top surface of the bowl. It should stay pretty close to this level when the bike is running, maybe a tad below when you WOT. I've only done this on a GS500, but its carbs were very similar to the Kat's.

[Stinger02]

well since im not near my bike what are you going to try TC?

[t.c.mitchell]

well since im not near my bike what are you going to try TC?

well, as far as what i am going to do is start with the easier stuff then work my way up to the harder.

as far as the fuel filter running uphill, since i just had the filter replaced by a place that i trust with my bike, which says a ton as i have managed express lubes and i hardly ever trust my vehicles with anyone, should i pull it apart and check it or do you think the shop would have picked up on that and fixed it?

[Stinger02]

did the problem start after it was in the shop?

[t.c.mitchell]

no, the problem was already doing it before i took it in. i went to buy the fuel filter and replace it myself but decided i had plenty of time so i just let them do it.

i do have more info. apparently it does it in every gear. so far 1st, 2nd, and 3rd. anytime it hits 8500 rpm's the rpm needle drops to zero. so i am guessing that it has something to do with WOT but am unsure what it is right now. not been able to tear into it yet!

[kevin2502000]

Turn it to PRI and try it, might be a bad petcock.