[Jechumanimal]

Hey all,
I recently got my first bike, a 2009 EX-500. I did the normal tune up stuff (oil, coolant, filter etc) and got it running pretty well. However, I kept noticing that at higher speeds, when I opened up the throttle, it was almost as if there was a delay in the power response and that when the power did come, it was slightly inconsistent. So, I decided to change the spark plugs. However, I hopped on the bike and now the problem is much worse. I rev it up to 4 or 5000 RPMs in any gear and it just does not give me power. It will slowly accelerate faster but is nearly unresponsive. I even tried throwing the throttle wide open but the bike just will not go any faster. Before I changed the plugs, I was thinking it was some kind of fuel delivery issue but the fact that new plugs made it immediately worse confuses me. Up to 4000 or so RPMs it is normal but after that all goes to hell.
Any ideas would be much appreciated!

 

[Sarge2481]

Did you service the spark plug wires and boots? How many miles are on the bike? Any other maintenance done recently? The more info the better.

 

[Jechumanimal]

Did you service the spark plug wires and boots? How many miles are on the bike? Any other maintenance done recently? The more info the better.

Bike has 8500 miles on it. Did not service the boots. Only other maintenance done recently was a brake pad/rotor replacement. Haven't touched the engine/carbs otherwise. I bought it about 3 months ago from a seller who had let it sit for about a year.

 

[Sarge2481]

I would start with servicing the boots since there was a change after messing with them. Because it did sit for a while there is the possibility of a carb problem as well if old fuel was left in the carbs. If you do end up taking the carbs out to service them, I would also check/adjust the valves and sync the carbs.

 

[ducatiman]

according to official Kaw maintenance schedule, a valve clearance check was due at 7500. OP don't blow it off.....a full service in your best interests and a long service life of your EX. Agreed, if sitting dormant for a year fuel related varnish buildup very possibly affecting performance.

You check air filter integrity and intake pathways clear?

 

[Screwofdriver]

Had similar problem, since this is effecting the bike at highish RPMs it sounds like your main jets are clogged or your pilot jet screws are incorrectly set. Id first start by screwing both of your pilot jet screws all the way and counting the rotations, write it down. Then back both out 1 3/4 turns, you will need a skinny short screwdriver to do this. Drive it, see how it performs, if better than that’s your problem and you just need to adjust them by screwing them in or out a 1/4 turn until the bike runs the best. If the adjustments throws it out of wack just set it to where it was and pull the carb and clean the jets. I’d clean the carb anyway since you need to pull it, but don’t mess with the diaphragms at all, you tear those and it’s a world of trouble.

 

[Jechumanimal]

I would start with servicing the boots since there was a change after messing with them. Because it did sit for a while there is the possibility of a carb problem as well if old fuel was left in the carbs. If you do end up taking the carbs out to service them, I would also check/adjust the valves and sync the carbs.

OK thanks mate ya will do

 

[Jechumanimal]

according to official Kaw maintenance schedule, a valve clearance check was due at 7500. OP don't blow it off.....a full service in your best interests and a long service life of your EX. Agreed, if sitting dormant for a year fuel related varnish buildup very possibly affecting performance.

You check air filter integrity and intake pathways clear?

Ya brand new filter pathway was fine. It does seem like some sort of blockage so definitely going to do that check... though I don't understand out why changing the plugs and air filter made it so much worse

 

[Jechumanimal]

Had similar problem, since this is effecting the bike at highish RPMs it sounds like your main jets are clogged or your pilot jet screws are incorrectly set. Id first start by screwing both of your pilot jet screws all the way and counting the rotations, write it down. Then back both out 1 3/4 turns, you will need a skinny short screwdriver to do this. Drive it, see how it performs, if better than that’s your problem and you just need to adjust them by screwing them in or out a 1/4 turn until the bike runs the best. If the adjustments throws it out of wack just set it to where it was and pull the carb and clean the jets. I’d clean the carb anyway since you need to pull it, but don’t mess with the diaphragms at all, you tear those and it’s a world of trouble.

Thanks mate yeah i'm definitely going to clean out the carbs and check the jets. Any ideas why changing plugs and filter would have made it so much worse?

 

[Sarge2481]

Thanks mate yeah i'm definitely going to clean out the carbs and check the jets. Any ideas why changing plugs and filter would have made it so much worse?

Just out of curiousity, what plugs did you put in and what did you gap them to? Gap should be 0.6-0.7mm or 0.024-0.028in

 

[Jechumanimal]

Just out of curiousity, what plugs did you put in and what did you gap them to? Gap should be 0.6-0.7mm or 0.024-0.028in

I put in NGK plugs. Got them from a local Kawasaki dealer and the guy said they were "pre-gapped" and that I didn't need to do anything with them. I just took his word

 

[Sarge2481]

They are SUPPOSED to be pregapped, but as plugs bounce around in the box during shipping, they can have the gap closed up. I always check plugs before install just to be sure. Same with my truck, the plugs I bought were "pregapped" yet when I checked them 5 of the 16 plugs were undergapped. (Dodge Hemi motor so 2 plugs per cylinder in case anyone was confused)

 

[Sarge2481]

What I think may be going on here is most likely a carb jet issue with some maintenance due (valve clearance for instance) and by changing plugs (possibly undergapped) and playing with the wires/boots, you have poked a different bear in doing so, making it run worse.

 

[Screwofdriver]

Its hard to say sometimes, I know when I replaced my air filter it threw my bike way off. I had no top end due to the new filter actually doing it’s job and restricting air flow to limit particulates, this threw off the airflow requiring me to turn the pilot jets in a full turn to lessen the gas flow since it was flooding. When i first got the bike I waited to change the plugs, when I got around to changing them I found that the old ones were not sealing correctly and I was loosing compression. The gain of compression was great but it again threw off my air/fuel mix and I had to adjust. Main jets don’t really need a reason to gunk up, just happens, a aftermarket fuel filter on the intake line will help limit that issue.

 

[bpe]

Could you possibly have over oiled the air filter?

 

[K-woppa]

Had similar problem, since this is effecting the bike at highish RPMs it sounds like your main jets are clogged or your pilot jet screws are incorrectly set. Id first start by screwing both of your pilot jet screws all the way and counting the rotations, write it down. Then back both out 1 3/4 turns, you will need a skinny short screwdriver to do this. Drive it, see how it performs, if better than that’s your problem and you just need to adjust them by screwing them in or out a 1/4 turn until the bike runs the best. If the adjustments throws it out of wack just set it to where it was and pull the carb and clean the jets. I’d clean the carb anyway since you need to pull it, but don’t mess with the diaphragms at all, you tear those and it’s a world of trouble.

I just want to mention; do not use carburetor cleaner in the carburetor without removing the diaphragms. The carburetor cleaner can get to the diaphragms and will surely ruin them if it does. Also, pilot jets contribute nothing to full throttle operation. They ARE a main source of trouble at small throttle openings though, because they're so small they clog easily with crap from modern gasoline.

I would definitely look at the spark plug wires and caps first. Disturbing them while changing plugs made the problem worse. and corrosion inside the cap and connections is a common problem for these bikes.

 

[Jechumanimal]

Its hard to say sometimes, I know when I replaced my air filter it threw my bike way off. I had no top end due to the new filter actually doing it’s job and restricting air flow to limit particulates, this threw off the airflow requiring me to turn the pilot jets in a full turn to lessen the gas flow since it was flooding. When i first got the bike I waited to change the plugs, when I got around to changing them I found that the old ones were not sealing correctly and I was loosing compression. The gain of compression was great but it again threw off my air/fuel mix and I had to adjust. Main jets don’t really need a reason to gunk up, just happens, a aftermarket fuel filter on the intake line will help limit that issue.

Ah interesting ya it seems that the new air filter might just be exasperating a clogged jet...

 

[Jechumanimal]

Could you possibly have over oiled the air filter?

that would make sense but nah got it from a dealer who told me it was pre oiled and not to put anything on it

 

[fog]

Remove the carb vent hose if you still have then throw it awayFOG

 

[Screwofdriver]

Is the vacuum line not needed? I thought the Petcock required a vacuum to work?