03 kx250 knocking/tapping noise

[03kx250]

I bought a used 03 kx250 a few months ago and rebuilt a two stroke for the first time last week! I cleaned the power valves well and installed them according to the manual. I re-jetted from 165 to 168 on the main, moved the needle from #2 to #3 position, kicked it twice and she started right up. While running there is a fairly noticeable knocking sound from idle on up through the revs. The noise does not change much at all when I pull the clutch. I have broken the motor in real gently, and it runs great all through the gears and the power is real strong. It is a little difficult to push it through more than one gear at a time though (like from 3rd to neutral when coming up to park). I have only ran it about 40 minutes since rebuild, the last 10 getting into some power, because I am nervous even though I hear these bikes generally give off some noise like this. I was told by the company who re-nikasiled the cylinder to just run it if there is no powerloss issues, but I do not want to spend another good sum of money if something serious is going to happen. Any advice would be greatly appreciated as I am new to dirtbikes. Thank you.

[vintageguy]

Run a higher octane and or different gas. Mix the gas at 32/1.

[03kx250]

The most octane gas around my area is 91, I am not sure if fuel additives will be more harmful than effective on my bike? There is a equipment collector in my area that buys 100 octane leaded gas for his older equipment and said that I could run that in my bike, but am nervous about trying leaded gas because I dont know why it has become "unleaded" over the years. I have been running 32:1 with Ams Oil Interceptor. The knock is fairly loud, but I pulled on the rod when I rebuilt and it didnt seem to move up or down any. Should I try gas additives or the high octane leaded gas? I am hoping to learn through more trial and less error if possible...

[vintageguy]

I wouldnt go with the leaded gas or additives. it may be something else

[Dell30rb]

Where did you get the cylinder re-nik'd at? *I just made that term up, like it?*

2 strokes will sometimes do that. The factories leave a little extra clearance with the piston to prevent retards from seizing the bikes by riding them hard when they're cold. If you use a wiseco, they are usually a little tighter fitting, and won't do that as much.

If its not absurdly loud... just run the bike, you are probably fine.

[03kx250]

I got the nikasil done at Kustom Kraft performance in Co. I got a pro-x piston from them also because the guy there liked them a little more than the wiseco. They sell both for the same price, so I just went with his opinion. As for the motor, I guess it is not "absurdly" loud yet. Since this is my first rebuild I am happy its running perfect but afraid to mess with a good thing by opening it back up if there is nothing seriously wrong. I live in the middle of nowhere and dont know anyone that is familiar with twostrokes bigger than chainsaws, so this is my best resource. Can I open up the bottom end with the motor intact on the bike and get at the crank bearings? I guess it would be worth a try then. If so, would all that needed to be replaced be the two main crank bearings? Any specific brands? Do the bearings normally only last a few years?

[acw592]

I also have an 03 KX 250. I had read while doing a search that the Kawasakis have a noisy powervalve. Mine makes a noise like your describing. I really notice it when I first start it up and the bikes cold. I think it quiets down after the bike warms up and youve ridden a little. That, or I just don't notice it anymore. I was not sure what to think of that noise either, but after searching a little, it seems to be fairly common. My top end has a few hours, but not many. Its fairly tight.

[acw592]

The noise is coming from your power valve. This noise is normal and is more noticable when the power valve is clean. As carbon builds up the noise is some what masked! But it is always there! Go Rid'in!!!!

I searched that again, and above is a quote from Crogg, who knows his stuff!

[03kx250]

Thanks for the info!!! The 15 inches of snow we have here is melting fast cause its 45 degrees today, so i will go let her rip!!!! I will also get back to you if anything blows up!!

[adamaus]

Originally Posted by 03kx250

The most octane gas around my area is 91, I am not sure if fuel additives will be more harmful than effective on my bike? There is a equipment collector in my area that buys 100 octane leaded gas for his older equipment and said that I could run that in my bike, but am nervous about trying leaded gas because I dont know why it has become "unleaded" over the years. I have been running 32:1 with Ams Oil Interceptor. The knock is fairly loud, but I pulled on the rod when I rebuilt and it didnt seem to move up or down any. Should I try gas additives or the high octane leaded gas? I am hoping to learn through more trial and less error if possible...

Kawasaki sugest atleast 95 octane fuels but don't go muck higher or u foul plugs alot,and don't run leaded fuels or u will clog up ur power valve.I would sugest useing motul 800 with 98 octane fule mixed at 35:1 with a br8es ngk plug take it easy and ur engine noise will more then likely go away as it losens up a bit more.

[adamaus]

Originally Posted by 03kx250

I got the nikasil done at Kustom Kraft performance in Co. I got a pro-x piston from them also because the guy there liked them a little more than the wiseco. They sell both for the same price, so I just went with his opinion. As for the motor, I guess it is not "absurdly" loud yet. Since this is my first rebuild I am happy its running perfect but afraid to mess with a good thing by opening it back up if there is nothing seriously wrong. I live in the middle of nowhere and dont know anyone that is familiar with twostrokes bigger than chainsaws, so this is my best resource. Can I open up the bottom end with the motor intact on the bike and get at the crank bearings? I guess it would be worth a try then. If so, would all that needed to be replaced be the two main crank bearings? Any specific brands? Do the bearings normally only last a few years?

If ur crank sharft bearings are worn past the service limit it will vibrate alot but not make knocking noises,You said u had a manual the service limit is in the bottom end section from memory i think it is 20 thou,You can not check ur crank sharft bearing free play without takeing the topend off so i would just ride it,it will not be anything major dude or 40 mins rideing it would of allready gone on you.

[xricer]

Originally Posted by adamaus

Kawasaki sugest atleast 95 octane fuels but don't go muck higher or u foul plugs alot,and don't run leaded fuels or u will clog up ur power valve.I would sugest useing motul 800 with 98 octane fule mixed at 35:1 with a br8es ngk plug take it easy and ur engine noise will more then likely go away as it losens up a bit more.

I think they are talking about research octane of 95......google it but r octane of 95 is actually alot less on the street. You are wasting cash if you buy 98 octane.