Piston Slaps

[Bennie]

I'm new to the MX scene but I just got me a 03' KX 250. My friend down the street from me tore into the throttle the first day I got it. Could that damage my bike if its not broke in. Because the bike was brand new like 2 weeks ago when my friend tore into the throttle. Well as I started getting use to how the engine sounds , it seems like my piston kinda makes this slappin sound mainly when it idles or I'm at lower RPM's.  Is it normal to hear that kind of sound? But as for performance the bike spanks my butt, very responsive probably would run straight up a wall if gravity would let it.  So is that sound normal though , plus when I rev or when I'm at high RPM"s I hear like a transmission spinning sound in the casing is that normal too?

[mikesmith]

Kind of hard questions with out hearing the bike,screaming the bike before its broke in is hard on it.Piston and rings or any metal contacting surfaces are not seated,more engine life/performance loss from this (or instant breakage).Only advice I can give is to let a shop or someone with experiance with a KX250 listen to it,and dont let your friend ride your bike anymore!

[Bennie]

Well the shop I bought it from said it sounded fine. But I just wanted your opionion. So you guys think Kawasaki is one of the best Manufacter's out there.

[gowen]

Bennie, I'm ""ASSUMING"" you are hearing the powervalves rattle. It is pretty normal, if you hit the throttle at idle, will it go away? If so, it is more than likely the powervalves. The KDX's were horrible for this. The transmission noise I'm betting is you hearing the chain running or the clutch spinning. CHange your oil soon too. I usally change the oil right after a break in. Everybody has their oppinions on breaking in their bikes. I usally idle it until warm, let it cool completely, ride it the next day until hot, let it cool, then run it and that is it. Never locked a motor due to imporper warmup. Just by losing waterpumps and crushing rod bearings that were long over due (10 years on a cr125 rod bearing, lots of abuse).

Use the search function and look for breakins if you want to learn more. Lots of good information on the KX in general is here.

Green is a great machine! I love the KX500, and now my KX250 has become my love. But, I will be honest and say that the YZ250 spanks the KX anyday on the track. Owning both, I can say that without a doubt. But, the KX is a sweet ride, I would not have purchased it if that was the case.

[Bennie]

Yeah man thank you for you  replying. I am thankful to get some positive assurance. Yes it goes away when I hit the throttle, I just hear it when its Idling mainly at low idle it tends to make that rattle or like clatter like sound it kinda blends in with the moter's normal idle sound but  the clatter sounds louder. I also hear it when Im riding but only when I coast at lower rpm.  Also my plugs are fouling and I'm almost positve its because the fuel air mix is too rich. But it was like this when I first bought it from the dealer. Do you think the dealer should make these adjustments for me? Should they be Liable even though all racin bikes aren't  under warranty?

[Bennie]

Waht do you mean you wouldn't have purchased it if that was the case?

[hughes]

Your dealer properly will charge you for jetting your bike. All bikes come with base jetting. You will need to fine tune your jetting for type of riding or skill level.

[Bennie]

What can I get alot more power if i change the jetting and still have it correct for my plugs? if so I'm already drooling lOL

[Bennie]

Its seems this bike is geared for short takeoffs or short distant runs . Well I mean the Manufacturers gfeared this.

[hughes]

Yes, More and smoother power can be as easy as jetting. Jetting will be a trial and error on your part. Their are a lot more poeple here that know more about jetting than I do. I jetted my bike by riding and listening and feeling what the engine was doing at diff. throttle settings and how it responed during rolling on the throttle.

[mikesmith]

They jet them rich in my opinion for a safer break in,if the bikes broke in-rejet, if not wait untill it is.Theres some post on how to jet and even your owners mauel will help you understand.Try one change at a time and ask for help if you get confused.

[Bennie]

Will it hurt my bike if I ride rich for another week? It is already broke in its been broke in for about a month now.  But  I can tell by reading my manual its runnin really rich my plugs are really wet and black when I check them.It seems to put out excessive  smoke when I I let it idle in neatral and when I hit the gas in neautral.  THe dealer tells me I should only try to adjust the jetting only if I have the 40 dollar service manuall. PLus they say to get it to run leaner you have to buy new jets.

[Bennie]

This guy was tellin me he had a yz 250 and prefered his kx250 on the track . He said he could corner much better and keep a straight line. I think he had some kit that made it run real fast.

[mikesmith]

Im not sure what oil you run,but can I suggest Maxima Super M or some like Bel-Ray MC1 (run it before and like it,but choose the Super-M) at 40:1. It wont hurt the bike to run rich (lean will hurt it),the owners manuel that came with the bike and this web site can help you sort out the jetting.Read up on jetting before tearing into it,and yes you will probally need a pilot and main jet but you can adjust the clip on the needle and air screw.Try to have an idea of what your doing and why it does what it does befor tearing into it,and try one thing at a time and take notes.Also just a note,altitude,humidity,and air temp all effect jetting.