Help needed with changing piston and rings

[Mr KX]

I just wondered if any of you Kind chaps could provide me with a step by step guide + Do's and donts for changing a set of piston and rings in my 97 KX250. Cos ive never replaced a set before.

Thanks in advance for any help you can give

[Crazy]

First off take off your tank and or plastic thats going to be in the way, this makes it easier to lift the cylinder off. First your going to take off the head should be like 4 to 6 bolts. Then after you take off the head this should give you enough clearance to pull the entire cylinder off the bolts that hold this on are on the bottom side of the cyclinder on the outside (if its watercooled ) and they hide in the fins if its not watercooled.

Pretty much slike the head up off the piston and the whole assembly is exposed. Once you are here you can remove the circlips/ piston pin easily

Just remember when putting it back together use new gaskets

[Mr KX]

Will I have to take off the reed block as well??
And what about the powervalve which is attached to the barrel, Ive heard they can be a bit tricky as far as setting them up is concerned :
Ill Have to invest in a manual but them thing never make any sence to me, I always find peoples instructions to be alot more strait forward.:

[char393]

I don't really know a whole lot, but I would most certainly suggest a manual. Even if they're hard to follow...the pictures can be pretty helpful. As for the powervalve, you may want to have a look at that as well. The way I remember, they tend to get all carboned(is that a word?) up and it may need some cleaning.

[Blitz393]

remember to drain all the coolant before taking the head off, or you will have a BIG mess to clean up

there should be 5 bolts on the head,
4 bolts on the cylinder base,
yes you have to take the reed block out,
make sure to clean the power valves before putting them back in, since they get sticky with time,
copy a page out of an owners manual for the powervalve setup, i have no clue about the KIPS system.

a HUGE tip, that will save you many many quid, (is that right?) is to remember to put the circlip gap in the 6:00 position (OR 12:00) because otherwise, they WILL get loose and fall out, destroying the cylinder, piston, and most likely bottom end. there is unimagineable G-forces going on in there at 8,000 RPM. if you dont believe me, when you have the head off, pull out the kick starter and kick it over a little, and that will give you an idea of about 300 RPM. :

Rob

[madcow393]

even drainign the coolant makes a big mess that stuff shoots out like a rocket(well it does for my bike)

[RedFan]

I used to have a 2000 KX 250 and the power valve linkage was found on the right side of the engine above the water pump. You would take off a small platice cover or rubber boot found there and remove a circlip and pull the actuator off the drive rod. Anyhow get yourself a manual and it will have some pretty good pictures of this. You have to disconnect the power valve before attempting to pull off the cylinder. If it still has a stock piston write down the letter on the piston crown and ask for one with the same letter from the dealer. Stay away from cometic gasket kits and aftermarket pistons IMO. I have had a bike sieze before due to a faulty gasket from cometic. You may also consider having the bore replated while you have it apart. It will cost about $100 but improves performance and reliability. Kawasaki is known to have inferior cylinder platings. US Chrome can replate and bore your cylinder if you choose. I highly recommend them.

[VirginRider]

put something around the crank and the upper opening to block anything from falling into the crankcase after removeing the cylinder.

[Yardpro393]

sounds pretty well covered.

i would disagree with the aftermarked gasket thing. i have rebuilt bookoos of bikes and always used athena and cometic gaskets with not one single problem. also the aftermarket pistons are as good or better than stock. Pro X is the exact same piston. they make the pistons for the factories.

one really important thing is to make sure your your bike is really clean before you start. this is super important.

[Dirtrydar]

and remember to put the rings on the piston before u put it on....
it happened to my friend who shall remain nameless(peter).... i dunno how he forgot but lets just say he had to replace a brand new weisco featherlight piston and his wallet didnt like that...

[TexTwister 393]

All i have to say is watch how you take it apart, blitz is correct on the piston clip and always remember to put the wring gaps 180 degrees apart from each other and point the arrow or mark on piston towards the exhaust and also make sure you put the rings on with the numbers or letter up...

[MotoMan]

Very well covered guys.

As was said, be sure and wash your bike throughly before you start to tear into the top end or anything for that matter. Normally I will even go as far as to remove the gas tank and seat and spray the bike without them on, it's amazing how much crap gets up under your tank.

I will agree with YP on the gaskets as well, Cometic makes a fine product, I have used them for years without a problem.

[TexTwister 393]

Never had a problem with them either..

[TexTwister 393]

Never had a problem with them either..

[TexTwister 393]

Never had a problem with them either..

[TexTwister 393]

Never had a problem with them either..

[cowboyona426]

Holy quadruple post Twister! :

[char393]

Tex...maybe just a stuttering problem?

[TexTwister 393]

Whatttt??

[TexTwister 393]

Man what happened there??LOl