cr250 piston & sleeve still good?

hey i know this is a noobish question but this is my first top end rebuild. what i wanted to know was if the piston and sleeve looked ok. i am on a tight budget for this rebuild, but i dont want it to come back and bite me in the butt later on. i cant feel any gouges or nicks on either the piston or cylinder with my nail. but the intake side of the piston is a bit shiny with some vertical streaks. but you guys go ahead and take a look. hope the pictures come out. haha

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your cylinder looks ok, give it a hone and it shoudl be fine, but..the piston has seen alot better days. get a new one.

If you have $100 you could do what chopper said.

Putting it back together how it is it will still run. Don't hone unless you replace the piston or at least rings.

Ideally hone the cylinder, new piston & rings....but I do appreciate that $$$ can be a factor. If you really have to build it the way it is, check the ring grooves for sharp edges and take the shine off the piston with some scotchbrite. (holds oil better)

ok. so i will probably put it back together the way it is and get her a fresh top end in a month or 2 when i have a bit more $$. but before any final decision is made is there any way to tell when the top end will finally die? and is the risk of a chipped or cracked piston high right now? thanks for all the help guys i just want to get her running for memorial day. :smirk:

Pistons fail after they have been used for a prolonged period. Some people change every 40-60 hours to prevent, what is in effect, metal fatigue. Of course, if your motor is jetted incorrectly or run with insufficient lubricant, it will seize before reaching this stage.

Your piston crown looks good with regards to jetting & the bore still has visible cross hatching. (Thats good) Only you know how many hours the piston has under its skirt (humour) If it has been in there a while, avoid long spells of WOT and you should be fine. If you are running 40:1 use more oil just to be safe.

ok. so i will probably put it back together the way it is and get her a fresh top end in a month or 2 when i have a bit more $$. but before any final decision is made is there any way to tell when the top end will finally die? and is the risk of a chipped or cracked piston high right now? thanks for all the help guys i just want to get her running for memorial day. :smirk:

Doesn't look bad. Inspect the intake side skirt closely for small cracks. If you don't see any, it will be okay to ran that piston/rings for a month, or so, until you can save the money for a new pistons/rings.

I prefer OEM piston and rings. I recently found a new OEM piston for my bike on ebay for only $40. I researched the correct Honda part number and searched for it on ebay. It popped right up. You have time to shop for similar deals.

@ dgcars well considering that i bought the bike last week and it needed new crank seals (running excessively rich). i have no idea how many hours it has under the skirt. (reply humor) :smirk: i figured that when i tore into it i might as well clean everything up super good and take a look at the topend, and this is what i found.

@ CamP just took a close look at the piston and there are no cracks at all (thank God) so i think ill do what dgcars said earlier and lightly scotchbrite it to get some of the shine off. also no offense but i have heard tons of horror stories about the oem pistons. when i get a new one i think ill go with wiseco, i ran those in my quads for a long time and never had an issue.

any recommendation on what direction to scotchbrite the piston? horizontally? vertically? circular? 45* cross hatch like in the clynder? and will super fine steel wool work or is that a big no no? sorry for all the questions, but on the bright side, i wont be back to ask the same ones over and over again. hahahaha :smirk:

No big deal. Aluminum...so it will only last a short time. Any thing short of af an angle grinder & you are good.

i have heard tons of horror stories about the oem pistons.

OEM pistons are excellent. The horror stories are waaaaaaaay overblown.

Believe me. I've been building race engines for over 32 years and I've never had a OEM piston break and haven't suffered a seized piston since 1980.

any recommendation on what direction to scotchbrite the piston? horizontally? vertically? circular? 45* cross hatch like in the clynder? and will super fine steel wool work or is that a big no no? sorry for all the questions, but on the bright side, i wont be back to ask the same ones over and over again. hahahaha :smirk:

Use scotchbrite and WD40 in the cylinder. Follow the existing cross hatch. Follow up with contact cleaner and paper towels until no gray residue shows up on the paper. Finish cleaning the cylinder in a bucket of soapy water.

On the piston, only touch it if you see any light scoring. If scored use vertical, then horizontal strokes on the skirt. Don't go nuts on it. Clean up the same as the cylinder.

awesome. if you guys think itll be alright ill take your word for it. im not planning on riding hard at all this is my first dirtbike so ill be taking it easy and learning the 2stroke powerband for a while. so according to your advice i will scuff it up for the sake of lubrication and saving money (temporarily). thanks so much for all the help guys. :smirk: :smirk:

When pistons wear, you get excessive piston-to-cylinder wall clearance. When you start the engine cold, you can hear the "piston-slap". It sounds like a clicking noise that follows the RPM's. When the engine warms up, the noise can go away. If it smokes like a dog when you open the throttle, and you hear a clicking noise all the time, ( even after it warms up ), you need to do a top-end. That is the OLD SKOOL method.

:smirk:

You can also do a compression test, but I have no idea what it should read.

:smirk:

awesome. if you guys think itll be alright ill take your word for it. im not planning on riding hard at all this is my first dirtbike so ill be taking it easy and learning the 2stroke powerband for a while. so according to your advice i will scuff it up for the sake of lubrication and saving money (temporarily). thanks so much for all the help guys. :smirk: :smirk:

To be honest, if I was only going to ride it long enough for me to save the money for a new top end, I'd just put back together and run it as is.

To be honest, if I was only going to ride it long enough for me to save the money for a new top end, I'd just put back together and run it as is.

yeah, but you've probably got a job. im a 17 year old kid who works as a snowboarding instructor in the winter, and the season is over. hahaha... so now ive got to find a summer job. so itll take me a bit longer to save up $170 bucks for a new topend. :smirk:

yeah, but you've probably got a job. im a 17 year old kid who works as a snowboarding instructor in the winter, and the season is over. hahaha... so now ive got to find a summer job. so itll take me a bit longer to save up $170 bucks for a new topend. :smirk:

The total cost for for an OEM top end, including gaskets is $137.70 if you mail order it from Apache or Pro Caliber. Pro Caliber has free shipping on orders over $89. You can make $138 in two days, even at minimum wage.

OEM pistons are excellent. The horror stories are waaaaaaaay overblown.

Believe me. I've been building race engines for over 32 years and I've never had a OEM piston break and haven't suffered a seized piston since 1980.

I totally agree with you CamP. My experiences dating back to 1972 have been the same as yours.

are you sure that's a sleeve? it doesn't look like it judging from the pictures.I can't see the sleeve joining the cylinder looking though the ports please tell me if I am wrong.

ok. very true. so about 140 bucks for piston, rings, wristpin, wristpin bearing, and gaskets. but how much $$ is the norm to have the cylinder honed?

@ dirtrider 11 yeah no sleeve just a cylinder. didnt even cross my mind when i typed it. :smirk: haha. my excuse is i used to build and race little radio controlled, nitro powered stadium trucks. and all of the engines had sleeves in them.:smirk:

sometimes the topend kits don't come with the wristpin bearing, make sure you replace it when you do your topend or even now before putting it back togather.

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