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When to replace piston? 03 CR 250

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03 CR 250 with a steel sleeve (don't ask). It has about 19 hours on it since I did the jug, new piston and rings. Factory service manual says 7.5 hours to replace the piston and rings if you are racing... While I don't race, I have been to the dunes but about 80% of the riding has been trail riding. 

 

Is there any factory service recommendations for riding outside of racing? 

 

Thanks.  

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03 CR 250 with a steel sleeve (don't ask). It has about 19 hours on it since I did the jug, new piston and rings. Factory service manual says 7.5 hours to replace the piston and rings if you are racing... While I don't race, I have been to the dunes but about 80% of the riding has been trail riding. 

 

Is there any factory service recommendations for riding outside of racing? 

 

Thanks.  

 

I would just keep an eye on the piston (through the exhaust port) and your compression readings.  While this is not a 250, it was a single ring 125 (higher rpm) and I got 40 hours out of it with little blow by.  I probably could have gone 50, maybe 60 on it.  I would think with a 2 ring 250 piston you should be able to get at least 40 out of it if not much more.

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I have to replace my top end on my 04 CR250.. The kick starter has hardley any compression. If my cylinder looks good I'm just going to have the shop hone it out and throw a wiesco kit in there..

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I have to replace my top end on my 04 CR250.. The kick starter has hardley any compression. If my cylinder looks good I'm just going to have the shop hone it out and throw a wiesco kit in there..

So testing compression with just the kick starter is considered accurate? Are you serious?

To the OP, you change the piston when it's worn to its service limit. Not a hard concept to understand.

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So testing compression with just the kick starter is considered accurate? Are you serious?

To the OP, you change the piston when it's worn to its service limit. Not a hard concept to understand.

you remind me of the'IT GUY' on Saturday night live. Quite a funny script back in the day...

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This is just opinion of course. My thinking is come up with a hour time that you feel comfortable with and replace the piston. 7.5 hours is not a lot of riding time. I personally would say 40-50 hours is about right depending on riding style. Dunes maybe 30-40 or even a little less. It's cheaper and way easier to replace a solid intact piston then one that grenades and makes a mess inside the engine (been there done that, no thank you!) Plus pushing a dirt bike through sand is not fun either, and trying to pull it out is near impossible.

Good luck,

Chris

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So testing compression with just the kick starter is considered accurate? Are you serious?

To the OP, you change the piston when it's worn to its service limit. Not a hard concept to understand.

 

You are right, it isn't a hard concept to understand.

 

What I don't understand is why in the factory service manual they do not have a recommendation for hours to inspect/replace a top end outside of racing.

 

That is the original reason why I made this post. Of course things need to be within service limits. If I were to follow the manual up to this point, I would of had the jug off three times already to inspect everything which seems to be a bit excessive since I am not racing.    

 

Thanks for the rest of the input everyone!

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You are right, it isn't a hard concept to understand.

 

What I don't understand is why in the factory service manual they do not have a recommendation for hours to inspect/replace a top end outside of racing.

 

That is the original reason why I made this post. Of course things need to be within service limits. If I were to follow the manual up to this point, I would of had the jug off three times already to inspect everything which seems to be a bit excessive since I am not racing.    

 

Thanks for the rest of the input everyone!

the bike was made for competition, for trails you were supposed to buy a xr.

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the bike was made for competition, for trails you were supposed to buy a xr.

 

Lol, true. I do love the XRs... heavier compared to the CR250 though. I prefer a light bike. I do ride a lot of wide open desert and trails. AZ surprisingly has a really good mix of terrain to ride. 

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not much for places to ride up here...damn tree huggers getting everywhere closed up.

 

and those hidden places people dont like to share...trails get flooded with new people and get shut down.

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You are right, it isn't a hard concept to understand.

 

What I don't understand is why in the factory service manual they do not have a recommendation for hours to inspect/replace a top end outside of racing.

 

That is the original reason why I made this post. Of course things need to be within service limits. If I were to follow the manual up to this point, I would of had the jug off three times already to inspect everything which seems to be a bit excessive since I am not racing.    

 

Thanks for the rest of the input everyone!

 

They write the manual for racers because the bike is built for them, simple as that.  :)   They could write 2 manuals but then that would be twice as expensive.  Either way, you can go much longer on a top end then what is reported in the manual.

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I don't know your oil, fuel, jetting, riding style, what parts, how often you clean the air filter, or if your airbox is sealed tight.

 

All of this has an effect on when the top end is due. Generally 20 hours is a solid amount of time. I strictly race MX, run forged pistons and never leave the house without a freshly oiled air filter. I also run good fuel with good oil at 32:1.

Edited by Socket

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HP2 blue bottle synthetic, 32:1, dialed in on the jetting 390 main, Wiseco piston, VP 110 non oxygenated, every ride or every other ride depending on if it was dusty/needs it. I sealed it with the MX bones kit, but when I go to the dunes there is still a fine mist of sand INSIDE the air intake boot. Running a UNI twin with the proper oil. 

Edited by Blaze45

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One method is after putting in a new top end and breaking in the engine, you take a compression reading and record that. Then, at 10 hour intervals, or even 5 hour intervals,  you re-check the compression level. This way you can see how much, & how fast, the compression is dropping off. You could set a target for yourself that once you reach a loss of 20% of the original reading you will rebuild it.  You could also say that you will rebuild it at 20% drop in compression or 40 hours-whichever comes first. This seems to be an even better way than even running an hour meter as you are actually measuring something tangible inside the engine. Of course my engine was running in tip-top shape right before it lost the piston skirt on the intake side.  I did record my compression after rebuilding my engine and have checked it twice since then. I have about 10 hours on the bike at this time and it is still testing within 5lbs. of the original test right after rebuild.

 

Enjoy your bike. They are soooooo much fun!

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One method is after putting in a new top end and breaking in the engine, you take a compression reading and record that. Then, at 10 hour intervals, or even 5 hour intervals,  you re-check the compression level. This way you can see how much, & how fast, the compression is dropping off. You could set a target for yourself that once you reach a loss of 20% of the original reading you will rebuild it.  You could also say that you will rebuild it at 20% drop in compression or 40 hours-whichever comes first. This seems to be an even better way than even running an hour meter as you are actually measuring something tangible inside the engine. Of course my engine was running in tip-top shape right before it lost the piston skirt on the intake side.  I did record my compression after rebuilding my engine and have checked it twice since then. I have about 10 hours on the bike at this time and it is still testing within 5lbs. of the original test right after rebuild.

 

Enjoy your bike. They are soooooo much fun!

thats a very good maintenance schedule to keep, can save a lot of money.

 

we all like to be cheap some times and run our stuff till the last minute, if we actually changed it just before we could save ourselves a lot of money and head aches.   

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