2009 CRF250R Piston replacement

[woodswpn]

Anyone agree with the stated 15 hour life of a 09 crf 250 piston? I dont ride MX, but do work it in the woods.

[Charlie C]

Only if you have a personal mechanic and money to burn. I go 20 hrs on the rings and 40 on the piston and so on. That would be if you race the bike to expect optimum performance. Being that you're more of a woods rider, you can probably do 30 and 60 and maybe more. Maybe someone that does that type of riding will chime in and give their thoughts on it.

[woodswpn]

Thanks for the info. That interval sounds more reasonable. The reason I ask is because I am a previous big bore rider, and piston replacement has never been much of a concern.

[Charlie C]

Thanks for the info. That interval sounds more reasonable. The reason I ask is because I am a previous big bore rider, and piston replacement has never been much of a concern.

It gets pretty expensive even on the 20 hr mark. The stock piston is a real poor quality piston. Installing a JE, Wiseco, CP or something of good quality makes a huge difference. Truthfully, just inspecting it once in a while and knowing your bike is what you really have to gauge it on. If you look on this site long enough, you'll see that some guys will go 80 hrs without any problems so it really has to do with riding style and how well your bike holds up to what you put it through. We have an 09 450 and I pulled the piston out at 70+ hrs with no sign of wear. Since I had the new piston, I replaced it anyway. Cross hatches looked like new. 86 hrs, KABOOM! Connecting rod broke. Cylinder still looks new minus the big piece missing at the bottom! So I know the big bore well and how well the piston holds up!

[woodswpn]

That is exactly what I would consider-aftermarket piston. Just the pictures I have seen of the factory unit kid of scared me. Con rod broke? must have fatigued. Yes, I agree that you need to know the bike. But my last bike (still have it) was an 00 XR650R. Hard to beat from a maintenance standpoint.

[moto_x2005]

Aftermarket is the way to go..

As for 15 hour rebuilds stated in the owners manual its just a selling tactic bike manufactures use to get you in the service dept or parts counter at least.. unless your a on the rev limiter riding pro i wouldnt worry about it.. i change my pistons out at 40 hours to be safe but I have gone upwards of 80 hours with no issues (mx)

[Charlie C]

That is exactly what I would consider-aftermarket piston. Just the pictures I have seen of the factory unit kid of scared me. Con rod broke? must have fatigued. Yes, I agree that you need to know the bike. But my last bike (still have it) was an 00 XR650R. Hard to beat from a maintenance standpoint.

Those XR's are dam near bullet proof! If the CRF was the same way, this would be an empty forum!

[woodswpn]

Yesss. I have no doubt that I will still have my 650 long after the 250 is gone. Thanks for the input guys.

[1st4stroke41]

I'd check it and rings at 50, in the woods 80 was a little quick and 100 about right. It's hard to wring them out in the woods.

[woodswpn]

I am betting that the majority of the piston failures that occur on these machines is due to lack of air filter maintenance. When I purchased my 250, the first thing I did was check the air filter. It looked like it was installed hastily, and did not appear to be sealing like it should. Glad I checked. Also tore down/re-greased all bearings that I could, which brings up another question: Why is Honda so tight on the amount of grease they apply at the factory? To sell more parts I am sure.

[moto_x2005]

Its not a Honda-only thing.. My Yz's had even less grease on the bearings!! Sure the airfilter will have an impact on the wear but its the valves that list the airfilter as its biggest enemy when not sealed/cleaned right or torn.. Dirt getting into the cylinder can score the piston and cylinder walls but not as common as a two-stroke since the air-fuel mixture runs through the crank case, up through the transfer ports and cylinder where the chance of bearing/piston failure is much more higher! Most 4t piston failures from what ive seen are from running them at to long of intervals, running them in worn cylinder, piston/cylinder clearance is to much or a defect in the piston.. These short pancake pistons will begin to "rock" and this will begin to wear on the bottom of the skirts to the point of making them weak and eventually breaking off..

[woodswpn]

That is what scared me after seeing pictures of that pancake piston-the short height. So from your experience, do the aftermarket pistons have a taller profile, or are they the same? An since we are on the subject, are these 250's weak as far as the crank & rod assembly?

[Charlie C]

That is what scared me after seeing pictures of that pancake piston-the short height. So from your experience, do the aftermarket pistons have a taller profile, or are they the same? An since we are on the subject, are these 250's weak as far as the crank & rod assembly?

The profile of the piston is pretty much the same until you get into the hi-compression pistons.

As for the crankshaft assembly, riding style and bad 2-stroke habits will kill the crankshafts. I wouldn't say they are weak, but they will go if you push them hard all the time. I'm on a 30 hr interval with replacement crankshafts. Hi-compression pistons attribute to the bottom ends going out sooner than the stock compression. It's additional stress. With added power is added stress on the parts. Riding style and maintenance I think has the most to do with the amount of time they last. You hear of some guys getting 200 hrs out of the crankshaft. I would be tickled shitless to see 50.

[moto_x2005]

Ive seen almost 120 race hours out of an 05 crank.. In terms of full on hard racing 80 is about average of what im seeing there..

Imo its not really compression ratios that make a piston stronger you are also looking at aftermarket pistons being forged, not casted like most oem pistons are.. Forged pistons are much stronger in strength and lighter in weight, not they are introducing boxed short skirt pistons more and more to the mx scene and this will help out even more with strength

[woodswpn]

200 hrs? That seems unbelievable. I suppose if you cow-trailing it most of the time. Anyway, I am not a racer. I do work the machine medium to hard in the woods, but I dont use more power than I need(try not to), and try to focus more on technique than the brute force method. I am all about maintenance; I just want to make sure there are no areas of major concern or historical problems with these machines. I am new to the CRF machines. Some of the areas that I ride in the Northwest would not be pleasant to get out of in the event of a failure(I know, they can happen) Thanks for all the info guys.