CR250 2002 Top End questions- OEM or Weisco?

[dirtbike_madness]

Just picked up an '02 CR250R in immaculate shape, guy said he took it out less than ten times, and it shows. However, I figure better safe than sorry, so why not do the top right? Anyway, since it's the first top end this puppy is getting, should I just stick with an OEM piston, or, should I opt for something different like a Weisco? Anything else I should consider for this bike first major service? Any input is welcome! Thanks in advance!!

 

[RIGG]

i always used oem/prox on my 2000-2004 cr250s and never had a problem as long as they were changed on time.used wiseco once on a 99 cr and the engine blew cos the pin that gaps the rings fell out.i was told by the local hop up guy that this had happened to other bikes and he diagnosed the fault before he d stripped the engine.

 

[rm_racer]

I was in the Yamaha dealer taking my friends banshee apart the other day and one of the mechanics there said go with oem parts because they are better. Weisco is good, but they do not last as long, but are cheaper. Really its up to you, and depends on how much you want to spend.

 

[dirtbike_madness]

I want to do it right, so I'm not too concerned with saving a few dollars. I may even have the dealer do this, even though I've done it before, I really want this done right because the bike is so cherry. Thanks for all the input...

 

[Bullwinkle58]

Wiseco pistons are top notch in quality. That's all I use, and i've never had a problem.

 

[Lissa]

Go OEM. Alot of these aftermarket pistons only use one ring as opposed to two like OEM. The one ring is suppose to have less friction equaling in more horsepower. The truth is it wears out quicker and lets more blow-by by. I've tried aftermarket pistons, but I always go back to OEM.

 

[RIGG]

on moving and load bearing parts oem can t be beaten.the r and d behind all jap firms is immense and quality usually isnt an issue.my girlfriend worked at a japanese manufacturing plant and she says through pride and respect they dont produce crap

 

[pace]

The standard Wiseco is two-ring, although they do offer a single-ring piston for the CR as well.

You're getting a lot of conflicting advice in this thread, and I'm not going to help that any.. My take is that Wiseco pistons are of outstanding quality, are stronger and more durable than the cast OEM pistons, and will allow you to go longer between top end service. I will only run Wiseco pistons in my CR (the two-ring piston).

AFAIK, Eric Gorr uses them in his big bore conversions. That should clue you in as to how they hold up.

-pace

 

[pace]

on moving and load bearing parts oem can t be beaten.the r and d behind all jap firms is immense and quality usually isnt an issue.my girlfriend worked at a japanese manufacturing plant and she says through pride and respect they dont produce crap

OEM pistons are plain cast. Wiseco units are forged. It's not an issue of whether OEM produce crap or not, it's simply that forging yields a stronger component (albeit one that is heavier and more likely to cause scuffing).

 

[dirtbike_madness]

Lot's of good advice! Nothing wrong with different opinions. How about this... Since this is the FIRST top end in this puppy, should I be worried about measuring the cylinder wall, ring gap, rod, etc.? I don't have any of those measurement tools. Dealer charges $285 labor + parts, but they will measure everything and let me know if anything is whacked. Opinions?

 

[RIGG]

just talking from experience and lots of sand riding. the past 5 years i change the piston every 8-10 hrs(race time) and havent had a problem.when i risked it for longer 12-15 twice the engine blew.

 

[shredda]

I had an 03 CR250 and used a wiseco piston when duing the top end. When comparing the wiseco piston to the oem piston, the wiseco felt lighter (even though it is forged). The pro light is a two ring piston so no worries there. I found that the wiseco piston actually had tighter tolerances than the oem piston, however, the oem piston had 20 hours the first time I pulled the cylinder so it isn't a fair comparison. The ring gap can be checked with a feeler gauge and so can the rod. Your jug should still have a cross hatch and should be in good shape. Make sure to check the exhaust bridge for wear and drill a lubrication hole in the new piston for the exhaust bridge (wiseco has instructions for this). I found that after 40 hours my exhast bridge was showing wear due to inadequate lubrication (the oem piston does not come drilled to lubricate that part of the cylinder).

 

[Rcannon]

I agree with Pace.

I would invite anyone to grab a Weisco piston and hold it up against an oem piston. The quality difference is obvious. The weisco is much better.
Lower cost and lasts at least twice as long. For me, there is no contest.

The only reason a dealer woudl recommend oem is that they make more money selling them.

 

[macscr125]

is there any top end kit for the 03 cr250 that u dont have to drill into the piston?

 

[GhostRider32]

I've never heard of drilling the piston, is that normal for just CR's or other bikes too?

 

[pace]

The reason for this is that the CR has a vertical exhaust bridge. Anyone that has pulled an OEM piston that has been in for a significant number of hours will notice scuffing and excess wear in a narrow strip down the exhaust side of the piston. Wiseco recommend drilling a pair of small holes where the piston meets the bridge - I assume for lubrication? In any case, the drilled Wiseco does not show the same wear characteristics at the exhaust bridge.

I feel pretty comfortable pushing a Wiseco to 40+ hours. After seeing my buddy tear up his KX topend from an OEM ringland failure, I'd not keep an OEM piston in service for that kind of interval. That seems to corroborate your experiences, RIGG. I'm sure that OEM units hold up just fine for folks who follow the recommended service intervals to the hour.

-pace

 

[rm_racer]

I have a Wiesco in my RM, and have been thinking about doing the top end because I dont know how many hours are on it becasuee I bought it used. I was also thinking on changing the the rings every 15 hours then the piston and rings every 30 hours. (a guy at the yamaha dealer suggested this scedual, and that is what he does on all his bikes). Is this a good idea?

Thanks!

 

[dirtbike_madness]

Holy crap, I opened up a can of worms.

 

[Rcannon]

Pace, the exhaust bridge theory sounds spot on. We did not drill this on an oem piston we used in a Honda CR 80 (same bridged design). I screwed up and did not drill.

At hour 7 the piston exploded. The grove became deep enough to catch the exhaust port...BOOM!

We also neglected to drill the holes the first time we used a Weisco piston. The piston still lasted 20+ hours. When I removed the piston the bridge had ground a groove in the piston 4 millimeters deep! The piston did not shatter, however.

Did you guys know that all the oem postons are made by the same company? Look under any oem piston and you will see "ART".

 

[keithb7]

Is there a specific year where the Wiseco pistons should be drilled due to the vertical exhaust valve? I have a '93, as far as I could tell the exhaust valve looks horizzonal to me. I put a new piston in it last week and did not drill the exhaust side.
Should I have done this on my 93?

 

[rob129]

If you look at OEM versus Wiseco, OEM is lighter yes so it will rev faster...more expensive...I seriously doubt it. Pro-X is and ART piston (ART makes all the Jap scooter pistons) which is an OEM piston with a different name. You can even turn the Pro-X over and look inside the piston and there it is ART. Pro-X is ok I ran one is my 89 CR500, I did not have a lick of problems. The skirt on a Pro-X is also coated with Bisulfide to aid in break in. Wiseco's, well they are forged and a tad bit heavier and if your not careful they will stick on you(do a good warm up). The thing about Wiseco's is if you have the bridge across the exhaust port you need to drill the piston (instructions come with the piston) and or have the bridge machined down a few thousands (relief). Being that the Wiseco is forged, it is stronger than your cast pistons. BUT!!!!, if you run any piston longer than your suppose to they will all crack from piston slap after the rings wear out.

 

[shredda]

The vertical exhaust bridge splits the exhaust port into two halves. The 93' CR250 does not have an exhaust bridge so the piston does not need to be drilled.

 

[GhostRider32]

Is this pretty much a CR issue or does it pertain to other bikes also?

 

[rob129]

Good info here for anyone with a 2-smoke........... :ride:

 

[pace]

Is this pretty much a CR issue or does it pertain to other bikes also?

I believe late model YZ125s and possibly KX125s have a vertical exhaust bridge. Not sure which others.

Marcus can probably better answer this..

-pace