Pro X Piston Kit

Bought this piston kit to try out. Exact size, and fits as described. Much better value than Slavens vortex kits.

-m-2018 BETA 300 RR--

Fitment and everything was great. No complaints. As long as it continues to perform I dont see any problems. Wish they would include the wrist pin bearing with this kit though. Almost missed ordering that separate which would suck.

-m-1998 HONDA CR250R--

Great quality for a cast piston! Definitely recommend on a budget.

Pro X is my go-to aftermarket supplier. Most are made in Japan and are a supplier to OEMs

Fit just right kx65 running like a champ , good product to kids be running hard for weeks now

I typically only use Weisco pistons, but thought prox products have been almost exactly the same as the OEM and for the price how could I pass up this piston.

Just to preface my comments, I've done hundreds of top ends.

The piston seemed to be a good quality and I really couldn't tell much difference between the Weisco and ProX. I did notice that the ProX lacked the same level of skirt coating that Weisco has which helps reduce the wear on the cylinder wall.

When inserting the ProX piston into the cylinder it went in super easy and that concerned me. The Weisco always seems to require a little more work to finesse it into the cylinder. I always coat the cylinder with engine oil prior to install so it's not a dry fit. First start with new piston the bike was angry and didn't want to start. Had to kick it 20+ times before it finally started. Yes, the timing was dead nuts on!!

First ride with the ProX I felt like the bike was lacking torque so obviously the compression was low. On difficult hill climbs and obstacles the bike kept dying on me. After about 3 rides I started to notice some piston slap so I immediately turned it off. Looked at the oil level window and there was way to much showing in it. Oil pressure wasn't there!

Went home and ordered the Weisco piston. Pulled the ProX and it looked okay and there was some wear on the cylinder walls where the skirt rubbed, but no damage. Installed the Weisco and it did require a little finesse and fit very tight in the cylinder unlike the ProX. Bike kicked over in 8 kicks unlike the 20+ with the ProX. Oil pressure is perfect and great compression is back! Bike runs like brand new and pops wheelies with ease. Hills and obstacles are no problem again.

-m-2007 KAWASAKI KX450F--

Great piston and packaging directions a toddler could comprehend and great price

-m-2001 YAMAHA YZ250F--

Good kit for the price. 02 CRF450R

-m-2002 HONDA CRF450R--

Got this for my 2015 yz125 and it was the wrong size. I was pretty mad because it was such a good deal for a piston kit. But apparently i needed a c piston and it was a b piston and no way to select the right one

-m-2015 YAMAHA YZ125--

used literally dozens of pro x pistons in 2 stroke and 4 stroke bikes with zero issues. if pro x makes a piston kit for your bike trust it, buy it.

Broke 25 minutes into warm up, 15 of which was three 5 minute idles. Never had bike past half throttle just trying to break in at a dry lake bed.

-m-2017 KAWASAKI KX450F--

Great item. Had no issues at all. It was a great value. Thanks.

Good fit as description says. I was impressed with the quality and fitment . I did need to reset the cylinder height ,but this should be done with all piston changes.

A very good replacement for OEM on KTM's. We replace the top in every 20 to 25 hours. We love the price and value of this piston.

Helps keep my engine pulse up. You push it down and it pops right back up.

Kx/rm 65..easy install..a good oem replacment..not a fancy forged piston but for a recreationally used bike, it does the job.

-m-2003 SUZUKI RM65--

Worked perfect in a 05 YZ85. ProX makes great pistons. They are shaped just like stock for reliability and power.

-m-2005 YAMAHA YZ85--

I bought this for a 2001 Honda CR 250. Items arrived on time as usual from Rocky Mountain. Once it arrived upon inspection I was impressed with the quality of the product and fitment.

-m-2001 HONDA CR250R--

cost less them an OEM and works just as good. Very nice piston. Package arrived fast and in great shape.

-m-2014 KAWASAKI KX250F--

this kit was everything I needed and install was easy
bike runs great and I would buy this again for sure

-m-2006 KAWASAKI KX250F--

Good run of the mill kit. Came with everything I needed to replace my YZ125 top end.

-m-2018 YAMAHA YZ125--

Love em!!! If you're just looking for an OEM replacement, look no further. Used pro x on a few different builds with nothing but great success.

Put this on my 2006 rmz 250 and it worked awesome! Noticeable power difference

This piston worked perfectly to rebuild my yz 125, I will purchase again

-m-2004 YAMAHA YZ125--

I decided to throw this piston in with a fresh cylinder and we're 70 hours going strong!!

-m-2006 YAMAHA YZ125--

Though the description says it’s a cast piston, for the Beta 300RR it is Forged. I referenced the Pro-X data sheet and confirmed this. It came with no coating, which was kinda disappointing. The ring locating pins seemed kinda small, but it went together fine and runs like new.

-m-2015 BETA 300 RR--

Fit well and seems to be durable, I have noticed a large price increase in the last year but hopefully i get more than 1 riding season out of it.

Good item it works great.and fast shipping too

-m-2007 YAMAHA YZ250F--

Easy install, noticeable power increase with fresh top end. I’ll buy it again.

Runs great in my '13 450sxf. Apparently the stock ones last forever so I probably didn't need it. Oh well.

I wouldn't put it in my ported & polished 450. But for most engines running on pump gas, and no engine mods this piston is great quality for money and isnt going to fail you.

-m-2014 KTM 300 XC-W (E-Start)--

Great quality and fitnent! Measured up exactly to spec for my stock cylinder bore. My YZ250 has 40 hours with this piston. Still going strong! Do not let the price fool you, this is a high quality product! Thanks Rocky Mountain

I just had to replace an old, completely worn out piston. This new top end gave me a lot more compression and a lot more power. I am very happy with Pro X.

-m-2004 SUZUKI RM125--

I had no issue installing this piston. Works and runs great

I bought this for my 300TE Husqvarna. When I took this piston out of the box, my first thought was, this feels heavy. I put it on the scale with the shock piston and it was 1/2 oz heavier, which doesn't sound like much, but percentage wise it was more than 5% heavier. That is very bad news for engine performance. I sent it back.

-m-2018 HUSQVARNA TE 300--

OEM quality top end kit. I have used these kits multiple times with success. It doesnt not include wrist pin bearing.

Great piston for the money went together super easy bike runs like brand new

-m-2000 HONDA CR125R--

Pro X is who makes most OEM 2 stroke engine components for Japan. Their quality is top notch and I've never had an issue running them.

-m-2004 HONDA CR250R--

Easy to install, instructions were detailed. The bike runs well now.

Holds up to the abuse of a 125

-m-2005 SUZUKI RM125--

My first time replacing my sons top end on his 50sx. Super happy with this pro X Piston Kit. Couldn't see the difference from the OEM parts

Got a non running ‘02 yz250f running and went in great

Ive had this piston since I bought my bike, and have put 68 hours on so far, at a track, and it has held up pretty well.

-m-2003 HONDA CR125R--

Went with the Prox because it is same as OEM for my CR125. Don't forget to order a wrist pin bearing, as this kit doesn't come with one.

-m-2001 HONDA CR125R--

I put this piston kit in my 2008 450 EXC-R before I left on the Trans America Trail. I put nearly 7000 miles on this piston/stock cylinder in the last month and a half. The bike is now burning oil and will get another rebuild soon. I will most likely buy this piston kit again. No problems with this product during the trip. Longevity had exceeded my expectations!

-m-2008 KTM 450 EXC-R--

Just installed pro x piston kit in my son's kx 85. Quality finish & fitment. Ring gap was right on, install was easy. Bike started 1st kick had great compression. Then we were off to the races where he placed third overall for his class. Not that it was all the piston but great product, will do it again next rebuild.

Good fit,ring gap was correct, casting seemed clean as well.

-m-2002 YAMAHA YZ125--

Went in and fit like it was supposed to. Can't comment on durability. I put it in. Ran just long enough to break in and sold bike.

-m-1999 KAWASAKI KX250--

Chose per other reviews. Very happy. Broke in easy. Even though I still have a leaking crank seal, bike starts up easy with new piston and ring. Recommend.

Worked great ran it in my superkart has no problems and I ran it hard