Doing a top end rebuild on my kids Kx 85. Wondering what would be best: forged (ie, Vertex, ProX) or Cast (OEM, Wiseco). Also, how the heck do you retorque the nut under the powervalve on this mini beast. My standard Craftsman torque wrench will never get into this tight *&#%# space!
He'd ride a KTM like the rest of us if the SX 85 was real and in person!
many of us have OPINIONS based on very little fact. i have had better longevity with oem honda on my cr. the wiseco had short life. ck. with some pro. tuners who have exp. with your bike.
First off, I believe you have it backwards (Wiseco is forged). Based on years of experience with high horsepower snowmobiles and racing off-road motorcycles, I can say that I personally have had far superior results with cast pistons. My only poor experience has been with Wiseco products. Truthfully, the biggest difference I have noticed is in the ring quality (nothing to do with forged verses cast). I have found that a quality piston & rings like Vertex or Asso with go twice as long as Jap OEM or Wiseco, and can easily be freshened up with new rings.
The piston question seems a popular debate right now. I just did the top end on my 96 SX 250 and the OEM Elko held up well. I went with a Wiseco mainly based on price and my experience with them in my CR-500.
On the cylinder bolts motion pro makes an extension for your torque wrench.
i have been using wiseco for 15 years and have never any problums, and i have blown up two stock pistons in rm's.the only time i seem to see problums with wiseco pistons is when people don't let there bike warm up before cleaning them out (reving the bike to high rpms)or riding the bike cold at full throttle. it seems like with forged pistons you MUST warm up your bike with out running it at high rpm's before riding and if you do they will last and last.personaly i think with the right warm up procedure and careful breakin they will out last cast pistons but if care is not taken to properly break in and warm up the bike before w.o.t. you might have problums.i am no expert though this is just my opinion.
Forged pistons expand more so need more time to warm up. Wiseco is forged, Vertex is cast.
Curious about the KX nut, just ordered piston kit for son'd KX100, what other surprises await me?
Also, been trying to get an engine manual for my '00 250 EXC, thought I'd freshen it up while leg is on the mend, seems they're back ordered. Anyone got one they'd feel like lending out or faxing off a few relevant pages?
Todays Quality cast pistons are very high quality. I even use them in turbo applications, somthing not possible 20 years ago.
I prefer cast pistons for the (generally) tighter tolerances and longer wear life.
I like forged pistons for race only applications where teardowns are frequent. However my Husky 360 uses a Gilardoni forged piston with tight clearances, similar to a cast piston. It has a very long life span. I have not found a source for "tight clearance tolerant" forged pistons for other applications.
Will do the teardown this weekend. Bought a Vertex complete top end kit for 89.95 from MOTOSPORT outlet in Eugene, OR.
RE. The kX nut, got the Motion pro torque wrench ext. for $15 from my local dealer. Will also replace coolant with Engine Ice when rebuild is done. Want to see if this helps with summertime racing temps.
Hope all goes well.