KDXRIDER.NET

i was starting to think i should change the piston/Rings etc on me KDX. Especially as it was standard and after hearing some horror stories on here about the pistons breaking up.
I bought the bike with only a few hundred miles use. It wasnt even run in so i knew it had been looked after for most of its used life as it was me who did all the work on it(been sat a long time but was immaculate).
Anyway, new Wossner piston, rings, gaskets, gudgeon pin blah blah blah is ordered.
KDX comes apart and guess what
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I could have run it another 4000 miles at least.
The engine is spotless. I wiped the cylinder head clean with one wipe of a cloth and it shines
Theres the smallest smidge of carbon on the crown of the piston and i mean a smidge. Bore is shiney and clean, crank as good as the day the bike was made etc etc.
Now you could say i was mechanically sympathetic with bikes. I guess doing regular oil changes after every other ride, MX7 2 stroke oil (The piston, gudgeon pin etc looked clean oiled. The little end was perfect) have helped etc but christ, what a bike
I love my little KDX.

my 03 220 has just over 4000miles on it, & its still on its original piston!..i run it on `rock oil` racing synthesis 2 pre mix fully synthetic at 40.1 with no problems what so ever..i think the secret it to let them warm up properly & regular servicing...i will be stripping it down this winter & treating it to a fresh piston..either wiseco or wossner along with a top end service & decoke..

+1000 for good synthetic 2-cycle oil.

Yep, them stock pistons are just fine right up until the point when they are not fine anymore. Unfortunately, you never know when that might be! I think it's foolish to even take the chance when there's all the evidence of failure out there, and a forged piston is about $130.

where is all this evidence of piston failures? I've done a couple searches and only found "ooooh, 220 - you're piston might blow up - replace is ASAP". I haven't seen any threads showing the damaged engine.

Not that I'm a non believer, but I'd like to see the damage.

You don't search too well, do ya?

First, a photo;

this 03 220 piston supposedly had 350 miles on it...




Here are a few quotes....

"The 220 I rode this year had same failure. Stock piston, skirt broke and fell into bottom end and cracked the case. Just replace it preventatively...much cheaper than if it fails. The bike is a 2000 and it failed this past spring. That doesn't tell you much about hour many hours were on the piston though."
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"My piston skirt shattered after 30 hours. I was fortunate that it didn't do any major damage, but it still cost me $700 to re-plate the cylinder and crack the case to fish out all the metal parts."
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"I purchased my 99' KDX220 used, and shortly after, my motor unexpectantly seized on a dessert ride in NV. The motor suddenly made a loud rattling sound - It sounded like a rock was trapped in the front sprocket cage, and then the motor stopped. When I tore down the top end, half of the piston skirt broke off and shattered into a million pieces. Luckily I was almost at idle when the piston went, so there was no damage to the lower end (cases). I still had to crack the cases to clean out all the metal parts.

FRP rebuilt it for about $700."
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"Hi all,
I the piston skirt on my KDX220 broke ridign on the ice.

In order to fix the bike I would need a new cylinder and
power valve assembly. So I wanted to give people here
a chance to make offers on any parts that they might be
looking for.

I have the entire bike including stock and after market
exhausts. Also have a black excel rim and excel spokes
on the rear and big bars with mounts on it."
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"The piston, which was also stock and probably never replaced, had a crack in the skirt. After some reading, apparently the stock KDX220 pistons are somewhat known to crack/explode and cause major damage. My crack didn't cause any damage, but I'm glad I narrowly missed the damage that could have happened."
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The list goes on and on....

I think I have a copy of google somewhere if you want to use it.... Here, this will even make it easier!

http://www.lmgtfy.com/?q=kdx220+shattered+piston

you could also search "kdx220 seized", "KDX220 piston crack", etc, and get even more results. The shattered piston search will probably give you enough to make you want to stop reading anyway.

Oh, and I really like to select "groups" sometimes from the "more" menu at the top. That searches forums and newsgroups and such. Neat. Yes, google is my friend.....

Oh yeah, not at all to take away from Rob's post. 4,000 miles on a single piston is a testament to the durability of the KDX, regardless of any issues with stock 220 pistons. I'd say there's a good bit of luck in that 4,000 miles too though, as far as that cast piston is concerned....

your search is very strong Julien. Thanks!

I was just searching here on kdxrider - I figured it was the most reliable source for KDX info.

heckler wrote:I was just searching here on kdxrider - I figured it was the most reliable source for KDX info.

It is but, not every KDX rider out there is a member here or even knows of this forum.

It is documented heavily here also... your search skills are not so strong.

I was bored at work. Spent about 15 minutes searching google groups and those were just some of the first results I found. It is indeed a common failure, unfortunately.

Well not to worry, i have a new piston etc.
Just out of interest, how long would you lot run a new piston and rings in?
Some say just thrash it from the off with how good oils are nowadays etc. Some say give it 100 miles of easy riding so on so forth.
Ive done about 50 miles so far just bimbling about and its tedious I've got a race coming up this weekend aswell and i dont fancy taking my Husqvarna TE450 as its a tight woody race.

Ride it like you stole it!

+1

I agree. Seems to me people that baby their bikes end up having babies for bikes. There's a lot of folks that believe you have to put a good load on the engine to get the rings to seat in the first few rides or they may never seat. That's not to say you start the thing from dead cold and pin it up a long hill, especially if you have a forged piston. I say warm it up, and go!

Colorado Mike wrote:I agree. Seems to me people that baby their bikes end up having babies for bikes. There's a lot of folks that believe you have to put a good load on the engine to get the rings to seat in the first few rides or they may never seat. That's not to say you start the thing from dead cold and pin it up a long hill, especially if you have a forged piston. I say warm it up, and go!

agreed my recent kx build required alot more space than my nieghborhood had to get those rings set... its funny how it smokes alot when the rings arn't set in...took a long fire road to get her hot enough to give in to the new rings and Eric Gorr cylinder

My 97 KDX200 at 3600 miles was only JUST in spec so far as piston/cylinder clearances and the piston/rings well well and truly worn. (Replaced as soon as I bought the bike).

Interesting how two bikes at similar miles can be different.

I'm assuming factors could be; quality of oil and fuel used?
And maybe mine was so worn as it was street plated so might have spent more time at higher speeds or coasting at similar RPM ranges? Interesting.

I know the KDX piston has lasted about 3 times longer than i have ever had with any other 2 smoker i have owned. I put a new Wiesco in when i bought the bike, but before install, i sent it to SWAIN TECHNOLOGIES in NY and had them coat the piston with PC9, and coat the dome wtih ceramic.... No idea of miles, but lots of riding, and almost no sign of wear.