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I am being given a solid running KDX220 (I think it’s a 2000 or 2001?) my brother-in-law needs to get out of his way but doesn’t want to sell it. I am a rider for many years (but this is my first 2 stroke) and will make this a dedicated trail bike. I have ridden with him and seen him ride it hard. I know he is at least the 2nd owner of this bike. I doubt he has changed the stock piston but I don’t know if the original owner did?

What sort of lifespan does the stock piston have? I’m trying to decide if based on its age and how its been ridden if I can assume its been replaced by the original owner or should I disassemble and plan to replace it anyway.

If I do decided to replace the stock piston with a Wiseco since it is running well should I expect to have to get the cylinder machined (and/or replated) or will piston and rings be enough?

Since I don’t ever expect him to ask for it back and the price is right I will do some simple performance mods that he won’t complain about but I don’t want it failing while I’m riding it.

Thanks in advance.

On a 220? 5 minutes.... after that your on borrowed time.

I would plan on replacing it. It's too much risk to leave it and assume it's fine. The cylinder may well be fine, you can clean it up with a scotch brite pad. If the plating is worn through , that indicates the cylinder needs attention but generally if the plating is intact the cylinder is good.

There is no meaningful lifespan of the stock piston. Maybe forever, maybe an hour.

Indawoods wrote:On a 220? 5 minutes.... after that your on borrowed time.

I guess I'll be pulling the head to see. (and may send head and carb to RB)

Any particular marking that I can tell from just looking down the cylinder to differentiate the Wiseco and stocker? Piston's are relatively cheap...but its the added cost of the cylinder that makes me not too excited about it. I guess it is better than complete rebuild?


PS...Inda that Avatar is freaking me out!

Pretty sure you're going to have to pull the cyl to tell.

raisedinal wrote:

Indawoods wrote:On a 220? 5 minutes.... after that your on borrowed time.

...Any particular marking that I can tell from just looking down the cylinder to differentiate the Wiseco and stocker? Piston's are relatively cheap...but its the added cost of the cylinder that makes me not too excited about it. I guess it is better than complete rebuild?...

Not sure what you mean by added cost of the cylinder since replacing the piston proactively does not mean a new cylinder unless the thing is in bad shape. If you mean the expense of a cylinder if the stock piston frags, that will be on the cheap side of things if you're one of the lucky souls. The damage caused by stock 220 pistons has been known to include the cases, crank and bearings along with that cylinder and head. On the bright side, I haven't heard of one killing anyone yet.

Just put a piston in it regardless. I'd never buy a used 2 stroke and not replace the piston. It's cheap, easy to install, and gives you a certain piece of mind. Unless you find a problem with the cylinder when you take it down, you don't have to do anything but install the new piston and rings, and check the piston clearance and ring end gap. Easy cheesy. Piston kit and gasket set will get you there.

juliend wrote:Just put a piston in it regardless. I'd never buy a used 2 stroke and not replace the piston. It's cheap, easy to install, and gives you a certain piece of mind. Unless you find a problem with the cylinder when you take it down, you don't have to do anything but install the new piston and rings, and check the piston clearance and ring end gap. Easy cheesy. Piston kit and gasket set will get you there.

What is ring end gap and how do you measure it? thx

I wouldn't worry about that... I never have.

Given that the price was right, I'd put a piston and rings in it and be done with it. If you keep the air filter clean a piston and ring set will outlast the rest of the bike.

If the cylinder is badly goobered up a replating may be in order. I'd cross that bridge only if necessary.

This is only my opinion - The stock pipe and silencer on the 220 with the just the head adjusted by RBD and carefully jetted makes for a very happy motor. I had one set up like that briefly while working on a hybrid and it was a joy to ride. It wasn't fast and snappy, but it was predictable and solid.

To check ring gap, place the ring in the cylinder so that the gap is not lined up with any port. then push it up with the piston so that it stays perpendicular to the bore. Get it up into an area where it's past the ports and use feeler gauges to find the gap between the two ends. There's a spec that should be in your kit instructions. My KDX needed no adjustment, but the YZ needed filing just to get the ring in the bore as I recall. If you need to file, use a very fine one, or emery cloth backed with a hard surface. File inwards to prevent burrs on the mating surface.

Great Info! I'll plan on a piston as soon as I pick the bike up next weekend. I've had every Honda XR made (currently have street legal XR650R) I'm really looking forward to putting the KDX through the paces. The only other thing I feel is a must is the fork springs set up for my 190lb weight but I'll find another post for that info! Thanks All!


JT

I went from an XR400 to a KDX220 in 2003.

At first I thought I had made a BIG mistake. What a weenie bike.

On the XR I could just dump the clutch and go. It would sign off pretty quick, though.

On the KDX I had to learn to use the clutch a bit more and ride in the upper revs. Ahhh, the sweet smell of pre-mix....