piston movement/noise

[karlosthejackel]

I removed the stator cover to check timing and while I was there I just rocked the flywheel lightly backwards and forwards. There is a "light clonking" noise coming from engine. I took the spannie off and there is quite a bit of movement in the piston I can even rotate it left and right very slightly. Being such a big piston im guessing there should be a bit of movement. is it normal? please say yes

[sandblaster]

Sorry buddy.... No bueno....
Time to take her down before you blow her up 

[karlosthejackel]

Well what can I say. Considering this engine has only just been split and rebuilt I think ive found some issues....




The pin is worn out as you can see. The piston is cracked but I think the liner is ok, It looks like a crack in the transfer port but on close inspection it just looks like casting to me close up. The piston is a standard size wiseco but seemed a bit slack in the cylinder but then ive never had a 500 apart before

[Foxx4Beaver]

yeah, you've definitely got some issues there....I wouldn't assume the cylinder plating is ok until you measure it, you may find it's beyond it's wear limit.
the factory castings suck around all the bridges, period.
depending how much you're willing to spend, I'd just have it stripped, all the bridges re-welded, and re-plated to the closest size to what it is now....you need a new piston/rings/pin/bearing/circlips anyways, maybe even have the head reshaped?...might as well just do it all now and be done with it.

[karlosthejackel]

The cylinder has a steel liner is that normal?

[Foxx4Beaver]

ahh...I didn't catch that...no it would've been installed by a previous owner.
it's not necessarily a bad thing, providing it was installed right...ports matched/cleaned-up..etc...sleeve isn't sticking up above the cylinder, you'd know if that was an issue as it would overheat and use coolant.

[karlosthejackel]

looks ok to me. As its a liner is it plated?

[Foxx4Beaver]

more than likely, no, at least from what I can tell in the pic...but I have heard of guys plating sleeves.
I'd still have that bore measured either way before you buy a new piston and such....one of the #1 reasons a piston cracks is due to excessive piston to cylinder wall clearance.

[karlosthejackel]

Ive tried to measure with electronic caliper im getting 85.95 at the skirt end and 85.5 at the top

[sandblaster]

What kind of caliper did you use?
Was it a Digital Vernier Caliper like this?



If so, did you use a Telescoping Gage along with your caliper?

[karlosthejackel]

electronic caliper yes.

other thingy no!

[sandblaster]

Ok, it can be difficult to use the back side of the calipers to measure the bore.
Although it's not unusual for the top of the bore to be tighter then the bottom as there is virtually no wear at the top.
If you were to measure the bore about a 1/2" from the top you would likely get a larger reading.

[karlosthejackel]

Im off to a meeting on the KTM tomorrow ill try see if someone has a tele gauge. Im guessing if the readings are all over the place it will need another liner?

[sandblaster]

Worst case scenario you can have the liner bored to the next size up that gives full clean up.

[Foxx4Beaver]

Worst case scenario you can have the liner bored to the next size up that gives full clean up.

that's the route I'd go regardless, since a new piston is needed anyhow, might as well keep everything uniformly new.