Just do rings??

[95jersey]

I rebuilt my 2014 ec300 last fall (Wossner Piston Kit), and are approaching 100 hours, so getting ready to do a freshen up this fall.

Since I bought the expensive forged piston kit last year, could I get away with just new rings? The piston looks fine to me, don't want to spend the money if I don't have to, BUT on the other hand don't want to make an expensive mistake by being cheap either.

 

[memphis2857]

I have never done just rings but, thats just my preference. I suggest getting out your calipers and taking some measurements. Also may want to check the wrist pin for wear while you have it apart. Then you can make a decision based on condition of the parts in question.

 

[hadfield4wd]

Pistons are relatively cheap. I wouldn't and never have done just rings

 

[motopsycho87]

Measure the piston to bore tolerance at the widest part of the skirt, that'll tell you. Look for signs of stress and heat underneath the piston too. Cracks etc...

 

[motopsycho87]

That and, I tend to do piston and rings one year, rings the next. Repeat.

 

[95jersey]

That and, I tend to do piston and rings one year, rings the next. Repeat.

This is what I am thinking. I bought an expensive Wossner forged piston last year and it is in perfect shape. A new Wossner kit is upwards of $280, where as the rings are like $30.

 

[motopsycho87]

This is what I am thinking. I bought an expensive Wossner forged piston last year and it is in perfect shape. A new Wossner kit is upwards of $280, where as the rings are like $30.

I measured mine after 2 years of abuse, 0.1mm down on the skirt, still ran fine but it's end of season now so finally getting it replated. Certain it could have ran a while longer

 

[dANbOT]

I have done "just rings" rebuilds @ low hours, but normally don't.
I would check for loss of diameter in the skirt zone, and any gap developing in the ring lands if your determined to do so. Piston fatigue is rarely visible by eye until it lets go lol

 

[barossi73]

...At which point it becomes visible by ear!

 

[Dirtrider]

What are the measurements and tolerances supposed to be for piston and bore? I have a 2013, assuming they are the same as the 2014? Thanks.

 

[motopsycho87]

There is no tolerance given for the piston. Normally measured at the widest point of the skirt, to just under the exhaust port, clearance new is 0.06mm, mine was still running absolutely fine at 0.16mm.

General concensus (and information from wiseco) gives standard clearance of 0.001" per inch. For performance applications up to 0.003" per inch. Using that

Minimum = 0.0028" rounded to 0.003" or 0.072mm
Max = 0.0085" rounded down to 0.008" or 0.20mm

I wouldn't exceed either of these limitations, and my bike running perfectly well at 0.016mm.

It is important to remember that the rings are what stop the piston from breaking in most instances, a new piston with way out rings will break in very short time.

Wiseco, Wossner and ktm all have the same ring end gap specs. The gasgas manual recommends 0.5 to 0.8, the rest of the world doesn't...

Minimum = 0.004xbore" so 0.0113" round up to 0.012 or 0.3mm

Maximum, ktm recommend 0.5mm (0.020") GasGas recommends 0.8mm (0.031"). I would stick to the ktm spec, as per my prior statement, rings cause broken pistons as they contribute greatly to piston slap.

Just got mine back from replacing, 0.06mm piston clearance, 0.3mm ring gap.