Since the stock cylinder is Nikisiled, so if your were going to put a new Piston in you still need to fit it to teh Cylinder, meaning check clearance, if too tight honed larger too fit, if too loose re nikisiled to fit, I am asking because it seems allot of the DS guys are just bumping up there compression in a stock bore are you all checking your clearences??

 

I've always thought that due to the hardness of the coating the cylinder will not get "out of round" or otherwise enlarge so...... If your piston is manufactured correctly and within the tolerances defined by manufacturer - you should only have to check the ring gap. Would I still check/measure the diameter of the replacement piston? Absolutely.

Just my opinion of course. ERBS

Dave

 

Be sure and always check clearances.

 

I dont know alot about the rotax engine, but in race engines (cars) , piston to wall clearances are a very important part of the package. Along with boring the cylinder with a torque plate. It simulates the distortion effect when you torque a head down on the deck. It distorts the cylinder so much that if you were to try to hone it without a deck plate it would chatter REALLY bad in the bore and possibly damage the hone, or cylinder. I have always wondered if any of this was important on a small engine.

 

What is the piston wall clearance to be on the DS? but think its determend by each piston MFG is that also determined by the compression to?

 

In all of my reading on this forum, BigChief650 your the first to mention torque plates. I know of no machine shop that can bore these small jugs that uses torque plates. They may be out there, but I know of none.
IMHO this is a mistake. One should do all they can to get the bore as round as possable. That goes for anything that has a bore and piston in it.