Rebuilding The Rotax 399cc

[rushking19]

This is how it looks when life happens, i blew one of the pistons on the snowmobile engine so now it will be a while longer till I get it running again till I can buy new pistons, I kinda knew this would happen so I'm not too mad about it and it would be a good experience to rebuild a snowmobile motor

 

[n3480h]

Ow. Well, the good news is that you'll learn a new skill and the engine will be much better than it was. Hope you'll post updates on the rebuild.

 

[firemanjim]

it! That's sucks.... You might have messed it up running it with only one chamber firing.....

 

[KartFab]

Aw man that blows....

 

[rushking19]

it! That's sucks.... You might have messed it up running it with only one chamber firing.....

One thing I noticed way before it blew it didn't want to start on that cylinder

 

[firemanjim]

One thing I noticed way before it blew it didn't want to start on that cylinder

That would have been the sign to not start it any more, and tear it apart before this happened. You might have been able to prevent this and the ultimate set back in time and $$$ . But, live and learn. I bet you don't do that again.....

 

[rushking19]

That would have been the sign to not start it any more, and tear it apart before this happened. You might have been able to prevent this and the ultimate set back in time and $$$ . But, live and learn. I bet you don't do that again.....

I did Tear the head off when I first got it even before I tried starting it and it looked Ok

 

[OzFab]

Maybe it's the pic, maybe it's the computer I'm using (not mine) but, I can barely see the problem...

 

[rushking19]

Maybe it's the pic, maybe it's the computer I'm using (not mine) but, I can barely see the problem...

That was before here's a picture of now

 

[rushking19]

I was thinking of replacing the other piston to but is it needed

 

[rushking19]

I think I'll just new rings on the other piston and clean it up

 

[rushking19]

Today I cleaned the good piston up

 

[OzFab]

I was thinking of replacing the other piston to but is it needed

Would you replace just one shock absorber on a car or just one brake pad?

 

[rushking19]

Would you replace just one shock absorber on a car or just one brake pad?

No,but I want to replace the rings on it because it doesn't look too bad

 

[Poboy kartman]

Pistons and shock absorbers are two different things. .....

Basically. ....a piston is almost a non-moving part as far as wear in many respects. .....the rings take the brunt of the cylinder wear while the wrist pin takes the rod wear.......and the cylinders wear the most. ....so unless you are boring to another size.....the new and old pistons are going to have similar slop.......

Of course. ....if it doesn't cost much and you are paying for shipping anyway. .......

 

[rushking19]

Pistons and shock absorbers are two different things. .....

Basically. ....a piston is almost a non-moving part as far as wear in many respects. .....the rings take the brunt of the cylinder wear while the wrist pin takes the rod wear.......and the cylinders wear the most. ....so unless you are boring to another size.....the new and old pistons are going to have similar slop.......

Of course. ....if it doesn't cost much and you are paying for shipping anyway. .......

So it's OK to use the good old piston

 

[Axx3d]

If everything is within tolerance you can reuse the old piston with new rings.

 

[rushking19]

If everything is within tolerance you can reuse the old piston with new rings.

Ok,because the piston looks ok

 

[OzFab]

Look ok & is ok can be worlds apart... just saying...

 

[Axx3d]

Get a digital micrometer and make sure it is within spec. Id also verify both cylinders are within spec as well and not ovaled..

As said "looks ok" is not the same as within tolerance...