I have a question for all you engine jocks, Today I was flying my sig 4 star with the saito 70 when all the sudden it made a grinding noise like it was dry inside..i quickly landed and listened to the sound, it was definatly a grinding sound every time the prop turned..and didnt have much back compression at all...help!!! does this sound like i need new ball bearings? I know nothing of 4 strokes except how to maintain ( fuel& trim) them. This engine is less than 3 years old and hasnt been used too much

answers?

HI.</p>

Sorry for the delay, I just got home from dinner out.</p>

I would not try to start the engine and would try to get in touch with their product support people and explain what's going on there. Were running it lean? What fuel are you using (oil content)?</p>

You probably already know this, but four strokes need lots of lubrication because they have more moving parts. High oil content fuel is mandatory as well as a good rich mixture (not to rich, but a bit more rich than you would have for a two stroke).</p>

I know this didn't help you much, but hopefully it will give you some ideas of what to do next.. ie.. call for support. Or maybe someone here that has used that engine has more information for you. Hang in there.</p>

CGr.</p>

You have most likely lost the main bearings in the engine

i have had several saitos break the cam gears and they make a grinding sound if it is under warranty take CGRetired  advice  let the dealer fix it for you. if it was run lean they wont honor the warranty.

Yup, sounds like bearings to me too

Sounds just like the noise my OS .91 is making!!Iknow, take the plane out of the van and quit flying it until Igive the poor engine a rebuild!!
OP, send it in and have it gone through, when you get it back it will be good as new.

ok this is making more sense now, and i feel it is the  main bearings could someone give me a link to the main beaings parts? or what to buy?

http://www.rc-bearings.com/catalog/p...a8d8a9dea9174e