black piston
 

The top of my piton is black and so is the bottom of my plug. Motor might have 1 1/2 gallons threw it. What does this mean? Seems to be running fine but I'm worried about damaging the motor. Also is there a way of removing the build up?

that is normal, and actually a good sign your fuel has caster oil in it......

I'm now using werks 30% if that makes a difference. The same thing happened to a motor last year and it seemed like it lost compression rather quickly. Both motors were orion crf 21 wasps.

if it lost compression fast it is likely you ingested dirt.......carbon buildup on the piston has nothing at all to do with it, in fact because it has a carbon buildup it means you weren't running lean......so the only reason to lose compresion fast is you ingested dirt and wore the piston down

here is how to tell if you ingested dirt....take the crank out and inspect for these markings..

http://i107.photobucket.com/albums/m...h172006032.jpg

Was your plug dry? Seems like its running too lean. Post a pic of what you are talking about.

if you get the erge to clean it....dont! send it to Maximo or someone who knows what their doing. ive run nitro for a few years now and hate taking them apart. i would rather sent them in and pay a couple bucks to have them looked over, then take them apart and waste a 250+ engine.

Heavy black carbon buildup is usually a super rich bottom and super lean top... the fuel builds up in the engine during low RPMs and gets burnt at a very high rate when the lean condition begins at near or wide open throttle, before it can be exhausted from the engine, same thing when you come back to an idle... the fuel will burn at a high rate while cooling the piston. Hence the run-on associated with that tuneup.

A lean HSN will shorten the life of an engine almost as fast as ingesting dirt. The piston is sent through a series of expansions and cooling cycles it prematurely wears the seal portion of the piston away.

If your engine has a crank that looks anything like Maximo's pic... your rear bearing is toast and the crank to block seal is most likely damaged to some degree. Dont even check the bearing, just replace it and hope the block seal is good enough for a decent idle.

some of the best performing fuels I have used have always left a heavy black carbon buildup on the piston......I actually feel safe when I see that as i know the fuel has a good amount of caster oil...the fuels that leave no residue are the ones that scare me ! Now of course I am into screaming the jeebus out of my engines, so I tend to stay away from all synthetic mixtures.... to me black residue means caster oil...clean piston means synthetic oils....caster protects better at high RPM's so thats why I prefer it........... However seeing a black buildup with synthetic mixture means it needs some tuning LOL !

I'll post pic tomorrow but as far as dirt I'm anal about keeping a clean filter on. I even use horse wrap. I'm just getting mixed signals on this whole deal and I have a reedy in my buggy and the plugs and piston seem in tip top. Not sure if this (2nd) orion is giving me a hard time.

So true
 

I like the way you think buddy.

It gets old hearing guys talk about how clean their engines are after 4 gallons. So silly. Take it apart and gently clean the engine. No big deal, but I usually wait until 5 gallons or so to change the rod and pinch it, inspect the bearings and so on. I woul not take the engine apart just to get the carbon off...Especially from 1-4 gallons. Let er rip :lol:

Caster is a love hate for engines... it doesnt combust to its a hate, but it does offer uncomprimising protection so its a love....

Its all in the tuneup. The little amount of caster in fuel these days doesnt result in carbon buildup, it results in a "sticky" residue inside the engine, its the rich LSN and lean HSN that creats carbon. A "lean and clean" LSN and slightly rich HSN rarely has any carbon buildup after many gallons. Not to mention caster retains heat and will add a few degrees to your temp gun and reduces runtime.... those are not things that are all the rage these days.

These are all my opinions, not to be taken as the "bible" lol

Now as far as taking temps...... I maintain the spec temps during breakin and keep an eye during the next few weekends but as far as that I just go by if it's producing smoke or not. I know I still have alot to learn on this engine deal and don't get me started on the suspension.

I usually tune for performance and sound....smoke is something that can be inconsistent depending on weather conditions and ambient temperature....Some days you wont see much smoke at all, other you will see a thick trail of smoke.... As a rule the exhaust note doesn't lie, if the engine is out of tune it will sound out of tune, if a engine is tuned correctly it will sound like it is tuned correctly........A properly tuned engine has certain performance characteristics that Ialso look for. Same applies to an improperly tuned engine.........Now of course when your racing at a indoor event, and even outdoor for that matter it can be very difficult to to hear your own engine run...which can make it a little difficult to tune by sound.........This is why I feel it pays to take time with a new engine away from the track, so you can learn its tuning characteristics in a environment where you can hear it exclusively.....learning to tune a new engine at the track is definitely much more challenging then learning to tune it on its own away from the noise of other engines....