Lesson learned....lean detonation!

[martrix]

Seems I made my SH .28 scream a little too much. Was tuning the HSN and then screaming around for a bit and blew 2 MC59 plugs. Replaced plug, richened hsn and never thought much of it.

Then the other day running it, I was chasing a tune for ages and could not get the thing to idle with out the wheels turning at a good pace. Couldnt get it to idle low enough and it would constantly flame out. No problem if you kept the revs and would still fly along at WOT. Sometimes the idle would just rev up like you pinched fuel line. When cool, the flywheel had become quite easy to turn over, so I thought it was time to open her up and confirm my worst suspicions. This engine only had about 2 liters through it (1/2 a gallon).

The piston can be pushed up the sleeve to flush and almost a little bit out. I believe they should stop about 3mm - 4.5mm from the top of the sleeve (1/8" - 3/16"?

 

[joneser4u]

yep it was definitly run lean.With no more fuel through the mill than that I would replace the piston/sleeve and check all your fuel lines for any small holes or maybe a clog in a filter,redo breakin and hope for the best.

 

[martrix]

I think also let the air filter get too dirty. I had an oiled inner foam and an un-oiled outer foam but the inside of the inner foam was quite dirty and there was a decent amount of abrasive oil mix in the intake tube.

From now on I will be religious about keeping the entire intake system squeaky clean and always check temps.

I am going to go with an upgrade motor and will decide later on if I am to rebuild it. I probably will seeing as though a new piston and sleeve for the SH .28P3 is only US$33 but I also have to add shipping to Australia.

That scoring on the skirt is on the intake side, so yeah it probably also ate some dirt.

 

[Bryson]

This may be a stupid question, but did you even break in the engine. At a half gallon I'm still in the female pee pee foot stage of driving a new motor, and it looks like you just pined it to win it the whole time lol. Oh well, used rc piston's make cool key chains.

Bryson

 

[martrix]

This may be a stupid question, but did you even break in the engine. At a half gallon I'm still in the female pee pee foot stage of driving a new motor, and it looks like you just pined it to win it the whole time lol. Oh well, used rc piston's make cool key chains.

Bryson

Yeah I did break it in for about 8-9 tanks taking it easy. I was probably a little impatient though. I think I did the damage when I was first tuning it for performance and ran it too lean for too long. Its "was" basically my first ever nitro . Next breakin I will be very careful and conservative.

 

[Cupooterluvr]

Oh well, used rc piston's make cool key chains.

Haha. I'm gonna have to make me one out of my brother's engine when I buy him a new one (I promised I would since that POS engine lasted less than a gallon...)