Nova let go today :(

[Blaise Recca]

Home blend, that dark color is a ultra thin coating that's just dark in color, bearing's were fine, I don't give out my oil % but 3 years of running this mix, this has been the only failure in a novarossi I own.
The crank was static balanced, I don't have a vibration problem with this engine, the piston was not modified, nor was the sleeve in any way.

Why the secret about the % of oil in the fuel? Do you know something that everyone else might find out about? Is this a special black magic fuel you are running?

 

[Andy Greene]

Something none of you mentioned was how discolored the P&S are. I think you are running way too lean. That baked on brown gunk is even in the sleeve ports. If that is not caused by heat then I would use a different fuel or oil.

I was wondering the same thing. One thing I learned a while ago (thanks to KP) was that all too often people run more oil in the small motors than needed. Also most tend to run far more water cooling than needed so the problem becomes two fold, the motor is colder than it should be and slogging through a "thick" fuel mix. That tends to get people to start really pinching down on the needle to "get it to go" and "clear out" and you wind up with a low oil situation from being too lean and the top of the liner being tight from being too cold that can lead to results alot like that pic. Now I'm not saying this is the case here but something to keep in mind. I do agree with the idea of taking a good hard look at the ramp "filler" causing a piston to stick & ripping out the wrist pin but too lean & too cold can and will do the exact same thing. I will say that once I started running 70% with 12% oil and really watching the head temps I found my 21 motors running faster, clearing out and really singing with longer bearing life and no failures, all the while running a richer mixture. Fuel makes power, the more fuel you burn the more power you make.

Not to get of track, but Don what kind of head temps where you looking for with those %'s (70/12) ??

Andy

 

[BB Mods's]

Home blend, that dark color is a ultra thin coating that's just dark in color, bearing's were fine, I don't give out my oil % but 3 years of running this mix, this has been the only failure in a novarossi I own.
The crank was static balanced, I don't have a vibration problem with this engine, the piston was not modified, nor was the sleeve in any way.

Why the secret about the % of oil in the fuel? Do you know something that everyone else might find out about? Is this a special black magic fuel you are running?

my oil is Motul 800 race + 2oz castor. nitro is 50% with 99.8%pure methanol. the total % of oil is my secret. No blackmagic, just prefer it stays that way.

 

[shoboat]

Tommy,

That H-4 must have been running good with that new pipe if it did that

kind of damage. Oh well that is testing. I'm with Tom on this one, Nova's

materials are not always the best recently(still very good though). I may

have some N/R 21 parts if you need them.

Thanks,

Mark Sholund

 

[BB Mods's]

got a 7 port or 8 port Long stroke sleeve and piston?

 

[ALLAN YUEN]

Home blend, that dark color is a ultra thin coating that's just dark in color, bearing's were fine, I don't give out my oil % but 3 years of running this mix, this has been the only failure in a novarossi I own.
The crank was static balanced, I don't have a vibration problem with this engine, the piston was not modified, nor was the sleeve in any way.

Why the secret about the % of oil in the fuel? Do you know something that everyone else might find out about? Is this a special black magic fuel you are running?

my oil is Motul 800 race + 2oz castor. nitro is 50% with 99.8%pure methanol. the total % of oil is my secret. No blackmagic, just prefer it stays that way.

That s why did you not use synthetic lubricants 100% then become high friction too hot and liner's cramp and piston ripped out down ( Bang)

 

[BB Mods's]

If that was the case, id have a graveyard of dead mac's and valvola's right now. I use the castor to help with top end sealing, lots of guys running there mix with castor, lots of guys going really fast for that matter. This cant be fuel or oil related, the skirt turned to dust. not just broke.

 

[Joe Warren]

Something none of you mentioned was how discolored the P&S are. I think you are running way too lean. That baked on brown gunk is even in the sleeve ports. If that is not caused by heat then I would use a different fuel or oil.

I was wondering the same thing. One thing I learned a while ago (thanks to KP) was that all too often people run more oil in the small motors than needed. Also most tend to run far more water cooling than needed so the problem becomes two fold, the motor is colder than it should be and slogging through a "thick" fuel mix. That tends to get people to start really pinching down on the needle to "get it to go" and "clear out" and you wind up with a low oil situation from being too lean and the top of the liner being tight from being too cold that can lead to results alot like that pic. Now I'm not saying this is the case here but something to keep in mind. I do agree with the idea of taking a good hard look at the ramp "filler" causing a piston to stick & ripping out the wrist pin but too lean & too cold can and will do the exact same thing. I will say that once I started running 70% with 12% oil and really watching the head temps I found my 21 motors running faster, clearing out and really singing with longer bearing life and no failures, all the while running a richer mixture. Fuel makes power, the more fuel you burn the more power you make.

I agree with Don & this is also a problem with 45 - 67 - 80 engines when the water is cold & the air is Good. Running cars taught me how important the head temps are. One of the Hot Orlic tricks on the N/R was to build a cooling head that eliminated about 60 percent of the cooling ring inside of the cooling head. Running a boat with a manual needle will also teach you that a Cold lake can Grab an engine after about 1 lap. It will sound good on the bank & @ launch But it will go COLD & RICH the 1st time down the front stretch, This is the water overcooling the engine & Changing the needle for you. Normally this is not a problem with the water is above 75. I Have a new 35 plus For sale $340

 

[Terry Keeley]

Any chance the rod got sloppy and the skirt hit the counterbalance ABDC?

I'd look for marks on the counterbalance...

ps: I've heard Motul is a good oil, but I'd ditch the castor!

 

[ALLAN YUEN]

where did you get Motul 800 race ? tell me website? thanks, Allan

 

[BB Mods's]

I buy motul locally.

Engine, head, crank case temps are my biggest concern. I have systems in place that prevent sudden cold or hot spikes.

 

[Terry Keeley]

Are you sure that Motul 800 is compatible with nitro? I got some Motul Kart Grand Prix a few years back and it wouldn't stay in suspension...

 

[BB Mods's]

Yes, the motul mixes up fine. I add nitro to my fuel at the last step, alky and oils get mixed first, then nitro last.

 

[BB Mods's]

Any chance the rod got sloppy and the skirt hit the counterbalance ABDC?
I'd look for marks on the counterbalance...

ps: I've heard Motul is a good oil, but I'd ditch the castor!

Don't think so bud, the rod was fine, bearing's are fine (novarossi ceramic's) and no marks on the cranks counterbalance. if a rod got lose enough to hit the crank or the back plate, The plug would have been punched, and this plug survived to run again.

I don't think Ill ever know what really went down, but I can say this, for all the damage that was done, I never hurt any part other then the p/s when it let go, wrist pin's got to be trashed just because.

 

[Marty Davis]

I had the exact thing happen to me last weekend. The piston in my MAC .21 broke in 3 pieces.

One thing that I think might have happened to me is that I set up the engine very tight initially. The piston and liner were exceptionally tight. I broke in the engine my usual way, heat cycling it. Once I got it broken in, I was ready for the Charleston Race. Ran it there without problem. When I got back, I spent a Saturday testing props and pipes with no problem.

Last weekend I raced at the Tampa 2 day race and the piston broke on the stand.

Not sure if I might have hydrauliced the engine on the stand or it just broke. This is the first time this has happened to me EVER on a .21 so I am kind of stumped.

I think that I will set up the fit a little bit looser this time.

Marty Davis

 

[jetpack]

My opinion the piston should not have black ash under the crown. If your piston is dry there, then for sure you are starving the wrist pin. All that black is carbon. Carbon should only be present at the exhaust outlet, if any. Looks like a lack of oil, and maybe even the wrong kind. Carbon black shouldn't be under a piston unless things stayed very hot.

The motor took more than one rev before it started to let go by evidence of fleck marks in the ash.

Motul 800 is for gasoline. Even if it mixes with alcohol theres a chance that it seperates in the intake fog drying the mix.

Not sure if anyone agrees, but these are just some of my thoughts.

 

[misshydro]

My opinion the piston should not have black ash under the crown. If your piston is dry there, then for sure you are starving the wrist pin. All that black is carbon. Carbon should only be present at the exhaust outlet, if any. Looks like a lack of oil, and maybe even the wrong kind. Carbon black shouldn't be under a piston unless things stayed very hot.
The motor took more than one rev before it started to let go by evidence of fleck marks in the ash.

Motul 800 is for gasoline. Even if it mixes with alcohol theres a chance that it seperates in the intake fog drying the mix.

Not sure if anyone agrees, but these are just some of my thoughts.

Has anyone tried SIG castor oil in there fuel???? Thats what I'm using with no proublems..

 

[SayMikey]

My opinion the piston should not have black ash under the crown. If your piston is dry there, then for sure you are starving the wrist pin. All that black is carbon. Carbon should only be present at the exhaust outlet, if any. Looks like a lack of oil, and maybe even the wrong kind. Carbon black shouldn't be under a piston unless things stayed very hot.
The motor took more than one rev before it started to let go by evidence of fleck marks in the ash.

Motul 800 is for gasoline. Even if it mixes with alcohol theres a chance that it seperates in the intake fog drying the mix.

Not sure if anyone agrees, but these are just some of my thoughts.

Has anyone tried SIG castor oil in there fuel???? Thats what I'm using with no proublems..

While the carmel color does cause concern the gouge in the piston seems to be the start of the failure.Lock the piston pull the pin

 

[BB Mods's]

Here is a re-cap

The scoring was caused by a retainer that let go AFTER the piston broke, this is a known.

The oil is not the problem, Every one of my engines gets a light coating of oil dye over them while im breaking a engine in, the color fades as i start to lean the motor down, after breakin.

iv ran this exact mix of fuel for 3 years, the is the only failure iv had, in 3 years.

top of the piston is clean and has no burn marks or detonation.

Ron had a idea Ill be testing in the morning, the sleeve is out of round is the idea, and the odd pattern of breakage leads me to believe this might be correct.

specs of white looking material under the piston is that powdered piston material I was speaking of.

 

[Anders_Martinelle]

Put the rest of the piston next to it in a pic........

Andes