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Old 08-13-2009, 12:29 PM   #1
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Questions?? PISTON Question

So I successfully changed out my Rod last night. The top of my Piston was black. Go some of it off with a rag ... is this due to the motor being too Rich or too Lean? Low end or High end?

Motor has been running strong for the last and first gallon. Just switched up to Maxys 30%

Picco Red Dot Evo3 w/Picco 2651 pipe and header
Running PowerMaster 30% fuel



Thanks!
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Old 08-13-2009, 12:34 PM   #2
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Originally Posted by SERPENT7twenty View Post
So I successfully changed out my Rod last night. The top of my Piston was black. Go some of it off with a rag ... is this due to the motor being too Rich or too Lean? Low end or High end?

Motor has been running strong for the last and first gallon. Just switched up to Maxys 30%

Picco Red Dot Evo3 w/Picco 2651 pipe and header
Running PowerMaster 30% fuel



Thanks!
Leave it there J you want that on the piston
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Old 08-13-2009, 12:43 PM   #3
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Originally Posted by SERPENT7twenty View Post
So I successfully changed out my Rod last night. The top of my Piston was black. Go some of it off with a rag ... is this due to the motor being too Rich or too Lean? Low end or High end?

Motor has been running strong for the last and first gallon. Just switched up to Maxys 30%

Picco Red Dot Evo3 w/Picco 2651 pipe and header
Running PowerMaster 30% fuel



Thanks!
The black stuff is just carbon build up, it means the motor is running good. Dont remove it from O.D. of the piston, it actually helps compression. Im sure Sam told you already, but Ill tell you anyways, run one tank at idle with the new rod before you hammer it, and if I were you I would richen the needles when switching fuel, you WILL have to retune it.
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Old 08-13-2009, 12:51 PM   #4
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Leave it there J you want that on the piston
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Originally Posted by nitrodude View Post
The black stuff is just carbon build up, it means the motor is running good. Dont remove it from O.D. of the piston, it actually helps compression. Im sure Sam told you already, but Ill tell you anyways, run one tank at idle with the new rod before you hammer it, and if I were you I would richen the needles when switching fuel, you WILL have to retune it.


OOOOO ok .. I will leave it .. I only took off a small small amount since it was caked on there soo bad.

1 tank idle .. NOTED! Dooooon't really wanna mess with the tuning since its been runnung so good so I'll just go back to the PowerMaster LOL

Thanks fella's ..

Steve Jon .. any of you guys comin out?
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Old 08-13-2009, 12:52 PM   #5
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Carbon is your friend!!!
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Old 08-13-2009, 12:56 PM   #6
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I just changed a rod in the same motor at the GLC and after the rod change i could not control the temp started to get to hot which was worse than befor the change.
I think for the price of the motor and the rod i will just run it until it BLOWS!
I still have the motor it is a Murnan Modified Red Dot if any body is interested i will sell it for $100 with both rods it only been ran at 2-Big races.
The motor is very clean and has had after run oil in it after every day of running.
later
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Old 08-13-2009, 12:57 PM   #7
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Leave it there J you want that on the piston
???

I thought ( excessive ) carbon build up on top of piston head can cause early detonation problems ie. higher engine temp, and scracth the cylinder liner.
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Old 08-13-2009, 01:08 PM   #8
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Im no expert in anything but I notice the dark color build up in my engines and I dont think it can be wiped off with a rag. I also noticed the black gunky stuff in a engine that hasnt been run out of fuel and then oiled at the end of the day. Maybe its just fuel difference.

Last edited by sheeley; 08-13-2009 at 01:35 PM.
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Old 08-13-2009, 01:30 PM   #9
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Im no expert in anything but I notice the dark color build up in my engines and I dont think it can be wiped off with a rag. I also noticed the black gunky stuff in a engine that hasnt been run out of fuel and then oiled at the end of the day. Maybe its just fuel difference.
I googled carbon build up and I guess that black gunk is carbon. I saw some rc pictures that I cant believe such thick build up could be good.
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Old 08-13-2009, 01:33 PM   #10
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I googled carbon build up and I guess that black gunk is carbon. I saw some rc pictures that I cant believe such thick build up could be good.
I do know that I run the fuel out of my engines and run oil threw them while still warm and after 4 gallons the top of my piston is pretty black color with nothing to whipe off
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Old 08-13-2009, 01:54 PM   #11
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Ok so I ran the first tank idle...towards the end before it ran out of gas it did the normal rev up and die...I tried to re start the motor but its frozen up.

I grabbed the flywheel with some needle nose .. wont budge... tried other various things and the motor wont turn over to at all...

Did I break something?
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Old 08-13-2009, 01:55 PM   #12
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Default carbon build up

While carbon buildup is not a desirable look it actually helps the compression of your engine. I am not an "Expert", However from experience too lack can also mean that your running too lean. Occassionally I would clean the top of the piston only this IMO keeps the engine running efficiently.

my 2 cents
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Old 08-13-2009, 02:09 PM   #13
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A recent topic:
http://www.rctech.net/forum/nitro-ro...une-color.html
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Old 08-13-2009, 07:10 PM   #14
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I've never seen my piston black but they are all a nice brown tan color. I run Byrons pro-driver 16%, The only time I've seen sludge (Unburnt castor) is when I ran Odonnels
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Old 08-13-2009, 07:26 PM   #15
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Originally Posted by SERPENT7twenty View Post
Ok so I ran the first tank idle...towards the end before it ran out of gas it did the normal rev up and die...I tried to re start the motor but its frozen up.

I grabbed the flywheel with some needle nose .. wont budge... tried other various things and the motor wont turn over to at all...

Did I break something?
stuck at TDC? better remove engine and check again...
at least openup the backplate and have a look.
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