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Post by userix on Nov 20, 2016 20:42:54 GMT -5
I have a 180CC big bore GY6 engine and after putting on a new piston, piston rings, and cylinder, I have heavy carbon build up on the piston head only after riding ~1200mi. I go for long cruises, not short city rides in stop and go traffic conditions. The scooter runs fine, pull hard and fast with no noticeable power loss. I have ensured the needle, needle seat, and float level are all adjusted properly. I have attached a picture of my spark plug, which shows a nice brown, tan color on the ground and center electrodes. If the jetting was slightly rich (even though the scooter is running great perfomance-wise), would this cause this much build up in such a short time. Or would this be caused by the vacuum pump overfueling the carb and causing excess fuel to go into combustion chamber. I run a mikuni vacuum pump with an inline fuel regulator to reduce the pressure of the pump in efforts to prevent overfueling. The carb float drain is not blocked and allows excess fuel to drain out back into the gas tank when the carb gets overfilled. So I find the overfueling situation unlikely.   |
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Post by cyborg55 on Nov 20, 2016 21:29:29 GMT -5
What fuel are you running?,,, burn rate on the plug looks dam near perfect,,,could be oil burn off from the build,,, just a thought
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Freshman Rider
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Post by userix on Nov 21, 2016 0:45:17 GMT -5
I only use Chevron 91 octane fuel. That's what I thought about the spark plug color too. Is it normal to have that much carbon on the piston?
Oil from the build? The top end was the only new parts put in. The rest of the engine is old and has been through 14k miles so far and running good.
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Post by hillbillybob on Nov 21, 2016 8:18:18 GMT -5
This is exactly why I add Marvel Mystery Oil, at the rate of 4/10 of an ounce per gallon, every time I fuel up, and not just occasionally. My bikes, the scooter, lawnmower, ATV.......all get treated every fill up.
In 2015, my scoot covered 3,159 miles, was fueled 32 times, burned 35.4 gallons of gas, to which I added 15 ounces of MMO. Total cost of MMO for the 2015 season..... $1.98......pretty darn cheap.
Do a search on the stuff, you may just want to try it.
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Post by pistonguy on Nov 27, 2016 13:01:39 GMT -5
Would like to see some more pictures of the Piston and cylinder head.
From what I see after 1,200 miles is not excessive,
The plug looks like your running rich to me, the Fire Ring is Black.
And why do you have the Head off at this time anyhow?
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Freshman Rider
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Joined: Apr 30, 2014 2:44:28 GMT -5
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Post by userix on Nov 28, 2016 2:10:32 GMT -5
Would like to see some more pictures of the Piston and cylinder head. From what I see after 1,200 miles is not excessive, The plug looks like your running rich to me, the Fire Ring is Black. And why do you have the Head off at this time anyhow? I don't have the head off. I used a borescope to go through the spark plug hole to capture that image. So this is normal level of carbon build up for the piston? I can't get a shot of the cylinder head without taking it apart. My borescope doesn't have mirrors for me to angle the lens. |
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Post by pistonguy on Nov 28, 2016 21:03:34 GMT -5
Would like to see some more pictures of the Piston and cylinder head. From what I see after 1,200 miles is not excessive, The plug looks like your running rich to me, the Fire Ring is Black. And why do you have the Head off at this time anyhow? I don't have the head off. I used a borescope to go through the spark plug hole to capture that image. So this is normal level of carbon build up for the piston? I can't get a shot of the cylinder head without taking it apart. My borescope doesn't have mirrors for me to angle the lens. ahh ok I get it At that milage an having annualized several thousand piston failures I don't see what you have going as a issue. its not broke so don't fix it. From the Fire ring on the Plug looks like you maybe a little fat on the jetting , but that may also be the fuel and Oil you are using. I run Non Ethanol  octane and Royal Purple Synthetic an she runs extremely clean. |
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octane and Royal Purple Synthetic an she runs extremely clean.