blew the R up dont understand why

[woodsracer144]

ok so i dont understand how i blew my R and i dont know why.

i was running my stock Ignition and i was running ice last weekend and I was 4 laps down on my practice and it bogged and i let off and coasted for a bit and down shifted hit the gas and she came back so i up shifted and pinned it down the back straight. to 3 and 4 a pulled out of 4th and bog again and this time i knew she was gone... coasted to gates and that was that.

i pulled it apart i thought it was running lean but i melted the piston up and put a hole right by the exhaust port.

plug is brown, black. new plug before the race and i dont understand why it went...

[Ruf Racing]

Any idea, what kind of compression you were running?

[trx293pv]

you weren't running with a removed exhaut bridge were you?

[jcs003]

how was your coolant level?

[2-330s]

you could be lean on the needle or pilot jet

[fearlessfred]

i would say lean on the main jet. if it went with throttle wide open, then that would be the main jet and overall plug color is not a good indicater of whats going on with the main.cold temps require richer jetting.you can be overly rich on jetting on the needle ,pilot and slide cutaway and still burn it up on the main jet. once the motor has cleaned itself up from overly rich condition in the lower circuts all else goes out the window,and all that matters is the main jet.i am not saying that it saying that the lean condition isnt being caused by something else (air leak of some kind.)to do a plug check for the main jet you would have to run thru a few gears wide open and pull in the clutch and shutting down the ignition at the same time and then check plug,but you do this starting off way fat on the main and then leaning it out intill you have good plug. any other way could cause a repeat of what just happen. from all of what i know a burned hole close to the exhaust is a lean condition and when i have done this to a motor a death rattle came at the same time as the hole was being burned

[born2ride14]

Most of the gas isnt used to be burned. It helps keep it cool. So if you didnt have enough, then you would create heat, therefore melting the piston

[2-330s]

fred i would agree with you but i've melted a few motors down in the winter on the ice. with woods description of good color on the plug and the weather here this weekend -20* - 0* i have changed the main and burnt them down on the needle before,it starts melting before you are on the main. i didn't race this weekend because the needle i'm running didn't allow me enough main jet to run this cold. i will be going to the dyno to find a richer needle soon.

some pics would help.

[fearlessfred]

no argument.u can lean one out anywere,but if the throttle is pinned.i would have to say main jet unless the tapper on the needle is so far off that it is still in play at wide open throttle.at wide open throttle the main jet should be the limiting facter in how much fuel is delivered and not the needle. i do not ride ice and dont know what u guys do for jetting so im no expert

[woodsracer144]

I'll post pics tomorrow. coolant was good, I just filled it the night be for cause i was having kicker problems and then drained the coolant and then refilled it and checked it before i hit the ice.

I thought i was on the rich side cause it was loading up a little bit for me when i would hit the gas. it took a few seconds for it to rev when you would pin it.

was running 180ish... or under 180 it was 178? some where in there when i built the motor and there wasnt much time on it.

I also was running belray MC2 i think... It was some Belray oil if the oil makes a difference with weather.

2-330s if you dont mind telling me what do you run for jetting in your carbs on ice?

[86 Quad R]

which carb and throttle blocki are you using?

[C-LEIGH RACING]

:( Pump gas, ??.
Neil

[2-330s]

55-58 pilot deg needle clip 2nd rich 225 main
mine loads up and sounds very rich after idling,blurp the throttle a few times and it clears out. you have to let them warm up for a long time.

my buddy's 86 atc 250r 40.5 kehin,no air box, fmf ram valve and fmf pipe. the rest of his motor is stock

52 pilot 185 main deg needle center clip.

what is your motor setup?

[woodsracer144]

I had a 35 PWK ( i know small) i dont remember jettin right off hand. I've had alot going on... yeah it was on pump gas.

[machwon]

Not enough octane.

[fearlessfred]

Originally posted by machwon
Not enough octane. have i been wrong in my thinking all these years (a real question) but lean detonation occurs from the piston glowing ,fromfrom being burned like a cutting torch was put to it. in other words the detonation is the result of being lean and not a octane issue? i have always been lead to beleive that a hole burned on the exhaust side was lean condition and a hole in the center or other, along with broken rings and ring lands was the result of detonation ( the damage would appear to be broken and not burned) . i have only seen detonation damage on other peoples motors and not my own. i have burned at least 2 pistons from leaning out and correcting the lean condition fixed the problem. one of the 2 times was caused by the carb being starved for fuel because the tank was low and i was on a hill climb at dumont(pretty stupid on my part) 2 330 your main jet size seems rather large are you running ethenol and what carb. neil what was your thinking, when asking {pump gas} all this is only what i have known to be true and would like to be corrected if i am wrong

[2-330s]

fred

i'm only running a 40.5 but with alot of timing and a good amount of compression.

thing is in this cold a little miss on jetting is big! in the summer a small miss on the jetting is just that. when it is as cold as it was last weekend it's alot of dense air and not enough fuel.

[fearlessfred]

Originally posted by 2-330s
fred

i'm only running a 40.5 but with alot of timing and a good amount of compression.

thing is in this cold a little miss on jetting is big! in the summer a small miss on the jetting is just that. when it is as cold as it was last weekend it's alot of dense air and not enough fuel. that is the part that i really dont know about. the coldest i have ever ran in would be about freezing. so as jet sizes go i never recommend a size because there are to many varibles. the largest jet i have ever run was a 185 on 39 pwk at dumont (sea level) and above freezing. how do you guys stand that cold.i like it around 100 degrees . in the suumer time when the sun goes down and were driving we will turn off the air conditioner and roll down the windows when it gets down to 100. i hate the cold

[2-330s]

lol i lived in florida for two years. loved the fishing!! salt,fresh or brackish within thirty minutes of my house.

the heat and humidity of that place not so much

[profab250R]

even if you put too much oil in your fuel. say you put 20 oz instead of 16 oz of oil in your 5 gal fuel jug then you efectively lean the engine out because your engine is getting less volitile oil and in turn more oxygen= hotter combustion temps, in the extreme cold this is REALLY easy to burn up a 2 stroke.

[C-LEIGH RACING]

Originally posted by fearlessfred
have i been wrong in my thinking all these years (a real question) but lean detonation occurs from the piston glowing ,fromfrom being burned like a cutting torch was put to it. in other words the detonation is the result of being lean and not a octane issue? i have always been lead to beleive that a hole burned on the exhaust side was lean condition and a hole in the center or other, along with broken rings and ring lands was the result of detonation ( the damage would appear to be broken and not burned) . i have only seen detonation damage on other peoples motors and not my own. i have burned at least 2 pistons from leaning out and correcting the lean condition fixed the problem. one of the 2 times was caused by the carb being starved for fuel because the tank was low and i was on a hill climb at dumont(pretty stupid on my part) 2 330 your main jet size seems rather large are you running ethenol and what carb. neil what was your thinking, when asking {pump gas} all this is only what i have known to be true and would like to be corrected if i am wrong


Please excuse my dumbness, I clicked the wrong quote button, was suppose to be machwons post.


What I've found, this pump gas today is junk.
That ethanol mix is death to a two stroke, UNLESS, you set the engine up for it to burn that mess.
E10 pump gas, your looking at 10% ethanol mixed with 90% gas & by using that mix your running the engine pretty close to 10% leaner than on straight gas.

If the engine has close to 190lbs compression, it wouldnt be safe using less than 100 octane & if you choose to use pump, better have those jets rich enough to keep the engine from revving out.

In some testing, I've found that to low of an octane, the extreme heat will eat away at the top of the piston on the exhaust side.
Seen it eat the piston away enough down & behind the rings to burn a hole completely through.
Every one that did it, the damage was on the left front top edge of the piston, every one of them.
Only thing I can figure, the angle of the carb on most every engine, must be projecting the greatest amount of fuel mix to the right side of the engine, so left side is a bit leaner than the right.

The right octane for the compression the engine has, only resulted in seizure on the sides when trying to run to lean.

Cold weather running with a 2 stroke, will either make you broke for rebuilding the top end or either learn you how to jet a carb REAL good.

I've said this before, it makes no difference who built the engine, be it machwon, Curtis Sparks, Allen Knowels or the best 2 stroke builder ever known, that engine will run no better or last no longer than, how much the person knows thats doing the jetting on that carb.
Neil

[fearlessfred]

Originally posted by profab250R
even if you put too much oil in your fuel. say you put 20 oz instead of 16 oz of oil in your 5 gal fuel jug then you efectively lean the engine out because your engine is getting less volitile oil and in turn more oxygen= hotter combustion temps, in the extreme cold this is REALLY easy to burn up a 2 stroke. x2

[woodsracer144]

sounds like im runnin it totally fat this weekend... shes gonna be cold/.... i dont know how you stand the 100*weather i'd kill my self in that ****.