Definition - "Burn Down"

[canadian madman]

Ok, feel a little silly asking this ...i mean i know a bit about all things mechanical, but not an expert by any means...and just starting to tinker and learn about 2 strokes...ordered a stage 2 kit for my M8 from SLP and they say you do not need a fuel controller for it - some people have debated that (and not trying to get opinions on that here) i'm just trying to learn the warning signs of a danger situation and judge for myself

I keep hearing everyone throwing around the term "Burn Down"...what I would like to know is if anyone has a decent explanation of exactly what happens when you lean out the fuel too much (assuming the engine just not getting enough fuel/oil mixture to lubricate causing overheating and alot of other nasty things - but not sure)....and what the warning signs are (if any) and what to do if you do notice any warning signs while out riding (maybe as simple as keep the rev's down?)

i've heard people say to watch the spark plugs and cylinder wash...ok sure...but ummmmm....what is it that i'm looking for exactly? Does anyone have pictures they could post of spark plugs at various stages to help me out (and prob a bunch of others out there who "think" they know what they're talking about)

thanks everyone...

 

[pipes]

Ok, feel a little silly asking this ...i mean i know a bit about all things mechanical, but not an expert by any means...and just starting to tinker and learn about 2 strokes...ordered a stage 2 kit for my M8 from SLP and they say you do not need a fuel controller for it - some people have debated that (and not trying to get opinions on that here) i'm just trying to learn the warning signs of a danger situation and judge for myself

I keep hearing everyone throwing around the term "Burn Down"...what I would like to know is if anyone has a decent explanation of exactly what happens when you lean out the fuel too much (assuming the engine just not getting enough fuel/oil mixture to lubricate causing overheating and alot of other nasty things - but not sure)....and what the warning signs are (if any) and what to do if you do notice any warning signs while out riding (maybe as simple as keep the rev's down?)

i've heard people say to watch the spark plugs and cylinder wash...ok sure...but ummmmm....what is it that i'm looking for exactly? Does anyone have pictures they could post of spark plugs at various stages to help me out (and prob a bunch of others out there who "think" they know what they're talking about)

thanks everyone...

No burn down is not from a lack of lubrication. It is the fire in the cylinder gets hot enough to melt the aluminum. the right stoichiometric mixture will give you the proper amount of fuel to produce maximum power and enough cooling to avoid burn down. (AKA melt down) to read your plugs. after warming your engine up do a full throttle run Hit the kill switch and brake to a quick stop. Then pull your plugs to read them. They should be a nice tan color. Look closely on the edges of the electrodes and watch for silvery coloration. If you dee this silvery coloration it means that you are running a little on the lean side. That silvery coloration is melted aluminum from you piston being deposited onto your plug.
cylinder wash is a science that I am not a hundred percent clear on. someone with more experience than me should probably explain that to you.

Once you've ridden two strokes long enough you get to know what they should sound like. A keen ear will be able to spot a lean engine but that comes with years of experience and burning down a few engines. LOL


Hope that this info helps you and that otheres chiome in and give you more info.

 

[Summiteer]

Spark Plugs

Pics of plug colors

 

[canadian madman]

thanks guys...both replies were exactly what i was for.

...and that spark plug page looks like a good one to print off and keep posted on the trailer wall

 

[SnowXTC]

I am going throw a wrench into this thread. What about detonation? Detonation is a more powerful class of combustion causing a shockwave and generating higher pressures. You can hear detonation, even mild detonation. Detonation will eat at the piston and can cause ring failure. It can also eat at the spark plug. Causes of detonation can be a too lean condition (even a very mild one), wrong grade of fuel, timing is incorrect and other things typically beyond our control.

For me, I had detonation in the mid-range. 5000 to 6500 rpms. It came down to switching needles. The 01 needles had a slightly larger taper than the 2000. I switched to the 2000 needles and problem solved. I have since refined this more. You will not necessarily see this condition in the wash or on the pistons, but it is something you will learn. I did. If it gets to the point that you can see pock marks in the pistons or the spark plugs, you are probably close to loosing the pistons depending on how bad it is.

Dealers tend to include a safety margin which is good for WFO, but does not always account for the mid-range. I highly recommend EGTs, but you still need to learn wash and spark plugs. EGTs are just immediate.

As I said the best indication of detonation as it is occurring is the sound change. You may think it is a clutch or something else, as it sounds kind of like a grinding noise. It is also said to sound like marbles in a coffee can.

Detonation and burning down a piston are two separate things, neither of which is good.

 

[SnowXTC]

Koby, very very true. Been there, did not quite burn it down. When she runs lean and changing jets does not do it and you go lean, rich, lean, rich, and then she dies when you are all alone 1200 miles from home in the Canadian wilderness and the tank does not look right, loosen the cap, then disconnect your froze up breather tube before trying to walk to a cabin that is 1.5 miles away, that you are actually crawling too.

Never made it to the cabin in 3 hours, but am again thankful for the radios we carry. Made it home in time for Christmas dinner, but it was too close and I was cold as hell.

 

[0neoldfart]

Reading piston wash - you should see a thumbnail sized area from the intake and transfer ports where any carbon is "washed" away from the crown of the piston. Please bear in mind that piston wash and plug readings should be used in conjunction with each other, do not rely on one or the other. Also bear in mind that EGT's will drop in temperature during detonation, not rise. Never rely on EGT's alone - they are a good tuning aid and a way to monitor a properly tuned engine, but plug color, piston wash, and sound are your best available tools.
A side note: many of the newer plugs are difficult to read, especially when combined with some of the synthetic oils that are out there, as the smokeless oils do not leave as much show on the piston tops...food for thought.

 

[swabby]

this term is used mostly by polaris riders lol... just funnin

 

[SnowXTC]

this term is used mostly by polaris riders lol... just funnin

Swabby, you are so funny.........................:d