I have eliminated almost everything except . . .
This engine did have 15K miles on it with new pistons and rings at 8K. I haven't torn it apart yet (beyond pulling the head). Once I saw the extent of the damage, I opted for a different set of cases and crank.
What do you engine builders think? I will upload better pictures once I get into it further. Any advice on what to check as I go?
btw: She was still running and wanting to go when I parked her to go get the truck and trailer.
- Crank Seal
- Crankcase Seal
- Exhaust Valve contact with piston and rings (not sure if it occurred before or during the burn down)
This engine did have 15K miles on it with new pistons and rings at 8K. I haven't torn it apart yet (beyond pulling the head). Once I saw the extent of the damage, I opted for a different set of cases and crank.
What do you engine builders think? I will upload better pictures once I get into it further. Any advice on what to check as I go?
btw: She was still running and wanting to go when I parked her to go get the truck and trailer.
YAMMIEGOD3:16
Active member
ding, i always went on old school thought here because i am old when ya show alot of damage to the top of pistons its lean/ fuel/ poor gas related. severe detonation. 3:16x (yammie tony)
Youllbe2nd
New member
Got too hot and ring broke and beat the shit out of everything. It likely leaned out. Could be bad seal, gasket or Intake boots cracked. Dirty carbs, pinched fuel line, too hot spark plug etc...there's alot of things just need to tear into it. Stock needle settings?? With today's gas you need to raise the needles in your vipe. The valve likely got smacked when the ring broke and found its way out the exhaust port.
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This engine was still running? I've had burndowns that didn't look this bad and I couldn't get my engine to hardly run on the 2 good cylinders.
Dropped a different engine (crankcase and heads only) in. Used the existing carbs, boots, exhaust valves (1 replaced), stator, oil pump, etc. It is running fine now. It also ran 15K miles on the carb setup, and yes I raised the needles back when it was new. The other 2 cylinders were good. This is why I say I have eliminated many items as root cause.
I do think the ledges that stop the exhaust valves were worn out on the original cylinders. This happens when you run with a pull-thru for any amount of time. If the valves are adjusted I don't think it matters, but if the cable pulls thru (this one was) then the valve can sit and vibrate on the ledges ultimately wearing them off. Again I am not sure if the valve dropped in and caused the issue, or if the burn-down caused the valve damage.
I do think the ledges that stop the exhaust valves were worn out on the original cylinders. This happens when you run with a pull-thru for any amount of time. If the valves are adjusted I don't think it matters, but if the cable pulls thru (this one was) then the valve can sit and vibrate on the ledges ultimately wearing them off. Again I am not sure if the valve dropped in and caused the issue, or if the burn-down caused the valve damage.
Vincent
New member
That's good long engine life still. I'm probably at 8k on mine. It mite be do for pistons and rings to.
Looking for more input . . .
I may be old, but I am slow !!!
I would go along with fuel supply / lean if there was any evidence in the other 2 cyls or the engine in it now showed any leanness. I used the same fuel, carbs, boots, etc. on the cylinders and crankcase I put back in it. It really does have me scratching my head. I am trying to figure out how to test the PTO crank seal with the head off. That said, I do agree it sure looks like a severe lean condition with the exhaust side melted away.
I did carefully check the carbs, carb boots and reeds out. All was fine including the air passages in the carbs. It had run 40 trail miles and then 30 minutes in powder, and then 20 miles back on the trail when she went.
roudyroy1
Active member
bad fuel or water in the fuel?
Youllbe2nd
New member
To test it the only thing you can do really without sealing the motor up is to remove the pto cyl and fill the case with gas or something and see if it leaks. Kind of red neck but hey... There's no pressure in the motor this way but if it's bad enough it will seep through. Leave it over night maybe.
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Thanks for the idea, unless I hear a better one I think this is what I will do.
I really want to know root cause. I have burnt too many engines down with repeats to have piece of mind until I see some good evidence of root cause.
all 3 were lean, the two that didn't burn up yet were ready to do so, there is zero wash on the pistons, they are dry and gray patches on them. Most likely bad gas(low octane) did this if you had the needles raised in the carb.
Thanks for the input Don,
I was noticing that there was less distinctive wash then normal. There is an area that is washed about a quarter in size, but not washed clean like it normally was. Doesn't show up in the pics because of coloring. Last time I did check these pistons there were distinctive half thumbnail sized clean washes at each transfer port opening. They showed up silver and shiny in the remote camera I use. Don't know why I discounted it but now that you say that I agree they aren't what they should be.
Here are the plugs (at time of burndown)
And the plugs after rebuild . . .
Wash has been looking normal again, but I am going to watch it closely.
Thinking about the gas. It was less than half tank at burn down time, and I filled it before running it more than the 3 mile checkout my son did. So it likely averaged the octane out. Now I am trying to remember where I got the fuel that was in it . . .
Thinking about the gas. It was less than half tank at burn down time, and I filled it before running it more than the 3 mile checkout my son did. So it likely averaged the octane out. Now I am trying to remember where I got the fuel that was in it . . .
looking at your current plugs need to be richened up some, as you can see its burnt clear back past the bend on the ground strap on the center and mag(higher compression cylinders) where as it should be 2 different colors and looks to be a little lean to me.
sure you have the needles raised from stock?
also what gas are you using as they are gray in color, instead of tan???
sure you have the needles raised from stock?
also what gas are you using as they are gray in color, instead of tan???
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burn down can happen over time, doesn't always happen within minutes of filling up so its very possible it happened over the half tank of useage, the time is dependant on how much load is being applied to the engine, or how and what kind of conditions its being ridden in. The typical exhaust burn back like what you had in the pto is a detonation low octane burn, the piston crown just erodes till it exposes the ring to the flame front, then the ring turns orange and soft and snags the powervalve and the exhaust port, tearing them up.
If the stop in cylinder was worn enough to let the valve contact the piston it would be an abrupt breakdown, either gouging the entire exhaust side of piston or completely locking up the cylinder as the piston tries to smash and pull the valve in as it comes up. Plenty of collateral damage valves like yours with exposed rings.
as mentioned before,the pistons are lean in those other 2 cylinders, right on the detonation, I bet the rings will show a water spot appearance on the flats. Even looking at your current plugs, looks lean to me, all gray and burned back beyond the curve with no color change, its either the gas your using or the carb specs. Those eya plugs are hard to read because of the split in the electrode, so it may be easier to keep track with just some br9es plugs till you know whats happening and adjust for it. If you have ethanol fuel and its low octane/quality where you buy gas when riding, you will need to upjet to compensate, raised needles and fatter mains may be in order to keep it going again for another bunch of miles. Fuels have changed a lot since these came out in 2002, they need to be compensated in specs to go along with the new fuels.
Thanks for the replies,
I am using Michigan pump gas usually with 10% Ethanol. I get Ethanol free when at a location that sells it. I usually get 91 octane when at a station that sells a lot of it (lots of sleds) and 87 when at a station that has very few sleds come through and mostly services cars and trucks. Theory being fresh 87 fuel is better than really old 91 fuel even if lower octane. I do recall the fuel truck filling at the station I filled at, and even asked the guy which tank he filled. I had already filled and it was the same tank he had just filled (87). He proceeded to tell me that with the 10% Ethanol fuels that the issue with stirring up junk is mostly eliminated now due to the Ethanol in the fuel. I don't know enough about fuel to even discuss it with him really so left it at that.
I am going to check for the gray color (possibly just the camera) and watch my fuel closer. I am going to check the needles to be sure again, but I have run them raised 1 setting since 2002.
Is there anything else I should be checking for in the new (newer) engine besides plugs, wash and settings?
I am using Michigan pump gas usually with 10% Ethanol. I get Ethanol free when at a location that sells it. I usually get 91 octane when at a station that sells a lot of it (lots of sleds) and 87 when at a station that has very few sleds come through and mostly services cars and trucks. Theory being fresh 87 fuel is better than really old 91 fuel even if lower octane. I do recall the fuel truck filling at the station I filled at, and even asked the guy which tank he filled. I had already filled and it was the same tank he had just filled (87). He proceeded to tell me that with the 10% Ethanol fuels that the issue with stirring up junk is mostly eliminated now due to the Ethanol in the fuel. I don't know enough about fuel to even discuss it with him really so left it at that.
I am going to check for the gray color (possibly just the camera) and watch my fuel closer. I am going to check the needles to be sure again, but I have run them raised 1 setting since 2002.
Is there anything else I should be checking for in the new (newer) engine besides plugs, wash and settings?