S
that should not matter. are the arrows facing the ex or intake on the pistons? scratches only come from a few things.....lack of lube and foreign debris are the top of the list.
Help diagnose toasted piston
- Thread starter specialk6r
- Start date
S
I used OEM pistons that have a little dimple which I believe faces the exhaust. I'm sure I did that part the correct way.
I marked the level in the oil tank and it is going down. Doesn't that plus the premixing rule out lubrication? Maybe my flushing of the crankcase wasn't thorough enough.
I'm still concerned about the difference in the appearance of the plugs. I guess the PTO should be running richer since the main jet is one size larger, but the color is totally different. Here's a very poor picture of the plugs. The PTO side is on the right. I know you can't tell but the electrode on the PTO plug looks whitish, and the MAG side is just wet metal. Both are wet around the first couple threads.
I marked the level in the oil tank and it is going down. Doesn't that plus the premixing rule out lubrication? Maybe my flushing of the crankcase wasn't thorough enough.
I'm still concerned about the difference in the appearance of the plugs. I guess the PTO should be running richer since the main jet is one size larger, but the color is totally different. Here's a very poor picture of the plugs. The PTO side is on the right. I know you can't tell but the electrode on the PTO plug looks whitish, and the MAG side is just wet metal. Both are wet around the first couple threads.
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I think its too early to read the plugs. I was more concerned with the sctratch in the bore. does the scratch look like it is cutting into the piston where it crosses the ring.......or is it more of a smudge?
I can't imagine the sled burining down just idling there, but if there is something that trips a ring you are not gonna be happy.
I can't imagine the sled burining down just idling there, but if there is something that trips a ring you are not gonna be happy.
S
I just ran out and checked it out. The scratches on the piston don't cross the rings at all, they are only in the middle of the piston, and only a few of them. I haven't pulled the cylinder off yet.
Did you say you have the pto side richer? Those motors run hot on the mag side, thats the side you want a bigger main jet in.
S
Well that might be a big reason for the huge difference in plug color. I'll check the jets and make sure I have them the wrong way.
Maybe the scratches are unrelated to the jetting and just from something left in the bottom of the engine.
Maybe the scratches are unrelated to the jetting and just from something left in the bottom of the engine.
S
Well I went out today to fix the jetting and it turns out that I had done it correctly: 400 main on the MAG side, 390 on the PTO (I but it back together last spring and couldn't remember.
I also noticed that the top of the MAG piston was wet with fuel and the PTO piston (one with the scratches) was dry.
Here's a good picture of the plugs. The black one is from the PTO side. Thanks for all the help.
I also noticed that the top of the MAG piston was wet with fuel and the PTO piston (one with the scratches) was dry.
Here's a good picture of the plugs. The black one is from the PTO side. Thanks for all the help.
S
Ttt
S
if the scratch is nothing like you say.....time to run it for a while and see whats up. I would not sweat the plugs, just the bore. if the plugs have you worried, pop the carbs off and dump the bowl and blow them out. watch for line kinks and run it on a track stand.
K
The plug on the right looks lean to me.
Regardless there seems to be a difference between the two.
Regardless there seems to be a difference between the two.
S
Spring snow here, thanks for all the time you've put into this. If the scratches are the start of major damage (which I'm worried might be the case since that dome looks dry and the other is wet) what would your recommendation be? Should I get a leakdown test done to check the PTO seal? I know the sled has blown a belt sometime before I bought it. Something seems fishy since everything on the MAG side seems normal, and if this thing burns down again it might be awhile before I can afford to fix it.
D
Have you checked the crank phase? If you blow a belt with load on it you can knock the crank out of phase. A weak fuel pump, wrong float levels, bad carb boots, and bad reeds can all cause eratic fuel flow.
S
That sounds like a good possibility. The previous owner said that he blew the belt crossing a lake, so probably under load. Is the crank phase also refered to as "index"? Is that something I can check at home? I have a CD manual but can't find anything about that.
The boots and reeds look perfect, but I'll have to check the float levels again. I haven't checked the pump, but wouldn't a week fuel pump cause lean issues in both cylinders?
p.s. do you guys have any tips for removing the carbs without spilling coolant everywhere?
The boots and reeds look perfect, but I'll have to check the float levels again. I haven't checked the pump, but wouldn't a week fuel pump cause lean issues in both cylinders?
p.s. do you guys have any tips for removing the carbs without spilling coolant everywhere?
plugs are way off
just put together the same motor for my brother and fired it for 1st weekend.
He torched it from overheating on a lake last winter.
From the looks of your plugs you have some kind of a lean problem with the white plug side. Even with way to lean jets you won't hurt this motor on a parking lot test ride.
Check to make sure carbs are clean, jets clean and clear, needle in? middle position if nothing else, and engine should idle fine and steady rpm, if it high idles likely an air leak somewhere......can be engine cases, carb boots, main seal, reed valve frames. Start up after rebuilt, hold oil pump wide open with wire with hook in end until the engine smokes the neighborhood at an idle so you know oil is flowing. make sure each oil line is open as I've seen them melted on the back of the engine, appear ok but and hardly passing oil from past abuse.
After 5 min idle make sure you have coolant flowing and make sure you've checked the thermostat, after a hot seizure you often find the thermostat stuck open or closed due to the stainless pin cockeyed in the pellet. Stuck closed they obviously overheat, stuck open you will have seemingly erratic jetting and poor warm up and sometimes cold seizures.
But with that white plug don't go to the trail or you may be buying a motor.
Take out the plugs, have bud pull the engine over fast and watch clutch and crank, usuallyout of phase or bent, it just won't look nice and concentric and you better scramble for a dial indicator.
Bad fuel pump, bad gas, crap in carb you won't seize it with a gentle parking lot test, just don't hammer it to try and clean things out, motors don't fix themsleves, if it doesn't seem right, it taint right!
When I earned a living saving sled motors, the quickie lower end job is, upside down with the high pressure washing wand, irrigate it until you are tired and wet, let the water drain out, blow it with air, spray it down with starting fluid, and work some Justus Bros. assembly oil into bearing, assemble it within an hour and fire the old girl up. Warn the rest of the guys in the shop cuase the smoke and steam will be ample. Not what I recomended to customers, but sometimes the wallet is the deciding factor.
just put together the same motor for my brother and fired it for 1st weekend.
He torched it from overheating on a lake last winter.
From the looks of your plugs you have some kind of a lean problem with the white plug side. Even with way to lean jets you won't hurt this motor on a parking lot test ride.
Check to make sure carbs are clean, jets clean and clear, needle in? middle position if nothing else, and engine should idle fine and steady rpm, if it high idles likely an air leak somewhere......can be engine cases, carb boots, main seal, reed valve frames. Start up after rebuilt, hold oil pump wide open with wire with hook in end until the engine smokes the neighborhood at an idle so you know oil is flowing. make sure each oil line is open as I've seen them melted on the back of the engine, appear ok but and hardly passing oil from past abuse.
After 5 min idle make sure you have coolant flowing and make sure you've checked the thermostat, after a hot seizure you often find the thermostat stuck open or closed due to the stainless pin cockeyed in the pellet. Stuck closed they obviously overheat, stuck open you will have seemingly erratic jetting and poor warm up and sometimes cold seizures.
But with that white plug don't go to the trail or you may be buying a motor.
Take out the plugs, have bud pull the engine over fast and watch clutch and crank, usuallyout of phase or bent, it just won't look nice and concentric and you better scramble for a dial indicator.
Bad fuel pump, bad gas, crap in carb you won't seize it with a gentle parking lot test, just don't hammer it to try and clean things out, motors don't fix themsleves, if it doesn't seem right, it taint right!
When I earned a living saving sled motors, the quickie lower end job is, upside down with the high pressure washing wand, irrigate it until you are tired and wet, let the water drain out, blow it with air, spray it down with starting fluid, and work some Justus Bros. assembly oil into bearing, assemble it within an hour and fire the old girl up. Warn the rest of the guys in the shop cuase the smoke and steam will be ample. Not what I recomended to customers, but sometimes the wallet is the deciding factor.
S
Like KillerK said, I thought the darker plug on the right was the lean one. If you click on it you'll be able to see the electrodes are turning white. Plus, that's the plug from the side with the scratched piston and dry dome (which had burned down in the first place.) The white plug seemed about right to me for being jetted fat and only run for a short while.
If the crank was out of phase would it only affect the PTO side? Thanks
If the crank was out of phase would it only affect the PTO side? Thanks
F
These have been around for awhile now. I've always thought they had one of the strongest bottom ends. Anyone else ever heard of this?
R
No piston wash= no fuel or the lack of. Is the sand in your filter black.
My 900 had the same thing. It is the fuel cap plastic.Turn the fuel cap over and scratch it. The plastic will flake off. Piston melt down on the ex side is usually from high temp or lead burn down. The crank out of index will cause
detination. Detination will take the carbon off the top of the piston and transfer piston onto the plugs. EGT guage will not lie and will take most of the guess work out of it. $320.00 Insurance policy.
My 900 had the same thing. It is the fuel cap plastic.Turn the fuel cap over and scratch it. The plastic will flake off. Piston melt down on the ex side is usually from high temp or lead burn down. The crank out of index will cause
detination. Detination will take the carbon off the top of the piston and transfer piston onto the plugs. EGT guage will not lie and will take most of the guess work out of it. $320.00 Insurance policy.
S
IMO, scratches scare the hell out of me. they only show up from bad things and lead to bad things. I agree with catsledman running it in the lot is not gona hurt it. a few seconds her and there will be fine. if it was me....I would pop the jug off and see what happened to cause a scratch. if it looks like debris, I would do just like catsledman said. pop the block and wash.....reassemble and ride. I would sure as heck go through my carbs and since you added the "lake" issue, I would be for dumping the tank and being dang sure it was free of water.
I can't help you on the crank phase.....by the grace of god I have never knocked one yet. checking all the seals, carb boots.....any plac that can leak air is cheap and easy to do. I use propane, but remember it is heavy and will sit in the pan.....keep that in mind.
I know it sounds like a lot more work, but it can all be done in a couple hours and you will know wats up. good luck.
I can't help you on the crank phase.....by the grace of god I have never knocked one yet. checking all the seals, carb boots.....any plac that can leak air is cheap and easy to do. I use propane, but remember it is heavy and will sit in the pan.....keep that in mind.
I know it sounds like a lot more work, but it can all be done in a couple hours and you will know wats up. good luck.
S
I already removed the tank and flushed it, pulled and inspected the intake boots and reeds, and sprayed starting fluid all around the boots and PTO seal.
When I had the top end off I poured premix over the crank bearings until the block was almost full, turned it over a number of times, pumped the fluid and debris out, then ran paper towels under the crank. I did this about 6 times, and the paper towels started coming out clean after 4.
I'm betting the scratches are from a lean condition rather than debris since: 1) I cleaned it fairly thoroughly. 2) The difference in the plugs, even though it's too early for an accurate reading. 3) The dry dome on the scratched piston.
I'm going to see if I can see any wiggle in the clutch and start it again and spray starting fluid around the engine cases to see if there's a leak. I'll re-check the reed cages and have a look inside the carbs again too while I'm in there. I should also have a look at the thermostat.
If it were a cooling system issue, would the PTO side get hotter than the MAG side, or would they get equally hot?
When I had the top end off I poured premix over the crank bearings until the block was almost full, turned it over a number of times, pumped the fluid and debris out, then ran paper towels under the crank. I did this about 6 times, and the paper towels started coming out clean after 4.
I'm betting the scratches are from a lean condition rather than debris since: 1) I cleaned it fairly thoroughly. 2) The difference in the plugs, even though it's too early for an accurate reading. 3) The dry dome on the scratched piston.
I'm going to see if I can see any wiggle in the clutch and start it again and spray starting fluid around the engine cases to see if there's a leak. I'll re-check the reed cages and have a look inside the carbs again too while I'm in there. I should also have a look at the thermostat.
If it were a cooling system issue, would the PTO side get hotter than the MAG side, or would they get equally hot?
motors obviously lean. scratches may be old debris coming up from crank area, when you burn down like u did the aluminum is so hot it sticks to internal parts. Sometimes this debris comes unstuck due to the presence of heat and combustion again. This motor is still lean. swap carbs to see if symptoms move to other side. if so trouble shoot carb. its better to start way richer than needed then go leaner, plugs will not lie. belts blow all the time, rarely does crank damage but it happens. if crank was out of phase it would run like crap, if seal was gone the test u did with starting fluid would of shown this unmistakebly. check that carbs are balanced. u need wash. antifreeze in motor would cause excessive wash, u have none. fuel bad??? elevation???
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