White deposits on spark plug Vk540

[likuidsnake]

Hi, first post here,

Can someone tell me what is this white deposits on the PTO spark plug? I think it may be aluminum since I got engine failure in the trail yesterday. I was riding groom trail at 70-80kmh when engine stopped. I can't open my engine now, can't reach my garage... I wonder if just by looking at the spark plugs someone could tell me what kind of repairs to expect.

Thanks

Mike

 

[Ding]

I would have a close look at the top of your piston (use a benda-light or similar) - also see if you can determine what material the whitish flecks are. That really don't look like aluminum to me but hard to tell in pics. Did this sled sit in a damp area for quite a while?

 

[likuidsnake]

Just inspected the spark plug under stereomicroscope (I work in a lab) There are 2 kinds of white deposits, grey and silver. Grey look like soot, silver is definitely metallic. Unfortunately I don't have a spectro or XRF to analyse the metal.

The sled usually spend winter outside under a cover and summer in a garage on concrete floor. It was, however, in a huge snowstorm without its cover 3 weeks ago. Engine compartment was filled in snow.

 

[Ding]

ok - now it looks like melted piston. Take a look down the spark plug hole with that cylinder at bottom of stroke. Likely a carb issue (lean) and slight piston burn-down.

 

[likuidsnake]

Thank you Ding, I'll try to check that tonight.

Now I need some teaching... The VK540 has only 1 carb, how can it be fine on the mag side but lean on the pto?

 

[wildthangci]

My guess would be an air leak.

 

[Ding]

One does run hotter than the other, but I also would check for an air leak as well.

 

[A couple of bucks]

Spraying brakeclean around boots,bearings,seals etc etc will narrow down faulty shtuff.

 

[likuidsnake]

So I maned up and shoveld a way to my garage. Removed both heads. Mag side is like new... pto, piston seems grooved and there are scratches and metal on the exhaust side.

Too lean and molten metal scratched the cylinder?

 

[roudyroy1]

yup looks like a the beginning of a lean burn down, does the exhaust side of the piston look rounded off?

 

[likuidsnake]

Piston looks eroded at the exhaust side

I'll remove cylinder this evening.

 

[mrviper700]

detonation for sure, your gonna need to replace piston, hone cylinder. You might need to use muratic acid on cylinder to remove the molten metal smeared on it, just don't get it on any other aluminum, it eats it.

There was a old trick to trimming the plastic engine cover on those engines to balance out the temps, 1 cylinder always ran hotter then the other did but still good to look at air leaks etc. when taking it apart.

 

[roudyroy1]

rounded off crown on the exhaust side, gonna say you have an air leak or partly plugged jet.

 

[likuidsnake]

I just finished lifting the cylinder. I noticed oil in one cavity of the engine block.

Carb was dirty, cloged jet may be one cause. I didn't see any filtering element in the airbox...

Pistons...

 

[roudyroy1]

looks like some scuffing on the intake side, maybe someone can confirm? that's usually caused by snow ingestion washing the oil film off the piston, which makes sense since theirs now filtering element?

 

[Willowbilly]

PTO shaft seal leaking air will cause this also you have one carb but you have a Y manifold pto side of manifold look for a loose or missing bolt where it bolts to clyinder ck or replace fan belt keep the belt tight they get hot stretch and slip