Why does my sled burndown? (pics)

Mars

Mars

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Oct 12, 2005
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Age
40
Location
Chelmsford, ON
The old Exciter went, yet again.

It burnt down the SAME way as it did the first time.

Both Mag sides got hurt bad.

blown_1.JPG


Piston tops

blown_3.JPG


And the usual "chunk" missing out of the PTO side :

blown_2.JPG


PTO tops

blown_4.JPG


What do you guys think? lean? wash seems lean. I'd like to hear what you guys think.
 
wash does look kinda lean in a few of those pictures. Wouldn't think twice about richening it up a size or two.
 
Great. Thanks!

Also the sled was overreving quite a bit. Could that cause it? Maybe 6-700 RPM over.
 
I know the carbs are clean.

Crank seals, you can check them by spraying wd40 on them while the motors running right?
 
Wow....that looks lean. Jetting can be wrong, air leak somewhere.
I would really make sure before you replace pistons and burn down again.
 
the manual wont tell you how to change them.did you find out if that was your problem??i got a ex.570 manual still in the plastic bag.id sell it to you if your intrested.
 
not lean

Starting with the BOTTOM picture as far as jetting goes – the right picture is almost perfect – maybe ½ a jet lean it’s so close. This is not a real plug chop – but generally. The piston on the left side is rich.

The next set doesn’t even look like it came from the same engine. This is a different wash for some reason – but still just lean but not bad. Again – the left one is slightly rich.

Notice in both pictures there is no piston erosion. Usually – too lean the top exhaust ridge of the piston would be eroded with a detonation look. The groves in the pistons are from spare parts flying around. ;):D

It’s hard to diagnose without seeing it – but I’d look at the ports in that area and see if it’s properly chamfered. :o|

It’s like the piston just broke. If you were lugging it – I’d say that’s bad – revving is not as hard on it.

What does the sparkplug look like?
 
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A 700 rpm over-rev may cause it over time with the 570. Your clutch will also show signs (like a clutch with 3000 miles or more), worn out parts with only 500mi on the sled.
 
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Have ya ever ran bore guage down thru both cylinders and see what each measures?/ have the ring gaps ever been checked?

How long of a time between burndowns is it?

while it does look lightly lean its not catastrophic lean, like someone mentioned they will erode the exh edge of the piston off before failing, once the ring is exposed to the combustion flame, its all over.

its possible it has a light airleak, carb boots,crank seal,base gasket leak,could be checked easily with running it and spraying carb cleaner or something and see if it drops the idle any.

check the first 2 thing s and let us know. I have seen a tight cylinder/piston ring do that, simply break off the ringland, a ring without any clearance will also do this in short order if its too tight.

just some ideas to check.
 
2 things,

I would check for an exhaust leak where the pipe meets the Y pipe, or even a hole rusted in the pipe. I would also make sure when you assemble it that the rings are properly located around the locating pins - it almost looks like a pin came out and the ring hung in the port, but doubtful to happen in both cylinders. Wash looks pretty good to me.
 
Check for crack in the rubber carb boots or anywhere air could get in near the carbs. This would explain the high idle and leaning out as too much air is being let in. I had a high idle with my Phazer and it turned out the clamps on the carb boots were loose.
 
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