Last spring I roasted a plug. This season that cylinder does not seem to fire consistently, if at all. Good spark, conductivity of plug wire same as the other. Can pull this plug wire while running and hear no difference in engine. Plug is wet when inspected - not wet fouled, just uncombusted gas. Runs at 2500 rpm and eventually will increase to 5000 rpm and maybe 40 mph @ topend after several hundred yards and downhill. Other plug is pretty tan in color and normal. Carb has been cleaned and is clear. Carbs and cables have been adjusted. What else is there? :crazy: Please reply with your ideas and questions to ICEFISH. Thx.

Ok, Formulaman too the rescue, but first I'm gonna pick on you just too loosen ya up
yeah tryed them roasted... yuck, plugs taste funny that way hehe if it's wet it's fouled not where this is going, but anyways... try new plugs ummm when you say roasted you mean it quit working, or there was evidence of some shiny metal transfer... the latter is gonna be costly :bash: check compression for diff between cyls. some guys will accept a diff of ten percent be me personnally a few psi. is all i allow. A leak down test is next but anyways you get the idea. Keep fingers crossed and hope it's just bad plugs. Btw I've seen three bad new plugs in a row all bought the same day good thing he had six lol

Ok, Formulaman too the rescue, but first I'm gonna pick on you just too loosen ya up
yeah tryed them roasted... yuck, plugs taste funny that way hehe if it's wet it's fouled not where this is going, but anyways... try new plugs ummm when you say roasted you mean it quit working, or there was evidence of some shiny metal transfer... the latter is gonna be costly :bash: check compression for diff between cyls. some guys will accept a diff of ten percent be me personnally a few psi. is all i allow. A leak down test is next but anyways you get the idea. Keep fingers crossed and hope it's just bad plugs. Btw I've seen three bad new plugs in a row all bought the same day good thing he had six lol
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OK Im loose now. Didnt lick the plug but the electrode was partially melted (last year) did not look like metal transfer just heat. Will try the compression test. Did take proven plug from working cylinder and it does not light the other side. Can the coil be bad and give me spark? Condenser box? I can pull plug and see good spark jumping electrode. Timing cant be off except at crank or ignition coil, right? I read about switching carbs. Have wet plug (& a headache) already though. Will also try all the plugs in the coffee can.
P.S Sorry bout the double click formulaman.

borrow coil and wires from a friend to test. you may have a bad plug cap.

Well, some of you guys are pretty good. Found NO compression in bad jug. Next step to pull head and look around. Likely culprit the head gasket or flange gasket or rings or all??? Piston strokes with no rattle so I suspect gaskets. What ya'll think??? Will check back here for tips and welcome them. :blush:

I'm betting there is a hole in the top of your piston.

I'm betting there is a hole in the top of your piston.
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:withstupid: I'm with fishy on this one ....

Like I said, someof you are pretty good. :thumbsup: Holein the piston. What caused it? Can I prevent?

Like I said, someof you are pretty good. :thumbsup: Holein the piston. What caused it? Can I prevent?
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Speaking from experience :whistling: if the other piston is fine, it's most likely you iced up the one carb, leaned out that cylinder and burned right through the top of the piston near the hottest part (plug) It's possible there was some other type of blockage in the carb but the culprit was most likely water/ice.

Prevention? Keep your carbs clean, (do this every pre season tune up) don't subject your sled to massive temp swings (storing it through the week in a heated shop is a non no, CONDENSATION!) use a bit of isopropynol with every tank OR some kind of "in tank" water eliminator, available at most automotive stores.

That should help ... good luck with it.

:withstupid:

make sure you clean your carbs before you run it again, just incase it wasn't water and you have a plugged jet.

Yep, makes sense, the carbs are cleaned and roughed in. New piston will be here early next week. While I wait how do I drain and clean the crankcase without pulling engine or whittling from the top down. I have no book on this doo just rebuild experience with lawn mowers and whatever I can get from the internet. :dazed: And, what are the specs/brands for crankcase oil?

is it not a two stroke?

if so, no crankcase oil needed

While I wait how do I drain and clean the crankcase without pulling engine or whittling from the top down. I have no book on this doo just rebuild experience with lawn mowers and whatever I can get from the internet. :dazed: And, what are the specs/brands for crankcase oil?
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Check the condition of the cylinder walls and head. The cylinder may need a quick hone (not likely) but check for scoring. Did you order a new wrist pin and bearing and a top end gasket set as well? you should ...... As Fishy said, no crank case oil, just use 2 stroke oil to lube up the piston and wrist pin as you put everything back together. Pay attention to the way it comes apart, the snap ring etc. are positioned a certain way for a reason, and the arrow on the top of the piston faces the exhaust port (front) You'll need torque specs for the jugs and head ......

It's not too difficult a job but it's simple to screw up, you may want to get an experienced hand to help you ...

There you go, my 4 stroke Briggs background getting in the way. You are telling me all bearings are sealed (except the wrist pin bearing) and require no lube, including the chaincase? Yeah, Im good on parts. There is minor scoring on cylinder to be honed. I know - risk losing compression but will reassemble with rings quartered away from score, check compression, run-in and recheck compression often. Have an old tractor that had low compression (Continental) that improved on its own with revs. Many thanks to the "professors" Fishhog and MikeD. This is a great site. Has saved alot of ... :cussing:

what kind of sled do you have.?

Success!!!!!!!!!!! With the help of the good folks of this forum I fixed the burnt piston and runs great. Now we need snow here in the lower great lakes. One more question... (when it rained, it poured)... getting the old wrist pin clips off popped one into crankcase through the belt slot (had the pushrod covered to prevent this from happening, but you know, Murphy's Law). Fished around with different magnets but could not snag it. Should I be worried that it will be picked up into fan belt, crank, intake?

oh oh not good. :(

WELL, DUH, ZIPPY!!!!!!!!!!(& it doesn't matter what sled I have). Put your head back in the snowbank, butt-out and let those who are helpful reply in this forum. Mike D and Fishhog may reply any time as they have actually provided the troubleshooting and solutions I needed. As I said, running great!