Burn Down?

jdsledfarm · Post by **jdsledfarm** » Thu Jan 15, 2009 8:50 pm

Well, its mighty cold out today, but it didnt stop me from getting the SF out. Warmed it up good, rode up to the house, and moved the E clip all the way down to compensate for the cold weather. I took off, and went around my 4 mile trail. I had to keep it pinned the whole way around, cause it was light powder, and real deep. When I got back, it wouldnt run under 5000 or so. Over 5000 it seemed fine.

I pulled the plugs, and the pto side was a little white, on one side, and cocoa brown on the other side.

The mag side looked fine.

I reinstalled the plugs and fired it up, and it ran on one side until it died again. I tried pulling it over a few more times, and it feels like it might have low compression on one side.

I have never burnt an engine down before.

Could it be burnt down, or maybe I just blew a head gasket?

Maybe I lost the PTO side crank seal?

Way to cold to do much at the moment, so I think I`ll hang out here tonight, plus my diesel truck wont start.

Mr. Deere · Post by **Mr. Deere** » Thu Jan 15, 2009 9:24 pm

Might have blown something. I had this happen when I gouged my Base Gasket area on my LIQ. Start on the side were the plug is white and spray starting fluid to see were the air leak is. I did this and ended up finding a huge gouge. I wouldn't ride it anymore. Also do a compression test.

jdsledfarm · Post by **jdsledfarm** » Thu Jan 15, 2009 9:55 pm

Yeah, not only do I not plan on riding it, but with it firing on one side, I dont think it would be alot of fun! I lost my compression tester, or someone thought they needed it more.

Im thinkin (hoping) its just a bad head gasket, and I really hope I didnt burn a piston.

Mr. Deere · Post by **Mr. Deere** » Thu Jan 15, 2009 10:54 pm

Look down the plug hole that will show you if there is a hole in the piston.

Post by **ICCSF 108** » Thu Jan 15, 2009 10:58 pm

By having the Throttle "pinned" I would say you burnt it down, this usually happens more on warm days on deep tacky snow when the engine is really working hard but maybe you were on the lean side on the main jet because of the cold?? Once moving up to speed You probably could have backed 1/2 way out of the throttle & still maintained your speed & not worked the motor so hard..
There has always been a misconception that holding the throttle wide open in deep snow will make you go faster this is not always true as the clutching is torque sensitive & by backing out of the throttle ( however much ) the motor doesn't work as hard & doesn't burn down... While still maintaining the same speed..

Kenny

jdsledfarm · Post by **jdsledfarm** » Fri Jan 16, 2009 12:19 am

Yeah, I wish I hadnt been so hard on her.

I was scared to let off, since I was almost stuck for the first two miles, then got to go a little easier, but not by much. I`ll tear into it this weekend and see what I find.

Anybody know where I can score some NOS pistons? :redface:

Post by **guitardude081** » Fri Jan 16, 2009 12:07 pm

Like Kenny said, WOT....not good. Fan cooled sleds don't like to be run wide open for extended periods of time. Engines use the fuel charge to help cool the piston. At WOT you're allowing a large amount of air to enter the engine, and the fuel can't cool the piston efficiently enough. The best thing to do in a WOT situation is to back off the trottle once in a while and give it a few "braaap braaap's" to cool the piston. This works good when deacclelerating as well. When you let off from WOT, some engines will run lean. (Especially piped 580 Polaris engines) Burping the throttle on the way down will help cool the piston, and backshift the secondary to help slow you down. I can get you a brand new piston from SPI for $55.00+shipping.
~Jack

jdsledfarm · Post by **jdsledfarm** » Sat Jan 17, 2009 3:48 am

I let off a few times, but I think its obvious I was on it too hard. Operator error.

:redface:

A 210 main jet probably woulda helped some, since it was below zero.

On the bright side I scored a running 80 Sport with a blown track, to harvest many parts from, for fifty dollars.

Its got working electric start too!

I would still be interested in some NOS parts to rebuild my current engine, especially jugs. Let me know.

Also I was thinking why one side was leaner than the other, and remembered why LF`s have a larger PJ on the PTO side. With the single carb, there is no way to compensate for the ignition advance, on the PTO side which is the side that burned.

Rodimus Prime · Post by **Rodimus Prime** » Sat Jan 17, 2009 12:29 pm

plug white one side cocoa on other...not a seal,or base gasket, blown headgasket much more likely. Base gasket or seal would be white all over. Probably had a noticable drop in power previously not alot but not up to snuff either.

Either way piston is probably toast either burnt lands and ring or missing chunks. cylinder might be ok though.

Think head gasket not retightened after running or warped head and you will see what i mean.

Wide open throttle is the usual mode people did for sleds, didnt matter which one or what engine. I have done wot for 50+ miles on my trailfire 340 carring two people (the skidoo broke down) no damage to engine or sled although our backs were sore for days. It was also very friggin cold too she ran like a champ never been more proud of her. She may not look pretty after a tree and going end over end twice but still starts and goes..time for rings though.

jdsledfarm · Post by **jdsledfarm** » Mon Jan 19, 2009 10:40 pm

Well, I took the heads off.

The pistons look fine, and a little bit of scouring on the cylinders.

I think I will completely rebuild it with new seals.

How am I going to check my belt alignment when its done with no tool? Maybe we`ll save that for a future topic.

I`ll take some pics of my cylinders here in a couple hours.

jdsledfarm · Post by **jdsledfarm** » Mon Jan 26, 2009 2:37 am

Or a couple days.

Attachments:

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jdsledfarm · Post by **jdsledfarm** » Mon Jan 26, 2009 2:53 am

Another

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400brian · Post by **400brian** » Mon Jan 26, 2009 3:19 am

Those pistons do not look fine to me.

jdsledfarm · Post by **jdsledfarm** » Mon Jan 26, 2009 3:30 am

Yeah, they are definately toast.

With the heads off, and the cylinders on, the tops didnt look melted or anything. Also, I dont have much experience with burdowns, cuz this is my first one.

Post by **ICCSF 108** » Mon Jan 26, 2009 5:54 am

It looks to me in the second picture that the rings are seized??
If it were mine, & IF the pistons aren't any worse than what I see, I would sand the pistons (with emery cloth), clean the ring grooves & put new rings on them.. But this would depend on if it's easier to find New rings then finding New pistons?? & Depending how bad the cylinders are? slightly hone the cyl.s, BUT I don't know how bad the cyl.s are either???

Kenny