ms460 big bore carnage

[Brian Carlson]

Well found out why my go to saw wouldn't start. Looks like back in the summer I found out why it started running funny one day. Well I wasn't showing it any mercy and it was very hot. Its a cheap kit and I am just gonna regroup and try again. Just a little transfer on the jug but the piston is trashed.

 

[Crzybowhntr]

Pics of the air filter? Maybe not enough air getting in???

 

[junkman]

50 to 1 ?

 

[Brian Carlson]

I was running 40:1 belray and the air filter was a little dirty but not what I would consider bad. I had it tuned pretty lean but it was still four stroking. It got really hot. I was running it hard in big cherry.

 

[skidooguy]

Have you identified the cause of said carnage yet? Just don't want to see you put a new slug in there and have it happen again from a problem somewhere else. I am no pro saw tech to say the least but I'm sure somebody with infinite knowledge will be by soon friend. Bummer on your big bore tho

 

[stihl saws]

Pressure and vac test?

 

[Brian Carlson]

Maw not yet. I think I just had the tune too lean and it got way to hot. I was kinda testing the kit for the past year and a half to see what it would take. Well I found out lol. I did also do a little grinding in the cylinder , who knows it might have something to do with it lol.

 

[skidooguy]

What's your plug look like? Just curious

 

[Brian Carlson]

It was dark as was the top of the piston. Not even light brown

 

[skidooguy]

To the op I'm sure you know way more about 2 cycle motors than I could ever hope to know I am just curious and like to see diaganosis suggestions and ideas from the people involved with this site. Thanks for the post. I hope I don't experience this in the near future

 

[skidooguy]

Is the damage only on one side of the piston or both?

 

[Brian Carlson]

Yea it's only on exhaust side.

 

[skidooguy]

Did your rings and pins all seem to look normal? Has that oil ever noticeably produced much carbon buildup for you in the past? I'm waiting for a guru to chime in and know what happened off the top of his head also. But I wouldn't blame it on lean if your plug was a dark color but I'm no expert either my friend.

 

[skidooguy]

How many hours on the saw since you took a grinder to it you think?

 

[Brian Carlson]

There was no excessive build up anywhere on piston or exhaust port. The wrist pin and clips where good. Maybe since they were aftermarket rings they wore kinda quick and allowed some scoring. I still think it got way too hot the last time I had it out. I need to check and see if the aftermarket jug has the same amount of fins as the oem one. I am willing to bet it doesn't so it can't get rid of the heat as easy.

 

[skidooguy]

What brand of big bore and were you impressed with it over a stock 460 since you had it? Aside from it getting torched.

 

[skidooguy]

Never had a big bore do just curious about how it performed.

 

[jmssaws]

I've fixed a bunch of saws that were seized with zero problems.

Sometimes they just seize,tuned a little lean or piston and cylinder clearance a little bit tight or bad gas or a combination of them all.

 

[TJ the Chainsaw Mechanic]

My boss ran a big bore kit once, and that was the last. He said the saw just didn't run the same. Vibrations were different. Felt out of balance.

 

[MustangMike]

Questions:

What brand big bore kit?

Did you pull the carb limiters?

How far out was your Hi screw set?

Do you still have the original cylinder, and can it be cleaned up? New OEM pistons are not that expensive. What happened to the OEM jug?

Is your muffler stock?

What air filter are you running, and how often do you clean it?

If there is nothing wrong with your saw (no air leak) these things should not happen, but as Jason says, "I have seen them".

Usually, the air filter is a little dirty, the muffler is too restricted, the tune is a little lean, and the chain is dull and being pushed. Scoring on the exhaust side only is reflective of a heat failure.

I have 3 ported 046/460s and have even milled with them in hot weather w/o any failures.