Stihl 046 Magnum Piston Help

[JWMUSTANGMAN]

I picked up my 046 magnum at a pawnshop about 10 years ago for 100 bucks. It has been a phenomenal saw. Always plenty of power and cuts like a dream. Last year all that changed when it just stopped running one day. After pulling the exhaust I could tell the piston was scarred pretty bad so I decided it was worth saving. I ordered a top end kit from eBay. I installed a new piston new cylinder new rings and new piston pin. Once I got it all back together it ran beautifully for about 10 minutes and then just died while idling. I could not pull it to start it back. I pulled the exhaust and the piston is scarred again on both sides of the exhaust Port. What did I do wrong? Is it just a poor quality piston and cylinder? I have three stihls and I want to know how to rebuild them because they are awesome saws. Thanks in advance.

 

[JWMUSTANGMAN]

 

[Seedling345]

Not my area but maybe get a hone for your drill and hone it but idk man

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[brad ruch]

Was this a cheaper kit?

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[brad ruch]

Also did you run it wide open rigjt away?they usally need a little break in.always wipe 2 stroke oil inside the cylinder when putting back together. Also if it was running to lean being new.it would get pretty hot.

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[backhoelover]

did you pressure and vac test after you rebuilt the engine

 

[backhoelover]

Also did you run it wide open rigjt away?they usally need a little break in.always wipe 2 stroke oil inside the cylinder when putting back together. Also if it was running to lean being new.it would get pretty hot.

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2 cycle run cooler at higher rpm and hotter at lower. when breaking in a saw i keep them from idling as much as possible and i dont put them under heavy load until after about 3 tanks

 

[backhoelover]

its not a cheap kit you can tell by the oil lines in the piston, look to be very good kit

 

[backhoelover]

now the cylinder that is a different answer. ports are not very clean. do you have a pic of the plug

 

[backhoelover]

white is lean, dark tan is good

 

[log_jammer]

I'm gonna go out on a limb here and say that your saw developed an air leak. You then replaced the damaged parts, but did not fix what caused the failure. Crank seals are pretty cheap insurance.

 

[JWMUSTANGMAN]

Was this a cheaper kit?

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Yea unfortunately. It was Russo I think. The box says farmer tech.

 

[JWMUSTANGMAN]

Also did you run it wide open rigjt away?they usally need a little break in.always wipe 2 stroke oil inside the cylinder when putting back together. Also if it was running to lean being new.it would get pretty hot.

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I was careful not to run it wide open for about 5 min. Maybe not long enough. What is the proper break in procedure? Mine has to be wide open at half choke. It won't come off full throttle til you bump the trigger and choke comes off.

 

[JWMUSTANGMAN]

did you pressure and vac test after you rebuilt the engine

No I did not. Everything went back together really nice tho. I did put the oil inside when assembling and everything was squeaky clean. I was careful about that. It started right up on like the 2nd or 3rd pull. It acted great for the first 10 min. I did some lite trimming and then cut about a 20" hardwood log. After that cut it went back to idle for a few seconds just fine, then died. It wouldn't pull so I figured it had locked up. It had. I had to tap the piston out with a dowel Rod.

 

[JWMUSTANGMAN]

2 cycle run cooler at higher rpm and hotter at lower. when breaking in a saw i keep them from idling as much as possible and i dont put them under heavy load until after about 3 tanks

So how do you break one in? Just run it high throttle without cutting for a few tanks of fuel?

 

[JWMUSTANGMAN]

its not a cheap kit you can tell by the oil lines in the piston, look to be very good kit

I read some reviews on the kit before I bought it. Several said they had good luck with it. It was sold as a "Russo" brand, but it says farmer tech on the box.

 

[JWMUSTANGMAN]

now the cylinder that is a different answer. ports are not very clean. do you have a pic of the plug

It was a new plug when I started.

 

[JWMUSTANGMAN]

I'm gonna go out on a limb here and say that your saw developed an air leak. You then replaced the damaged parts, but did not fix what caused the failure. Crank seals are pretty cheap insurance.

How do I test this theory?

 

[JWMUSTANGMAN]

I just thought of this. I couldn't find the stock 52mm kit, so I got the 54mm overbore. Is that relevant?

 

[log_jammer]

How do I test this theory

I'd say it's just a simple question. Did you replace the crank seals when the saw originally failed? I reread your original post and did not see them listed. I'd say if you still had an air leak, it would run about ten minutes before locking up. Don't ask me how I know. I've done the same. Also, I don't think it's the Farmertech kit, or the big bore.