Stihl 084 Project

[jmester]

So I am going to get my 084 powder coated by Mike. While tearing the saw down I found this mark on the exhaust skirt. Trying to figure out what is going on. It doesn't look like transfer to me.

I should say this cylinder was reused from when i got the saw. Someone put a new piston and cylinder on it but didn't fix the air leak. It caught a ring and tore up the floor of the exhaust port. I cleaned up the floor and beveled it.

Let me know your thoughts.

 

[Agent Smith]

Just my thought but almost looks like a tight spot between the piston and cylinder wall. When the ring hung, it may have distorted a little section of cylinder wall and the piston is riding on a high spot. Check the exhaust roof. The problem looks to be up there somewhere.

 

[jacob j.]

You might want to do some hand-sanding around the exhaust port. If I re-bevel a port, I hand sand it to make sure I've not left any high spots.

 

[jmester]

Thanks for the feedback. It crossed my mind about a high spot. I will go back over the port and bevel. At least it didn't trash the piston.

 

[Redfin]

Slide a ring up the ex floor. Check to make sure you have no daylight under it.

 

[Wood Doctor]

Seems to me that a very small chunk of metal about the size of a pinhead could have caused this. It likely blew out the exhaust and is gone forever. I just had this happen to a 660 and it left the same mark on the piston and cylinder. I did some honing as best as I could. After re-assembly, engine seems to run fine now with 150 psi compression. (Knock on wood)

 

[jmester]

I dont see any day light. But i am still going to go over the bevel again just to be sure.

 

[jmester]

Got my case halves,recoil and sprocket covers ready to send out to @Glock37 for some powder.

 

[jmester]

Evened up the exhaust floor. Went over the bevel and sanded the bevel.

 

[drf256]

What did you use to rebevel? I use diamond balls, I feel they work the best. A small round stone can work as well.

Do you have another bad piston, or anything cheap that fits that bore size? Sometimes I’ll lube the bore up with some light oil and scotchbrite then clean the skirt of a cheap or bad slug. Slide up and down with pressure against port. You’ll find some grooves and scratches right away with that.

I know it sounds nuts, but you can also get some debris stuck there that will be spit out. I went through 3 oem slugs on an 036 once that has a bad large end crank bearing. Was about to toss the jug after 3 reworks of the ex port. The crank was spitting metal.

 

[jmester]

I just used the same burr I used to even up the port to bevel. Then I used sandpaper to sand to bevel. I will say this that I will sand bevels from here on out they are super smooth and make a nice transition.

I do not have any bad pistons. You can almost check and see if you have any high spots with your method above.

I am beginning to think it was a small piece of metal as more than one person has alluded to that.

 

[jmester]

Worked out a trade with @K Mueller on a filter base and filter cover that matches my cylinder shroud better.

 

[jmester]

Got my muffler mod done. I have been on a pipe style mod for a while. Like the look of them. The spring clamp holds the spark screen well.

 

[jmester]

Had some time to get my handlebar polished up. Seems like vanity and probably is. It does look nice. Used mothers PowerCone and mothers aluminum polish. First pic is half done second is finished up.

 

[jacob j.]

Very nice Mr. J - this saw is going to be a dandy once you're done with it.

 

[jmester]

Thank you sir. Means alot coming from you.

 

[jmester]

Got the carburetor rebuilt. Inlet screen had a white film over it from ethanol and the pump diaphragm was stiff.


I also used the hydrogen peroxide method to try and clean up the plastics. Product I used was salon care 40. It worked better on a 361 tank that i did back in the summer. The sunshine and warmth seem to work better.

 

[jmester]

Definitely not new looking. But better than what it was. Not making a shelf queen but a nice clean work saw.

 

[smokey7]

I hope your carb has a fixed auxiliary high speed jet since you have 1/4 turn high setting.

 

[jmester]

Carb is a Tillotson HT-2.
I think the HT-5 and HT-7 when the carbs went to 1 and 1 on the high and low speed.