What happened to my MS390?

[a. palmer jr.]

Did a rebuild on a MS290 using a 390 kit. These have always turned out pretty good for me, just put it together, prime it and start it the first time. Except this time I couldn't get it to run but just a little while and now it seems to not have as much compression. I primed it with fuel mix that I use in my other saws so I don't know why this one turned out like it did..Even if I had straight gassed it the saw only ran for about 2 seconds, probably not enough to damage it.

 

[cuinrearview]

Chinese kit?

 

[a. palmer jr.]

Yes, Chinese kit. I've had pretty good luck with them in the past but that may be what it was..The first time I tried it it pulled the rope out of my hand about like starting an 044 but now it's easy to pull..

 

[cuinrearview]

"You no get round piston and cylinder round eye".

 

[lone wolf]

"You no get round piston and cylinder round eye".

 

[Tom B.]

When you pull it can you hear escaping air? Much like I can on the MS270 through the decompression valve.
Did you get interrupted when assembling it? A bolt or a few weren't completely tightened up & when it ran for a moment the pressure loosened them more?
From an outside point of view, third person sorta thing. ;-)

 

[cuinrearview]

Haha I said it in another thread today but it's happening here too. It must be your fault @a. palmer jr.

 

[a. palmer jr.]

When you pull it can you hear escaping air? Much like I can on the MS270 through the decompression valve.
Did you get interrupted when assembling it? A bolt or a few weren't completely tightened up & when it ran for a moment the pressure loosened them more?
From an outside point of view, third person sorta thing. ;-)

I put a plug in the hole where the de-comp valve should be and I know I got it tight. Just went out and checked the ignition module, thought maybe it quit but it was working. I didn't have any interruptions but I did quit several times, waiting on parts, etc.

 

[a. palmer jr.]

Haha I said it in another thread today but it's happening here too. It must be your fault @a. palmer jr.

Ya reckon? You asked earlier if it was a Chinese kit and I said yes but I just assumed it was. I bought it from a US vendor.

 

[dmb2613]

put some oil in the cylinder I never prime a new cylinder just pull it until fuel gets to the carburetor.

 

[HarleyT]

Ya reckon? You asked earlier if it was a Chinese kit and I said yes but I just assumed it was. I bought it from a US vendor.

It was a Chinese kit...

 

[pioneerguy600]

If it wasn`t bought through a Stihl dealer then it was most likely made in China. Is there any other manufacturers making aftermarket sets/engines etc.?

 

[cuinrearview]

Ya reckon? You asked earlier if it was a Chinese kit and I said yes but I just assumed it was. I bought it from a US vendor.

It's like my buddy always says "play stupid games, win stupid prizes". The Chinese make some parts consistently bad, and all parts bad inconsistently.

 

[HarleyT]

If it wasn`t bought through a Stihl dealer then it was most likely made in China. Is there any other manufacturers making aftermarket sets/engines etc.?

If it was a Stihl oem kit.
He wouldn't buy it!!!

 

[pioneerguy600]

Well I have measured some of their offerings, they never went into or on any of my saws except for a couple of outer orange body covers.

 

[HarleyT]

Yeah, having to drill the holes larger for the starter to fit on a saw,
doesn't instill much confidence on their quality.

 

[a. palmer jr.]

Not my saw...owner doesn't want to pay a Stihl price to get it fixed.

 

[a. palmer jr.]

If it wasn`t bought through a Stihl dealer then it was most likely made in China. Is there any other manufacturers making aftermarket sets/engines etc.?

Probably not for a homeowner saw. I don't know that the "brand" names weren't made in China. Stihl even gets some of their stuff from them, I hear...

 

[pioneerguy600]

The stuff Stihl has made in China is made to standards and put through quality controls. The cheap AM stuff certainly is not made with any standards and has zero quality control. The Chinese are more than capable of making precise components but with precision and strict quality control the price is much higher than the cheap stuff made by sub standard or on a sub standard production line. All this BS I keep on reading about Stihl parts coming from China so they must be on the same level as the sub standard AM parts is complete milarky . A clone is a clone, it could be made with the same standards as the big saw companies demand but the price would be much higher, for the cheap AM stuff out there there is no quality control, some work but much does not work or last.

 

[pioneerguy600]

Tolerances can be off between piston to cylinder clearance, ring end gap, squish is usually excessive but could possibly be too tight. Just about all clearances need to be checked at assembly time, port shapes can be ragged or too flat at the top of the exhaust port, rings catch, wrist pin circlips are thrown due to being too soft or having ears that break off. The quality control is terrible.