Stihl MS361 help for a newbie

[chopchop]

Yeah, I agree. Has farmertec written all over it (not literally. Would have passed it by!).

 

So..what to do now? Obviously not going to throw money at it but it's still a saw for £40. Worth getting it running I guess as no other option. Will pressure test later when gauge arrives. Thank you

[pleasant]

Put it back together, take it a boot fair ask £100 quid for it and take 80 quid. Youve doubled your money and got out of it.

[Muddy42]

I agree, the MS 360 writing looks totally wrong.  I guess you now have to decide whether to give up, persevere with the diagnostics or even spend money on the thing.

 

As a separate point, you can buy a small bolt to replace the decomp valve fairly cheaply.  This bolt is quite useful to have because you can put it on any stihl to quickly diagnose issues with the valve (or while you order a replacement).

 

I'd get the cylinder back on, pressure and vac test. I don't like the look of that seal, has it been rubbing on the flywheel?  Assuming that's OK focus on getting the flywheel fitting properly with the right timing. Quality of spark/timing and flywheels are not my special subject (!) so I have a friend who looks at these aspects for me!

[chopchop]

The seal? Do you mean the cylinder gasket Muddy42? Flywheel reattached now. No obvious issue with the flywheel key or slippage. Not sure how to check timing (don't have a timing light) but will search on here. Thank you

[pleasant]

They are referring to the crank seal behind the flywheel. Timing is fixed by the woodruff key on the end of the crank....or the cast keyway in the alloy flywheel. Either way if the key is in place and undamaged, your timing will be fine. You don"t need a timing light.

[ChrisNewport]

If you look at the pic of the flywheel you can see red on the boss which has come off the crankseal, the flywheel shouldnt be touching this seal. Either the seal hasnt been tapped in far enough or the flywheel is oversize.

 

It shouldnt take much to get it going, as you say it flooded. It needs a good pull over upside down with the plug out.

 

[chopchop]

45 minutes ago, ChrisNewport said:

If you look at the pic of the flywheel you can see red on the boss which has come off the crankseal, the flywheel shouldnt be touching this seal. Either the seal hasnt been tapped in far enough or the flywheel is oversize.

 

It shouldnt take much to get it going, as you say it flooded. It needs a good pull over upside down with the plug out.

 

Thank you both. The crankseal might explain the shameful 60psi it just managed eh? Looking like a full strip down I suppose...

[Muddy42]

5 minutes ago, chopchop said:

Thank you both. The crankseal might explain the shameful 60psi it just managed eh? Looking like a full strip down I suppose...

Yes I was referring to the fact that it looked like the flywheel had been rubbing on the crankseal.  I am no expert but if that happens too much it could cause the seal to fail and an air leak in the crankcase.  To test that you need to do a vacuum/pressure test.  This is different from a compression test, which is what I think you have performed? Ideally I'd want to do both.  Plenty of help available on youtube.

 

- A vacuum pressure test tests the integrity of the whole crankcase, after blocking the exhaust and intake ports.  If its letting in/out air, the tuning will be variable and you could cause the saw to run lean and hot.

- A compression test, checks how much compression is generated, only in the smaller space above the piston.

 

Yes 60 psi isn't enough compression.  Have you ruled out the decomp valve and spark plug hole?  Try pumping air into one of these and apply soapy water around the other, bubbles will form if there is an issue. As said before, the decomp valve can be stripped, cleaned and reapplied with grease.  But also plugged with a blank nut.  Did the piston and rings fit snuggly into the cylinder? The rings should have some springiness to them. Were there any marks or roughness on the cylinder or piston?  I guess there could be a fundamental issue with the cylinder - the transfer ports in the wrong location etc.

 

  

[ChrisNewport]

Have you got a compression gauge with a schrader valve fitted or a standard one for 4 strokes without a schrader valve? 

[Stubby]

2 hours ago, chopchop said:

Thank you both. The crankseal might explain the shameful 60psi it just managed eh? Looking like a full strip down I suppose...

It may well be more than 60psi .If you are not using the correct compression tester for a single cylinder 2t engine it will read low . just a point .