Stihl MS290 problems

[Aledafis]

Hi, I'm new here, and hope that you can help me.

 

I bought a Stihl MS290 fom ebay to cut up some wood for my woodturning hobby and am having some trouble getting it running as it should. I've adjusted the carb so that it runs nicely when cold, but after cutting for no more than a few minutes the saw looses its power badly, so much so that the chain stops turning and eventually stalls in the cut.

 

The saw is used, and the cylinder bore and piston shows some scoring, but I had hoped that it would work well enough for some intermittent work as and when I needed a few blanks cutting. Is it worth me getting hold of a carb kit to try out first before I go about any further surjery.

 

Any help would be most appreciated.

 

Thanks in advance

Aled

[wisecobandit]

First check the fuel line and filter to make sure its not gone soft.

Second check the impulse line and rubber inlet manifold for ant signs of splits or tears.

Then as you suggest a carb strip and maybe new gasket kit, you may find its just a blocked mesh filter in the carb that's blocks as soon as it starts pulling more fuel thru under load.

If you have a compression tester that's suitable for 2 strokes see what compression you have. I take it you have removed the exhaust to see the scoring?

[spudulike]

Lets take the muffler off and take a picture of this scoring so we can see its extent.

 

It sounds like the saw has enough compression when cold but when it gets warm, the compression drops a bit and power is lost - the hot metal thins the oil in the fuel and generally causes around 15psi drop in compression.

 

This isn't a problem on a saw running decent compression but on a scored cylinder, it will cause issues.

 

If you can measure the compression - anything 150psi or over is good.

 

If the saw has scores, the cylinder probably has aluminium transfer on the bore and scored piston and rings, the saw may well be able to be fixed but these saws are a bit of a mare to strip and repair:thumbdown:

 

Post a pickie please:thumbup:

[Aledafis]

Thanks for the quick replies. The fuel line looks good, but i've not looked at the impulse line yet. I'll order a carb kit to see whether that helps at all.

 

I'll take a pic of the bore tomorrow night and report back. Unfortunately I don't have a compression tester, but will ask around to see if anybody i know has one. I have a bad feeling that this may be the problem, and that's the reason why it was sold on ebay for a very reasonable price... In which case it's my fault as the seller was quite open in stating that the saw wasn't running perfectly, I took my chance that it was just a carb adjustment issue.

 

Here's hoping.

 

Aled

[spudulike]

Thanks for the quick replies. The fuel line looks good, but i've not looked at the impulse line yet. I'll order a carb kit to see whether that helps at all.

 

I'll take a pic of the bore tomorrow night and report back. Unfortunately I don't have a compression tester, but will ask around to see if anybody i know has one. I have a bad feeling that this may be the problem, and that's the reason why it was sold on ebay for a very reasonable price... In which case it's my fault as the seller was quite open in stating that the saw wasn't running perfectly, I took my chance that it was just a carb adjustment issue.

 

Here's hoping.

 

Aled

 

Personally I would get a view on the piston before clutching at straws on a new carb kit! If you do buy a carb kit, get it from Rowena Motors, crap website but email Hugo the saw details and ask him to send a paypal request, the kit will arrive in one or two days and cost under half of the Stihl kit plus it will be genuine Zama or Walbro.

 

I have had troublee with these carbs before and have had success in ultrasonically cleaning the carbs but look at the piston first - just what I would do:thumbup:

[Aledafis]

Dammit, I'm just too impatient, and have ordered one off ebay, less that a tenner though so it won't break the bank. I can see what you mean by that "crap" website, but I've bookmarked them for future reference.

 

I'll definitely take a pic of the piston/bore tomorrow night for you. Would it be a case of fitting new rings, or go the whole hog and go for a new piston/cylinder assy. (about £40 on ebay, non OEM of course).

 

Many Thanks

 

Aled

[spudulike]

My personal method would to be to clean the bore and if it isn't bad, would fit a new piston, preferably a Meteor one!

The Chinese quality can be hit or miss

[wisecobandit]

If it does need a piston and cylinder then you may want to upgrade to the 390 cylinder and piston. Its a straight swap and gives you a bit more oomph. Just make sure the carb gets retuned once fitted.

[Aledafis]

Sorry guys, I didn't have enough time tonight to take a pic (another hobble took president as it's needed for the weekend), but did manage to get hold of a compression tester, which gave me the bad news I was expecting - 120psi max. So it's going to be a new piston.

 

Where can I get hold of a Meteor piston Spud? I've had a look on the web, but can't seen to source one from the UK. The other option is to go for an ebay import, in which case, would it be worth going for the piston and cylinder combo for £36. I also assume that I'd need a new set of bearings and oil seals. The 390 piston/cylinder combos are about £55, is the difference in power worth the extra £20?

[spudulike]

Sorry guys, I didn't have enough time tonight to take a pic (another hobble took president as it's needed for the weekend), but did manage to get hold of a compression tester, which gave me the bad news I was expecting - 120psi max. So it's going to be a new piston.

 

Where can I get hold of a Meteor piston Spud? I've had a look on the web, but can't seen to source one from the UK. The other option is to go for an ebay import, in which case, would it be worth going for the piston and cylinder combo for £36. I also assume that I'd need a new set of bearings and oil seals. The 390 piston/cylinder combos are about £55, is the difference in power worth the extra £20?

 

The Greek fella "Leo" and MAx from Latvia off ebay are both good traders, had loads of pistons off Leo, best delivery 4 days from Greece, no complaints.

 

You will need to make sure the bore is clean before getting the piston.

 

The Chinese kits may give you a cheap option but rings can be fragile, circlips that can pop out and a piston to bore size that can be at best, iffy.

 

The choice is yours but I always try to salvage the original cylinder. They don't cost 8 times the price of the Chinese ones for no reason:001_rolleyes: