MS290 Carb spitting out fuel

[JP56]

Here we go again with my STIHL MS290! Was cutting up downed trees after the storm that hit here 2 weeks ago. Saw began bogging down & stalling. Checked filter, clean. Fuel good. Got it running again & tried to tweak the carb settings. Stalled and died, couldn't restart. Pulled carb, cleaned and rebuilt it put it back on, and could only get it to run on 1/2 choke setting and it was screaming like WOT +.

Just put on a brand new carb right out of the box, get it started on 1/2 choke, tap trigger, kicks choke off, idles a bit, blip trigger to WOT, it sprays fuel out the carb all over, let trigger go, it stalls and dies. Now hard to restart and keep running!

What could be causing this? I really need to be pointed in the right direction here.

Time for a tear down again to test for air leaks? Desperate here for answers. Did a complete tear-down, & cleaning awhile back, new seals, new carb and fuel lines & filter, and vac & pressure tests all passed. Also checked the ignition gap before disassembly, because from day 1 it was a horror to start cold, & found that was off, so reset that as well, then it would always start on 3 pulls or less, and all was well for awhile. Now THIS!!!!!! I really have had it with this boat anchor, a real turd since the day I bought it home brand new!

I really would love to replace it but just can't afford to right now, so I would also like any opinions on the ECHO CS490

 

[Crispexx]

Hows the spark arrestor look?

 

[user 122190]

Hows the spark arrestor look?

A good regular maintenance item. I hadn't looked at mine for years. I did so a couple of week ago and everything looks perfect, arrestor screen, piston&rings, etc. This ms290 really impresses me. Coughed into starting after one pull after I finished reinstalling the muffler.

 

[JP56]

I'll give it another check, but last time I looked at it, it was black from heat but little to no carbon build up, I could see light right through it. I was just out trying it again, and I can actually get it to start on full choke after one or 2 pulls, (as opposed to getting that little popping sound), & naturally it stalls right out after it starts, then I flip it to 1/2 choke and it starts on 1 or 2 pulls, but it screams like I am running it at WOT, with a fine fuel spray coming out of the carb, and as soon as I pull the trigger, it stops spraying the fuel, and if I pull the trigger and pop the choke to the run position it runs at WOT, but as soon as I release the trigger it idles down to a semi normal idle and then just dies.

I saw a video yesterday, (I think it was posted here someplace) of a guy using brake cleaner spray on a saw that wouldn't run right, as soon as he hit the seals with the spray on either side of the saw it would instantly die, and he said that it was common on that brand of saw (can't remember if they were Husqvarnas?) for the seals to leak and cause them to run really bad or not at all, so I tried that on both sides of mine on both sides, while it was screaming on 1/2 choke and it died instantly. So, if that is a good or true test for leaking seals on other brands, I am guessing that my new seals may have failed for some reason after about 3 hours run time, and they were not 3 hours straight either but split up.

I am just a home owner, not a woodsman or arborist, so it's not like this thing has a lot of hours on it since I got it around 2006, but I did have to change the seals on it once already. It cuts like crazy when it starts and runs right but what a pain in my A it has been since I got it & it is a pain in the A to do the dam disassembly/ reassembly on it to boot, especially the brake spring!

 

[rupedoggy]

Since I build and run a lot of saws I am asked which brand is the best, Stihl? I can't answer until I know the usage, experience and most importantly the model.

 

[HarleyT]

Look at the fuel line carefully, and take the carb off and look at the piston condition on the intake side.

 

[RED-85-Z51]

Spitback isnt abnormal at high rpms...fuel and air is rushing in and the piston abruptly blocks it and it reverberates back out...i see it alot when the tune is rich

Sent from my LM-G820 using Tapatalk

 

[JP56]

Look at the fuel line carefully, and take the carb off and look at the piston condition on the intake side.

Harley, you have been such a great source and help to me since I made my very first post here about this turd I bought! I was afraid I would hear something like this from someone! This thing is such a pain in the A to take apart & put back together

What exactly will I be looking for on the cylinder or fuel lines? I did put new fuel lines in it already. Any chance a pinhole or split in one of the lines causing this? As to the intake on the cylinder, am I looking for grooves or bad rings?

 

[HarleyT]

Harley, you have been such a great source and help to me since I made my very first post here about this turd I bought! I was afraid I would hear something like this from someone! This thing is such a pain in the A to take apart & put back together

What exactly will I be looking for on the cylinder or fuel lines? I did put new fuel lines in it already. Any chance a pinhole or split in one of the lines causing this? As to the intake on the cylinder, am I looking for grooves or bad rings?

You won't see the rings from that view, but may likely see piston damage from dirt ingestion. It would explain the symptoms.

 

[JP56]

Look at the fuel line carefully, and take the carb off and look at the piston condition on the intake side.

Harley, You sure use the right picture on here cause you really are a dog, with that teaser hint you gave me .I went back to it very saddened to have to pull that SOB apart yet again, so I start on the carb side and can only see the pretty little shiny perfect piston. So I figure OK, lets get the entire handle & intake engine cover off it so I can get a really good look at it, and there I find my PROBLEM before I even get the cover all the way off! That stupid rubber boot from the the Carb to the intake was completely open right around the edge of the intake nipple after the clamp, from 9 o'clock over to 3 o'clock!After I stopped laughing, all I could think was that Harley really is a dog giving me a mysterious clue instead of just saying "check the intake boot". Made my day, so thank you! Funny thing is, I had already bought one of the boots to keep as a spare the last time I had it apart, because I kept reading how that seems to be a very common problem on these things with the boots cracking or tearing. Now, can you tell me why my oil "adjustable" pump can't adjust and is leaking all over the dang place? Is there an O-ring rebuild kit for that? I can't find a part number for the service kit or the oil pump itself and you have that Gold Mine of STIHL info, if either number exists, I am sure you would know it! Thanks AGAIN Harley.

 

[HarleyT]

Harley, You sure use the right picture on here cause you really are a dog, with that teaser hint you gave me .I went back to it very saddened to have to pull that SOB apart yet again, so I start on the carb side and can only see the pretty little shiny perfect piston. So I figure OK, lets get the entire handle & intake engine cover off it so I can get a really good look at it, and there I find my PROBLEM before I even get the cover all the way off! That stupid rubber boot from the the Carb to the intake was completely open right around the edge of the intake nipple after the clamp, from 9 o'clock over to 3 o'clock!After I stooped laughing, all I could think was that Harley really is a dog giving me a mysterious clue instead of just saying "check the intake boot". Made my day, so thank you! Funny thing is, I had already bought one of the boots to keep as a spare the last time I had it apart, because I kept reading how that seems to be a very common problem on these things with the boots cracking or tearing. Now, can you tell me why my oil "adjustable" pump can't adjust and is leaking all over the dang place? Is there an O-ring rebuild kit for that? I can't find a part number for the service kit or the oil pump itself and you have that Gold Mine of STIHL info, if either number exists, I am sure you would know it! Thanks AGAIN Harley.

 

[HarleyT]

Here is more... of the part numbers list..

 

[JP56]

You ARE the MAN Harley !!!!

 

[farmguywithasaw]

Just so you know there are two types of crank seals hard ones which you have to split the bottom end to put in. Soft ones that can be put in without a complete tear down

 

[HarleyT]

Like this...

 

[JP56]

Just so you know there are two types of crank seals hard ones which you have to split the bottom end to put in. Soft ones that can be put in without a complete tear down

Thanks, but I already knew that from Harley way back when I first started looking into why this thing was such a turd. I also see that he re-posted it here now too. Back then, I did do a complete tear down and put the hard ones in. With my current starting/running problem, my money is riding on the split intake boot I found yesterday!

 

[HarleyT]

I did do a complete tear down and put the hard ones in.

Good advice for many things...