MS 290 Stihl help, new top end

[scoobydoo24219]

Hey everybody
I had another thread going earlier but can't find it. Anyway I ended up buying a new top end for a MS 290 from Bailey's. I got it installed and everything seems fine. It starts up but then quickly dies and I can't get it to run for long, though it continues to start up and run. I tried fiddling with the idle screw but can't seem to get it right. Any ideas. BTW I also decided to do a little muffler mod while I was at it. I drilled a hold through the middle to get directly to the port and opened up the covers opening a little too, not too much of a mod but something to keep in mind. Please start throwing me ideas, I just spend a lot of time (and money) on this thing and it seems so close.

 

[H 2 H]

Did you do anything to the carb ?

Turn both the H and L screw out 1 1/2 turns out from being seated and try that and adjust from their

 

[038mag]

Hey everybody
I had another thread going earlier but can't find it. Anyway I ended up buying a new top end for a MS 290 from Bailey's. I got it installed and everything seems fine. It starts up but then quickly dies and I can't get it to run for long, though it continues to start up and run. I tried fiddling with the idle screw but can't seem to get it right. Any ideas. BTW I also decided to do a little muffler mod while I was at it. I drilled a hold through the middle to get directly to the port and opened up the covers opening a little too, not too much of a mod but something to keep in mind. Please start throwing me ideas, I just spend a lot of time (and money) on this thing and it seems so close.

well i have been into alot of the 290 platform saws, 310, 390, 290 etc, and have found that if u do not seal the crank seals with a little sealant were the crank seal meets the two halves of the motor it will pull air right there and cause it to run rough, also did u change crank seals on your rebuild? i always put a little sealant on my finger and go around the whole crank seal were it touches the cylinder and pan, this assures a air tight seal. like i said in the corners by the seal were the two pieces come together is a must for a fat bead of sealant. i hope this helps

 

[nstueve]

I know this is kinda obvious but did you tighten your spark plug down? if you don't have enough compression the fuel will swap the cylinder and give you enough to start with a loose spark plug and then die when the fuel is burned up. I've done several dozen of these this summer alone and it's the small things you tend to forget... Also if the old fuel filter is clogged up you'll only pull enough fuel for it to run for a bit until it runs dry and dies.

Also I would suggest about 1 full turn out on each. You'll be really close with maybe a small adjustment on the H and L screws. If it doesn't start with a 1:1 on the carb you have something wrong.

If you used new oil seals you should be fine as long as you put a nice thin coat of sealant down to seal the clam shells back up.

Did you check the fuel and impulse lines for cracks? I usually use my mightyvac to leak check the fuel lines to make sure they don't leak.

Also hope you checked spark and have the ign system sparking? I have had the woodruff key break off the flywheel before and then not allow proper timing without marking the flywheel location before seating and bolting it down.

 

[sefh3]

Did you buy a 290 cylinder or a 390 kit?

Check your fuel line. They are known to crack. More than likely this is what caused your saw to lean out and seize the saw.

 

[scoobydoo24219]

OK so top end came in one piece, so I didn't have to deal with any of that. I tried turning the H and L screws but they only have 1 turn in them (is that weird?). Otherwise when she starts up, before I give her any throttle, she revs up and then dies, on her own. I've heard two strokes can do this when they run on fumes, so maybe I have a fuel line issue? I didn't put new ones in when I replaced the top end because I checked them over and they looked good, no cracks. Any ideas? New lines?

PS I did clean the carb with some carb cleaner when it was out

 

[scoobydoo24219]

did buy the 390 kit but also did close compression

 

[sefh3]

Check fuel line and impulse line for cracks.

 

[nstueve]

OK so top end came in one piece, so I didn't have to deal with any of that. I tried turning the H and L screws but they only have 1 turn in them (is that weird?). Otherwise when she starts up, before I give her any throttle, she revs up and then dies, on her own. I've heard two strokes can do this when they run on fumes, so maybe I have a fuel line issue? I didn't put new ones in when I replaced the top end because I checked them over and they looked good, no cracks. Any ideas? New lines?

PS I did clean the carb with some carb cleaner when it was out

Any time I've done one of these farmboss's I have ALWAYS replaced the fuel and impulse if they were good or not. You are usually on borrowed time with stihl rubber lines. I actually take the impulse and fuel line out, cut the grommets out of the old lines and use my dremel to hollow the grommets out. then I replace the rubber line with tygon. easier to replace down the road. Was the old top end torched? If so there was a leak somewhere on the saw before swapping the top end and it usually doesn't come from the oil seals...90% of these saws torch themselves due to limiter caps, being strait fueled, or cracked fuel lines.

Speaking of which did you take the red limiter caps out of the carb?????? You have to take them out to be able to screw them in all the way clockwise until seated and then 360* back out.

did buy the 390 kit but also did close compression

you bought the proper plug for the compression seal off?

 

[CREC_Sawyer]

Call me a pessimist but it sounds like an air leak to me, had something very similar happen on a rebuild I did.
I would do a comp/vacuum test and see what that tells you if you haven't already.
Good luck

 

[blsnelling]

While they do come assembled, it's been mentioned several times that in no way are they properly sealed and ready for use.

 

[Andyshine77]

Brad is correct!! they are not sealed properly. Why they sell them this way is beyond me. I'm sure many unknowing customers have fried saws, because they thought the top end was ready to go out of the box. You will have to disassemble the saw and engine block to seal it up properly.

 

[H 2 H]

If it's sealed right sure sounds like the H and L screws are not opened up enough to me IMO

 

[scoobydoo24219]

Ok everyone thanks for all the input. The thing appeared to be sealed correctly but I have no way of doing a vacuum test to be sure. Before I tear the whole thing down again I will take the limiter caps off the H and L and turn those a bit more and once again check my fuel line. Next question is if I have to seal it better what are my steps?

Also the last top end was torched, unknown reasons (this is not my saw) but it appears that someone put straight fuel in it.

 

[H 2 H]

Ok everyone thanks for all the input. The thing appeared to be sealed correctly but I have no way of doing a vacuum test to be sure. Before I tear the whole thing down again I will take the limiter caps off the H and L and turn those a bit more and once again check my fuel line. Next question is if I have to seal it better what are my steps?

Also the last top end was torched, unknown reasons (this is not my saw) but it appears that someone put straight fuel in it.

Remember that there is plastic surrounds both screws

You have to pull both screws all the way out to get all the plastic off of them

 

[scoobydoo24219]

Ok took the red limiter caps off and still no go, maybe I need to toy with them more but here is what is happening. The saw starts everytime. Then it revs itself up and dies. Sometimes if I reach quick enough and hit the throttle it goes and works just fine, but as soon as I lay off it it dies again. I am going to assume that Bailey's sealed its product correctly at this point and I suppose my next step is to do some line replacing unless anyone else has some suggestions?

to recap it does start just fine, but revs herself up on own then shuts off....

 

[Andyshine77]

By all means try and tune the saw properly, buy a leak test is still a must with these top ends.They all looked sealed, but that means nothing, IMHO you have to perform a leak/pressure test, and their is no way around it. If you have an air compressor and regulator you can set to 5psi, all you really need is some inner tube rubber. Cut a piece of rubber the size of the exhaust flange, punch holes in the rubber for the mounting screws, than tighten the can down. Install the intake boot and boot mount, then use the carb in the same fashion as the exhaust can. Hookup the the air nozzle to the impulse line and pressurize the case, "make sure the spark plug is in as well". Spray soapy water around the base of the cylinder and seals, if you see air bubbles that's your leak.

I've also seen the seals not seated properly on these top end kits, so you may need to seat them properly.

 

[Andyshine77]

Ok took the red limiter caps off and still no go, maybe I need to toy with them more but here is what is happening. The saw starts everytime. Then it revs itself up and dies. Sometimes if I reach quick enough and hit the throttle it goes and works just fine, but as soon as I lay off it it dies again. I am going to assume that Bailey's sealed its product correctly at this point and I suppose my next step is to do some line replacing unless anyone else has some suggestions?

to recap it does start just fine, but revs herself up on own then shuts off....

It's not sealed!! that's a classic air leak symptom. You can't assume you don't have a leak, it doesn't work that way.

 

[griffonks]

The Bailey's 390 kit comes in two choices. Assembled, sealed and tested OR un-assembled.

The un-assembled kit looks assembled. Please verify which kit you bought.

If you bought an assembled kit and it's leaking call Bailey's and ask for Jennifer.

 

[scoobydoo24219]

Gotter working. Just needed to rebuild the carb. Thanks for all the help, the muf mod I discovered from this site is working great too. Stand by for next saw advice question....