Dolmar ps420 starts then bogs

[67x]

Saw sat for a year. Put fresh gas in it and got it started. It will start and idle but when I try to increase the throttle it bogs. Sometimes I'm able to achieve higher rpm's. I replaced the fuel line from tank to primer and the one from carb back to tank. The line from primer to carb is a bit smaller and my local shop doesn't have this size line. I'd like to check the line in the tank with filter, but I'm not 100% sure how it comes out. Any thoughts? Thanks

 

[merc_man]

Was saw stores with fuel?

Im guessing carb

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[CoreyB]

Ya carb. Debris, hard diaphragm, ECT.

 

[67x]

Was saw stores with fuel?

Im guessing carb

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Yes, the saw was put away with fuel in it. I drained the old fuel, then topped off with fresh fuel. Saw didn't want to run. I bypassed the primer and she fired right up. I ran the saw for an hour (cut a few downed limbs), then let it sit till the next weekend. That brings me to now. I originally thought primer bulb was bad, but with it bypassed it runs the same way. I went ahead and replaced the two fuel lines I mentioned above and no change. I was just wondering if the line inside the tank could be cracked and sucking air? I'm going to pull the saw apart tonight and may pull the carb and just go through everything. My concern was with the fittings on top of the gas tank. It's all plastic and I don't want to crack anything. Wasn't quite sure how that tank line came out.

 

[Finnrpm]

...... this is from old stihl 07 barn find.......... back then this was the best kept secret.... wood dust fuel filter!!!!

My vote is for the carb.
RV

Last minute edit.... Check that primer for right fuel line installation, should "suck" gas thru carburetor...

 

[67x]

...... this is from old stihl 07 barn find.......... back then this was the best kept secret.... wood dust fuel filter!!!!
View attachment 610290
My vote is for the carb.
RV

Last minute edit.... Check that primer for right fuel line installation, should "suck" gas thru carburetor...

my fuel filter definitely doesn't look like that! I double checked the fuel line orientation. I found an old thread that showed correct routing just to make sure I didn't have it wrong. I will check again when I get back to it tonight. I wasn't even drinking last night....hmm, maybe that's the problem!

 

[Finnrpm]

He was..........

 

[67x]

 

[merc_man]

If your storing for any period of time drain fuel and let idle till stalls.
Iv had saws sit for years with no isues by doing this.

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[grizz55chev]

If your storing for any period of time drain fuel and let idle till stalls.
Iv had saws sit for years with no isues by doing this.

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Doesn't really help the situation at hand to tell him what he should a done. My guess is a bad fuel line from the tank to the carb, store them with gas and they turn soft and mushy, restricting fuel on high demand. If that doesn't fix it take the carb off and look at the screen on the fuel inlet side of the carb, they like to plug with debris and again restrict fuel delivery. Just a few places to start looking, good luck!

 

[merc_man]

Doesn't really help the situation at hand to tell him what he should a done. My guess is a bad fuel line from the tank to the carb, store them with gas and they turn soft and mushy, restricting fuel on high demand. If that doesn't fix it take the carb off and look at the screen on the fuel inlet side of the carb, they like to plug with debris and again restrict fuel delivery. Just a few places to start looking, good luck!

No it dont help the situation. Just trying to help the OP to not have this happen again once he fixes the isue. Probobly carb related.

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[CoreyB]

Anytime one component of the fuel system fails. (Primer bulb) how far behind can the rest of the system be? When ever i mess with a fuel problem i replace all the componets. Overkill? Maybe. Not having to tear into 3 times replacing things that I already had my hands on. Worth it.

 

[67x]

I took the carb apart and cleaned everything with carb cleaner. Blasted all the holes, nooks and crannies. screen was clean and light passed through. Diaphragms were all pliable with no cracks/splits. put everything back together making sure everything went back as it was taken apart. put saw back together and filled fuel tank. It fired right up on choke. The second I took choke off it tried to rev up then die. I'm a little more confused now. I looked at the throttle linkage and it is operating correctly. nothing is binding and with finger off trigger it's returning to idle. I must've goofed something up. I'll pull carb off tomorrow and see what I might have done wrong.

 

[merc_man]

I took the carb apart and cleaned everything with carb cleaner. Blasted all the holes, nooks and crannies. screen was clean and light passed through. Diaphragms were all pliable with no cracks/splits. put everything back together making sure everything went back as it was taken apart. put saw back together and filled fuel tank. It fired right up on choke. The second I took choke off it tried to rev up then die. I'm a little more confused now. I looked at the throttle linkage and it is operating correctly. nothing is binding and with finger off trigger it's returning to idle. I must've goofed something up. I'll pull carb off tomorrow and see what I might have done wrong.

Did the diaphram feel nice and soft or kinda stiff. I would try a carb kit.

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[merc_man]

Did you happen to take any pics when you had it apart?

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[67x]

Did you happen to take any pics when you had it apart?

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No pics, I will tomorrow for sure. The diaphragm was very soft. Not stiff at all.

 

[grizz55chev]

I took the carb apart and cleaned everything with carb cleaner. Blasted all the holes, nooks and crannies. screen was clean and light passed through. Diaphragms were all pliable with no cracks/splits. put everything back together making sure everything went back as it was taken apart. put saw back together and filled fuel tank. It fired right up on choke. The second I took choke off it tried to rev up then die. I'm a little more confused now. I looked at the throttle linkage and it is operating correctly. nothing is binding and with finger off trigger it's returning to idle. I must've goofed something up. I'll pull carb off tomorrow and see what I might have done wrong.

If the carb adjustment screws still have their limiter tabs, cut the them off and open up the "H " side 1 half turn in the counter clockwise direction.

 

[67x]

Saw sat for a year. Put fresh gas in it and got it started. It will start and idle but when I try to increase the throttle it bogs. Sometimes I'm able to achieve higher rpm's. I replaced the fuel line from tank to primer and the one from carb back to tank. The line from primer to carb is a bit smaller and my local shop doesn't have this size line. I'd like to check the line in the tank with filter, but I'm not 100% sure how it comes out. Any thoughts? Thanks

If the carb adjustment screws still have their limiter tabs, cut the them off and open up the "H " side 1 half turn in the counter clockwise direction.

Update: I pulled everything apart and the only thing I noticed is the plate on the bottom of the carb(square with 4 bolts and drain? hole) may have been rotated 90 degrees. There's a little cutout under the carb (plastic case of saw) that has some foam that seals under the carb and around the hole for the lower carb cover. Everything looked good and I reassembled. Saw fired up and ran like my original post. So now I was back to square one. I turned the H screw in 3 turns( it didn't bottom out) then backed it out 3 1/2 turns. Saw didn't want to start at first. I choked it, pulled once, then took it off choke. It started and ran on high idle until I hit the throttle. It took the gas and sounded good. Let off throttle and it wouldn't idle. increased idle speed so it would idle and made 2 cuts. Ran good sounded good. Now i just need to tune it b/c I have no idea where it is.

 

[grizz55chev]

Update: I pulled everything apart and the only thing I noticed is the plate on the bottom of the carb(square with 4 bolts and drain? hole) may have been rotated 90 degrees. There's a little cutout under the carb (plastic case of saw) that has some foam that seals under the carb and around the hole for the lower carb cover. Everything looked good and I reassembled. Saw fired up and ran like my original post. So now I was back to square one. I turned the H screw in 3 turns( it didn't bottom out) then backed it out 3 1/2 turns. Saw didn't want to start at first. I choked it, pulled once, then took it off choke. It started and ran on high idle until I hit the throttle. It took the gas and sounded good. Let off throttle and it wouldn't idle. increased idle speed so it would idle and made 2 cuts. Ran good sounded good. Now i just need to tune it b/c I have no idea where it is.

Lotsa posts on tuning, let your fingers do the walking.