Dolmar ps 421 (bogging)

[mkinslow]

Hey boys. I just rebuilt the carburetor on my Dolmar ps-421. I rebuilt it because it was bogging in the cut. After rebuilt I reinstalled carb and adjusted one turn out on needles and started saw. It would idle fine but would bog at full throttle. Played with adjustments and ended up with 1.5 out on low side and 2.25 out on high side. Also I did the muffler mod on this saw also about a month back. I may be wrong but something doesn't seem right. What's yalls opinions boys.

 

[TBS]

Take a look at the fuel line coming from the tank. The line could be partially collapsed or have a hole in it.

 

[mkinslow]

Take a look at the fuel line coming from the tank. The line could be partially collapsed or have a hole in it.

Was thinking that also. But I got frustrated with it and locked up the shop and called it a night. Should have went ahead and got some lines anyway. Cutting corners doesn't always pay

 

[dugide]

the base settings are 1 1/2 and 3 with limiter caps removed. the bog probably is hitting the limiter.

 

[mkinslow]

the base settings are 1 1/2 and 3 with limiter caps removed. the bog probably is hitting the limiter.

Caps are removed. That was done when MMwas done. It four strokes at 1.5 and 2.5. But has difinite bog at 1 and 1. Just think it's strange to need to be out that far before it started acting right. Just don't seem right to me . I can hear the four stroking in two strokes. It's very plane to me

 

[Ozhoo]

the base settings are 1 1/2 and 3 with limiter caps removed. the bog probably is hitting the limiter.

I'm showing 2 1/4

 

[TBS]

Caps are removed. That was done when MMwas done. It four strokes at 1.5 and 2.5. But has difinite bog at 1 and 1. Just think it's strange to need to be out that far before it started acting right. Just don't seem right to me . I can hear the four stroking in two strokes. It's very plane to me

The thread type on the adjustment screws determines the number of turns and that varies between manufacturers.

 

[mkinslow]

The thread type on the adjustment screws determines the number of turns and that varies between manufacturers.

Yep you're right brother. I didn't think about that. I remember hearing about that from someone a few years ago. But I'm pretty sure this is the first time I've run across it so that's probably why it threw me off like it did. Thanks

 

[mountainlake]

Open the high until its really blubbering then gradually back in until it cuts the best. You could be up against the rev limiter which sounds a lot like 4 stroking, just the fact that it bogs easy makes me think its lean.. Keep in mind with the EPA the recommended settings are going to be lean. Steve

 

[pro94lt]

Did you check the compression

 

[Ozhoo]

To complicate things, that DM23 has an accelerator pump. Pretty sure they're the problem for most of the worlds strife and unrest.

 

[Chris-PA]

I like the idea of an accelerator pump, but the way Walbro and Zama make them is a cheap and stupid design. The pot metal casting is not hard enough for the bore and the throttle shaft flat puts side thrust on the piston, pretty much ensuring the bore will wear/gall. That said, I have several carbs that have them and have no issues at all (yet). I'd bet that 421 doesn't have enough hours on it for the pump to wear out yet, but who knows?

 

[mkinslow]

Did you check the compression

Compression is 180

 

[mkinslow]

I like the idea of an accelerator pump, but the way Walbro and Zama make them is a cheap and stupid design. The pot metal casting is not hard enough for the bore and the throttle shaft flat puts side thrust on the piston, pretty much ensuring the bore will wear/gall. That said, I have several carbs that have them and have no issues at all (yet). I'd bet that 421 doesn't have enough hours on it for the pump to wear out yet, but who knows?

It had three tanks through it when I bought it off CL

 

[mkinslow]

the base settings are 1 1/2 and 3 with limiter caps removed. the bog probably is hitting the limiter.

Readjusted starting with this and is much better now. Thank you sir for your help

 

[swenny]

question for you guys, i recently did the muffler mod also and i'm having trouble getting the hi/lo setting right, when setting do you bottom out both hi/lo counter clockwise than back off desired turns 1.5-2.5

 

[Ozhoo]

... do you bottom out both hi/lo counter clockwise than back off desired turns 1.5-2.5

Yes, just be gentle when you bottom them out. Don't worry about the high side till you get a stable low side.

 

[mkinslow]

question for you guys, i recently did the muffler mod also and i'm having trouble getting the hi/lo setting right, when setting do you bottom out both hi/lo counter clockwise than back off desired turns 1.5-2.5

It worked for me brother. Good luck