Carbs without hi speed adjustment screw. Do they work? EDIT: Possible solution for me.

[ANewSawyer]

I was at my local pawn shop looking at 2 cycle tools. They had a (can't spell the name) Muccullough, IIRC. Strange in that the spark plug was below the throttle trigger. But what caught my attention was an Echo SRM-210 trimmer/brushcutter. I have been looking for a brushcutter and this one would be cheap. But in doing research I discovered that the carb is supposed to not have an adjustable hi speed screw. Wouldn't that make it run wrong sometimes? Just because of changing conditions, I mean. You know changes in altitude and other things. I don't yet believe that the fixed hi speed is a good thing. I know that I have adjusted a couple of carbs and I just can't fathom how a fixed hi speed would be a good idea. But maybe you guys can comment on whether the fixed hi speed is a good thing. Or, as the case may be, a bad thing.

Thanks!

 

[old-cat]

NOT good!

 

[rich450es]

i throw them in the trash and find a fully adjustable carb (yes even a chincom carb is better )

 

[Duke Thieroff]

Fixed jet carbs can be a little rough if you live at extreme altitudes or if you expect the very most out of your equipment.

The vast majority of units sold with those carbs operate for years without issue but then you have guys like us who like to tweak things.

With that being said most guys chuck the fixed jet carbs for fully adjustable ones. Sometimes they can't be had and you can change the jets.

Grab up an IPL and see if you can order different jets if the piece of equipment doesn't run to your liking.

Chris

 

[fearofpavement]

I haven't had issues with anything I've had with a fixed jet carb although I'd rather have a fully adjustable carb.

 

[ANewSawyer]

Actually, in doing more research, it seems that there a plug over the high speed screw on some carbs. Info from this thread: http://www.arboristsite.com/community/threads/echo-trimmer-carb.135417/

And here is the parts list: http://www.ereplacementparts.com/ec...er-brushcutter-parts-c-35043_35180_35368.html Part number 10 is the magic number. I will go back and have a look Monday to see if it has one of the carbs with a plug.

 

[GrassGuerilla]

They run. But at 21cc a 210 is by no means an ideal brush cutter. It will likely last the rest of your natural life as a weekly grass trimmer. But the flex cable drive isn't well suited to brush cutter duty. Very, very dependable trimmer.

 

[XSKIER]

Every fixed jet carb engine I have runs quite well. It's the as knowitalls that seem to have a problem with them.

 

[woodeneye]

I have an srm-225. Came with plugs over the high and low adjustments. Easy fix-just find the smallest screwdriver you have and grind the shanks down so it's a very skinny flat screwdriver. Heat end with torch, insert into plug, let cool for a few seconds. Then twist the plugs out. Super easy.

 

[ANewSawyer]

They run. But at 21cc a 210 is by no means an ideal brush cutter. It will likely last the rest of your natural life as a weekly grass trimmer. But the flex cable drive isn't well suited to brush cutter duty. Very, very dependable trimmer.

I agree, solid shaft is better for cutting lots and lots of brush. I have blackberries and some small (less than 1/2 inch) woody overgrowth that I am trying to clear. But I am also on a budget and at least this trimmer can be converted to take a blade. But what you saying , even with the blades, I would wear the trimmer out cutting small stuff with it?

 

[heyduke]

i have a stihl fs250 string trimmer that i bought from my local stihl dealer. his tech had worked on the carb and couldn't get it right. what i finally figured out is that it has only one metering needle, actually more of a cylinder or rod, no taper, that is threaded backward, turn right to enrich and left to lean. after i figured that out it was easy to get it running very well. it's neither lo nor hi but controls the mixture across the entire range. the tech had also installed the throttle cable incorrectly so it would only open half way, sad state of affairs. dude must be blind.

 

[ANewSawyer]

i have a stihl fs250 string trimmer that i bought from my local stihl dealer. his tech had worked on the carb and couldn't get it right. what i finally figured out is that it has only one metering needle, actually more of a cylinder or rod, no taper, that is threaded backward, turn right to enrich and left to lean. after i figured that out it was easy to get it running very well. it's neither lo nor hi but controls the mixture across the entire range. the tech had also installed the throttle cable incorrectly so it would only open half way, sad state of affairs. dude must be blind.

I haven't liked any of my local dealers, that I have been, enough to use them. Some dealers are good and others are... not so good. My area seems to mostly have the later kind. I get great service from my local Lowe's though. So great that I, shame of shames, bought my Husqy 125B blower from them and did my own tune on the carb. I just wish it didn't have a catalytic converter in the muffler.

 

[Little Al]

Actually, in doing more research, it seems that there a plug over the high speed screw on some carbs. Info from this thread: http://www.arboristsite.com/community/threads/echo-trimmer-carb.135417/

And here is the parts list: http://www.ereplacementparts.com/ec...er-brushcutter-parts-c-35043_35180_35368.html Part number 10 is the magic number. I will go back and have a look Monday to see if it has one of the carbs with a plug.

The Echo Brushcutter I had, the carb fitted only had an idle speed adjustment screw no mixture adjustment needle screws. It ran fine for about 6 years but then started acting up & as a replacement carb was around 65euro's I moved it on for parts. Looking at the IPL the fitted carb has no external mixture adjustments

 

[ANewSawyer]

The Echo Brushcutter I had, the carb fitted only had an idle speed adjustment screw no mixture adjustment needle screws. It ran fine for about 6 years but then started acting up & as a replacement carb was around 65euro's I moved it on for parts. Looking at the IPL the fitted carb has no external mixture adjustments

I think it depends on the carburator. The one I linked to doesn't have a idle mixture adjustment screw, just the idle speed adjustment. But the carb I linked to does have a hidden high speed screw. BUT! The carb on this Echo SRM-210 may not have a screw there.

 

[heyduke]

I think it depends on the carburator. The one I linked to doesn't have a idle mixture adjustment screw, just the idle speed adjustment. But the carb I linked to does have a hidden high speed screw. BUT! The carb on this Echo SRM-210 may not have a screw there.

What you're describing sounds like the zama carb on my stihl fs250, just one adjustment screw that appears to be an idle speed adjustment. it's in the same position as an idle speed adjustment and has a large head. however it doesn't contact the throttle lever and is threaded left handed and is actually a mixture adjustment. you can see it thru an aperture in the bottom of the throat, about where the high-speed jet would be. it's 1 or two mm in diameter and not tapered. there is no idle speed adjustment. it took a lot of head scratching to figure that out.

 

[LegDeLimber]

Is this the correct carburetor?
http://www.ebay.com/itm/GENUINE-ZAMA-CARBURETOR-RB-K70A-ECHO-A021000721-/110875527456
Interesting how there's about a $30. USD, range of prices asked for it.

 

[ANewSawyer]

What you're describing sounds like the zama carb on my stihl fs250, just one adjustment screw that appears to be an idle speed adjustment. it's in the same position as an idle speed adjustment and has a large head. however it doesn't contact the throttle lever and is threaded left handed and is actually a mixture adjustment. you can see it thru an aperture in the bottom of the throat, about where the high-speed jet would be. it's 1 or two mm in diameter and not tapered. there is no idle speed adjustment. it took a lot of head scratching to figure that out.

If that is the idle mixture screw that would be awsome! There is a hidden screw on the bottom of the carb behind a plastic plug. This video explains it better than I could.

I will try to find a better video later.

EDIT: Found it. Start watching at one minute. The screw I am talking about is on the primer bulb side of the carb:

 

[LegDeLimber]

A little better focus in this one (when he gets it in the cameras sensor area).
I do not think that's an adjustment, just a simple jet ( and not a "needle" either).

As for the "Mr fixit' video, A bit better focus and overall wouldn't be too bad.
But it really..., really... irks me to see someone force a clamped piece around
like he did to that front handle, without loosening it first.

 

[ANewSawyer]

BTW, that is the correct carb you linked to. I had just looked it up this morning.

A little better focus in this one (when he gets it in the cameras sensor area).
I do not think that's an adjustment, just a simple jet ( an not a "needle" either).

As for the "Mr fixit' video, A bit better focus and overall wouldn't be too bad.
But it really..., really... irks me to see someone force a clamped piece around
like he did to that front handle, without loosening it first.

You are probably right in that it isn't a needle and, I think, the second video makes that pretty clear. So it really isn't adjustable after all since it is a simple jet screw? The screw I am talking about is part number 11 in the IPL that I linked to earlier. (heyduke, I think you are talking about part number 7. This is the one: http://www.ereplacementparts.com/idle-adjust-screw-p-502361.html?osCsid=91oss37k4kmgg9e0afs0hauq51) Anyway, I am very much a novice to working on engines. I don't suggest you do anything in either video, I am just trying to illustrate what I am talking about.

 

[heyduke]

If that is the idle mixture screw that would be awsome! There is a hidden screw on the bottom of the carb behind a plastic plug. This video explains it better than I could.

I will try to find a better video later.

EDIT: Found it. Start watching at one minute. The screw I am talking about is on the primer bulb side of the carb:

thanks for the vids. your carb looks nothing like the stihl/zama on my fs250. mine has a single mixture adjustment screw placed exactly where the idle speed adjustment should be. there are dimples in the casting where low and hi adjustments should be but they haven't been bored. there is no idle speed adjustment. my stihl ealer said that this is just one of nine different carbs that have been used on this string cutter. i suspect that all of this type but mine have been replaced with a more conventional carb because no one could figure out how to tune them. as i said the mixture adjustment screw (which looks exactly like an idle speed screw) is left-hand threaded and you have to turn to the right to enrich, left to lean, go figure. i had to examine it at length with good magnification before i got it. it's been working well ever since, abundant power, lots of cajones, starts and idles nicely, but i nearly ordered a new carb from ebay before the problem was solved. leave it to stihl to complicate things.