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spudulike

What's on your bench today?

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55 minutes ago, bmp01 said:

2 feeds, the jet feed,  therefore a constant fuel feed, probably suppying most of the fuel. That leaves the high speed screw to fine tune the small additional flow supplied through the second hole.

Yes I think so and posted such earlier.

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I suspect when you sprayed carb cleaner  through the high speed screw the stuff went down to the check valve and some of it bounced back up fix jet drillng. How about you refit the high screw and bottom it, then spray down the jet feed....does any spray come out the second feed?

I think so but the main test will be to try Spuds suggestion and  block both ports from the metering chamber and see how much comes out of the choke.

Quote

 

Your earler blowing down a hose test: with the high speed screw bottomed as you did, you should be able to blow through the check valve. You should not be able to suck through the check valve though. But wait, before you conclude check valve is knackered you need to know the accelerator circuit also feeds fuel to the check valve..... 

 

Do you know where the accelerator piston is?

Nope, cannot see it has one

Edited by openspaceman

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Try this link:

https://arbtalk.co.uk/forums/topic/122598-still-m181c-help/page/2/

 

Be nice to confirm were the fault lies before bailing on it. Pretty close now I think. 

 

Try Spuds carb cleaner treatment and if no joy I have one last test, zero cost.

 

After that either it works or send it to me, I have a few big hammers to fix it. Usually the microscope and lathe are  more useful for this sort of project though 😃

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11 minutes ago, bmp01 said:

Thanks, I will also go and read the whole thread . This carb has a white plastic plug there.

11 minutes ago, bmp01 said:

 

Be nice to confirm were the fault lies before bailing on it. Pretty close now I think. 

 

Try Spuds carb cleaner treatment and if no joy I have one last test, zero cost.

 

After that either it works or send it to me, I have a few big hammers to fix it. Usually the microscope and lathe are  more useful for this sort of project though 😃

Thanks I'll try Spuds idea and I'm not bailing just sitting back for a bit. I have some fairleads to fit on the County and see if I can get the exhaust manifold off. The earlier thread mentions an after market carb which I will investigate.

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19 hours ago, openspaceman said:

Thanks, I will also go and read the whole thread . This carb has a white plastic plug there.

Thanks I'll try Spuds idea and I'm not bailing just sitting back for a bit. I have some fairleads to fit on the County and see if I can get the exhaust manifold off. The earlier thread mentions an after market carb which I will investigate.

I masked off the two holes, applied  carb cleaner to the H screw hole and it all squirted out of the jet in the choke tube.

 

I shall put it all back together and clean out the fuel lines and see what happens.

 

I checked out those cheap carbs on ebay  but the nearest match to the C1Q-S192 seems to be ZAMA C1Q-S269 which fits the ms181, is it likely to be much different from what I need?

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Ok, nice to have an update. 

I take it none of the carb cleaner came out the accelerator jet circuit then if as you say ' it all squirted out of the jet in the choke tube'

 

If so that just leaves a question mark over the check valve operation.

 

Fingers crossed.

 

 

Edit: sorry, i have no useful info regrading replacment carb.

Edited by bmp01
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If you shoot carb cleaner down the H screw hole with the two jets covered, you expect a stream of cleaner to come out of the check valve in to the carb venturi /bore big hole in the middle). This test shows you that the check valve does flow fuel in to the carb.

The other check valve fault can be that the thing is stuck open.

If the check valve is not opening, you will lose all high revs and the saw will die if the throttle is open. (yours looks to be OK)

If the check valve is stuck open, the saw will struggle to start, it won't idle but will run flat out but be very lumpy on any other revs.

That leaves the accelerator pump. The fault is generally the idle is impossible to set and on idle, the revs will pick up like it is running out of fuel and then just die. Larger saws tend to bog when the throttle is grabbed open so you don't get a nice crisp pickup.

Changing them isn't for the uninitiated but is up to you if you are at the stage where you want to or to try a cheapo Chinese carb.

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On 14/01/2022 at 20:02, spudulike said:

Changing them isn't for the uninitiated but is up to you if you are at the stage where you want to or to try a cheapo Chinese carb.

L&S supplied me with an aftermarket carb for my Stihl long reach hedge cutter at just over the cost of a carb kit, it has been faultless so I wouldn't discount them.

 

In this case it is not necessary as I put the carb back on the saw, set the screws to factory 1 turn Lo and 3/4 turn Hi, primed it with the purge bulb with hardly any bubbles of air and it fired first pull. Started on tickover  and after quite a few seconds of fluffing revved up  and cut well. Idle is 3500 and Hi idle 12500 rpm.

 

I don't know what caused it to change but it may have been the carb cleaner. I only replaced the tank filter, fuel line from tank to carb and two lines from purge bulb And I forgot the pump and metering diaphragms and gaskets.

Edited by openspaceman
missed out carburettor kit
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Thank the Lord, I was about to call a Priest for an exorcism:thumbup: 

Sounds like the saw has given it in and started to work again...Hurrah!

That was easy, on with the next one.

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