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This thing is flooding like crazy. THE only way to keep it running is to shoot air in the venturee, constantly. Take the air away, and it floods. out.

Question: Is this solely a needle/Seat issue?

The gaskets and everything inside looks good. Metering leveler was spot on. It holds 7lbs
After cleaning it (not in the ultrasonic, which is broken) putting it all back together, pressure testing it and firing it up. It didn't flood like it was before. It'll start without pushing air thought it. But can't get it to idle for long. Not long enough change the low side. I removed the H so I could get it off what sounded like the strokin sound. Well, that worked except I was able to screw it in and it never got to the lean running sound.

Darn thing is giving me fits. I remember someone mentioning a H side that runs the same closed as open. But can't remember what they said about it.

Zamas had a problem with the welch plugs falling out.


Here is the 2019 retail price from the Stihl dealer around here:

4140 120 0619 Carburetor C1Q-S186 $34.50

Sorry about the above post, I was so aggravated, It didn't come out right.

I meant to say, I removed the limiter of the H. And put it back in. That's when I realized that it would stroke when out too far. And would get pretty close to being spot on at WOT. But screwing it in the rest of the way, nothing changed. I held the trigger, after the H bottomed out for about 30 seconds or more. So I'm sort of remembering what @bertsmobile1 (IIRC) said about this. That all the fuel, that was allowing it to run high RPM's, with the H closed, is coming through the low idle side. Which tells me that there's something internally wrong on the L side.
There's nothing in the L side hole, except the jet, right? So I can't understand how it would let the engine run at those RPM's just from the L side fuel.

As Fish said some Zama have welch plugs that fall out leading to flooding issues. What the problem is Zama doesn't provide the correct size to replace them so you have to replace the whole carburetor. I usually see this on Stihl equipment only.

StarTech said:

As Fish said some Zama have welch plugs that fall out leading to flooding issues. What the problem is Zama doesn't provide the correct size to replace them so you have to replace the whole carburetor. I usually see this on Stihl equipment only.

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After cleaning it out and pressure testing, (and it holding at 7lbs) I think I fixed the flooding problem. Unless it's still flooding through the L side.

It seems Stens and the DC Spares don't have this carb. The kit, IIRC is an RB-100. Is that correct?

BTW, the welch plugs haven't fallen out.

Please verify the carburetor model number. As if it is the C1Q-S186 the Carburetor kit is RB-161. Stihl PN 7010 871 0222

As for pressure test that only test the fuel pump, metering needle and seat. It soes not the check the metering side of the carburetor as that side can't be pressure/vac tested.

Looks like that carb has a purge bulb.
Be sure the fuel inlet side holds 7psi.
Then press and release the purge bulb. Pressure should drop slightly an hold each time you press bulb.
Apply 7 psi pressure to purge line barb. Should hold pressure. If those are good look for bad check valve or welch plug fallen out.

PTmowerMech said:

After cleaning it out and pressure testing, (and it holding at 7lbs) I think I fixed the flooding problem. Unless it's still flooding through the L side.

It seems Stens and the DC Spares don't have this carb. The kit, IIRC is an RB-100. Is that correct?

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I wish Stens would stock that carb, It seems like that is the most popular part number for carb replacement on Stihl trimmers.

The following seem reasonable enough.

http://www.boxstoreparts.com/Stihl-OEM-Carburetor-C1Q-S186-4140-120-0620.htm

StarTech said:

The following seem reasonable enough.

http://www.boxstoreparts.com/Stihl-OEM-Carburetor-C1Q-S186-4140-120-0620.htm

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WOW.. Thanks man. I didn't get this site when I googled this. This is a great price.

Hammermechanicman said:

Looks like that carb has a purge bulb.
Be sure the fuel inlet side holds 7psi.
Then press and release the purge bulb. Pressure should drop slightly an hold each time you press bulb.
Apply 7 psi pressure to purge line barb. Should hold pressure. If those are good look for bad check valve or welch plug fallen out.

Click to expand...

I need to do some research on check valves. I've never messed with them.

PTmowerMech said:

WOW.. Thanks man. I didn't get this site when I googled this. This is a great price.

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That looks like the newer style carb, your throttle cable might not work. That is why I include the throttle cable with mine.

PTmowerMech said:

I need to do some research on check valves. I've never messed with them.

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Most check valves are not serviceable. You can usually check them with a piece of fuel line held on it and the use mouth to suck and blow. Should only work one way. If bad need new carb.

Does your old carb have ref. #7?

The carb in that ad shows a carb that takes the z-bend end.

I think I have the carburetor issue worked out. I got the new US cleaner in today, then reinstalled the kit. Everything seems to be pretty smooth. Except the idle is a tad rough.
The problem is now, just suddenly it'll die. Like you hit the switch. Sometimes, it'll start right back up. Sometimes it's several pulls. BUT, and here's the funny part, it won't just die, at WOT. At idle, it seems like a switch or coil problem. But seems like it wouldn't matter if it was WOT or not, if it was the switch or coil. Right?

I've had about all I can stand with this 2 cycle stuff.

Fish said:

Does your old carb have ref. #7?




View attachment 54260View attachment 54261

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Yes, the wire groove with the bigger hole on one end.

Well, if the carb in the pic is what they are selling, it will not work.

Fish said:

The carb in that ad shows a carb that takes the z-bend end.
View attachment 54262

Click to expand...

I went ahead and ordered one of these. The customer service guy says the arms are interchangeable. According to him, it's an easy thing to do. I've never tried it, though. He said the ones with the wire groove, you can't get anymore.

ILENGINE said:

I wish Stens would stock that carb, It seems like that is the most popular part number for carb replacement on Stihl trimmers.

Click to expand...

When chasing up service information & parts for a concrete saw, I emailed Walbro as I could not find even genuine Walbro parts for it.
The reply floored me.
Husqvarna paid for the developement of the carb so they owned the IP for it and even Walbro were not allowed to make the carb or any part for the carb without Husqvarna's approval .
So it is a new ( read very expensive ) carb only available through a dealer or nothing .
So Stihl probably have a similar deal with Zama considering they own 1/2 the Chinese factory that makes them

PTmowerMech said:

I went ahead and ordered one of these. The customer service guy says the arms are interchangeable. According to him, it's an easy thing to do. I've never tried it, though. He said the ones with the wire groove, you can't get anymore.

Click to expand...

I have had a few aftermarket carb i had to change the throttle or chike shaft to make a carb work.

PTmowerMech said:

I think I have the carburetor issue worked out. I got the new US cleaner in today, then reinstalled the kit. Everything seems to be pretty smooth. Except the idle is a tad rough.
The problem is now, just suddenly it'll die. Like you hit the switch. Sometimes, it'll start right back up. Sometimes it's several pulls. BUT, and here's the funny part, it won't just die, at WOT. At idle, it seems like a switch or coil problem. But seems like it wouldn't matter if it was WOT or not, if it was the switch or coil. Right?

I've had about all I can stand with this 2 cycle stuff.

Click to expand...

When you have a 2 stroke that has idle issues it is best to do a vacum and pressure test. A leaking crank seal will first show problems at idle. Also, make low needle adjustments and wait 15 to 20 seconds before making another adjustment. Set the low screw a little on the rich side. Usually get better throttle response and less chance of dying. 2 smokes are not that complicated. Just have to hold you mouth just right.

bertsmobile1 said:

When chasing up service information & parts for a concrete saw, I emailed Walbro as I could not find even genuine Walbro parts for it.
The reply floored me.
Husqvarna paid for the developement of the carb so they owned the IP for it and even Walbro were not allowed to make the carb or any part for the carb without Husqvarna's approval .
So it is a new ( read very expensive ) carb only available through a dealer or nothing .
So Stihl probably have a similar deal with Zama considering they own 1/2 the Chinese factory that makes them

Click to expand...

Just for the sake of all this, I ordered an Amazon carb for it. I want to thank you again for all the 2 cycle advice you've given me over the years. I've learned a lot from you and the others here.
But I'm getting to the point that I'd rather eat a few cheap carbs, than deal with this crap. There's just not enough money in 2 cycles for me.
At least not until I get a lot more knowledgeable. Plus a tool to check for crank case air leaks and such.

You can use this for pressure and vacum tests. You use a piece of inner tube to block off exhaust port and intake port then use a spark plug adapter to hook pump to engine.

The ones with the groove are still available. On making it work, did he say that you should swap the throttle shaft?

Hammermechanicman said:

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You can use this for pressure and vacum tests. You use a piece of inner tube to block off exhaust port and intake port then use a spark plug adapter to hook pump to engine.

Click to expand...

I have one of these. Been using it for about 6 months now. I got the one that bert advised. The metal one. Never install a carb without testing it. But never used it to check engine leaks.

Fish said:

The ones with the groove are still available. On making it work, did he say that you should swap the throttle shaft?

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He said to remove the butterfly and the little clip on the end of the shaft. Then it comes right out. And of course the OEM just slides right into this one. So I'm guessing (and hoping) the ID's are the same. I ask him about leaks from there, he said it wouldn't.
It would seem he's been through this with other customers before.

I remember encountering the problem before, and I don't remember the swap being able to work. Which is why I just sell the throttle cable with the carb.

https://www.ebay.com/itm/Stihl-FS38...655879?hash=item2f4a28e0c7:g:u2oAAOSwImpXpQAH

PTmowerMech said:

I have one of these. Been using it for about 6 months now. I got the one that bert advised. The metal one. Never install a carb without testing it. But never used it to check engine leaks.

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If you plan to work on chainsaws you should learn to vacum and pressure test crankcases and intake boots. Air leaks will burn up an engine. Trimmers and blowers usually just run bad. You can drive yourself nuts trying to fix an engine with an air leak. Since most OPE engines are piston port and not reed valve or rotary valve troubleahooting is fairly simple if you test and not guess.

Doubling up on what Hammer has just said.
Very first test is to pull the fuel line off the carb and see if the tank will hold 5 to 10 PSI,
Most don't because the fuel lines are leaking where they pass through the tank or the carb check valve in the purge bulb is faulty
Slip the return line off the carb and pop a golf T in it then test the tank again
Swap to vacuum
Any vacuum reading = bad cap or vent
I replace at least a dozen caps a year now

At least 1/3 of the hand helds that come in have no engine problems at all, just leaking fuel tanks
So it is new cap, new spark plug, test OK then send it back $ 45 ( Aus ) + parts for 1/2 hours work .
You can go mad trying to get one to work reliably, you tune it then it goes out of tune so you do it again then 1/2 latter it is bad because the pressure in the fuel system is consistantly changing .

Bert, Stihl International GmbH is the owner of Zama currently. And recently even Stihl is having Zama website purge of the Stihl equipment only Zama carburetor information.

StarTech said:

Bert, Stihl International GmbH is the owner of Zama currently. And recently even Stihl is having Zama website purge of the Stihl equipment only Zama carburetor information.

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I know Stihl own Zama but when the factory moved to China they became a part owner of the factory
No one from the West can set up in China without a local business owning 50 % which of course keeps a good amount of the profits in China & prevents it becoming a slave economy .
CTS is to old Zama factory in Hong Kong , apparently run by a lot of the old management .
Of course I forgot that the Zama brand & there fore web site is 100% Stihl owned so they can do with it as they like.
Good thing I kept all of the old wholesale paper catalogues so at least I can cross for older stuff .

Another job for boring TV nights, download all of the IPL's off the Zamma site
Might check Wayback to see if they purged it from there as well.

This explains why CTS quality seems as good as Zama carburetor kits and they are adding some of the newer carburetor kits. I just just some RB-186 kits that just became available. Darn local dealer was wanting $25 per kit and CTS was $20 for 10 kits. Their Walbro kits are just as good too. It just the time delay in getting the kits that can be a problem.

The problem I have with Stihl is they changed the Zama RB numbers in their system to Stihl PN numbers. This makes it nearly impossible to even a get kit from the local dealer as they too can't seem to cross or even order the kit when given the Stihl part number. Their solution is to just order a complete carburetor. At least the Stihl 2019 Technical Reference I have helps a lot as the local dealer I purchase from apparently don't have it.

And like you Bert I am an info pack rat on things I work on; although, most mine is in electronic format.

It never fails to amaze me the greedy mark ups that make people look for alternatives
If the factory sold to the wholesaler for the same price & they put a 100% mark up then they would be $ 4 / kit + tax, $ 5 if you add a freight fee .Then the dealer could do a 100 % mark up which would make them $ 10 tops, a price I would be happy to pay to save the time hassel .
Now of course the factory is probably selling very large volumes to the wholesaler for well under $ 2 a hit so some one is making a killing while simultaneously cutting their own throats. \
RGS is the local Walbro distributor and kits cost about 5 to 10 times the CTS price but I am happy to pay that most times for the convienance of being sent a paper catalogue with equipment to repair kit cross reference, complete with photographs which is a big time saver and I get to tell the customer it was genuine Walbro pars fitted.
However their Zamma kits come from Oregon and are almost the same price as a replacement carb so it is CTS for Zamma & Tillotsen kits + manifold & exhaust gaskets.

And yes the mower folder is getting very large as is the paper library .
Very soon I will need to start cataloguing it .
Even worse for me as model numbers & Names change from the USA to Aust and then we have the local rebranding of imported equipment to deal with.

Always fun isn't it? At least with good computer programs we can work around some of the problems by inputting the crosses and let it keep track of them for us. I only got 326 different directories just for the lawn care stuff which help file surfing. Just make sure you check your paper files every so often as silverfish can destroy a lot info before you know it.

Here most distributors have gone paperless so snagging a PDF here and there is important to me especially anything electrical schematics.

As for Walbro most of cube kits are fairly reasonable when need on an one time deal. I even was getting the kits for the Stihl carburetors through my Zama distributor until this year when Stihl barred Zama from selling through the distributors. CTS and DC Spares have been life saver as many of the trimmer simply would not be repaired here without getting kits from them.

And one of the local Stihl dealer has no feelings for the customer with a $150 Stihl chainsaw when they want $100 just to look at it.