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STIHL Carb Alpha-Numeric Designations & Setting an HD-18D 1127-120-0604

JP56

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Joined here in 2018 after having some problems & questions about my MS290, and got a lot of great info & help form Harley & a few others. Also learned a lot about the AM carbs for these, but learned the hard way by Trial & Error before find out so much about them here & the pit falls of buying after market parts.

This saw was difficult to start from the day I got it home, but it ran well once you got it started. I ended up having to reset the coil gap, and that cured my starting problem once I mastered the art required by STIHL, or recognizing the "burp" on initial pull and flipping the lever to 1/2 choke, & I got a lot of use from it over the next several years, & then it began running badly and I just could not get it set right.

Having said that, I checked compression which is at 143 consistently, then tested engine for Pressure/Vacuum, which it passed, by holding almost 8 lbs. with no leak down at all. So, I figure the only thing left to do was try replacing the carb, so I just purchased an OEM STIHL 1127-120-0604 HD-18D Carb, as it is listed in the Parts Info passed on to me thru this site, as 1 of 3 carbs listed for this saw.

It is my understanding from both this forum & from what I can see in the STIHL Manuals, that the 029/MS290 are basically the same, MS310, and 039/MS390 are basically the same, and that all 5 Models have a lot of interchangeable parts for certain things, but I am confused by the Carb numbering specs.

I purchased the STIHL 1127-120-0604 HD-18D as a replacement, because it is 1 of 3 spec'd out by STIHL as a Replacement.

The original I took off the 290, (see photos) is an HD-18C 1127-120- ????. It is stamped as 18C on the casting, but I do not see a Reference on any of the Specs listed as to letters C or D or anything else.

I also see that the 06o5 is only listed for the MS310, and no part number is given as a substitute for it, but it can also come with a HD-21 1127-120-0605, with no substitute number given for that either, YET the other 4 Models get an HD-19 1127-120-0650 listed as a substitute for the other numbered carbs.

STIHL Carburetor Reference Charts & Kits For Chain Saws

Model # Carburetor Model Carburetor # Substitute
029/MS290 HD-5 1127 120 0601 1127-120-0650
HD-18 1127 120 0604 1127-120-0650
HD-19 1127 120 0650 1127-120-0650

MS310 HD-19 1127 120 0650 No # Given
HD-21 1127 120 0605 No # Given

039/MS390 HD-5 1127 120 0601 1127 120 0650
HD-19 1127 120 0650 No # Given
HD-21 1127 120 0605 No # Given

So, I have some questions regarding these carburetors and the way they are Spec'd out:

1) Where the 1127-120-0650 is given as a SUBSTITUTE Carb for the HD-5 0601, HD-18 0604, is the 0650
an HD-02, or an HD-18 or an HD-19 ?

2) What is the designation HD-X or HD-XX and what is the reasoning behind that, and Where does the designation C or D come into play and what is that about?

3) Can an 1127-120-0605 ONLY be replaced with a 1127-120-0605 because of the HD-21 designation, or can any of the other ones be used?

Lastly & my most important question: Are these Carbs somewhat Pre-Set from the factory so after bolting them on, the saw SHOULD start, and then be fine tuned for best running, or is it a crap shoot right out of the box?
 

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dmb2613

dmb2613

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I run 440 carbs on some of the 390s with a pop up piston in them. They come with both needles turn out about 1 turn. that will get you started. They also come with the red caps to prevent from turning over about 3/4 turn. the caps will have to be pushed in to lock them. I cant tell you to take them out as I am a Stihl tech but I don't have them on my saws
The only big difference in the carbs are the jet sizes any of them will work though
David
 
Jkstihl

Jkstihl

Chainsaws make me fap.
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I run 440 carbs on some of the 390s with a pop up piston in them. They come with both needles turn out about 1 turn. that will get you started. They also come with the red caps to prevent from turning over about 3/4 turn. the caps will have to be pushed in to lock them. I cant tell you to take them out as I am a Stihl tech but I don't have them on my saws
The only big difference in the carbs are the jet sizes any of them will work though
David

Which is the best one hd17?
 

JP56

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Nov 14, 2018
Messages
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Location
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I run 440 carbs on some of the 390s with a pop up piston in them. They come with both needles turn out about 1 turn. that will get you started. They also come with the red caps to prevent from turning over about 3/4 turn. the caps will have to be pushed in to lock them. I cant tell you to take them out as I am a Stihl tech but I don't have them on my saws
The only big difference in the carbs are the jet sizes any of them will work though
David

I watched those limiter caps fall off the new carb when I took it out of the box.;)
 

JP56

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Here is a bulletin....

Thanks for the bulletin Harley, but this just addresses upgrade/changes to the available parts for newer and repaired older models, yes? It still doesn't give me a clue to their crazy confusing Carb designations.

If anything, it only confuses me more as written, because my factory installed carb was HD-18C and now it's HD-18D. So by the newer standards, I guess if I order another in the future my carb will change from an HD-18D to an HD-19D ?

"3. Carburetor (throttle shutter)
To improve operation, the throttle shutter
1127 121 3300 is generally (on HD -18 and HD -21)
replaced by the version 1133 121 3301. The
carburetor type designation consequently changes
from HD-18B to HD-19C and from HD-21 B to
HD-21C."
 
HarleyT

HarleyT

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Thanks for the bulletin Harley, but this just addresses upgrade/changes to the available parts for newer and repaired older models, yes? It still doesn't give me a clue to their crazy confusing Carb designations.

If anything, it only confuses me more as written, because my factory installed carb was HD-18C and now it's HD-18D. So by the newer standards, I guess if I order another in the future my carb will change from an HD-18D to an HD-19D ?

"3. Carburetor (throttle shutter)
To improve operation, the throttle shutter
1127 121 3300 is generally (on HD -18 and HD -21)
replaced by the version 1133 121 3301. The
carburetor type designation consequently changes
from HD-18B to HD-19C and from HD-21 B to
HD-21C."
Lol,
I usually just bolt the carb on and start the saw!!!
 
HarleyT

HarleyT

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These letter changes are just denoting slight modifications, I doubt that you could only find a couple of people at Walbro that could tell you what the differences are.
 

JP56

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Messages
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Location
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These letter changes are just denoting slight modifications, I doubt that you could only find a couple of people at Walbro that could tell you what the differences are.

I would bet that unless I found a really old timer there I wouldn't find anyone at all that could answer any of those questions, especially after browsing their website looking for cross reference numbers.
 
HarleyT

HarleyT

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Yeah, the same model carbs have a variety of letters after them, and they are spec-ed for the same saw, and have the same Stihl part number, so it is best to not worry so much..
 
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