6GN20 needle
- Thread starter fastmax
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Apsley Max
Member
I just bought 4 of these for my 94 big bore.But after seeing that they are a bit thicker/bigger ,which means LEANER,I am reluctant to stick them in.I cant find any needle specs/dimensions to get an exact comparison of these two needles, 6GN14 against 6GN20.Like the specs found in back of Mikuni carb tuning handbook.I thought when I bought them ,they would have been richer!!! wrong. Steve C
Mad Powersports
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Steve, this post has been on my mind since I first saw it. Twenty-five years ago I could have told you off the top of my head what the difference was between the two, but alas not anymore.
Rebuilding carbs was my forte since the mid seventies up until their demise with the introduction of EFI.
I looked through all my carb literature and cannot find them numbers anywhere. Granted I was more focused on the automotive side but we did have plenty of farm toys along with the neighbor’s kid’s toys that I needed to keep running.
The difference between those two is going to be where the taper starts. I believe the 6GN20 taper is going to be higher up on the needle. But without actually measuring the two I can’t be certain. It could be vise versa but I don’t think so because the 6GN20 was probably produced after the 6GN14 thus giving it a larger number after the taper letters.
Here is some info on Mikuni jet needles for those who want to know.
The metering needles are identified by a code such as 6DH2. The first number
indicates the needle series. This determines the length of the needle and what series carb it is intended for. IE: A 4DN1 is 40-50 mm long and used on the 4xx series, and a 5BF3 is used for the 5xx series and is 50-60mm long.
The following letter/s indicate the needle taper. If there is
one letter, the taper is uniform along the length of the needle, but if there are two
letters, this indicates that the taper changes midway along the tapered section. The place where the taper changes can also vary. The first letter indicates the upper taper and the second letter the lower taper.
Starting with letter A, which has a meaning of 15 minutes of arc, each letter in
sequence denotes an additional 15 minutes to the angle between the two sides of the
needle. Therefore a DH taper has an angle of 1°0' on the top, and 2°0' on the bottom
taper. A GN would have a top taper angle of 1°45' and the bottom taper of 3°30'.
The number after the letters is a manufacturing code, which indicates how far
down the needle the taper starts and/or the initial needle diameter, e.g.: needles marked
6DH2 and 6DH3 have the same taper, but 6DH3 is the richer needle as the taper starts
22.0mm from the top of the needle, whereas the taper begins 28.0mm down with the
6DH2. See chart below.
This information can only be obtained by referring to the needle dimension chart which gives the needles diameter every 10 mm therefore showing us where the second taper starts, or by physically measuring every 10 mm and comparing each needles measurements.
And last but not least, if the needle is identified as a 6DN3-3, this would
indicate that the needle is a 6DN3 and that it is fitted standard with the circlip in the
third groove, counting the top groove as number one.
Although all this may seem a bit techy to some folks, it is data that any serious tuner should understand as small incremental changes can have very significant effects on engine performance and longevity.
I must also add that this is only one of the many variables in carb tuning.
Ron
Rebuilding carbs was my forte since the mid seventies up until their demise with the introduction of EFI.
I looked through all my carb literature and cannot find them numbers anywhere. Granted I was more focused on the automotive side but we did have plenty of farm toys along with the neighbor’s kid’s toys that I needed to keep running.
The difference between those two is going to be where the taper starts. I believe the 6GN20 taper is going to be higher up on the needle. But without actually measuring the two I can’t be certain. It could be vise versa but I don’t think so because the 6GN20 was probably produced after the 6GN14 thus giving it a larger number after the taper letters.
Here is some info on Mikuni jet needles for those who want to know.
The metering needles are identified by a code such as 6DH2. The first number
indicates the needle series. This determines the length of the needle and what series carb it is intended for. IE: A 4DN1 is 40-50 mm long and used on the 4xx series, and a 5BF3 is used for the 5xx series and is 50-60mm long.
The following letter/s indicate the needle taper. If there is
one letter, the taper is uniform along the length of the needle, but if there are two
letters, this indicates that the taper changes midway along the tapered section. The place where the taper changes can also vary. The first letter indicates the upper taper and the second letter the lower taper.
Starting with letter A, which has a meaning of 15 minutes of arc, each letter in
sequence denotes an additional 15 minutes to the angle between the two sides of the
needle. Therefore a DH taper has an angle of 1°0' on the top, and 2°0' on the bottom
taper. A GN would have a top taper angle of 1°45' and the bottom taper of 3°30'.
The number after the letters is a manufacturing code, which indicates how far
down the needle the taper starts and/or the initial needle diameter, e.g.: needles marked
6DH2 and 6DH3 have the same taper, but 6DH3 is the richer needle as the taper starts
22.0mm from the top of the needle, whereas the taper begins 28.0mm down with the
6DH2. See chart below.
This information can only be obtained by referring to the needle dimension chart which gives the needles diameter every 10 mm therefore showing us where the second taper starts, or by physically measuring every 10 mm and comparing each needles measurements.
And last but not least, if the needle is identified as a 6DN3-3, this would
indicate that the needle is a 6DN3 and that it is fitted standard with the circlip in the
third groove, counting the top groove as number one.
Although all this may seem a bit techy to some folks, it is data that any serious tuner should understand as small incremental changes can have very significant effects on engine performance and longevity.
I must also add that this is only one of the many variables in carb tuning.
Ron
Apsley Max
Member
Thank you .Very informative.
needles
just a quick thought come across my mind so for all of us who have stock carbs cut 2 36 i,m sure nobody as redone the needles or we should say updated so now we have some ponies left on the table along with miles an hour, so go get em lol AL i know this has got me lookin at this for sure all makes since
just a quick thought come across my mind so for all of us who have stock carbs cut 2 36 i,m sure nobody as redone the needles or we should say updated so now we have some ponies left on the table along with miles an hour, so go get em lol AL i know this has got me lookin at this for sure all makes since