VM26 Mikuni Clone Carb Air/Idle Screw Adjustment

HawkTwoFifty · 11-25-2017, 06:17 PM

So I just swapped out my stock carb on my Hawk 250 for a new VM26 Mikuni clone and am having an issue with the idle being way too low. My VM26 carb didnt come with any tuning instructions or manual so I am unsure which screw on the carb would require adjustment for increasing my idle. I searched online for answers but am still unsure what screw requires adjustment. With this being a Mikuni clone carb, I am finding it difficult to find answers or guides online for tuning this carb.

Before installing this new VM26 carb, I replaced the main jet to a 110, replaced the pilot jet with a 25, and put the clip on the needle 2 clicks up from the very bottom (pointed side) of needle. With the carb installed, I just took it out for a ride and in addition to the very low idle (will definitely stall without throttle), there seems to be a total lack of acceleration within the range of 1/4-1/2 throttle. So I couldnt get the bike over 30mph during my test run today. Every time I pulled the clutch in the bike would stall out so I know for sure that the idle requires adjustment but know that there must also be another issue since I have no midrange power.

Any help would be appreciated. Also, is there a Mikuni carb manufactured which is very close to be similar to this carb that I could use as a reference? When I look up a genuine VM26 Mikuni carb, there are definite differences between the two. If I could find a Mikuni carb which is nearly identical to this carb, than I would be able to find the info that I need. I just havent found such info yet. Any help is greatly appreciated, THANKS!!

Azhule · 11-25-2017, 08:09 PM

Usually, it's on the "right side" of the carb/bike there is a "Phillips head" looking screw on these mikuni clones, that will be the one that will raise/lower the idle speed

Look for the "Blue/Purple marker" in the pic below, if this is the same carb you have, that is the screw to look for

Megadan · 11-25-2017, 08:17 PM

The idle speed screw is in the same location as the stock carburetor, it just lacks the thumb screw to allow adjustment by hand, and instead requires a screwdriver.

As far as the lack of acceleration. Before we go into too many possibilities, let us just confirm the choke is in the right position. Set your idle speed and then ensure the choke handle is pushed all the way down. Take it for a ride and see how it goes, then report back any changes or lack of changes and we can go from there.

HawkTwoFifty · 11-25-2017, 08:45 PM

Quote:

Originally Posted by Azhule

Usually, it's on the "right side" of the carb/bike there is a "Phillips head" looking screw on these mikuni clones, that will be the one that will raise/lower the idle speed

Look for the "Blue/Purple marker" in the pic below, if this is the same carb you have, that is the screw to look for

Thanks Azhule, I appreciate the help!

HawkTwoFifty · 11-25-2017, 08:49 PM

Quote:

Originally Posted by Megadan

The idle speed screw is in the same location as the stock carburetor, it just lacks the thumb screw to allow adjustment by hand, and instead requires a screwdriver.

As far as the lack of acceleration. Before we go into too many possibilities, let us just confirm the choke is in the right position. Set your idle speed and then ensure the choke handle is pushed all the way down. Take it for a ride and see how it goes, then report back any changes or lack of changes and we can go from there.

Thanks Megadan, you are always a HUGE help here for me here. I can definitely confirm that the choke was off and in the down position when I went for a ride today after the new carb install. I will adjust my idle speed and report back.

Thanks again!

Ariel Red Hunter · 11-25-2017, 09:53 PM

Quote:

Originally Posted by HawkTwoFifty

Thanks Megadan, you are always a HUGE help here for me here. I can definitely confirm that the choke was off and in the down position when I went for a ride today after the new carb install. I will adjust my idle speed and report back.

Thanks again!

Yes, this is all true. But, a small point. Do not raise the idle speed by turning the idle speed screw unless you first open the throttle a bit, and turn the screw "in" to increase idle speed. Then close the throttle again by letting go of the twist-grip. If necessary, repeat until you have an idle speed that you are satisfied with...ARH

11-25-2017, 06:17 PM	#1
HawkTwoFifty Join Date: Oct 2017 Posts: 93	VM26 Mikuni Clone Carb Air/Idle Screw Adjustment So I just swapped out my stock carb on my Hawk 250 for a new VM26 Mikuni clone and am having an issue with the idle being way too low. My VM26 carb didnt come with any tuning instructions or manual so I am unsure which screw on the carb would require adjustment for increasing my idle. I searched online for answers but am still unsure what screw requires adjustment. With this being a Mikuni clone carb, I am finding it difficult to find answers or guides online for tuning this carb. Before installing this new VM26 carb, I replaced the main jet to a 110, replaced the pilot jet with a 25, and put the clip on the needle 2 clicks up from the very bottom (pointed side) of needle. With the carb installed, I just took it out for a ride and in addition to the very low idle (will definitely stall without throttle), there seems to be a total lack of acceleration within the range of 1/4-1/2 throttle. So I couldnt get the bike over 30mph during my test run today. Every time I pulled the clutch in the bike would stall out so I know for sure that the idle requires adjustment but know that there must also be another issue since I have no midrange power. Any help would be appreciated. Also, is there a Mikuni carb manufactured which is very close to be similar to this carb that I could use as a reference? When I look up a genuine VM26 Mikuni carb, there are definite differences between the two. If I could find a Mikuni carb which is nearly identical to this carb, than I would be able to find the info that I need. I just havent found such info yet. Any help is greatly appreciated, THANKS!!
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11-25-2017, 08:09 PM	#2
Azhule Join Date: Dec 2015 Location: CO Posts: 1,525	Usually, it's on the "right side" of the carb/bike there is a "Phillips head" looking screw on these mikuni clones, that will be the one that will raise/lower the idle speed Look for the "Blue/Purple marker" in the pic below, if this is the same carb you have, that is the screw to look for __________________ "Think as you like... but this self proclaimed Professor is always right" - Buckshot "You never know what someone is hiding beneath their smile..." - NinjaTom - R.I.P.
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11-25-2017, 08:17 PM	#3
Megadan Join Date: Apr 2017 Location: Omaha, NE Posts: 8,149	The idle speed screw is in the same location as the stock carburetor, it just lacks the thumb screw to allow adjustment by hand, and instead requires a screwdriver. As far as the lack of acceleration. Before we go into too many possibilities, let us just confirm the choke is in the right position. Set your idle speed and then ensure the choke handle is pushed all the way down. Take it for a ride and see how it goes, then report back any changes or lack of changes and we can go from there. __________________ Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124
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