1973 MIKUNI CARB PROBLEM
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Stage II
Joined: Jul 2007
Posts: 2
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1973 MIKUNI CARB PROBLEM
WHATS GOING ON FOLKS!!!! HAPPY HOLIDAYS TO ALL
I JUST REPLACED MY OLD BEAT UP BINTEX CARB WITH A NEW'R MIKUNI VM 40 MM ROUND SLIDE. IT MOUNTED UP GREAT, BUT IT WONT FIRE. MY OLD BINTEX WOULD SQUIRT GAS IN THE JUGS WITH A TWIST OF THE THOTLE. NOT SO WITH THIS CARB. WHATS THE DEAL. IT NOT CLOGGED OR ANYTHING. HAS ANY ONE DONE AN UPGRADE OF THIS KIND OF CARB? ANY HELP WILL BE GREAT!!!!! MY BIKE IS A STOCK 1973 1000 XLCH CHOP BOB
THANKS AGAIN
I JUST REPLACED MY OLD BEAT UP BINTEX CARB WITH A NEW'R MIKUNI VM 40 MM ROUND SLIDE. IT MOUNTED UP GREAT, BUT IT WONT FIRE. MY OLD BINTEX WOULD SQUIRT GAS IN THE JUGS WITH A TWIST OF THE THOTLE. NOT SO WITH THIS CARB. WHATS THE DEAL. IT NOT CLOGGED OR ANYTHING. HAS ANY ONE DONE AN UPGRADE OF THIS KIND OF CARB? ANY HELP WILL BE GREAT!!!!! MY BIKE IS A STOCK 1973 1000 XLCH CHOP BOB
THANKS AGAIN
Seasoned HDF Member
Joined: Dec 2004
Posts: 11,068
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From: Texas! Ya mean there's someplace else?
RE: 1973 MIKUNI CARB PROBLEM
It doesn't "squirt" 'cause it doesn't have an accelerator pump like the Bendix had. I ran a 38mm round slide Mikuni on a stock motored '72 CH, and later had it on the same bike after the motor was punched to 77". With the correct jetting, it worked great. But that was 30 years ago.
How old is this carb? What kind of shape is it in? Does the enrichener circuit work?
Personally, the 40mm is a wee big for a stocker, but should still work great. But it has to be jetted correctly. Do you know anyone with experience on these carbs?
How old is this carb? What kind of shape is it in? Does the enrichener circuit work?
Personally, the 40mm is a wee big for a stocker, but should still work great. But it has to be jetted correctly. Do you know anyone with experience on these carbs?
Road Master
Joined: Aug 2006
Posts: 751
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From: 500 miles south from Artic Circle
RE: 1973 MIKUNI CARB PROBLEM
with correct jetting it should work fine, sure it doesn't have accelatorpump as pococj wrote.
You need to check that enrichener, otherwise you never get your bike started...
One -81 XLS with dragpipes and bafflers and 40mm Dellorto and K&N cone...Main jet 175 intermedia jet 60, you should also check what are: slide? needle? needle clip position ?
You need to check that enrichener, otherwise you never get your bike started...
One -81 XLS with dragpipes and bafflers and 40mm Dellorto and K&N cone...Main jet 175 intermedia jet 60, you should also check what are: slide? needle? needle clip position ?
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
RE: 1973 MIKUNI CARB PROBLEM
Like poco said, the 40mm is really too large for a Sportster. It was made for a big twin.
Anyway, the question is really academic because parts for these carbs (I have one) have not been available since before year 2000. I have talked to Mikuni (Sudco) directly in 2000 and they did not even have a float bowl gasket. They told me the carbs were obsolute then, and no parts of any kind were even listed, much less carried in stock any longer. And that is too bad because it is a really fine carb.
You may find some kind of aftermarket gasket kit around, but I was never able to find it myself.....pg
Anyway, the question is really academic because parts for these carbs (I have one) have not been available since before year 2000. I have talked to Mikuni (Sudco) directly in 2000 and they did not even have a float bowl gasket. They told me the carbs were obsolute then, and no parts of any kind were even listed, much less carried in stock any longer. And that is too bad because it is a really fine carb.
You may find some kind of aftermarket gasket kit around, but I was never able to find it myself.....pg
Cruiser
Joined: May 2007
Posts: 207
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RE: 1973 MIKUNI CARB PROBLEM
Make sure the enrichener fueljet is not plugged. when you crank with enrichener do not open the throttle, as that will bypass the the enrichener venturie (you might want to check that the slide is fully closed, not held open by a misadjusted throttle cable, or throttle stop screw)
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Stage II
Joined: Jul 2007
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RE: 1973 MIKUNI CARB PROBLEM
THE CARB SEEMS TO BE IN GREAT SHAPE, IF THE SLIDE ISNT GOING DOWN ALL THE WAY, I MEAN FLUSH, CAN THIS CAUSE PROBLEMS
ALSO, ********* SAID THAT THE ENRICHER NEEDS TO BE IN THE DOWN POSITION? IF ITS UP DOES THAT MEAN ITS ON??WHEN THE PLUNGER IS IN?
IS THERE A CERTAIN WAY TO START THIS BIKE WITH THIS KIND OF CARB??
ALSO, ********* SAID THAT THE ENRICHER NEEDS TO BE IN THE DOWN POSITION? IF ITS UP DOES THAT MEAN ITS ON??WHEN THE PLUNGER IS IN?
IS THERE A CERTAIN WAY TO START THIS BIKE WITH THIS KIND OF CARB??
Road Warrior
Joined: Dec 2006
Posts: 1,883
Likes: 17
From: Williamsport, Pa
RE: 1973 MIKUNI CARB PROBLEM
have you tried starter fluid to get it running yet? then you can see how it performs and if theres any leaks. I had a super e on mine when i got it definetly thought it was to big but i took it down to my carb guy and hes got it running like a champ to my suprise. I was thinking about a cv carb thats on my other bike as a switch but Its runs great now the only problem i have is leaning it deep to the right and throttling it then it definetly floods it but its a tad rich to begin with. at first it didnt work. also check your valves if you havent. I ve learned a lot from hear and try to share with everyone interested but definetly I aint no expert and dont know much about your carb this is just what ive been doing for the last 3 weeks every night, my neghbors are probally going to lynch me.
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Cruiser
Joined: May 2007
Posts: 207
Likes: 1
RE: 1973 MIKUNI CARB PROBLEM
enrichener up is on (for starting)
this should be the procedure. ign. off/enrichener on(throttle closed)- kick thru about 3-4 times - turn the ign.on and she should start on the next kick, after it starts you can open the throttle and close the enrichener. I ran theold MICcarb. on a sporty, and Norton I had. they are one of the most trouble free carbs ever made.
this should be the procedure. ign. off/enrichener on(throttle closed)- kick thru about 3-4 times - turn the ign.on and she should start on the next kick, after it starts you can open the throttle and close the enrichener. I ran theold MICcarb. on a sporty, and Norton I had. they are one of the most trouble free carbs ever made.
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Road Master
Joined: Aug 2006
Posts: 751
Likes: 6
From: 500 miles south from Artic Circle
RE: 1973 MIKUNI CARB PROBLEM
this type carbs are use in snowmobiles, so spareparts can be asked from there...
As crampfan wrote: slide needs to be completely closed that enricher works. Don't touch to throttle while starting cold. Also as PG wrote carb is little oversize to IH but it should work
As crampfan wrote: slide needs to be completely closed that enricher works. Don't touch to throttle while starting cold. Also as PG wrote carb is little oversize to IH but it should work
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