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It certainly sounds like you're too lean. I'm not a CV carb guy, but I'd suspect something wrong with that carb. You could try a bigger jet like moosh sez, but I'd be thinkin' about a new carb.
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Location: NC and across the Mississippi every opportunity
Posts: 1,118
Too lean on the main jet sounds like.
I had nearly the same thing the other day when I went from 3 to 2 on the needle with a 185. It'd dig real hard from any rpm, but the first 1/8 throttle it was near dead like out of fuel. And I still wonder if I had a slight vacuum leak on the grommet... but went back to 3 on the needle and removed the (new) grommet, wiped and lightly greased. It was happy again, but not as hard pulling. Dropped 5 on the main today (180) but too tired from work for anything other than the long loop home to warm the oil, but it felt good.
170 is usually a tick lean without with a drilled slide. I was running (stock) a 175 which was a little lean and after I drilled the slide, and it was way lean!
Pull your carb and grommet, wipe it off good and get the bolts snug before you try anything else much.
PS was running 48/175 @ 46/52 mpg before I drilled and switched needle. 45/185 until today @ 42/49mpg
I have been wondering about a bigger main jet. I have a 180 and almost put it in last week but at the last minute didn't. I was putting a 45 slow in at the time and I am trying to do this one at a time to see if I can figure out the issue. Maybe tomorrow morn I'll put the 180 in before I ride the half hour to the closest dealer. See how it feels. I have a 48 too so I'll put that on the list of things to try. I am going to pull the manifold off so I might as well change the gaskets while I am in there even if they look ok. I'll get a 89 sportster needle too just in case I want to try it.
I made a manifold bolt tool from a 1/4" ball end allen. I heated the ball end with a torch and bent it over 90 degrees. I did it on my friends 100 year old anvil (pretty cool) and quenched it in cold water after. And it even fits. Life is good.
All the reading and searching I've done in the last 2 weeks point to either leaks and or a lean condition so that's what I've been basing my fiddling on. Just finding the combination to get things right is a pita but I am going to win this fight. 10 years ago this carb would have been laying on the rifle range full of .308 holes by now. I'm a little more patient these days so I'm not gonna let it off off easy though. I still have a few things to try before I load up my FAL.
Ok, you state the cough is at 1/4 throttle. At this point the pilot system is the main control and it is in transition to the needle/slide. You state that you can turn in the mixture screw all the way and the bike will still idle. This shouldn't happen, the screw on a CV controls how much air is admitted to the mixture. By closing it you are admitting no air. Therefore you have a lean mixture. The first thing I would do is rebuild the carb. Soak it in lacquer thinner/carb cleaner then blow out all passages. Replace all gaskets and o-rings, reset float level. Then replace all manifold gaskets and check the vacum lines and diaphragm in the carb for leaks.Then try readjusting the air mixture screw.
Drilling the slide out can work on lighter, well geared bikes and is an old trick for the racing crowd. However on the street it causes the slide to rise too soon and can cause a flat spot, cough and poor mileage. Hope this helps feel free to call us at 518 469-8426.
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SPEED COSTS, HOW FAST DO YOU WANT TO GO ????
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Yeah that makes sense. Thanks for the help. I am getting crappy mileage too. I'll get a rebuild kit and try that too. Aside from the carb rebuild and the 3 gaskets for the manifold, what else would you be looking at for a leak?
I have the same nuisance problem. Right from idle to 1/8 turn on throttle the bike coughs, and putts like on one cylinder, if I immediately let off and hit the throttle harder is goes. Once I get pass that the rest of the throttle is great. If I lug the motor in top gear and crank the throttle gently I can create the same sputter; but just slightly.
I have checked everything else and am suspecting a problem with the pilot needle, but I’m not sure what could be wrong with it.
I’m running a Mikuni carb but they all work the same generally.
Miacycles is probably giving us the best advice…but it would be nice to find and easier solution!
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Atlas frame, 99 evo, head Quarters cam & ignition, wiseco pistons, mikuni carb, primo/vera pro clutch
I am going to rebuild the carb, but of course the dealer doesn't have a rebuild kit. I can look thru the book and tell them what gaskets and such that I want so HD can nickle and dime me to death buying each piece seperately. I'll find a kit online and save my nickles and dimes for the gas tank. The dealer didn't have some of the basic orings and rubber gaskets for the carb anyway. lol They did have the intake rubber gaskets so I got a pair of those and the one that goes from the carb to the manifold. I'm going to at least replace all those and then go shopping on the www later for a rebuild kit. I wish I hadn't drilled that slide. Maybe I'll get a new slide Whatever, live and learn.
Thanks for all the input on such a dead horse subject everyone.
I have the same nuisance problem. Right from idle to 1/8 turn on throttle the bike coughs, and putts like on one cylinder, if I immediately let off and hit the throttle harder is goes. Once I get pass that the rest of the throttle is great. If I lug the motor in top gear and crank the throttle gently I can create the same sputter; but just slightly.
I have checked everything else and am suspecting a problem with the pilot needle, but I’m not sure what could be wrong with it.
I’m running a Mikuni carb but they all work the same generally.
Miacycles is probably giving us the best advice…but it would be nice to find and easier solution!
try 0 lash at the pump push rod, this should help
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trouble with Italian food ? ..... 3 days later your hungry again
So I put the new intake gaskets and grommet in today. The old ones were tired but seemed serviceable. Also put a 180 jet in (ah why not?).
So right now I have the dynojet still in and a drilled slide, 45/180, dynojet needle with the clip on 3, and I stopped 4 times while out riding to change the mix screw starting at 2 and ending at 3.
It seems to run a little smoother, but it still coughs, farts, sneezes, or whatever you like to call it. Bastard thing. Guess I'll try again once I get a rebuild kit.
I beat the rain home by this time though so the day did have at least one victory for me.
