Another thing to mention about tuning, a rich setting will run a little cooler, while a lean setting will run hotter. I prefer mine on the rich side as well. Also, check your spark plugs. If they have a lot of black with carbon buildup, you are too rich. If your spark plugs have no black but more of a smokey color or white, you are probably too lean. Just my experience. Ride Cool Guys!!
Thanks for putting this together, very helpful! On mine I set the screw to 3 3/4 which really improved idling and throttle response. From stock seems these carbs are set up to run very lean.. (oh and subbed 😁)
I'm rebuilding my CV for a 2001 Dyna. Before I got it, this bike had literally been sitting out in the weather since 2004 or so. The carb was completely gummed (it ran however - with the float valve stuck wide open - lucky I didn't burn it to the ground). I tore it completely down and cleaned it thoroughly. The low-speed needle levels at 1-3/4. I'm waiting on the kit to see how the new needle measures up. Thanks for this great work.
Question: when I turned mine all the way in it seemed to make no difference. I thought it should cut fuel. Spark plugs looked rich (not sure though iridium) I down sized to 42 pilot jet. Had stock 45. Haven't tried to tune again yet due to fixing oil leak but will it be too lean?
Assuming yours is also a Twincam 88, 45 slow (stock from 2000) should work nicely, allowing you to tune it perfectly to a set of open pipes and high flow air cleaner. 42 pilot jet which was in the 1999 models only is too small). If it didn’t stall turning it all the way in, then it would be worth taking a look at your pilot screw. (Maybe the tip is damaged or someone enlarged the hole), check your float height (level might be too high so extra raw fuel is coming through), check your jet needle (it might have been replaced to a high performance one with notches).
@@susandavis5833 Update on my end. I received the rebuild kit and have the carb back on. I also can't get the engine to quit by fully seating the pilot needle. Also, it does NOT want to accelerate and dies unless I pump the throttle.
Thanks for your reply. My bike is actually a 96 fatboy with evo. Hi Flo air and thunderheader exhaust. I let it sit too long and it was cheaper to put new after market carb on. Original jets were 45 and 175? With stock needle new carb was same. Bike ran great when I bought it. However it doesn't run as good now. Thanks again for info. Really helps newbies like me.
No problem. I’m glad the videos are useful. One thing with these Harley carbs is that it’s always best to refurbish your original Keihin carb. No aftermarket replicas can beat them.
The difference in engine running temp at the sweet spot is a lot. ⅒th turn too far in and the pipes will be very hot after 20 minutes cruising. Back out a fraction and the cooling should cope well enough for the cam casing to be no hotter than a very hot drinks cup. Popping on decel is more because you like the idle too low, I like the lope but prefer to be able to use engine braking. At 900 idle hot I get lots of overrun and chugging decel. Set to 1000 and I have to try to get overrun popping. Yes the valve stems are a scary colour with everything set up properly but the plugs tell if it's right or not. Factory setting is too hot is something we can all agree on. Don't run too small main jet for land speed record attempts. Happy days.
Great videos 👍 could you make some video about check valve for the Acceleration pump in the bowl I have 3 bowls where I can only hear it in 2 of them when I shake them
Great info thanks l, had mine 3something turns and running too rich… have It at 2.25 turns now and seem to run fine, any signs if I’m running it too lean to look for?
So you want it to just be flush is what I’m getting from the video I opened the throttle up looked down there got it to be flush bike idles good it’s about 70 out today and it is starting with no enricher like right away only let it sit for about a hour each time I have fired it up
No, this video is only about showing people that your mixture screw base line can vary when you turn it all the way in to seat it. Now disregarding it being flush or not, turn it all the way in until it seats and turn it out 3 turns. That should be a good starting point for fine tuning. (Provided you’re running stock jets and open pipes)
i have a 90 flht with cv40 carb, not original. has evo motor and i am sure it is stock, not sure what exhaust or pipes as i bought it from someone else not running. I am trying to get it running properly without the cough through the carb i know it's running lean cause pipes started getting red after trying to adjust and test the jets. what jets do you think i should try? i also have the easy adjust mixture screw in currently thanks in advance
I’d put a 45 slow in there and then adjust mixture screw when warmed up. I think your main is 165 stock. You can leave that in or bump it up to 180 (it won’t hurt)
Good afternoon, I am the owner of a 2006 Sportster 1200 Custom Harley. The carburetor is stock, it has never been opened, I replaced my bike with vance and hines exhausts and a K&N high flow filter in its original cover, only the filter is a K&N brand. My bike feels slow and gives me very few kilometers per liter in the city. I have heard that I have to change the low and high jets, change it to the size 46 and 185, what do you recommend friend? Thx for all your vids
Hi there, you don’t need to change your jets. What you could do though, is giving your carb a good clean inside, check float level etc. new gaskets, and fine tune it with your mixture screw. Worth checking your spark plugs as well.
@@aronsgarage834 do you have an idea why after startup has a crude gas smell, is it too rich, and also when I apply the gas sharply, it cannot be forced in the low revs, it struggles for a second
I just rode my 99 EG 2200 miles from IN to CA with 95 big bore kit. It ran great for the entire trip until I got to CA. It now backfires through the carb. I replaced the 3 gaskets on the intake. It did not help. Could it simply need to be tuned for the elevation here? Where do I start? Mixture screw? Slow jet? TIA
@@aronsgarage834 mine 97 Evo road king is doing the same thing while warming up from cold engine start on 45 pilot and 180 main with sportster 88 " mid rich" needle, Big sucker air filter and V&H pipes. When engine is wormed up, runs quite ok 99% - accational carb bacfire. I did tried 48 pilot and spark plugs were to black running rich but did run much better when engine was cold and quite sluggish when engine was hot. Im constantly checking every time for intake leak with propane gas and brake cleaner but nothing to be certain for leak - i did changed the seals and new intake flanges. Maybe its an Evo warming up thing, since beeing my first evo...earlier i had 2000 TC 88 dyna never behaved like that while warming up. every time
@@aronsgarage834 My thought to. using 45 and warm bike sputters on idle when 1/2 turn out so i have mixture screw on 3-3,5 turns out for now. after that is no efect at all or even worse - slugish on idle and acceleration. Becouse of that fact i would maybe try even 44 if i had it- afcourse expecting worse carb bacfire until engine is warmed up. When using pilot 48 i had 1,5-2,5 turns out but bike rans even with screw fully in without any efect on sputtering so i figured that 48 got to be to much becouse of that, thats why i insist trying with 45 and suspecting on some air leaks but cant find them. maybe 46 would be the magic number heheheh when i had TC88 dyna y2000 sparks looked totaly diferent and much more healthier , thats why im insisting in trying to achive that .... Something crossed my mind this moment - float setup? i do have it maybe a little on the rich side, couse i remember of trying to compensate or eliminate cold backfire with some "rich" fuel height in bowl ... do you think maybe the float hight couses rich efect on sparks - maybe efecting on emuslion tube and atomization of fuel in without wanted efect on backfire? damn, this is science heheh... maybe i should of get my masters from HD and carbs not chemistry hehehehehehehhe
I left the 195 but went to a 50. Cleaned the carb and it ran better with no backfiring for a few hundred miles again. Mixture screw is 1.5. Now it is leaking out through the plunger boot so I am going to replace the float needle and accelerator pump diaphragm. I set the float at the correct position on the bench at 15degrees. To me none of this makes sense if it was running perfect for 2200 miles and then all of a sudden it starts back firing. Nothing internally changed so it must be a leak but no leaks. Similar elevation as IN but way less humidity. I am at a loss!!!!
It might be a bit lean, or you have an air leak around the air cleaner, vacuum hose or breather. Or, which actually happened to me, the port hole of the slide in your carburetor is overly drilled out. People used to drill it out like crazy in the attempt to tune and gain better throttle response, but all it did was mess up idling when coming to a stop. Well, it definitely did for me. Hope this helps
Sir, can you please help me understand this? When you turn out the fuel mixture screw to where it no longer sticks out of the car mouth, and is barely visible, for example, at 1 1/2 turns out, do you then continue to turn out the mixture screw something like three more turns, for a total of 4 1/2 turns?
@@aronsgarage834 Thanks, but I thought of another thing. When you have the carb on the bike, but with the air cleaner off, can you look inside the mouth of the carb to see if the tip of the fuel mixture screw is still visible?
@@aronsgarage834 I’m not sure as I just inherited the bike a few months ago I think it’s 155 it has Vance and Hines pipes on it but original breather. when I put new plugs in it runs great for a while than back to popping I have an ez adjust I’m putting in today and didn’t know how many turns out I should go out.
@@aronsgarage834 my float bowl gets hung up too so I cleaned it all out and put it back together but still has gas on floor when fuel left on over night could my float bowl height make the bike run rich?
First you want to pull the carb and find out what size pilot jet you got in there, as well as what kind of needle. They affect mixture a great deal. Only then you can experiment with the turns.
What a great tip!! I've always counted the turns...but never made sure the mixture screw was level with the throat body first. That's a good one!!
Thanks for the feedback!
Another thing to mention about tuning, a rich setting will run a little cooler, while a lean setting will run hotter. I prefer mine on the rich side as well. Also, check your spark plugs. If they have a lot of black with carbon buildup, you are too rich. If your spark plugs have no black but more of a smokey color or white, you are probably too lean. Just my experience. Ride Cool Guys!!
Thx a lot bro
Thank you explains why I was having a hard time going by the book I’ve got the second carburetor
Thanks for putting this together, very helpful! On mine I set the screw to 3 3/4 which really improved idling and throttle response. From stock seems these carbs are set up to run very lean.. (oh and subbed 😁)
Most welcome! Yeah, they are set pretty lean, especially when we throw on the high flow air-cleaners and open pipes 😁
I'm rebuilding my CV for a 2001 Dyna. Before I got it, this bike had literally been sitting out in the weather since 2004 or so. The carb was completely gummed (it ran however - with the float valve stuck wide open - lucky I didn't burn it to the ground). I tore it completely down and cleaned it thoroughly. The low-speed needle levels at 1-3/4. I'm waiting on the kit to see how the new needle measures up. Thanks for this great work.
No problem. Good luck with your project.
Question: when I turned mine all the way in it seemed to make no difference. I thought it should cut fuel. Spark plugs looked rich (not sure though iridium) I down sized to 42 pilot jet. Had stock 45. Haven't tried to tune again yet due to fixing oil leak but will it be too lean?
Assuming yours is also a Twincam 88, 45 slow (stock from 2000) should work nicely, allowing you to tune it perfectly to a set of open pipes and high flow air cleaner. 42 pilot jet which was in the 1999 models only is too small). If it didn’t stall turning it all the way in, then it would be worth taking a look at your pilot screw. (Maybe the tip is damaged or someone enlarged the hole), check your float height (level might be too high so extra raw fuel is coming through), check your jet needle (it might have been replaced to a high performance one with notches).
@@susandavis5833 Update on my end. I received the rebuild kit and have the carb back on. I also can't get the engine to quit by fully seating the pilot needle. Also, it does NOT want to accelerate and dies unless I pump the throttle.
Thanks for the update 👍
Thanks for your reply. My bike is actually a 96 fatboy with evo. Hi Flo air and thunderheader exhaust. I let it sit too long and it was cheaper to put new after market carb on. Original jets were 45 and 175? With stock needle new carb was same. Bike ran great when I bought it. However it doesn't run as good now. Thanks again for info. Really helps newbies like me.
No problem. I’m glad the videos are useful.
One thing with these Harley carbs is that it’s always best to refurbish your original Keihin carb. No aftermarket replicas can beat them.
Thank you
Thank you Sir!. Please Mikunu HSR 42 video
The difference in engine running temp at the sweet spot is a lot.
⅒th turn too far in and the pipes will be very hot after 20 minutes cruising. Back out a fraction and the cooling should cope well enough for the cam casing to be no hotter than a very hot drinks cup.
Popping on decel is more because you like the idle too low, I like the lope but prefer to be able to use engine braking.
At 900 idle hot I get lots of overrun and chugging decel. Set to 1000 and I have to try to get overrun popping.
Yes the valve stems are a scary colour with everything set up properly but the plugs tell if it's right or not.
Factory setting is too hot is something we can all agree on. Don't run too small main jet for land speed record attempts.
Happy days.
Great videos 👍
could you make some video
about check valve for
the Acceleration pump in the bowl
I have 3 bowls where I can only hear it in 2 of them when I shake them
Sorry I only saw this now. It’s probably stuck. Did you try carb cleaner and compressed air?
Great info thanks l, had mine 3something turns and running too rich… have It at 2.25 turns now and seem to run fine, any signs if I’m running it too lean to look for?
Yes, too much popping on deceleration, white ish color on spark plugs, and not dropping quick enough when blipping throttle it would hang a bit.
So you want it to just be flush is what I’m getting from the video I opened the throttle up looked down there got it to be flush bike idles good it’s about 70 out today and it is starting with no enricher like right away only let it sit for about a hour each time I have fired it up
No, this video is only about showing people that your mixture screw base line can vary when you turn it all the way in to seat it. Now disregarding it being flush or not, turn it all the way in until it seats and turn it out 3 turns. That should be a good starting point for fine tuning. (Provided you’re running stock jets and open pipes)
So all the way up, the needle is allowing more gas thru? And down is taking gas away? Or is that backwards
Backwards. When needle is down disappearing in the carb body it’s letting more gas through (as you’re turning anticlockwise.
i have a 90 flht with cv40 carb, not original. has evo motor and i am sure it is stock, not sure what exhaust or pipes as i bought it from someone else not running. I am trying to get it running properly without the cough through the carb i know it's running lean cause pipes started getting red after trying to adjust and test the jets. what jets do you think i should try? i also have the easy adjust mixture screw in currently
thanks in advance
I’d put a 45 slow in there and then adjust mixture screw when warmed up. I think your main is 165 stock. You can leave that in or bump it up to 180 (it won’t hurt)
Good afternoon, I am the owner of a 2006 Sportster 1200 Custom Harley. The carburetor is stock, it has never been opened, I replaced my bike with vance and hines exhausts and a K&N high flow filter in its original cover, only the filter is a K&N brand. My bike feels slow and gives me very few kilometers per liter in the city. I have heard that I have to change the low and high jets, change it to the size 46 and 185, what do you recommend friend?
Thx for all your vids
Hi there, you don’t need to change your jets. What you could do though, is giving your carb a good clean inside, check float level etc. new gaskets, and fine tune it with your mixture screw. Worth checking your spark plugs as well.
@@aronsgarage834 I'l do!!! thx bro
No probs, brother:)
How did you bypass the EGR system?
I don’t have EGR on mine.
Hi, is that mixture screw for air or gas flow on the CV carburetor?
Gas. You’re adjusting how much gas goes through the idle port hole.
@@aronsgarage834 do you have an idea why after startup has a crude gas smell, is it too rich, and also when I apply the gas sharply, it cannot be forced in the low revs, it struggles for a second
Could be too rich. Check spark plug to verify (should have a light tan look) and if smoke is black then you’re definitely rich.
I just rode my 99 EG 2200 miles from IN to CA with 95 big bore kit. It ran great for the entire trip until I got to CA. It now backfires through the carb. I replaced the 3 gaskets on the intake. It did not help.
Could it simply need to be tuned for the elevation here? Where do I start? Mixture screw? Slow jet?
TIA
Is it backfiring more while warming up from cold start up or more like when it’s fully warmed up?
@@aronsgarage834 mine 97 Evo road king is doing the same thing while warming up from cold engine start on 45 pilot and 180 main with sportster 88 " mid rich" needle, Big sucker air filter and V&H pipes. When engine is wormed up, runs quite ok 99% - accational carb bacfire. I did tried 48 pilot and spark plugs were to black running rich but did run much better when engine was cold and quite sluggish when engine was hot. Im constantly checking every time for intake leak with propane gas and brake cleaner but nothing to be certain for leak - i did changed the seals and new intake flanges.
Maybe its an Evo warming up thing, since beeing my first evo...earlier i had 2000 TC 88 dyna never behaved like that while warming up.
every time
Yeah 48 is too big even for TC88. How many turns out is your mixture screw at?
@@aronsgarage834 My thought to. using 45 and warm bike sputters on idle when 1/2 turn out so i have mixture screw on 3-3,5 turns out for now. after that is no efect at all or even worse - slugish on idle and acceleration. Becouse of that fact i would maybe try even 44 if i had it- afcourse expecting worse carb bacfire until engine is warmed up.
When using pilot 48 i had 1,5-2,5 turns out but bike rans even with screw fully in without any efect on sputtering so i figured that 48 got to be to much becouse of that, thats why i insist trying with 45 and suspecting on some air leaks but cant find them. maybe 46 would be the magic number heheheh
when i had TC88 dyna y2000 sparks looked totaly diferent and much more healthier , thats why im insisting in trying to achive that ....
Something crossed my mind this moment - float setup? i do have it maybe a little on the rich side, couse i remember of trying to compensate or eliminate cold backfire with some "rich" fuel height in bowl ... do you think maybe the float hight couses rich efect on sparks - maybe efecting on emuslion tube and atomization of fuel in without wanted efect on backfire?
damn, this is science heheh... maybe i should of get my masters from HD and carbs not chemistry hehehehehehehhe
I left the 195 but went to a 50. Cleaned the carb and it ran better with no backfiring for a few hundred miles again. Mixture screw is 1.5.
Now it is leaking out through the plunger boot so I am going to replace the float needle and accelerator pump diaphragm. I set the float at the correct position on the bench at 15degrees.
To me none of this makes sense if it was running perfect for 2200 miles and then all of a sudden it starts back firing. Nothing internally changed so it must be a leak but no leaks. Similar elevation as IN but way less humidity.
I am at a loss!!!!
My bike starts and idles fine, after stopping it idles high.. Can you help me out?
It might be a bit lean, or you have an air leak around the air cleaner, vacuum hose or breather. Or, which actually happened to me, the port hole of the slide in your carburetor is overly drilled out. People used to drill it out like crazy in the attempt to tune and gain better throttle response, but all it did was mess up idling when coming to a stop. Well, it definitely did for me. Hope this helps
@@aronsgarage834 Thanks.I'll let you know.
I changed the spring and kept tweeking on it. Seems to have done the trick.It's a fine line to get it right..Thanks
Glad it’s good now. Did you have a short aftermarket spring in it?
Sir, can you please help me understand this? When you turn out the fuel mixture screw to where it no longer sticks out of the car mouth, and is barely visible, for example, at 1 1/2 turns out, do you then continue to turn out the mixture screw something like three more turns, for a total of 4 1/2 turns?
That would be too much. Try another 1.5 half turns. That would be a total 3 turns out. That’s a good starting point for tuning.
@@aronsgarage834 Thanks, but I thought of another thing. When you have the carb on the bike, but with the air cleaner off, can you look inside the mouth of the carb to see if the tip of the fuel mixture screw is still visible?
Yes you can. You just need to open the throttle to raise the butterfly, and you might need a flashlight.
Mine only runs rich at first when bikes warmed up it doesn’t. My plugs are black and it pops when I’m giving it gas?
You’re definitely rich if plugs are back. What pilot jet are you running? What’s your setting?
@@aronsgarage834 I’m not sure as I just inherited the bike a few months ago I think it’s 155 it has Vance and Hines pipes on it but original breather. when I put new plugs in it runs great for a while than back to popping I have an ez adjust I’m putting in today and didn’t know how many turns out I should go out.
@@aronsgarage834 my float bowl gets hung up too so I cleaned it all out and put it back together but still has gas on floor when fuel left on over night could my float bowl height make the bike run rich?
First you want to pull the carb and find out what size pilot jet you got in there, as well as what kind of needle. They affect mixture a great deal. Only then you can experiment with the turns.
Oh yes it does. If it’s set rich, you’ll be rich and can’t set it properly with the mixture screw.
I’ve cleaned my carb, every part of it, it runs with the choke out but when it’s in, it dies
Sounds like you’re very lean. How many turns is your mixture screw set at?
I would say your low jet orifice is pluged ,mine was like that until I ran a very fine wire through it. It was like brand new after.