I am making this post because I see where alot of people are posting about lack of speed, gas mileage, jetting issues, over jetting, do's and donts, leaks and general carb questions.

Most mechanics will have you think that the problems with your harley are worse than they really are (we have all been there) but instead of paying and ive heard of even as 120$ a hr for labor work that may or may not be the issue and the problem seem to return after a few days or in cold or super hot weather.

First is the symptoms of the bike::::::
1: how fast did the problem occur (hours, min, days, etc)
2: determine the sound its making (pop, bang, blub blub, wip, pshhh, cough)
3: Mileage is only for determining the age of the carb before modifications so we can decide where to go from there and what to check next
4: check the obvious (plug wire off, bad plug, no gas or bad gas, petcock off, vacume leaks)
5: Make sure your choke aka en-richer cable is not just moving on its own when riding down the road

Ok some issues that I will describe will have the same symptoms and may leave you confused but i will try to make them as clear a possible and even then you may have to check multiple things to fix a problem.

First do a oil change and change spark plugs and hell even new plug wires and get a new stock air filter do not get the paper filters unless you had one before, make sure your choke is working and screwed all the way in to the carb (this is 20% of all harley issues in the carb area which most dont think about) next adjust your fuel float to the correct level watch video at (www.youtube.com/watch?v=Xj220oY26Yo) and if you are leaking fuel adjust fuel float and if it still floods then change your fuel stop needle or plunger or whatever some people call it make sure you buy the right one 3 or 4 guide fuel stop needle (www.cv-performance.com/carburetor-parts/) and use premium (93 octane) fuel just in case you have pre-detonation and gap you plugs to .035 or .040 and check to make sure your accelerator pump is working its on the side of the carb.

You will find that this may fix your issue congrats you just save a lot of money. You may find yourself with a new issue when you accually fix those problems as explained above but when you take it to a shop a lot of harley mechanics know a quick fix which include shimming the choke cable or unscrewing (just a little) of the choke cable connected to the carb which will fix a lean low jet condition meaning coughs or spits back threw the carb and then you get charged a butt load for labor and a jet kit never installed..... If ya have problems still well keep reading for more issues.


1: bad gas mileage- average most twin harleys will get 30 to 50 mpg depending on you modifications to the carb, pipes, air cleaner and the way you drive.
2: lack of speed- well if it rolls and goes down the road threw all gears and clutch grabs good and motor is running ok, with occasional smoke in hot weather or even a backfire out the exhaust...........Your bike is to rich (meaning to much fuel) this would be a jetting issue or air fuel screw needs to be turned in 1/4 turn

If your bike spits or coughs back threw the carb assuming your timing and everything else is ok....then your low jet is to lean may or may not do it wide open throttle
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OK here is where these issues may fix multiple problems

3: jetting issues- ok if you have a stock bike with nothing done to it then leave it alone if there is nothing wrong with it...... unless your looking to upgrade a few basic items like the exhaust and air filter to make it cooler or faster or whatever your flavor is, any other things like cams and polishing is far more complicated and is really a waste when trying to do anything other than doing drag racing unless you like wasting money that you will never use as a daily driver bike.


All these lower calculations are based on a stock 1340 motor and a minor modified 1340 anything else should be done by the guys that do drag racing for a living or people that have lots of money.

ATTENTION FUEL IDLE NEEDLE turn it out 3 full turns from lightly seated to get your starting point because the max turns out is 3 turns recommendation no more

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Pilot Jet (Slow Jet)
50 richest will cause blub blubs slug mode and will fix coughs back threw the carb and will cause possible backfire threw the exhaust at idle speeds and idle, will cause slow overall speed at cruise.... in unmodified 3 1/2in bore evo motors..... UNLESS you are the 3 5/8in bore evo motor, suggested items may vary for this jet is a washer under the main stock needle, 1/8 drilled out hole on the vacuum slide, no restrictions exhaust, high flow air filter or no filter,cam ,rollers rockers ,port and polish .... and still may vary on ignition and bore size and weight and may have to go higher on jet

48 when in doubt use this jet this usually cures, cough back threw the carb, blub blub slug , most speed issues, backfiring, gas mileage will be reduced by a little....don't use this jet if you are stock evo UNLESS you are the 3 5/8in big bore stock, this jet can handle drag pipes and high flow air filer and (optional) cam and (optional) ignition and stock bore of 3 1/2 and one small washer under main jet needle and 1/8 drilled hole in vacuum slide

46 (http://www.cv-performance.com/harley-pilot-jet/) this is the best jet for exhaust and air cleaner changes and a good starting point for your jets can handle drag pipes and k and n air filter and cam with 3 turns on the fuel mixture screw and one washer under the main needle and 1/8 vacuum slide hole drilled, giving you the best gas mileage for your loud cool look.

45 usually stock for most 3 1/2in bore evos if not stock then this jet will be too lean bit not in all cases like just changing to medium restricted exhaust or a medium restricted intake, you may just be able to turn up the idle mixture screw 1/4 turn and it fix everything if you do this and still cant fix the problem it will cause a spit and cough back threw the carb called a lean condition and will do it at high speeds also may not cough or spit back threw once the throttle is wide open

42 lean (can be found in some evos only to be used with air restricted intakes and exhaust and altitudes issues and epa restricted areas) this may vary greatly will give great gas mileage if you can get your mod bike to run


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Main Jet 200, 195, 190, 185, 180, 175, 170

Contrary to popular belief this is not to important till after about 3000rpm and even when this jet starts to work the low is still helping with fuel also.
First thing with you low speed jet taken care of and vacuum hole on the slide drilled to 1/8 and a washer under your STOCK STOCK STOCK needle start the bike and warm it up then turn the throttle at a medium speed to full throttle and go back to no throttle as fast as possible if it sounds good as in smooth revs up and smooth decel down then its good you didn't have to change your stock main jet and your getting max gas mileage if it just sounded bad or seems to be getting hotter than normal go up one main jet size never hurts to go up one to see if it fixes the problem.


DO THIS AFTER YOU HAVE STARTED YOUR BIKE WITH THE 3 TURNS OUT ON THE FUEL IDLE NEEDLE AND YOUR NEW JETS INSTALLED when picking your jet it will make it easier and also easier when you screw it back in a 1/4 turn at a time till the stumble happens if there is no stumble when you screw it all the way to lightly seated then chances are you may have the wrong low jet but maybe you like the blub blub sound or your idle is way over 900 rpms fix if ya want if not then screw it out 2 turns and then road test it if it dont pop or slug along or cough then you good but do this after you have everything fixed to achieve the maximum gas mileage for your mods

The 1/8 hole in the vacuum slide you dont have to do its just to drop rpm rate faster

!!!!!!!!!!!!!!EDIT!!!!!!!!!!!!!!!! One thing i wanted to mention that i failed to mention in my original post
IF it coughs at idle threw carb your low jet is to small, if your Mixture screw does nothing when screwing it in after your 3 turns out, then your low jet is to big.
IF you turn your throttle slowly and the slide starts to move then it coughs back threw the carb the you need to add one more small washer under your needle or more till its smooths out, this is your mid range on your carb
IF it coughs back threw the carb when max throttle is applied then your main jet is to small

IF it backfires threw the exhaust at idle your low jet is to big go down a jet or two
IF it backfires threw the exhaust when you start to roll the throttle and the slide starts to move then you have to many washer under your needle, take one away
IF it backfires threw the exhaust at full throttle then your main jet is to big, go down one or 2 sizes




OK guys this is a general idea this may not work for all harley carbs and I cant see your mods or hear your bike. So well i hope this saves yall some money and if you need more help ill try my best. So if i did make a error in all this madness or you can explain eazier than i did feel free to help thats what we are here for.

ENJOY THE RIDE

 

So.... Who are you?

 

Just a guy who fixes harleys evos in his free time

 

Welcome to the nut house!!!!

 

good advice and explanation welcome

 

Speaking as a Harley mechanic I think you are seriously off your meds........

 

well some people don't understand the mechanic talk, so i figured i break it down for them make it easier and with alot of the sites or advice i noticed its vague about jets and there explination making the complexity of the issue into something big when carb problems are actually fairly easy fixes and most dont even say about checking the obvious, it was more or less something for people looking to get into fixing there own bike or just naturally curious about how to fix there bike or upgrade and what they can expect

 

Thanks for the info. Welcome to the asylum.

 

thanks its nice to finally be able to share some knowledge about what ive learned about evos for the past 10 years.

 

One of the hardest parts was breaking the damn bowl screws loose. Mine is stock except for VH Longshots and hypercharger and I'm running 45 185 with a 88 Sportster needle. I did drill the slide with 7/64 bit and sand it smooth with 2000 grit paper. Mine runs like a champ.