It seems that I have some serious carb cough issues...not on normal, highway speeds, but during start/stops on heavy traffic or when changing gear from 1st to 2nd (or 2nd to 1st)...I sometimes get 2-3 coughs in a row, even had the engine stopped running a couple of times... I tried to rejet my carb with the help of my uncle (who runs a bike workshop, not on Harleys, but has great expertise on bikes in general) but no solution to the problem...

We then asked another mechanic, who has some experience on Harleys (I know this may sound weird, but Harleys are not that popular in my area, damn Japanese bikes...there are about 40-50 Harleys here and no Harley dealer or workshop), so he said that this is common on all carburated Harleys, not even the MoCo can make these bikes run smoothly and with no problems...he then said that the problem is not the carb but the engine's tuning (he said something called advance or avance)...anyway, he explained, at some points, the cylinder fires with the piston being half-way up and with no fuel in the chamber...when the piston is full up and fuel enters the chamber, there is no spark so the engine spits the unburned fuel, causing this gap in the engine's run... the engine must be tuned to eliminate, but not completely vanish, the problem...he said that fixing the problem on low rpms could start another problem on high rpms etc and proposed not to change engine's tuning but change my driving habbits, e.g. use linear throttle acceleration and not reving the bike during gear changes...no clear solution...

The bike is stock at the moment...I plan to get new pipes and air filter...will these improve engine's run? How can I fine-tune my engine? H E L P please!

 

First, this other "mechanic" doesn't have a clue of what he is talking about. Stay away from any of his advice.

What size jets (pilot & main) are in the carb?
How many turns OUT is the mixture adjustment screw?
Are you following the proper procedure for adjusting the mixture screw?
How many miles are on the bike?

 

Well, all these he said sounded weird to me...ok, I understand the fact that the bike may need to be tuned, but not the fact that this is how it is supposed to work...

The bike is completely stock, so I guess everything in the carb is stock (I don't know if this answers your questions on carb details)...my uncle just twisted the mixture screw a bit to see if the carb stops coughing...it's a 2006 model (purchased on August 2006) and it only has 1500 miles (1000 miles when I bought it a month ago)...it had a service at 700 miles about 2 years ago, just oils, oil filter and changed something called crankcase sensor...the bike rested a lot in a garage...I feel my bike needs a good service from a Harley expert (also install pipes and air filter), which means 7 hours in a ferry or 300 mile coast trip to Patras...

Thanks for your reply...

 

With that few miles on an almost 5 year old bike, it has spent most of it's life just sitting unused. There's a very good chance that the carb is just gummed up from the previous owner letting it sit with stale gas in it. I would start by disassembling the carb and giving it a good cleaning.

 

I think the reason carbs spit back is usually caused by a lean condition.

I don't know anything about the carbs Harley used, but most have idle speed mixture adjustments, slide adjustments, needle adjustments, and main jet adjustments, each one does mostly one point in throttle opening.

You could try easy experiments like raising the needle (richer 1/4 to 1/2 throttle, adjust the idle mixture screw richer, and see what happens.


On my old Triumphs, they would pop through the carbs from time to time when grabbing a handfull of throttle at idle, as the sudden opening of the carb did not allow enough gas for a moment.
Modern carbed bikes have cv carbs and should not do that if set right, that is the reason they use CV carbs, more steady mixture control...

I agree, a bike that does not get used a lot often has all sorts of problems.
Bikes with carbs should have the gas drained out of the carb and the fuel line plugged when not in use for a while.
I dont know how many carbs I have seen that were totaly hosed up or ruined from sitting with gas in them.
I think modern gas goes bad faster then the old stuff used to.


Brett

 

Adjust the idle air mixture screw first and go from there.

 

I doubt the carb is stock, seeing that it has an a/f enrichment screw in place already. Follow cHarleys advice and start by cleaning the carb and going from there. This will also give you a chance to note the jet sizes while your in it.

 

Try putting premium gas in it . That stop most of my coughing issues.

 

Hello to Greece, Maidenas try putting some good fuel treatment in the tank first. I do not know if you can get a product called Sea Foam over there, but it is exellent stuff.

If no S/F then use a quality treatment doubling the rate stated to use and see if coughing/spitting improves. If it does not then you will have to disassemble and clean the carb. Sitting in the garage is Not what a Harley likes to do.

Go do a search for CV carbureator and you will find the info that you need.

 

Maybe this is why god made fuel injection.