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2003 Harley Sportster Backfires through carb when I let it idle down and give it gas quick. I put a #45 pilot and #170 Main with no luck. Runs great other then the popping. Sometimes I believe it is running lean.

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6 Suggested Answers

6ya6ya
  • 2 Answers

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Posted on Jan 02, 2017

landsend
  • 1066 Answers

SOURCE: runs great until hot.

put some fuel cleaner in the fuel tank and replace the spark plugs.

Posted on Mar 22, 2009

  • 5 Answers

SOURCE: bike will not idle witout having choke on a bit

I have a supermagna and used fuel stablizer once and it wasnt fit it gummed my carbs up,ive cleaned mine often and it isnt rocket science,remove the tank airbox assembly,loosen up the boot flanges that hook the carbs to the motor(ones on carb)then remove the carbs,then the cables,choke and throttle,do not remove carbs from assembly(leave all 4 together)remove the bottoms and tops of a carb,removefloat and jet,then remove all the brass jets and clean them so you can see through holes,,blow out all the holes in carbs,and reasemble,works for me every time,about two hours to do,good luck

Posted on Apr 05, 2009

  • 1 Answer

SOURCE: 1983 honda GL1100I, New spark plugs, good

When I recently ordered parts from Saber Cycle, they included a piece of information that pertained to my motorcycle, which is also a 1983 Honda Goldwing GL1100 Interstate. Here is what it says, I hope this helps:

Air Cut-Off Valve

The air cut-off valve is an extremely important part of the fuel/air intake system that is frequently missed even my competent mechanics, most of whom are not even aware of its existence or how it functions.

Every GL1000 has one, located in the air intake tube, between the air cleaner box and the manifold. Every GL1100 has four, located in the top air intake passage of each carburetor, and every GL1200 has one located in the plenum box below the air cleaner box similar to the GL1000.

These valves are "air blockers", along with the carburetor o-rings, serving to restrict air flow and increase the fuel/air mixture ratio when the carb slides are in the lower RPM range, up to closed so that the machine will start and idle smoothly with virtually no choking and accelerate rapidly, with no stumble or hesitation.

When typical starting requires heavy and prolonged choking to keep the bike running, when stalling and hesitation occurs even while "warmed up" and when backfiring pops while the throttle is shut off while cruising, most people will start fooling with the air screws to try to overcome the problem, only making it worse along with reducing their gas mileage.

Running with dysfunctional air cut-off valves can causes severe engine damage or failure. When the valves are dysfunctional, the engine pulls nearly total air in the low RPM range through the carbs and on to the combustion chamber. The fuel/air ratio is extremely poor with pre-ignition long before the normal 38 to 40 degree firing point, generating an enormous amount of heat, with no power, which is trapped a longer period of time in the cylinder before the exhaust valve opens.

This heat goes mostly up through the cylinder head, gradually incinerating the head gaskets and allowing engine coolant (anti-freeze) to seep into the engine. You can easily spot when you are in trouble by a puff of bluish-white or white smoke on first starting the engine. Don't leave it alone. Change head gaskets immediately or you could take out your bottom end bearings, ruining the engine.

For those of you installing new exhaust systems, you will discolor your headpipes, either blue (lean state) or gold (rich state). You can destain your pipes using "blueaway" or "blue-off" but be careful not to rub the chrome, just dab gently.k These compounds are usually purchased at a Harley dealer or Harley oriented aftermarket shop.

Honda genuine pipes, like many Yamaha pipes, have a double wall for a portion of the headpipe which masks this discoloration-but also masks a bad state of tune. Even if your pipes are original and still in good shape, don't think that you are OK if the bike has any or all of the dysfunctional air cut-off valve running and performance characteristics.

If your 1975 to 1987 Gold Wing is not getting 50-58 miles per gallon (20-23 KM/Liter), you have one of the most obvious signs of trouble. It is likely your air screws have been backed out to try overcome the effects of the poor running, stumbling, starting and stalling and quitting.

Resynchronize all four carbs to the #3 carb vacuum level using mercury carb sticks or vacuum dial gauges. Stay with strict use of the setting levels in either the Honda, Clymer or Haynes manuals. Do not attempt to tune any other way! Guessing will not work and can cause considerable engine damage!!!

Posted on Sep 26, 2009

  • 6 Answers

SOURCE: 2002 HONDA SHADOW ACE 750 CARB

It sounds like you may have or will be jetting your carbs. I did this using the directions with the kit and used the Clyman manual for this bike to show me step by step how to remove the carborator. You will only need to attach 2 of the 4 hoses on your carb. syncronizer. If I remember right, you need to remove the bolt-on cooling fins to expose the engine block. The is a black screw or bolt that you take out and screw the threaded metal adapter of the sync tool. Be careful using the sync tool. Be very light on the throttle or the vacuum in the cylinder will **** in the mercury from the sync tool - not good. The problem you are stating on idle & backing off sometimes happens when the carbs are running rich (too much fuel) Hope that gets you in the right direction.

Posted on Oct 03, 2009

1fastbob
  • 301 Answers

SOURCE: Honda Valkyrie Interstate 1999: 25000 miles Cobra

Stock size for the slow jet is 35. Some guys put in 38's to make them less prone to getting plugged. I would say that you still have gunk in the slow jets. Also turn the pilot screws out 2 1/4turns. If the exhaust pops and you have no exhaust or vacuum leaks turn the pilot screws in 1/4 turn at a time till it goes away.

Did you change the plugs and the air filter? How about checking and or replacing the vacuum lines?

You might try a full bottle of Techron fuel system cleaner in a tank of gas. It may clear the problem up.

I had to clean the jets on my 1999 I/S twice and it's not a fun job.

Hope this helps.

Bob

Posted on Oct 14, 2009

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1 Answer

2003 hd hugger wont idle. runs at speed no sitting idle


if it runs only with the choke out then you need to drop the bowl of the carb and clean and clear the pilot jet

Sep 26, 2014 | 2003 Harley Davidson XLH Sportster 883...

1 Answer

Harley sportster won't accelerate after warm... Idles fine top end is fine


Hi Anonymous, if you have a carburator the usual suspects are:
1. Damaged or restricted fuel tank venting system (gas cap).
2. Inlet system air leak.
3. Vacuum piston malfunction.
4. Accelerator pump leaking or no output.
5. Plugged bowl vent.
6. Fuel level (float chamber) too low.
7. Restriccted fuel supply passages.
8. Plugged jets or passages.
9. Worn or damaged needle or needle jet.
10. Enrichner valve not seated or leaking.
Good luck

Jun 25, 2012 | 2005 Harley Davidson XL 883 Sportster

1 Answer

My 2004 sportster back fires when im down shifting or going down the road


If your bike is equipped with a carb and you can get to the idle mixture screw, turn the screw counterclockwise about a half turn. Also, check your exhaust system. If the gaskets at the heads or the crossover are leaking, they will "**** air" inside and cause the backfires though the exhaust.

If the engine is spitting out of the carb, your carb is jetted too lean. If the carb has a #42 jet in it, go up to a #45. You can also raise the needle in the carb by removing the needle and adding a single 3mm flat washer under the needle stop. The small flat washer is approx. 0.023" thick. The stop is the 'swelled' portion of the needle that keeps if from falling through the slide. Put a little grease on the washer and thread the long end of the needle though the washer. Then install the needle in the slide. This "raises" the needle just a bit enriching the mid-range mixture ever so slightly. You're bike will run much better.

Good Luck
Steve

Aug 18, 2010 | 2004 Harley Davidson XL 1200 C Sportster...

1 Answer

2003 Harley Davidson XL 1200 C Sportster It starts and runs perfect when cold.When it warms up to 150 degrees at wide open acts like it is running out fuel,At 180 does it at half throttle and above,At 190...


That's a strange one. The only things I can think of suggesting are:
  • Clogged gas cap vent. The next time is starts running poorly, remove the gas cap briefly and see if things improve. If so, then the cap is not venting as it should.
  • Moisture trapped in float bowl. Drain the contents on the carburetor float bowl into a clean container and check for dirt, rust, water, or anything else that doesn't belong there.
  • Dirty fuel filter. If there is one, replace it.
  • Air leak between carb and engine. Check tightness of clamps and manifolds for cracking. WD-40 sprayed around those areas with the engine idling will help detect any leaks.
That's all I can think of. Please let me know if any of my suggestions fixed it.

Dec 09, 2009 | 2003 Harley Davidson XL 1200 C Sportster...

1 Answer

Sportster spits back when i go to give it gas at times


Try going to a larger pilot jet (low speed) A 45 should do it, maybe a 48 if you have a freeflow air cleaner and exhaust. You also will have to remove the plug in the idle mixture well so ya can adjust the idle mix. It's underneath the carb. Probably your best bet would be get a performance kit like Yost or Thunderslide. There are WAY cheaper kits around, and as almost as good. They have the jets, drills and instructions to make your CV carb work decent.

Jul 05, 2009 | 2005 Harley Davidson XL 883L Sportster

1 Answer

Sportster Missfiring


Sounds like a carby jetting issue. Sounds like she's running lean above idle, after you zero the enrichener. Suggest adjusting the pilot air screw ( air mixture screw) under carby. You need to remove a blanking cap to do this. See eg Buzz Buzzelli's book for this, or a Sportster forum. I'd back it out to 3-3.5 turns, very gently by 1/4 turns till she runs well. Good Luck.

May 17, 2009 | 2005 Harley Davidson XL 883L Sportster

1 Answer

Acceleration problem


If you are not running an open or free flowing exhaust go back to the stock size jets but use the DynoJet parts instead of the stock.
DJ jets tend to run bigger than oem jets

Jan 28, 2009 | 2005 Harley Davidson XL 1200 C Sportster...

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