Question about Honda Motorcycles
Hi, Archie if you have changed your fuel delivery system, air filter size or flow rate, mufflers or exhaust system or a significant change in altitude your carburetors need re-tuning and if your fuel system (gas tank, filters, fuel valve and carburetor) is contaminated with ethanol sludge, varnish, rust, dirt, water etc. or your bike has been sitting for months or years without running these components must be "PROPERLY" cleaned and reassembled "CORRECTLY" before any adjustments can be made. Tuning your carburetor is fairly simple once you understand the basic principals. You engine is a simple airbox sucking air in and blowing it out, it is finely tuned at the factory for maximum performance once you upset that delicate balance by changing air filters, camshafts or exhaust systems your performance may go down the and the engine may run poorly, you need to compensate the air-fuel mixture in the carburetor in order for the engine to run smoothly and at peak performance. If you are running multi carburetors you need to sync them first and make sure your air cleaner element is clean and dry for paper elements or lightly oiled for foam and meshed elements and properly installed. Here is how and where you compensate trouble: "TIP" if your engine "BOGS" your not getting enough fuel.
1. Closed to 1/8 throttle is managed by the air screw and pilot/slow jet.
2. 1/8 to 1/4 throttle is managed by the air-screw, pilot/slow jet, and throttle slide.
3. 1/4 to 1/2 throttle is managed by the throttle slide and jet needle.
4. 1/2 to 3/4 throttle is managed by the jet needle, needle jet, main jet, and air jet.
5. 3/4 to wide open throttle is managed by the main jet and air jet.
6. Wide open throttle is managed by the main jet.
If you are running lean, spark plug electrode color is white, engine runs hot and feels like it is starving for fuel you need to go up on the jet size or move the c-clip down one notch. If you are running rich, spark plug color is black or dark gray, the engine runs cool, and bogs down when accelerating you need to go down on jet size or move the c-clip up one notch. When your carburetor is properly tuned for maximum performance your spark plug electrode will be a light tan color like coffee with cream. If you prefer fuel economy over performance you can go down on main jet sizes until a satisfactory level of lower performance is acceptable versus MPH, your spark plug color will be whiter and your engine will run warmer. These tuning adjustments will only make improvements if your intake and exhaust system have no air leaks or sealing issues and the entire electrical system is in proper working order and you have no mechanical issues.
For more information about your issue and valuable "FREE" downloads that you will need please click on the blue links below. Good luck and have a wonderful day.
Carburator Theory and Tuning
How To Carburetor Idle Pilot Screw Adjustment Honda XR70
CR80R RB CR85R RB 1995 2007 Workshop Manual Models Download Manuals... $10
Posted on Jul 23, 2017
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Posted on Jan 02, 2017
yes there should be one adjusting screw normally it is a flat head screw driver with a spring around it adjust in to lean fuel mixture and out to enrich fuel mixture should be located near bottom of carburator
Posted on Jun 12, 2009
You can adjust it by removing the EPA anti tamper caps. When you get them removed, turn the A/F screw out in 1/4 turn increments till you reach the desired result. You can also replace the pilot jet in 1/2 steps.
Posted on Jun 13, 2009
Check the free manuals at this site, one of them may have what you want.
Posted on Dec 31, 2009
Run the motorbikes engine to a normal running temperatue and thn set the air-fuel mixture by ...tightening all the way in taking care not to over tighten it as you may damage the tip of the screw,usually its thn 2 and half turns outwards or 3 , you will notice the change inthe idling of the bike's engine.
Its better to check the spark plug gap and also check the air filter, blow it with compressed air or if its tht dirty best would be to replace it.
Posted on Apr 03, 2010
lean out the carb, you do this by letting the engine idle and turning the air/fuel mixture screw until the engine starts revving up(without turning the throttle) when it revs as high as it will go by turning the air/fuel mixture screw, then lower the idle with the idle adjust knob. as for oil, most of the major companies make a 10w30 for motorcycles. if you can afford it royal purple for motorcycles is the best, but i use castrol 4t for motorcycles its a 10w30
Posted on Aug 23, 2010
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