Question about 1981 Honda CX 500 B

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Honda cx500 only fires on 1 cylinder

Won,t run on left cylinder ,good spark but lack of fuel,have stripped carbs but i,m new to this ,not sure which screw does what any help welcome,i don,t have a manual so i,m working blind but i will get 1 cheers gary

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Pull the bowl from the left carb and remove and clean the float needle and jet. It sounds to me that this passage is plugged. You might as well clean the whole set since you have it off.
It is a common problem for those carbs on the older bikes for the jets to plug up from old gas, or material such as rust in the tank. Check your fuel filter if you have one. If not I would suggest you install one when you are done.

Posted on Mar 11, 2009

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Posted on Jan 02, 2017

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Cx500 deluxe I have 152psi of compression in both cylinders I went through the carbs, I even replaced the fuel pet **** diaphragm the bike runs great until about 55 mph

Hi, Daniel and the usual suspects are:
1. Severely discharged or a damaged battery, should have 12.5 volts or better and be able to pass a load test if necessary.
2. Check battery terminals for damage or corrosion, check the battery cables at "BOTH" ends for loose, corroded, or broken connectors, "INSIDE" and outside the cable harness, perform connector wiggle test and check cables with an ohmmeter if necessary.
3. Faulty main circuit breaker and or connections.
4. Faulty ignition coil and or connections.
a. Faulty high-speed coil and or stator
5. Faulty spark plug, oil or gas fouled, wrong heat range or service type, wrong gap, loose in the cylinder head, broken electrode or insulator.
6. Faulty spark plug cables, leaking or broken, internal damage.
7. Faulty ignition module, switch, CKP, MAP, CMP, sensor and or any connector in the ignition circuit could have corroded, loose, or broken pins/sockets
8. Burnt exhaust valve or air leak in the exhaust system.
For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
Loss of power
Honda CX500 Service Manual Honda GL500 GL650 Service Manual

May 17, 2016 | 1981 Honda CX 500 B

2 Answers

1980 CX 500. Why doesn't left cylinder fire until high rpm?

could be a spark plug failing under the higher compression of the increased rpms
start by changing the plug and or HT lead or coil if independent of the other cylinder

Apr 02, 2016 | Honda Motorcycles

1 Answer

NSR 250 timing

Just a hunch. Clearly there is a fuel issue on one of the cylinders. Although you cleaned the carb, please confirm that the intake valve is clean and/or reed valves are working properly. It is possible that the 2nd cylinder is only firing occasionally even at the higher RPM but it's less noticeable because of the engine's inertia at that speed makes it "seem" to be running smoother. The clue lies in the fact that the engine runs smoothly at idle when the choke is applied and starts to miss when choke is open ... this is indicative of fuel starvation. And yes, on a 2 cycle, a lack of fuel means a lack of lubrication.

Out of curiosity, take both spark plugs out and crank the engine. Do this outside away from an open flame. Compare the amount of misted fuel that comes out of each cylinder head with the choke closed and then again with the choke open. If it isn't even then the cylinder that is blowing less fuel is being starved. This should identify the problem cylinder and help to narrow down the elements left to troubleshoot and replace/repair/clean. Good luck and hope this helps

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1 Answer

2002 honda vt 750 shadow spirit one cylinder won't fire what's the problems

Pull the plug out and test it on the frame. If no spark you need new plugs. If it does spark look at the plug. If the plug is black and wet it is getting to much fuel and flooding. You will need to adjust your carb's air to gas mixture.

Apr 02, 2013 | 2002 Honda VT 750 CD Shadow A.C.E. Deluxe

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Honda GX 240 engine has spark, new carb; won't fire. what do I do?

remove the muffler and try it there is a screen inside the muffler that get carbon build up if it runs with out the muffler pry it open and clean it

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1 Answer

1979 honda cx500 only runs on one cylinder! I have good spark and feeding it fuel and still wont run !so I'm totally lost on what to do please help???

If you are sure that the idle jet in that carb is clear (spark plug getting wet is a good quick indicator) then I would check the valve clearances as they would be the most likely problem.

If they are o.k. then do a compression test...

Apr 26, 2012 | 1979 Honda CX 500 B

1 Answer

Number 1 cylinder has spark but not firing, I have gone through the carbs, and new plugs, I switched 1 and 2 plug wires and it did not help

Hummm, well to fire you need spark (at the correct time), compression, and fuel.
It sounds like you have spark, so do you have COMPRESSION? It needs to be similar to the other cylinders +/- 15% or so.

IF you have spark, and compression, try an external fuel source diagnostically, in the #1 cylinder. Spray some carb cleaner into that carb when unit is running.

Did you balance the carbs? Carb surgery often gets balance all out of spec.

Jun 24, 2011 | 1983 Suzuki GSX 1100 E

1 Answer

My 650 csr is not running on all fours i determed this mostly by the tempeture of my header pipes three are very hot while 1 is barley warm, i checked for spark and it seems to be ok, this is the left...

Hi there,
You will need to do some diagnosing of the problem. Some things to check
  • compression check across all cylinders. Low compression(less than 100 lbs in a cylinder will prevent it from firing. They should all be with 20 pounds of each other.
  • carby to that cylinder may have a clogged air passage or jet.
  • try a new plug in that cylinder.
  • check for air leaks about the problem cylinder air intake. Use aerosol carb cleaner to spray about the manifold gaskets and carb mount. The revs will change if there is an air leak.
MOst probably you will need to strip and clean down the carbs if you have good compression and spark. Fuel is the only thing left :) Sometimes running some fuel system cleaner additive will also resolve the issue for you without tearing down the carbies. Goodluck regards robotek

Apr 20, 2010 | 1981 kawasaki Z 650 SR

1 Answer


Check for these three necessary elements: spark, fuel, and compression. In order of likelyhood, 1)There's either a plugged up carburetor, 2) defective spark plug, or 3) lack of compression on the non-functioning cylinder.

Oct 23, 2009 | 1999 Honda VT 1100 C3 Shadow Aero

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1981 honda cx500 idle problems I have a 1981 Honda CX500 Custom. It putters real bad almost to the point of stalling but only when its warmed up. This sucks because it putters at every stop sign or red light I hit. I have the haynes manual so i checked everything it suggested including cleaning the carbs twice, checking the valves, adjusting air fuel ratio, renewing spark plugs, checking for air leaks (I have cracks on my intake boot, but don't go through to the interior). I tried the carb cleaner approach but didn't get any results. At one point it was so bad to the point that it would stall every time I would start out in first gear. I then found a loose wire connection on a yellow wire which led to the ignition coil. Tightening that helped drastically until this current problem. What has me puzzled is that it ran fine in the early spring, even after sitting for four years. Whenever i don't want to be embarassed, I will put the choke on just slightly and it will idle high, but smooth. I don't ride with it on for more than 10 seconds. There is a small oil leak from the clutch cover but I don't think that would cause an issue. I changed the oil at the beginning of spring but I plan on doing it again soon since I have a new filter on the way. I am all out of options and need someone else's advice! The bike has 34k miles and am not looking forward to rebuilding it if that is the problem. I am going to look more closely into the electrical side tomorrow to be positive there are no loose wires going from the computer to the ignition coil. Any ideas will be appreciated.

Jun 22, 2012 | 1981 Honda CX 500 B

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