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Discussion Starter · #1 ·
Picked up a cb500t and it was firing on the right cylinder only. Adjusted the cam Chain. Adjusted the valves, cleaned the carbs. And put in new points and set the timing. Now it's only firing on the left cylinder. And the right carburetor is bucking every once in a while like there's pressure building up and it's trying to fire.
I have a video of the bucking and a picture of the right side plug. Any suggestions?
 

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First I'd check for a healthy battery while cranking or try kick starting it. Then I'd get a strobe and confirm timing. Then I'd take another look at the carbs. Did you set the float heights)
 

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Discussion Starter · #3 ·
The battery is good. I set the timing according to common motors method and I think it's good but I'll confirm with the strobe. Was planning on pulling the right carb and going through it again. I guess I can't post a video but was wondering if the bucking carb was a symptom anyone know of


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Usually, it's a lean backfire, spits back into the intake. Spritz a little carb cleaner or gasoline into the carb throat of the dead hole and see if it picks up a few revs.
 

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1. check to make sure you are getting sparks from the plugs.
2. check ignition statically
3. check cam timing
4. make sure you are getting fuel to both carbs.

If you spray some starting fluid into the right carb intake, does it then fire? If so then you have fuel issue. Could be stuck float valve,stuck piston, dirty jet.

What does "battery is good" mean? What voltage reading are you getting from the battery at rest? Anything below 12.6V is suspect IMO/IME.
 

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Discussion Starter · #6 ·
Battery is 13.8
Strong blue spark both sides.
Ignition statically checked.
Don't know how to check cam timing. Fuel to both carbs that stopped with the floats up.
Mike.. it could be the carb just needs to be richer i.e. Fuel air mixture screw adjustment?


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Try it with a little starting fluid on the non-firing cylinder and see it will pick up. If so then you can be sure it's a fuel delivery issue as I stated before.
Air/fuel mixture screw - starts with 1-1/4 to 1-1/2 turns out.
 
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Discussion Starter · #8 ·
Try it with a little starting fluid on the non-firing cylinder and see it will pick up. If so then you can be sure it's a fuel delivery issue as I stated before.
Air/fuel mixture screw - starts with 1-1/4 to 1-1/2 turns out.
Just spray it on the air filter?


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On the air filter or you could even take the spark plug out and spray a little directly into the cylinder. BUT... Use this stuff only as a troubleshooting step and not as a regular starting routine. Starting fluid can be pretty harsh on gasoline engines.
 

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Discussion Starter · #10 ·
On the air filter or you could even take the spark plug out and spray a little directly into the cylinder. BUT... Use this stuff only as a troubleshooting step and not as a regular starting routine. Starting fluid can be pretty harsh on gasoline engines.
I took off the air filter and sprayed some starter fluid and the right side started firing a little. So it does seems to be a fuel issue.
When I take the bowl off the carb there is fuel flowing into the carb itself. When I let the float drop it flows. So it must be the carb itself. Should I take the carb off and clean it again? I already took it all apart once and cleaned all the jets etc


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Discussion Starter · #11 ·
I took the carb out and Took it apart and clean everything. One of the jets was a little dirty. Cleaned everything and put it back in. Both sides fire up but there's an occasional jump where each carb jumps back and forth occasionally like it's gulping for air or fuel. I'm figuring i should re check the timing.


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Discussion Starter · #13 ·
Double checked the timing with the gun and it's spot on. Still having issues with that right carb. It's firing but when I shut the bike off the bowl is filled with gas and it pours out the overflow tube. I've already cleaned the float a few times and there no cracks in it. Should I get a new needle and jets or just keep cleaning and running it?


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Check your float again and make sure the level is adjusted correctly.
Make sure it's not punctured and can still "float" per se.
Shake it a bit and listen to see if there is fuel inside the float, if so then it's no good and will either need to have the leak repaired or replaced.

Your float needle might be stuck also.

I would also take the bowl out and inspect the overflow drain pipe for small cracks. Fill it up with fluid and see if you can see any leaks. You can solder any cracks to fix it.
 

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Pull the plugs and see if it is running rich.
 

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Discussion Starter · #16 ·
Pull the plugs and see if it is running rich.
I bought a carb rebuild kit and replaced a lot of the parts of the carbs and now can't even get it idling long enough to even do a plug chop.
Is there an after market carb the would be recommended for this bike?


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I bought a carb rebuild kit and replaced a lot of the parts of the carbs and now can't even get it idling long enough to even do a plug chop.
Is there an after market carb the would be recommended for this bike?


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What exactly did you replace on the carbs? Do not replace the jets and other hard parts as most of the times the aftermarket parts will not fit correctly.
The only parts you should need to replace on the carbs are the o-rings and gaskets.
 

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Discussion Starter · #18 ·
Pull the plugs and see if it is running rich.
Got the bike to idle nice but when I pull the throttle it's running super rich. I can rev it in neutral but it's So rich it doesn't accelerate under load.
I was curious why you anticipated that being the case


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Discussion Starter · #19 ·
What exactly did you replace on the carbs? Do not replace the jets and other hard parts as most of the times the aftermarket parts will not fit correctly.
The only parts you should need to replace on the carbs are the o-rings and gaskets.
Also. I put the original jets and needle back in.


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Make sure your float levels are correct. There should never be any overflow.
 
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