Afterfire/Popping from exhaust. - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
 
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post #1 of 9 (permalink) Old 12-21-2016, 12:19 AM Thread Starter
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Afterfire/Popping from exhaust.

So! I found a 96 Royal Star on craigslist with original 6,000 miles on it and was a good find. I did however have to run through the bike and change all fluids as well as tear down the whole carb assembly, dip them each and replace all rubbers, needles and pilot screws...and intake boots too. New NGK spark plugs. Throw the bike together, sync the carbs up and dang...number 3 cylinder (Right rear) is afterfiring in the exhaust and popping slightly on accelerate and decelerate. I have checked the exhaust and pipes, exhaust gasket, intake boot, clamps, carb assembly, pilot screw, slide and butterfly outer seal, ngk spark plug gap, good gas...compression is at 170. I have no clue now. Maybe valve adjustment but for 6,000 miles barely? Any thoughts? The spark plugs on all the other cylinders are good and white, but this one is brownish and looks like a coating of shiny varnish is on it...The inside of the cylinder looks wet and dark brown.

Last edited by Nwcali01; 12-21-2016 at 12:34 AM.
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post #2 of 9 (permalink) Old 12-21-2016, 12:29 AM Thread Starter
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Pics of plug.
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post #3 of 9 (permalink) Old 12-22-2016, 11:51 PM Thread Starter
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Swapped the coil and even the ignition module from my Palomino and still no change. Threw in some seafoam and ran that bad boy for about an hour with the choke on at high RPM's and nothing. Kept the sync tool on it as well to monitor and each cylinder is running the same...the one thing I did notice is that the exhaust is alot cooler than the rest of the cylinders...incomplete combustion?
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post #4 of 9 (permalink) Old 03-30-2017, 05:35 PM
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Sounds like a fuel problem to that cylinder.
You sound pretty competent with the tools so I can only suggest that you recheck carb screw settings, float bowl level, choke operation and cable slack, and if that fails do a replacement of parts like all high speed and low speed jets, float needle etc.
It sounds like incorrect mixture because of damaged of gummed up parts or incorrect settings.
Cheers.
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post #5 of 9 (permalink) Old 05-25-2017, 12:19 PM Thread Starter
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Forgot about this post...sat down and really thought about it...had to be internal inside the carb so I removed the problem carb and replaced with spare and transferred parts. Done. Prob gunked up even after I dipped each one but wasnt gonna take a chance.
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post #6 of 9 (permalink) Old 07-11-2018, 08:38 AM
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Have you removed the brass plugs, as to adjust air fuel mix, on the outside of the carbs? These bikes run pretty lean from factory for emission control.
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post #7 of 9 (permalink) Old 07-11-2018, 08:42 AM
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Also ONLY run regular unleaded...like 87. Premium doesn't burn right and will create soot in exhaust. It states to only use 87...maybe under the seat?
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post #8 of 9 (permalink) Old 07-19-2018, 10:28 AM
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I would like to correct myself on fuel to use...it says under my seat to use 91 not 87...sorry. I have been using 87 myself for some reason...ugh.
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post #9 of 9 (permalink) Old 09-14-2018, 07:25 PM
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Quote:
Originally Posted by ChadP View Post
I would like to correct myself on fuel to use...it says under my seat to use 91 not 87...sorry. I have been using 87 myself for some reason...ugh.

I just got a 2000 Royal Star.

The owners manual says to use 87 octane, which is 91 RON or something in another standard. That might be whats on your sticker.

Everything I have seen on the carb'd royal star bike specs says "regular octane" fuel. Pretty sure its the same for fuel injected bikes too.

The RON 91 must be a standard used in other countries. Its still regular octane.
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