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I own a 2000 Honda Shadow 750. When I first got it the engine was having misfires and not getting full power. The dealership looked at it, came back and said that they found a blown gasket and after replacing it the bike was good. I test drove it and got it home and the bike was running fantastic.

Now a week later the bike is misfiring again, having a lot of pops, and not sounding quite right.

What do you think the issue could be? Carb needs adjusted? New spark plugs? They said they put a new carb on and when I looked at the spark plugs they looked pretty good. Where should I start with troubleshooting?
 

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I think that popping, especially when the throttle goes from open to closed on deceleration, is most often associated with a lean mixture. I'd be looking for air leaks at the intake passages between the carbs and the head. What gasket did the shop say was bad? Check the fasteners they would have undone for looseness.

Lean running can result in overheating of cylinders and exhaust, and pinging, and in worst case, engine damage. A quick and dirty way to diagnose for lean running on many machines is to partially choke the engine and see if the symptom is reduced. If the bike is showing symptoms while idling or running the engine stationary, it's possible to spray the intake area with carb cleaner to find the general area of the leak. Another, more precise method of detecting the source of air leaks is to play the stream of propane gas from an UNLIT propane torch on the areas under suspicion. When the bike running gets smooth, that's where the air leak is. Be careful whenever using flammable materials and keep an extinguisher handy.

Is your bike stock, or does it have any modifications?
 

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My Suzuki GS 850G did this for a while last year. Checked everything up and down and everything looked okay. Finally, I got pissed off and decided to do an "Italian Tuneup" banging off the rev limiter going through the gears. The problem went away and never came back. :)
 

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My Suzuki GS 850G did this for a while last year. Checked everything up and down and everything looked okay. Finally, I got pissed off and decided to do an "Italian Tuneup" banging off the rev limiter going through the gears. The problem went away and never came back. :)
Those Italian tuneups as you call them MM, have been known to cure a myriad of ills. Carbs can be finicky and dirt is there enemy. If it ran fine after the gasket fix and then a short time later it no longer ran as it should, I would not think the air filter was at fault. With a 20 year old bike there could be any number of things. Vacuum leak, old cracked hoses but now I become redundant. Good luck dude...
 

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Possibly bad fuel filter, is there any rust inside your tank? Have you used fuel specified in the owners manual? My 00 GSX600F ran boggish when I used regular instead of premium. Try adding a little bit of seafoam or some other cleaner through your tank. Tune ups are a great way to start if it was pre-owned (Oil+filter, spark plugs+wires, fuel filter, air filter, ). Make sure your spark plug wires are fully seated in sometimes they can pop out. Maybe you forgot to shut the choke off after warming up, it happens. Hopefully this will help clear up your issue.
 
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