'84 Big Red still won't run

[BigRed1984]

I put a new ebay carburetor on it a couple days ago, and it ran PERFECT for about 20 minutes.

Now it starts hard, won't idle, acts like it's starving for fuel without choke. Sags, sputters, backfires. It will run with choke, but poorly.

I thought it was a fuel supply problem, but I have a test tank on it with plenty of fresh gas and full flow. No difference.

There is not a speck of dirt anywhere in the carburetor. I've pulled it apart a dozen times, blown out every hole and orifice I can find. I can see daylight through every hole. Put it back together exactly the way I took it apart. No difference.

I would think if it was a valve issue, it would run fine cold, but it doesn't.

I need ideas here. Some hole in the carburetor that isn't obvious that I'm missing?

[atc300r]

Have you tried another spark plug,coil checked timing. Alot of time a bad running trike, bike, quad is chalked up to carb out of adjustment when its a bad coil,cdi spark plug,timing jumped,flywheel key sheared dirty air filter,gascap vent clogged.and so on.

[oscarmayer]

Is the vent valve on the gas cap turned on? Some reds have a lever on the take that shuts vent off. Try taking the gas cap off and see if she runs.


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[81k]

Also, if you haven't already, you might want to check fuel flow at the petcock. I've had some flow well on res??erve, but poorly on ON. Just something you may want to verify and rule out.

[atc007]

Also, if you haven't already, you might want to check fuel flow at the petcock. I've had some flow well on res??erve, but poorly on ON. Just something you may want to verify and rule out.

Thank you. Your petcock /tank need cleaned.

[BigRed1984]

New spark plug. New coil. New plug wire.

Using an open test tank, so ventilation and fuel flow are not an issue.

I may have made some progress. This carburetor has an adjustable main needle on the throttle plunger. It was on the 2nd slot. I moved it to the 3rd slot, and then I could actually flood it with the choke, but it was still running lean. Went to the 5th slot, but that was too far. The 4th slot seems to be a little rich but it's the best setting I could find.

[RubberSalt]

Make sure the coil doesn't have rust on the grounds.

Check stator resistance. If the carb is clean, and it's getting gas, then it's more than likely ignition. Rust under the coil (bad grounds). Magnets on flywheel may have old metal/rust stuck them. Ignition timing can be thrown off by the ignition pick/trigger/pulse coil (which ever it is)

[tripledog]

Make sure that the airbox isn't filled with rodent made goodness. I know it seems obvious, but I have had it happen to a few of my machines.

[oscarmayer]

Make sure the exhaust is not plugged up.
Is this a Chinese carb? I have has issues with some Chinese carbs and decided to only use Mikuni on the 200s


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[Scootertrash]

oscar-Got a link to those Mikunis? :naughty: