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Wrong size 2100 on my 390. What are my options?

 
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Old 07-11-2019, 09:34 AM
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Question Wrong size 2100 on my 390. What are my options?

My 390 has a 2100 but its 1.21 bore instead of the 1.23.
It also has 53F jets which sounds small to me.
The engine runs a bit hot being lean and it has dead spots in the throttle.
Should I just buy an =listing-final-manufacturer AUTOLINE =listing-final-partnumber as-link-if-js buyers-guide-colorC834A which is the right carb or should I try to get this working?
=listing-final-partnumber as-link-if-js buyers-guide-colorI opened it up and its clean as a new carb should be but its not the correct one.

thanks
 
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Old 07-11-2019, 11:39 AM
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Originally Posted by Cartel View Post
My 390 has a 2100 but its 1.21 bore instead of the 1.23.
It also has 53F jets which sounds small to me.
The engine runs a bit hot being lean and it has dead spots in the throttle.
Are you certain that it's running lean, or, maybe the ignition advance isn't operating correctly? That will cause hot running and poor performance as well. The rule of tune-ups is always ignition first, the. carburetion. You might be right, but I'd think a 1.21" should run just fine on that.

Believe it or not, carburetors that are too big tend to run lean. Post a clear close up pic of a spark plug or two. When engine tuning it's important to use the stock heat range plug starting out. Post a clear, closeup pic of a couple spark plugs.
 
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Old 07-12-2019, 03:12 AM
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I pulled these out, drove it 30-40 miles when I got it
 
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Old 07-12-2019, 09:52 AM
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Thanks for the pics. Those look real bad, and they are fairly new looks like. Have you done a compression test? Don't worry about the carb or jetting just yet. A couple of those are so fouled they have barely been firing, if at all.
 
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Old 07-13-2019, 12:24 AM
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Yea, it's not running lean. The cfm rating between a 1.21 and a 1.23 is miniscule. Sitting on a 390, it'll virtually flow the same as a 1.23. Looks like you have at least half the valve seals shot. Or the guides under them bad.
 
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Old 07-15-2019, 10:12 AM
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Half of those plugs are running on oil rather than gas.
 
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Old 07-15-2019, 10:51 PM
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Three oil fouled. Three look Ok. One looks slightly hot on the Ok side and one looks slightly lean and maybe questionable. What is the timing running at? That strap mark on the lean one, which is visible looks too far down.
 
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Old 07-18-2019, 06:30 AM
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I got a compression tester and a vacuum gauge coming I'll post the results.
Pretty sure I'm gonna be pulling the engine out
 

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