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Discussion Starter · #1 ·
ok so i just got gas and i tryed to fire it up and i poured a little bit of gas in the sides of carb to fill up the float blows, i didnt pour it down the intake....

and it started for a second and then it died, so i tryed to start it again, and i got this white smoke back firing out of the carb....

and it ran good when we broke it in, so the ignition is correct.

Any Ideas on whats doing this?
 
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Discussion Starter · #2 ·
Sorry guys i forgot that my fuel to air ratio was probably off and that what causes the backfires, i wish i delete my stupid posts sometimes  ::)

 

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Is your timing set correctly?

Chris
 
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Discussion Starter · #7 ·
wycowboy said:
Is your timing set correctly?

Chris
the timing hasnt moved since we broke it in, but i think it is, it ran good when we broke it in

and Smoke y, how do i know what degree the dist. is set to?
 

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Well, I would still suspect it is off a little bit. Air/fuel mixture being off shouldn't cause a backfire. If the choke is closed too tightly it could cause one though. Was the choke open or closed? All the way open can also cause a backfire.

Chris
 
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Discussion Starter · #9 ·
wycowboy said:
Well, I would still suspect it is off a little bit. Air/fuel mixture being off shouldn't cause a backfire. If the choke is closed too tightly it could cause one though. Was the choke open or closed? All the way open can also cause a backfire.

Chris
the choke was all the way open should it be 1/2 way open??
 

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Half way isn't enough. The choke plate should close within about an 1/8 to 1/4 inch of all the way closed. Once the engine starts, which it should easily do, then the plate will open a little more and continue to open as the engine warms. It should be all the way open within 5-10 minutes depending on the temperature outside.

Chris
 
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Discussion Starter · #11 ·
wycowboy said:
Half way isn't enough. The choke plate should close within about an 1/8 to 1/4 inch of all the way closed. Once the engine starts, which it should easily do, then the plate will open a little more and continue to open as the engine warms. It should be all the way open within 5-10 minutes depending on the temperature outside.

Chris
so if its 103* outside when we start it up it is still important to have the choke open 1/8-1/4 inch open on a somewhat "cold" start-up....
 

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It'll start, or should, with it all the way open no matter what the temperature is. 103 above or 30 below. The difference is how EASY it will start at what temperature. The colder it is, the more times you would need to pump the pedal before cranking if the choke is open. The choke plate being closed just makes it easier (less pumps of the pedal) because it richens the mixture by limiting the air available to the engine. At 103 degrees it should start whether the choke is closed or open, even on a cold engine, with one pump of the pedal but it may not. Every engine is different. Thats why I like a manual choke. I can set it or not based on what that engine needs.

Since you are working on a newly rebuilt engine which has new tuneup parts in it (or should anyway) and newly rebuilt carb (again, it should anyway), new fuel pump and filter (it does right?) and the timing is close, if not set correctly then I would think that at 103 degrees the engine should easily start without the choke being closed. If it was me though, I would set it so it is about 1/8 to a 1/4 open on a totally cold engine.

Chris
 
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Discussion Starter · #13 ·
wycowboy said:
It'll start, or should, with it all the way open no matter what the temperature is. 103 above or 30 below. The difference is how EASY it will start at what temperature. The colder it is, the more times you would need to pump the pedal before cranking if the choke is open. The choke plate being closed just makes it easier (less pumps of the pedal) because it richens the mixture by limiting the air available to the engine. At 103 degrees it should start whether the choke is closed or open, even on a cold engine, with one pump of the pedal but it may not. Every engine is different. Thats why I like a manual choke. I can set it or not based on what that engine needs.

Since you are working on a newly rebuilt engine which has new tuneup parts in it (or should anyway) and newly rebuilt carb (again, it should anyway), new fuel pump and filter (it does right?) and the timing is close, if not set correctly then I would think that at 103 degrees the engine should easily start without the choke being closed. If it was me though, I would set it so it is about 1/8 to a 1/4 open on a totally cold engine.

Chris
Thanks Chris that makes since,

but what doesn't is the fact that it backfires with the choke open??

cause when i think of backfiring i think of a valve being open when a spark plug fires.....
 

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Yep, if it is backfiring that is usually it. The timing should be set about 10* BTDC or Before Top Dead Center. That means that the spark plug is firing when the piston is at 10 degrees before the top of the stroke on the intake cycle. So, the intake valve is still slightly open. I am thinking that your timing is off, say 15-20 BTDC or so.

Chris
 
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Discussion Starter · #15 ·
wycowboy said:
Yep, if it is backfiring that is usually it. The timing should be set about 10* BTDC or Before Top Dead Center. That means that the spark plug is firing when the piston is at 10 degrees before the top of the stroke on the intake cycle. So, the intake valve is still slightly open. I am thinking that your timing is off, say 15-20 BTDC or so.

Chris
if the timing was that far retarded they could that cause it to idle rough?

or idle fast like 1000 rpm?
 
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