80cc engine wont start and hasnt yet

shane irl

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Feb 24, 2010
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ireland
hello,
i built my bike on monday and it hasnt started yet .the spark plug is sparking and its gettin petrol and air compression is good i think maybe its my fuel mix its a bit rich and harder to ignite.please help with this problem
thanks,shane.
 
I usually have to start it by putting the choke on for a bit and then put the choke down and try it again. it should start right up. remember to keep the mixture low before its broken in. (about two tanks)

Mike Frye the bike guy
 
if you take the spark plug out and lay it on the head with the wire connected (on a bike stand) then rotate the crank and pop the clutch there should be a spark.

if no spark then its time to check your electrical system.
 
i checked it there and its sparking ...... what could it be if it is sparking and is getting petrol?
 
does it turn over at all? or is it just the popping from peddling. make sure the carb is correctly assembled. make sure the idle screw isout far enough. make sure the carb is pushed onto the intake manifold all the way.
 
does it turn over at all? or is it just the popping from peddling.

'Turning over' and 'firing' are two entirely different things. Popping?


make sure the idle screw isout far enough.

'Idle screw out far enough?' Turning the idle screw out will slow the engine at idle, but won't affect starting.


Shane, if it's got spark and fuel, it could be too much or too little fuel.
Mike didn't necessarily mean 'run it rich', just one attempt at full choke, the engine might fire and cough once or twice, but won't run.
Then, turn the choke off and try again - it should fire up.

You are aware, I hope, that the choke is 'off' when down and 'on' when up?
(Mike sort of mentioned this, but you might not have noticed.)

Keep us informed,

... Steve
 
I always think of the choke lever as a light switch. Up is on, down is off. It's easier that way.
When you take out the spark plug after trying to start the engine is it wet with fuel or dry?
Wet would indicate that the carb is giving out too much fuel, and dry...well, I think you can figure out that one.
If I am not mistaken, the initial setting for the idle speed screw is 3 1/2 turns out from all the way in. That will at least get the slide in a position to get the engine running and from there you can adjust the idle speed screw to obtain a good idle speed. Adjust it after the engine is warmed up well. In is faster, out is slower.
 
Up is on, down is off - works for the choke and for power switches in the US, but here, down is on and up is off.
I put a bit of thought into this once. Your system is definitely more sensible. Let's say a broom is leaning against the wall and falls over, hitting the switch. In the US, the switch will turn off. Here, it will be turned on. Potential disaster.
This goes for anything 'gravity-driven' that might bump a switch.

Shane, I just noticed your previous post about the slide-needle falling out. Are you sure that you have it in place correctly, with the spring pushing down on the 'c' washer on top of the needle's 'c' clip to hold it in place?

... Steve
 
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