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  #6351  
Old 11-08-2013, 02:31 PM
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Default Re: what did you do to your motorized bicycle today?

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Originally Posted by BonusParts View Post
Oddly enough i've noticed that at low rpm it runs great on low throttle input, but at wot it just bogs. not four stroke, bog. Not sure what to make of it. I shortened the header, but it was rainy all day so no test yet.
By bog, if it just looses power and seems to be running flat while you are riding at top speed, it is tuned too lean. It needs a larger main jet.
(Note, a highly restrictive or clogged exhaust will cause this symptom too even though the carb is tuned correctly.)
Now that said, if you whack it WOT from idle speed and then it bogs that too is a lean condition but good luck tuning it out. The carb has no accelerator pump and it cannot accommodate large throttle input changes without temporarily leaning out.
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  #6352  
Old 11-08-2013, 03:37 PM
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Default Re: what did you do to your motorized bicycle today?

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Originally Posted by GearNut View Post
By bog, if it just looses power and seems to be running flat while you are riding at top speed, it is tuned too lean. It needs a larger main jet.
(Note, a highly restrictive or clogged exhaust will cause this symptom too even though the carb is tuned correctly.)
Now that said, if you whack it WOT from idle speed and then it bogs that too is a lean condition but good luck tuning it out. The carb has no accelerator pump and it cannot accommodate large throttle input changes without temporarily leaning out.
You absolutely confirmed my sneaking suspicion.... I had a feeling I needed to switch back to a .68 jet, seeing as both my crank and head compression have been raised some, that and I noticed it more after I installed the jaguar CDI. I perhaps didn't realized that I had equipped the engine to finally handle the potential of the small NT speed carb....

Well, back to jet seeking!
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  #6353  
Old 11-08-2013, 09:44 PM
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Default Re: what did you do to your motorized bicycle today?

I'll throw my bit in amongst you smart lot:
Is there something in being able to adjust the timing at all by gapping the plug?
I'm sure I read somewhere you can advance it by closing the gap, and vise versa.
If so it's another factor to play with.
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  #6354  
Old 11-08-2013, 10:01 PM
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Default Re: what did you do to your motorized bicycle today?

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I'll throw my bit in amongst you smart lot:
Is there something in being able to adjust the timing at all by gapping the plug?
I'm sure I read somewhere you can advance it by closing the gap, and vise versa.
If so it's another factor to play with.
I think that might be an old husbands' tale.
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  #6355  
Old 11-09-2013, 12:50 AM
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Default Re: what did you do to your motorized bicycle today?

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Originally Posted by Cruise View Post
I'll throw my bit in amongst you smart lot:
Is there something in being able to adjust the timing at all by gapping the plug?
I'm sure I read somewhere you can advance it by closing the gap, and vise versa.
If so it's another factor to play with.
I can't really see how changing the gap by a few thousandths of an inch is going to have any significant effect on the millisecond(s) it takes for a spark to jump the gap. At a level beyond common measure there may be a difference, but to find it I'd suggest you get good walking shoes and turn right at the decimal point.
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  #6356  
Old 11-09-2013, 03:15 AM
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Default Re: what did you do to your motorized bicycle today?

Cruise, electricity travels at 186,282.397 miles per second. Changing the gap on the spark plug a few thousands of a inch will not affect the timing.
Perhaps you were thinking of changing the gap on the points of a traditional points/breaker style ignition? Changing the gap on that will definitely affect the ignition timing.
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  #6357  
Old 11-09-2013, 04:23 AM
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Default Re: what did you do to your motorized bicycle today?

Thanks all for your diplomacy and light humour! I've played lots with cars but am new to these cool little motors. Now I reckon I'll leave that gap out of question.
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  #6358  
Old 11-09-2013, 10:53 AM
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Default Re: what did you do to your motorized bicycle today?

How's this for an idea??


http://www.youtube.com/watch?v=0Z8dFlVNrY8
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  #6359  
Old 11-09-2013, 11:44 AM
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Default Re: what did you do to your motorized bicycle today?

[QUOTE=xseler;524721]How's this for an idea??

I note that the vid is considerably speeded up.
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  #6360  
Old 11-09-2013, 11:48 AM
crassius crassius is offline
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Default Re: what did you do to your motorized bicycle today?

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Originally Posted by GearNut View Post
Cruise, electricity travels at 186,282.397 miles per second. Changing the gap on the spark plug a few thousands of a inch will not affect the timing.
Perhaps you were thinking of changing the gap on the points of a traditional points/breaker style ignition? Changing the gap on that will definitely affect the ignition timing.
I note that it may be the case that a larger gap could cause the spark to wait fractionally for the voltage to climb higher to jump the gap - in fact, a too large gap may cause the spark to wait forever.

Also, this may affect the quality of the spark in terms of its ability to start a good burn.
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