rpm drops in idle mode?

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Faxe400
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rpm drops in idle mode?

Post by Faxe400 » Thu Aug 16, 2018 7:39 am

Hello together,

finally I got through the technical inspection and got my licence plate. So I started some test drive. My NC24 runs fine. First thing to notice is the the red speed light that turns on at about 90 km/h. I guess this has same japanese regulation origins.

The temp gauge stays at the lower end. It moves only about 3mm above the small black interruption. I would expect it to stay in the middle of the large White area.

What worries me more are some rpm drops (at warm engine). When slowing down (i.e. in front of red traffic lights) I switch down the gears, pull the clutch and switch into neutral gear. Just when pulling the clutch rpm goes down to idle (1200) after some seconds the rpm drops to 800 (or lower) for a short time and rises back to idle. In 50% of the cases the engine just goes off :x . When starting you need some throttle to get it running again.

Is this a known issue? Shall I rise idle rpm? I could be voltage drop that influence ignition or some missing fuel, maybe due to hot engine warming the carbs :?:

I will do some technical maintenance soon. There I will check batterie charging / generator-rectifier. And also fuel system & carbs. But i would be nice to have some trips before.

magg
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Re: rpm drops in idle mode?

Post by magg » Fri Aug 17, 2018 10:52 am

Idle mixture setting too lean perhaps. Would agree with general tune up and check over, including the electrical system.

Neosophist
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Re: rpm drops in idle mode?

Post by Neosophist » Fri Aug 17, 2018 11:11 am

12/1300 is correct idle so its dropping below and then returning or stalling out completely?

this is usualy a rich condition (gets worse as bike warms up too)

try backing pilot screws in half a turn each and see if it improves it. (air filter clean and ok?)

nc24 with good cooling system needle barely goes out of the cold thats fine.
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Yakama
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Re: rpm drops in idle mode?

Post by Yakama » Fri Aug 17, 2018 11:17 am

Is the choke stuck? I had similar problems with a choke sticking on slightly even though it looked like it was off. Try freeing it off with some WD40 and see if that helps

Faxe400
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Re: rpm drops in idle mode?

Post by Faxe400 » Mon Aug 20, 2018 9:24 am

Thanks for your answers. I came back late to this thread due to some stomach flu.

I observed that it gets worse with warmer engine. The warmer the engine the higher is the chance that it totally stalls out.

A friend also suggested it is probably carb idle mixture to look at. So when I feel better, I will look there first including choke cable.

Faxe400
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Re: rpm drops in idle mode?

Post by Faxe400 » Tue Aug 28, 2018 8:28 am

Just a short update, last weekend I had a look at the bike.

The previous owner cut out the paper from the air filter. I put in a complete but that didn't solve the Problem. Need to have a 2nd look.
Someone had opened the carbs before. There is some light green rubber seal around the carb fuel chamber.

I replaced the contacts from the AC Generator to the rectifier. Electric circuit seems to be o.k.


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