http://t2.gstatic.com/images?q=tbn:A...nClZeT_m6oX47A
see if you can get it to idle at 1500 RPM.
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http://t2.gstatic.com/images?q=tbn:A...nClZeT_m6oX47A
see if you can get it to idle at 1500 RPM.
It can idle at 1500 RPM, no problem. Problem is...well, I don't know how to say it in that particular technical language, but I'll try. problem is: it feels like the carb is resetting itself "to defaults". E.g.: I adjust the idle screw, it idles fine. Then the next day I start it with choke, warm it up, ride, it cuts off in traffic again. I adjust the idle again and it's OK for a day. The next day - the same thing. WTF could that be?
If PZ type carburetor, then it would be easy to solve the problem.
Since I do not need to remind you that my English is awful, I will simply copypaste, without translation, a simple method for PZ type carburetor adjusting, who wrote DED @ moto.com.ua forum. Is true that it is written in the topic about mopeds with Super Cub's motors, but the essence is the same.
If this helped, please translate this text into English, because it will surely be of use to someone else too.Quote:
Приступая к регулировкам необходимо быть уверенным что;
1). Свеча исправна.
2). Уровень масла в норме.
3) Уровень в поплавковой камере – «по разъем крышки камеры».
4). Игла дросселя на среднем делении.
5). Клапана имеют соответствующие зазоры ( Альфа – 0.05 выпускной и 0.03 впускной) согласно мануалу.
6). Воздушный фильтр чистый и нет подсосов воздуха в корпусе или патрубках.
7) Нет неисправностей в системе электрооборудования.
8). Правильно отрегулирован трос газа (полностью открывается и закрывается дроссельная заслонка и нет заеданий).
Настройка карбюратора.
На хорошо прогретом двигателе, закручиваем ВК (винт качества) до отказа. Запускаем двигатель. Ручкой газа держим МИНИМАЛЬНО УСТОЙЧИВЫЕ ОБОРОТЫ, не давая ему заглохнуть, ЗАКРУЧИВАЕМ винт ВХХ (винт холостого хода) пока двигатель будет сам держать МИНИМАЛЬНО УСТОЙЧИВЫЕ ОБОРОТЫ - без помощи ручки газа. Затем медленно выкручиваем ВК. Двигатель начнет увеличивать обороты. Постепенно выкручивая ВК добьемся МАКСИМАЛЬНЫХ ОБОРОТОВ (если обороты будут слишком высокими – немного выкрутить ВХХ до приемлемых). Добившись максимальных оборотов ВК, проверяем, что дальнейшее ВЫКРУЧИВАНИЕ винта на дает увеличения оборотов, пробуем ЗАКРУЧИВАТЬ его до НАЧАЛА уменьшения оборотов, оставляем его в этом положении и затем, выкручивая ВХХ, выставляем приемлемые обороты холостого хода. Операцию можно повторить пару раз. Если таким методом не получается - значит карбюратор засорен, есть подсос воздуха или бракованный.
Is there a small spring around idle screw?Quote:
Originally Posted by Steve_Halt
Or borrow a nail polish from your wife, and just before setting idle, and smear some on the threads of the idle screw. This way idle screw will not be able to move because of vibrations.
No spring down there. Actually I thought about superglueing it once and for all. Something stopped me :)
That manual might be useful, indeed, here we go:
Before fine-tuning your PZ carb make sure that:
1). The spark plug is fine.
2). Oil level is fine.
3). Gas float level in the float bowl is "by the brim of the float bowl".
4). Throttle needle is on mid setting.
5). Valve clearance figures for 50 cc horizontal engine are: 0.05 and 0.08. For any other type of engine valve clearance recommendations are different.
6). Air filter's clean and there're no holes in the airbox/hoses.
7). Electrics're OC.
8). Throttle cable's fine (doesn't get stuck, etc)
Fine-tuning PZ Carb Procedure:
Engine should be warmed up.
1. Tighten the mixture screw to the max. Start the engine. Use throttle to keep the engine running at minimum idle (not letting it stall).
2. Tighten the idle screw until the engine can idle by itself (that is, you don't have to throttle it to keep it running).
3. Unscrew the mixture screw (slowly). The engine will start revving up. Unscrew the mixture screw until you get the highest revs (if it seems the revs are too high, unscrew the idle screw a bit).
4. Make sure that further unscrewing the mixture screw doesn't increase the revs.
5. Tighten the mixture screw until the revs START to drop. Leave it like that.
6. Unscrew the idle screw to set appropriate idle revs.
This procedure can be repeated for better result.
If this doesn't work, the carb is dirty/has sideways air intake/is faulty.
It is good that you're not thinking in the direction to solder idle screw to the carburetor body.
If there really is no spring, try to put some spring like a half of spring from a cheap ball pen.
Regarding point number 5: the translation is wrong. It is always bigger valve clearance on the exhaust valve. And I personally could add, that these figures, are for 50 cc horizontal engine and that in my experience this too tight - 0.05 and 0.08 is a better combination. Of course, for any other type of engine valve clearance recommendations are different.
And check whether the needle is fixed and does not move freely up and down through slide.
Well noted: translation corrected. I'll get to installing some spring on the idle screw as soon as I'm free from work and got a day off :)
Man, thanks for the .pdf!!! Makes it extremely clear for (I'm not a carb pro at all). Much obliged.