mixed up mixture !!!!

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Ken Graham

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Hi Folks
I am having problems with a rich mixture at tickover on my 1974 850 mk2a running on the original Amal Mk1s and pea shooters .
The bike runs rich at tick over , but if you lean the mixture down then it starts popping back mid throttle.
I have read that I could fit a smaller main jet ( running on standard 260 ) but I am unsure how many sizes to go doing ?
has anyone had similar experience - and what jets have you used.
Cheers Ken .
 
Thanks guys , I took my info from the surrey cycles amal book and suggested the main jet at tick over and the throttle slide at 1/4 t0 3/4 opening.

I will have a look at the link , thanks .

Cheers ken.
 
Ken,
First of all, make sure the carb. settings are exactly as book. Your Ign. timing is right.
Check you don't have any airleaks in your intakes or balance hose. Also check the O rings on the pilot adjustment screws, they cause hell when they go.
 
The real first thing is to establish is baseline float/fuel level and that is done by adjusting the valve seat till you get best idle at close to 1.5 air screw turns out. If better idle with screw turned in then float set too rich and visa versa. This of course assumes the ignition timing is about spot on. If you can't get 1.5 turns out best idle then you will know the pilot jet is clogged or of wrong size. Carb ware nullifies anything til renewed enough to seal air sneaking in, but that over lean condition so may not apply to your case. All else in carb depends on fuel level in bowl.

Some say to heat carbs in hot water before moving the float valve seat but I found its hardly in there tight enough so just a blunt finish nail and very light tapping moves it easily. Then again its British product so may vary to be murder to move.
 
Thanks guys

It seems so simple yet so far away !!! I will double check all settings and levels and see how it goes.

Cheers Ken.
 
hobot said:
The real first thing is to establish is baseline float/fuel level and that is done by adjusting the valve seat till you get best idle at close to 1.5 air screw turns out. If better idle with screw turned in then float set too rich and visa versa. This of course assumes the ignition timing is about spot on. If you can't get 1.5 turns out best idle then you will know the pilot jet is clogged or of wrong size. Carb ware nullifies anything til renewed enough to seal air sneaking in, but that over lean condition so may not apply to your case. All else in carb depends on fuel level in bowl.

Some say to heat carbs in hot water before moving the float valve seat but I found its hardly in there tight enough so just a blunt finish nail and very light tapping moves it easily. Then again its British product so may vary to be murder to move.
Click to expand...

Was' all this,well it's british, so it can't be made very good, bit.
 
Re: mixed up mixture !!!! result

Ok , looks like we are going places . checked both the float levels and neither were the same or correct.

Plus the main jets were both marked 260 but only one of them was stamped Amal !!!!!! result - if you dropped the needle down inside each there is a differance of between 3 - 4 mm in the height that the needle seats at.

Have ordered 2 x rebuild kits from Amal.

Should all be good after that, thanks for all the advice .

Sometimes you just need a wee pointer.

Cheers Ken.
 
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