Adjusting carb mixture?

[SaffaChris]

Hey,

So my NT400 is running pretty rich... airfilter and choke cable aren't the problem. After I've given the carbs a clean, it might be time to try adjusting the mixture. The pilot screw plugs have been removed by a previous owner, so the screws are visible.

My question... is it best to try adjust pilot screws from their current position, or screw them until seated and adjust from there?

Thanks!
Chris

Stock Bros NT400 Mk1

[JR]

Might be worthwhile screwing the mixture screws in until they just seat and counting how many turns, just to see if both carbs have the same setting. This means you can restore them back as you found them if required. The 650 is normally about 2 1/2 turns out from seated so not sure about 400.

Was it running rich before you cleaned the carbs?

Also just because the choke cable is moving how do you know the choke plunger is not faulty?

[HypnoToad]

I would mark the position by counting how many turns to put it back in.
and then store that number for reference. after that you can go back to it if everything fails.
But there might be a better way of doing it.

[SaffaChris]

Haven't investigated the choke plunger! Will look into it.

I haven't cleaned the carbs yet, so yes, it was running rich before touching anything.

With the pilot screws... further out is richer?

Thanks for the tips!

[DefTrap]

With the pilot screws... further out is richer?

Yep.

[SaffaChris]

My GOD!

What an improvement... like riding a different bike!!

Took the carbs apart... they were spotless, so I just blew some compressed air through the jets. Whacked them back together, put in a new set of plugs, and adjusted the pilot screws 1/8 and 1/4 leaner in the front and rear.

Man, she goes like a rocket compared to before! No hesitation throughout the revs, power over the whole range. She used to struggle getting to high revs in 5th... that's been solved, so my top end speed is much better too.

Thanks for all the advice guys!!!

[squirrelman]

one common method for adjusting mixture screws involves slowly screwing in screw until cylinder just starts to loose power and cut out, then backing out between 1/2 and one turn or whetever.

[DefTrap]

I tried that. Didn't work for me.

[squirrelman]

if screwing in mixture all the way does not cut that cylinder, then you probably have a damaged screw or damaged seating area for screw or missing o-ring and washer....engine should be at operating temperature to do this.

[nitso]

What an improvement... like riding a different bike!!

Took the carbs apart... they were spotless, so I just blew some compressed air through the jets. Whacked them back together, put in a new set of plugs, and adjusted the pilot screws 1/8 and 1/4 leaner in the front and rear.

Man, she goes like a rocket compared to before! No hesitation throughout the revs, power over the whole range. She used to struggle getting to high revs in 5th... that's been solved, so my top end speed is much better too.

Thanks for all the advice guys!!!

Hello ,
can you explain to me please ,how many turns you mean with your phrase :"adjusted the pilot screws 1/8 and 1/4 leaner "

[giannisblest]

Hello ,
can you explain to me please ,how many turns you mean with your phrase :"adjusted the pilot screws 1/8 and 1/4 leaner "

he just screwed in the pilot screws.1/8 for the front and 1/4 for the rear.

[nitso]

he just screwed in the pilot screws.1/8 for the front and 1/4 for the rear.

From the begining or from the initial setting(2+1/4 turns) ??