How can I enrich the air/fuel mixture?

[Padmei]

These cheapy air filters from motorworks are they the ones sold with the complete service kits? If so I have one - what's wrong with them - do they not let as much air though as a BMW one?

New to airheads & mech stuff...

 

[bernardofeio]

Now that you mention it I changed the normal paper filter to a K&N “normal” rectangular filter…

 

[Rob Farmer]

These cheapy air filters from motorworks are they the ones sold with the complete service kits? If so I have one - what's wrong with them - do they not let as much air though as a BMW one?

New to airheads & mech stuff...

I've had problems with them swelling up and reducing the air flow dramatically. I always buy genuine but if your happy with the ones you are buying don't worry about it.

 

[bernardofeio]

Hello

So to summarise (and please correct me if I’m wrong)

I can adjust the how lean or rich is the mixture at idle with the outside adjustment bolt (and this adjustment bolt will only work for the idle)

For the middle range it’s not adjustable (?)

For the high range I can change the needle position and/or jet diameter

 

[ians]

Changing the needle position or size changes the middle range.

All of the adjustments affect each other as when the engine is on idle it uses the idle mixture, in the middle range it uses the idle mixture AND the needle mixture, on full throttle it uses the idle mixture, the needle mixture and the main jet mixture.

This is very crudely explained but you get the picture.

 

[Padmei]

Cool thanks for that.
SO it is quite a techy performance synching all three adjustments or is it a bit of slight adjustment here & there as well as repacing the needle?

Just interested...

 

[slowkitty]

Hello

So to summarise (and please correct me if I’m wrong)

I can adjust the how lean or rich is the mixture at idle with the outside adjustment bolt (and this adjustment bolt will only work for the idle)

For the middle range it’s not adjustable (?)

For the high range I can change the needle position and/or jet diameter

bernardfeio,

I can understand how you feel because I went through the same thing. I would suggest the following which worked for me:

1. Before you adjust the carbs, make sure that your timing is right (use a timing gun if possible), and that your valves' clearances are good. Naturally, bad coils will have a bad effect too.

2. Service your carbs, change the o-rings, jets, throttle springs etc. These are not that expensive and will save you much trouble later (I got mine from Motobins). Also get the fuel level in the bowl correct (I believe that it is half-inch from the top of the bowl). Set the needle to stock setting - 3rd notch from the top.

3. Set the idle screw and the mixture screw to stock settings. I believe that in the manual it is (a) idle screw - screw set at paper "feeler" thin then 1 turn out, and (b) mixture screw 3/4 turn out from tight.

4. You also have to ensure that the throttle cables are properly tensioned at the carbs, there should be some freeplay like 1 or 2 mm but most importantly both cables must be pulled at the same time.

5. After setting the above, go for a 10-mile ride to set the bike to running temperature.

5. Set the idle using the idle screws; modern airheads about 1050 rpm (Don;t ask me how to get the "50" - I just try to get it a hair above 1000 rpm. I use a twinmax to sync the carbs. Adjust the mixture screws to sync the carbs.

It was a learning curve for me, but it is worth it. Bike is running great now.