Just fitted a Jitsie knurled wheel air mixture screw to my 2016 Beta Evo 4t to make adjustments easier.

( Not an easy change, very fiddly ).

Counted the old air screw as three out from fully wound in, did the exchange, putting the o ring and spring from the old jet on the Jitsie, wound it in, backed it off three turns, put it all back together.

Fired up ok , but wouldn't tick over, I had to readjust the tick over, now runs just the same as before  ............bit bemused, any ideas guys or anyone fitted a Jitsie with the same issue. Got to say the Jitsie product is well made, I'm not saying it's that that's faulty.

Thanks.

I think you will find it is a fuel screw not air. What is the problem? How did it run before?

The new one might have a different tip profile than the original, which could explain some of the difference. Put them side by side to check.

4stroke.........as I said, not a problem, but the replacement fuel screw caused the tickover to alter. I had to increase it.

Think heffergm may have the answer, tip profiles.

It runs as it did before , just required the tickover turning up.

Heffergm, took me an hour to swap it over, I'm not taking that rascal out again unless I have to ?.

Well at least you will have no trouble adjusting the pilot mixture in future. I made a tool to do this as mine suffered from the dreaded backfire on over run, now spot on.

The only way your new Jitsie mixture screw can alter your tickover speed is by changing your mixture setting from previous...probably towards lean side. So either that has happened or you tweeked your throttle stop screw whilst digging around under there.

2 hours ago, 4stroke said:

Well at least you will have no trouble adjusting the pilot mixture in future. I made a tool to do this as mine suffered from the dreaded backfire on over run, now spot on.

What did you do to get rid of the "dreaded backfire"?

Turned the mixture screw out half a turn.

Where did you find the Jitsie mixture screw? Been looking for one and was told Jitsie don't make them any more. Anyone know where I could find one?

23 hours ago, 4stroke said:

Turned the mixture screw out half a turn.

Out! More air? Leaner?

Out is more fuel, in is less fuel. It is nice as it is numbered.

According to this it's an air screw. And it was my understanding that this little table originates from Beta, but I may be wrong.
 

Full name could be air/fuel mixture screw commonly air screw.

The air screw can be located either near the back side of the carburetor or near the front of the carburetor.

If the screw is located near the back (close to airbox), it regulates how much air enters the circuit. If the screw is turned in, it reduces the amount of air and richens the mixture. If it is turned out, it opens the passage more and allows more air into the circuit which results in a lean mixture.

If the screw is located near the front (close to the engine), it regulates fuel. The mixture will be leaner if it is screwed in and richer if screwed out.

Edited September 23, 20178 yr by klonheadd

Trapezeartist, ran it today at a trial and had no backfire..............

But, it ran very rich, black smoke when I reved it waiting in sections.

Concerned the profile of the jet may not be the same as the original jet as its wound out the same 3 1/2 turns as the original.

Found it harder to start today than before, I'll keep on tweeking it and let everyone know the outcome.............keep your feet up guys.

Sorry guys just read some previous threads, some say it's wound in less fuel, some say wound in more fuel,which way is it??