Hi all
Finally its time to dial in the needles after break in. No matter how hard I tried, still couldnt get the punch at the low end..
Only with the help of one of the racers. Mr CK Lee, managed to get the low end power. What he did was to richen the MSN by nearly halff a turn from default. It was always recommended to leave the MSN at default. How does the MSN works?
Im running 30% byron, OS P4 and dyn 053 pipe with the extra head shim.
Thanks

I have about a half gallon on mine from just running around in the back yard. It's starting to come alive very nicely. Can't wait to track tune it this weekend. My mechanical pinch is almost gone.

Has anyone had theirs lose their mechanical pinch in under a gallon?

What size venturi are you running?

Venturi is a 7mm which i took from my old RB engine. Btw, can anyone enlighten how the 3rd needle works..?
Thanks

MSN = Mixture

It controls the air/fuel ratio.

The tapered end of the LSN (a needle valve) fits into the open end of the MSN, sometimes called the spray bar, while fuel passes through the MSN and around the LSN.

Adjusting the MSN moves its end position/spray bar relative to the convex shape on the slide valve (this is where air mixture changes)... as well as in relation to the LSN (this is why fuel mixture changes). Hence, the MSN is always a secondary adjustment! You must have the HSN and LSN set prior to the MSN. Furthermore, even though the mechanics of the MSN take place at low speed settings, the results produced are seen in the midrange... which is why the mixture is sometimes mistakenly called the mid needle.

The original VZ was designed to run 8 and 9mm inserts. Running smaller than that closes the tuning window (I've seen people running a 6mm venturi).

Of course the best way to get run time is run a larger venturi and learn throttle control.

Unfortunately, there is no set formula or magic guide on how to tune the MSN; but you can use the MSN in your favor once you understand how it works... You can richen the mixture needle a touch when running a small venturi, lean mixture on colder days when air is dense, etc.

Razzie, I run a GO GXII with the same looking 3 needle carb (possibly out of the same factory, the new JS also), we found the lsn needle needed to be around 1mm-0.75 mm out from flush to get the motor to idle well and have good take off power, any further in and the fuel is not able to get by the lsn at idle causing it to be too lean... you can test this by blowing through your fuel line when the carb is closed, it should feel as if its almost closed off...opening the msn has in effect done the same thing in allowing some (still minimal) flow of fuel at idle.

Well, im just sharing what ive done on my Arrow. I have a xzb as well and ive never touched the msn. Its that im only dissapointed at first when no matter how hard I tried, i simply cant get the low end power. Ive heard of many gpod things of how this engine can perform. And after opening the msn by half a turn by an expert racer, u can really see the difference it makes. Extremely smooth powerband from the low to mid range...
And that for sure has made up my mind to get another of this awesome Arrow engine...:)

This motor keeps getting better and better and runtime is out of this world can't wait to get my second one of these up and going in my truggy these motors are rockets

Yes so far there are only good from this engine.best match with OS 2060 pipe.can tune at 230 degree.

i'm running the hong nor 2080 with nice temps 120-125 and getting about 14 min runtime with a 6.5mm ventri with heaps of power

That a bit hot.I had tested at 115 degree,the plug are dry.that is about 220 degree

Mine took about 2 1/2 gals what temps wers you running. and what breakin method?

but you just said 230 tuned???? 120 -125 isn't that hot the all my other motors ever os i've run at those temps and they have ran great

Is my pipe that make the engine hot

ok but when i do the spit test it just simmers there for about 3 seconds then its gone and thats how i've always done my motors and they have all seen 20-30 litres of fuel some have gone more