See post above # 2480

Thanks but I mean for the mk1 carb that I have. That settings is for the mkll carb l think.

Oh miss understood, but sure I read it in here some where or maybe the other thread.

Hey Hypernator,

Just want to make sure we are on the same page with the carbs.

The motor you brought has the original "3" needle carb with chrome throttle slide - yes ? Not the "2" needle carb as distributed in the US ?

To the best of my knowledge no motors fitted with the original "3" needle carb, or any of those carbs by themselves ever made it into the US market (I am just assuming you are in the US).

The GXII has come out in three versions so far:

Standard GXII two needle carb

GXII with MkI three needle carb (for a limited time of around 4-6 months)

GXII with new MkII three needle carb (only released from factory a few weeks ago).

Standard "2" needle GXII carbs - HSN flush, LSN flush to start with. Lean from there depending on pipe and fuel etc.

MkI "3" needle GXII carbs - we found a good race tune with these using the 2072 pipe was - HSN 1.5 - 1.75 turns in from flush, LSN .25 - .5 turns out from flush

MkII "3" needle GXII carbs - these are looking to give a race tune at around - HSN .25 - .5 turns out from flush, LSN around .25 - .5 turns out from flush.
We are still running-in and experimenting with the new model. New owners have only had them here for around a week, so early days as far as full on race tunes go.

Oops double post

Thanks alot grizz! That info realy help us racers here in sweden. Great!

MkII 3 needle showing white insulator and new anodised throttle slide.

I've had so much great performance with my current Go motors that I went ahead and got the new one. Now questions on the tuning strategy for the 3needle carb.
On my GX5R I like to get the top end close, then tune for good low lean idle, then tune the top end just above lean bog and test on the track.

With the GXII5RHO MkII 3needle, what is the best tuning strategy for truggy once it is run in? Does it tune more like the short LSN or still the same long LSN?

What's the recommended glow plug for a GXII-5R w/2072 pipe? Don't remember if I saw it in this thread or the other one. For some reason my iPhone won't let me search for some reason.

well im useing the O donnel T97 at the moment and that does well for the engine and holds a real smooth idle.. at temp especially...

Hi AZTman - Tuning strategy is pretty much the same as for the long LSN.
The 3 needles still have the long LSN set up, but the HSN is far more adjustable than the 2 needle. With the 2 needle you were adjusting no more than a couple of hours in from flush on the top end - with the 3 needle you can adjust in 1/8 or 1/4 turns. Much more user friendly.
Mid range fuel tube is air flowed and set at the factory for peak performance, and it's recommended not to adjust this. If you feel you absolutly can't resist having a tinker, reference the factory setting first - but honestly it's best left alone (like all other mid range needles / fuel tubes).

Ball park figures running the 2072 pipe, 97T plug and Byrons ProDriver 30% fuel - HSN 1.75 turns in from flush, and LSN 1/4 turn out from flush.
This is at sea level and around 17 - 20 deg C.




O'Donnell 97T is pretty much all we run in these motors. They perform great and last for ages

Hey guys. I have a silver head 5 port engine that has barely gone thru break in. Seems most of the go rods are the same, but places like amain show a 15.5 and a14 mm wrist pin. So seems to me theres some confusion somewhere. any ideas on what to get.
And by the way, these older version carbs were a pain enough, mine has an OS20C carb on it

second question would be the pipe. Got an 801 GO pipe when I bought it. Whats the difference between it and the 2072 that seems to be preferred?

Those dimensions are quoting wrist pin length.
21= 4x14mm
25= 4x14.75mm
28= 4x15.55mm

21GX engines = P-0414-3
21GXII engine = PS-0414
25Pro = P-0415
28Pro = P-0416