You will be after a GO 21-2003-A (short needle) unless Trey the US distributor has changed the normal parts numbers around for the US market, where all the GX motors are imported with the short needle. So he may be calliing the short needle a GO 21-2003. Best check with him.

The MG66 and all GO GX engines (outside of the USA) are distributed around the world with the factory standard long needle fitted. It's up to the individual distributor to decide what he wants for his own market basically.
The long needle is easy to tune once you see how it works. Go to the Tech Tips page on my website and check out the tuning guide for the long needle carb www.go-racing.co.nz Once you have mastered it you may not want to change to the short needle. The MG66 is designed to run with the longer needle which when tuned correctly helps to give a very smooth power band with no LSN - HSN transition . Will save you a few bucks too Having said that, the motor will run fine with the shorter needle. Up to your personel preference really.

great fuel milaage...

i'm having problems to get a good mileage here.

my track: http://www.youtube.com/watch?v=0zSwH...layer_embedded

i can run 5 minutes....

i'm runing gx-5r, byron 20%, 7.5mm venturi, stock shims (1x 0.3mm + 2 x 0.1mm)

next saturday, i'll try 1x 0.3mm + 1x 0.1mm and 6.5mm venturi...

will it work better?
sunday will be the racing day

Im gonna say yes. The 1 less shim will give it more power but be harder to tune and the smaller venturi will help too.. How lean are you running? Get her up to 240.

last race my car stoped less than 5 min... but i was runing cold (185)..
this saturday i'll try to tune all the engine

the richer the more fuel your sucking(i think someone correct me if im wrong). Lean it out i mean dont be afraid to get it up to 230-240. Those are great temps

su3zero, from the video u won't get too much better milage due to the track having next to no grip!
u spend most of your fuel trying to get traction !
leave your shims where they are & try a softer clutch spring, put the 6.5 restricter in lean out your H/S/N & richen your L/S/N to compensate to get engine to a more efficient temp.
try different tyres aswell
good luck & let us know how u GO

Is the engine broken in? How many gallons through it? Here's the deal with most of these engines-we all,or most of us will run the lsn to lean opening the idle. In my experience it will seem like the engine is close in tune when in fact it is sucking fuel harder to keep the fat idle going. With that said on my 5 port I run byrons 30% with a os-p3 plug. The p3 plug is what you should be using right know with 20% The way things sit right now I would not remove a shim yet until you are sure the engine is broken in. Then I would put in a os-p3 plug,set the needles back to flush. Then turn the hsn in 1/2 turn-lsn 1 full turn and start from there. Also make sure your air filter is in top condition. and no air leaks. I went through all of this and more with my mg-66. With the help of some people on here I was able to tune it right and went from 7-9 minutes run time to over 12 min. Just remember to have engine up to temp before you try tuning,and make very small adjustments. And 99% of the adjustments will be to the lsn/idle. You will touch the hsn once? One last thing ,use temp gun only after engine is broke in and is running like a raped ape! Then that temp is only for reference. What I'm trying to explain here is that with the engine out of tune you will suck fuel like crazy. When I actually fattened up the lsn and reset idle,boom everything came together.

my mg66 and mbx6t

a loser look.. i love this engine

+1 on everything Matt has said. Idle gap is soooo important on these motors.
The wide idle gap / rich bottom / lean top is a very common error when tuning.

IF AND ONLY IF your motor is fully broken in AND you are ONLY RUNNING 20% you can shim down to the 1 x .3mm alloy shim only. You can run the higher compression if your using lower nitro percentages. The fact you are running standard shims and 20% may well be effecting your economy due to low compression and low engine temps - neither are very effecient.

Definitely run the 6.5 restrictor, that will give you plenty of power for the loose track surface you are on.
As suggested look at a softer clutch set up and maybe thinner oil in your centre diff. If you are running say 5-5-2 now, drop down to 5-3-2 to help eliminate some of that wheel spin and save on fuel.

Even in those conditiuons you should be able to get at least 7.30 to 8 min I would say.

P.S. Read Massives shimming 101 article here http://www.massivemods.com.au/produc...roducts_id=192
Should help to explain things even more

thanks guys!

I'm running odonel medium glow plug, Brazilian Go dealer sugest me to run it.

Run almost 2 galons! I guess my engine is full broken in...

I got the tuning guide from Massive mods site, i'll go to the track tomorrow to tune the engine for the race.

I just remove the shim because my piston was a bit darker.

Check this.


i'm reading all yours help to try tomorrow....

thanks again for all help guys!

It appears that your head shims weren't sealing properly. The tracks of oil across the top of the sleeve would indicate that. Were your head screws tight? Also, the oil looks dark, like dirt might have gotten into the engine. Remove your carb and look at the crank through the carb opening. If it has scratches all over it, this could be a sign that dirt got in it. Does it still have good pinch?

i'll check it, but there's no dirty at the piston, i guess the dark oil is the after run. But i'll open the engine tonight

Su3ero,

One of the tracks i race its very new to that video you posted.

Im using more or less this setup :

- .21 GX5R engine
- GO 0801 pipe
- Aluminum clutch show with .9 springs (x3)
- 7mm carb insert, with 75% carb opening (epa)

Im geting like 09.45 minutes for a tank on Buggy ... so i pit every 8 no problem.

Another thing that helps on low traction and big/open tracks like that on the video, and obviously helps on fuel consumption is to go +1 teeth on clutchbell.

hope this help,

cya !

I'm running EFRA 2072
Stock Losi 8ight 2.0 Clutch set
(was 7.5mm carb insert) i'll try 6.5mm with 70% Epa