Thats MASSIVE !!!!!!! Ha ha - I couldn't resist doing that :p

Great job Adam

One turn in on the HSN is way too much.
Like Retro said, it sounds like you have a very rich bottom end (possibly being masked by a too wide an idle gap), which you have compensated for by leaning the top end too much.
Set the idle gap by sight to .7 - 1mm. Flush both needles. The motor should start and run with both needles flush. Warm up the motor by running on the ground for a half a tank.
Now lean the bottom end until you have a reasonable take off with little or no bogging. Now fill the tank up and run it to empty. During this tank tweak the top end needle for clean performance up to full throttle. You should only need to go in a MAXIMUM of 1/4 turn from flush to achieve this.
If at any stage during this tank you get lean bog - richen the HSN a screwdriver width at a time until the lean bog goes. This should now be your optimum HSN setting. Re tune the LSN if required for clean crisp take off.
Idle gap is super important. If the initial gap is set wrong you will chase your tail all day trying to get a good tune, and invariably end up with a wide idle gap, rich bottom and lean top - which will run sort of OK, but will result in a crazy idle, mediocre performance at best, and will run the motor too hot at the bottom of a tank.
Hope this helps. When you get the 7 Port tuned in properly it will scare the pants off you :D

Shane my high side is about 1/2mm in from flush. on the gen 4 and goes like a rocket :sneaky: dont know how many turns it is but it at least 2 if not more. i was experimenting last weekend.

Just my 2 cents on this and i may be way off the mark but i tried tuning to this method and it just did not work. Trying to get it to shut off at the 7 sec mark made it way to rich on the bottom end, it would not idle properly and i gave up and went back to the old method of tuning the low to give good takeoff and performance then fine tune the top end as per Grizzs advice. The HSN doesnt need much tweaking from flush.

I dont know who else has tried this 7/8 sec magic number tune method and would be keen to hear who has, like i say i may be missing something but that was my experience.....

Thanks for all your help,

looking back at the day I think your spot on, I was definately chasing the tune and to be honest the performance was nothing to shout home about, to be honest was struggling to make the doubles, when i set the idle on the box had to keep turning in to stop engine over reving when pinching the pipe, first thing i did when running at the track was adjust the top needle for top end performance as i had set the lsn for 7 secs and the info said leave alone when at this stage,
will start again and follow Grizs instructions, tuning bottom for take off and manually setting idle.

Will let you know how I get on
will be a few days though as waiting for replacement parts for the car as blew a shock, have now stripped down for a total clean and maintenance.

Hmm - it's hard to argue with Massive's wisdom. He is the GO Guru !!
I must confess I have always used the 4 - 5 sec pinch rule for the LSN. Pinch off the line and the motor should rev up only slightly (indicating a correct idle gap), then should die between 4 and 5 seconds. This has worked in the past on the Gen 5 motors I have run, but it may be a little different with the new GX and MG carbs with the new HSN needle etc.
Be aware that a rich bottom end will also give a high rev when you pinch the fuel line off, as you are leaning a motor that is too rich, so it will speed up before it dies. Conversely if your bottom end is too lean the motor will simply stop fairly quickly with no rise in revs at all.


Hi Jeff - My old Gen 4 was a bit like that. The needle settings were way different to the Gen 5 and younger motors.
As long as it's haulin butt and you have smoke right through the rev range it must be good.

I tune mine to the 7/8 second pinch, and it seams to be a great start point!

I only let the motor warm up for about 1 min before i get the 7 sec pinch, maybe you are getting the motor to hot before the pinch!?

At any rate who cares if this method isnt working for you, if you can get the motor to run great using your own method, go for it i say use wat works!!:nod:

base settings are always good but has been my experiance that you can not always rely on this , as fuel glow plugs pipe where you live make a huge differance for example if i run base settings my motor is so friggen lean my hsp is flush but my lsp is about 2mm out when tuned perfect for where i live and the fuel i use

no matter the carby or engine if you get a pinch 4-5 secs on the bottem end you will be close to where it will need to be from there on just make small adjustments from there

Yep Matt has a point, i am 400kms north of him , same motor/pipe/fuel/glowplug combo but i am a hair under flush HSN and about 3mm under flush LSN!

Just goes to show the difference!:nod:

You are right Grizz it is hard to beat mark with a go tune but as i say if someone elses method aint working for you use wat works! Personaly i found massives advice to be golden!!!:nod:

What would be the result of giving too high an idle gap, if the engine ove revs with a rich lsn then i wound in the idle then this may have been the problem as the idle should have been ok as i had set this manually, had to probably go in 1/2 to 3/4 turn to control revs before setting lsn

Where is ur track and is it indoor or outdoor?

Track is Frankley in Birmingham UK.
Outdoor Astro track, as I said was about 4 - 5 deg temp and damp at first, track was wet and very slippy

I've never had much luck with the pinch test either but I found the one golden rule with GO motors is manually set the idle gap to .7-1mm before you start..remove the carb insert and use a drill bit to set it..I have some old imperial bit i found that happens to be .8mm..perfect..if the motor won't idle with this idle gap your mixture is WRONG somewhere..HSN flush and LSN flush or maybe 1/2 a turn in is where I've always got the initial idle stable..I started with a gen 4 7 port then a gen 4 3 port then gen 5 and 5.5 7 ports and now the MG66 and I set them all the same..set idle gap..start the motor ..if it chokes up a lot and won't idle unless you keep blipping it then lean the LSN a bit BUT DON'T TOUCH THE IDLE SCREW!! then I sling it on the ground and run very gentle figure 8's till I've most of a tank through it.you need to heat the chassis plate as well as the motor..to get a reliable tune EVERYTHING needs to be up to temp..then LSN for a nice crisp takeoff with plenty of smoke but not a huge cloud as it struggles to clear out excess fuel..NOTE!! if you have been idling for maybe 30 seconds the engine WILL load up a little and probably struggle to clear the unburnt fuel for a second or so..this is normal and doesn't necessarily mean the LSN is too rich.blip the throttle to clear out the motor then idle for 10-15 seconds max before trying a clean takeoff test..I can't speak for the GX motors but the 5.5 carbs are pretty sensitive..you only need to adjust maybe 1/8 of a turn at a time..SO USE A LIGHT HAND .hehe..then do a few good high speed runs and maybe tweak the HSN in a little..again bear in mind that as you lean the top end you are also leaning the bottom so you might need to revisit the LSN and richen it a fraction.Personally I always leave the LSN a touch rich at first and then it usually falls perfect when I tweak the HSN..

I'll be near birmingham over xmas..I dream of an astro turf track..we've had 6 weeks of monsoons here and now it's minus 8..so from the track being under water I now break pickaxe handle trying to do any work on it...I'm thinking of a 1/10 onroad with drift tyres on my frozen pond is the way to go for winter this year..