You will actually gain top end when adding shims, but you lose a little bit of bottom end, there should be a total of .55mm to .60mm shims if using 25% fuel.

which one is better the 353 or the 353 tune? Why?

Performance wise, the 353 tune would be better. I have seen a tuned's crankshaft and it has some nice cuts... I do not know if they changed the 353 tuned's timing. If they didn't I'd suggest getting the stock one, because the tuned one does not have any sleeve modifications...

well I race down at 301 and I need a motor with some legs and some punch I don't if to get the +12 or the 353

I have heard the novarossi plugs don't last long.I know a couple people are using ninja plugs in theres.Are there any other plugs that work for this motor or are designed to work with novarossi.I have a 35plus21lc/wc.Thanks

Nova and RB plugs are great. Ninja's and GRP are even better.

I think ninja plugs are the best I've been using them in my novarossi motors and they last a VERY long time unlike novarossi plugs!

In my 353 I still have the plug in it that I broke the engine in with and I got the motor new in april. pluse in 321 in my 960, that plug has been it it sence the 8th scale nats.

It is almost a year since i last played with my G4S. It is powered by a Novarossi Rex engine(RE 12S3). I was expecting some difficulties in starting up the engine. But it turn out to be effortless.The compression is still strong. Thumbs up for the quality in Novarrossi engines. The car "shoots" like an arrow at the slightest pull of the trigger. A lot of power in it. But there is a problem; the engine can't hold the idling, it just dies off after a few seconds if i stop pressing the throttle. What could be the problem? How can it be resolved? Please advise me. Thank you.

u might try increase your idling screw abit...

check your idle and low end mixture and if you haventd one so already try a new plug and fresh fuel

Thanks for your reply. When idle screw & low end needle are mentioned, do you mean clockwise or counter clockwise? How to determine when to stop turning the screw? By listening to the sound of the engine or what? Oh yes my engine produces a "rough, dry" sound. Does it mean it is lean? The G4S is no longer in production. What are the essential spare parts i need to get(parts that wear @ fast rate)? Are they compatible with G4RS? Thanks & have a nice day.

I'm running 353 how come after straight then getting into concern. The car seems still want to run. I have richer the low end and it helps a bit but still happening the problem. If I richer too much low end, the engine has worse response. What should I do?

either your idle is too high
or
your clutch is dragging

The idle can't low anymore. If I lower it, engine will be die after the car stoped when the rpm goes down.

I have tried to adjust the clutch with harder tension. But i think if I do it more, I will have too much cap on throttle before the car moves.