7mm is always my all around favorite. Need to also make sure you limit the throw after going from the 9 to the 7. If he leaves it opening as far as it was with the 9 he won't see much improvement.

What glow plugs are you guys running with the Fire11?

I am currently running Odonell 97T plugs.
I am also looking for more run time, currently have the oval 7mm venturi and getting around the 7.5-8min run time.
Was thinking of giving the 6 mm venturi a go aswell.

The F11 isn't going to be a great fuel mileage engine in stock form. How much fuel do you have thru the engine? What are your temps? Do you feel you have it fully leaned out and running the best it can? What pipe do you have on the engine? Also, in general the cooler plug you run the more spot on you will have to be on the tune which can in some cases yield better mileage because many times people are running rich and they don't realize it. If the plug is too cold you will know because it will want to constantly load up and die.

good day, i need replace my old plus 21 4C, an i see a X11 o F11, please need coments about the botton end, of this engines.

i like a engine with good booton end, but the F11 is good choice for the price, but i like the prestations of the Plus 21.

but i like RB. i need choice one.

I have never owned a +4 but have driven a few and helped tune a few. I would say the X11 is close to the same as the +4 when it comes to bottom end. IMO the F11 has more bottom end than both.

thanks for the answer,

is to big the diference, in botton end, in plus 21 4 Vs RB X11?? if the maximun calification is 10, please rate both engines.

If I was going to rate them on a 1-10 scale for bottom end I would do it like this.

X-11: 5
+4 : 5
F11 : 7

That is just my opinion and what I have experienced. I have never owned a plus4 to be able to try numerous pipe/header combos to get better bottom so maybe the +4 is actually better than a X11. This is just based off of helping local folks running a +4 and was always on a 9901.

hi guys wondering if i could use nova connecting rods to the rb engines like the fire11 for example?

I would not do it, the Nova and RB have slightly different crank pin sizes which would make that busing at the bottom of the rod slightly different as well.

My ongoing search for a deal on a 2058 pipe for my Fire 11 is not having much luck(nobody seems to run them over here..) Have found a deal on a 2013 though.. How should that match up with the F11(in general, and then in comparison to the 2058)? If anybody also happens to know how the 2013 should work on my Argus and modded Jammin JPX-21 I'd be keen to hear that too..

The 2013 will work great on the F11. It will have more bottom end than the 2058 and it will sound AWESOME!!!

RB makes a great engine. Why so little talk about them? Are they not being used?

It normally picks up in here as the race season gets into full swing.

Thanks Chris. Even in the summer it's still pretty quiet compared to others.

RB makes just as good a engine as any.

RB seems to have had a rough go in the US over the years.

They are great engines indeed!!! I think they have been hard to get and expensive here in the US which has made them not as popular here as other countries. The US distributor has changed a lot since I started running RB 7 years ago, now that Jim at Fusion took over maybe he can help them gain some popularity around here.