Originally Posted by
Arushmen
Hi, I have a new (2 race) novarossi plus 21-4btt on my mbx6 and I really disappoint with it
My idle is very unstable
My top end is very bad
I have a lot a flame out in my last race
I use it with the 41039 manifold
I put it another .1 shim because the engine broke 4 plug
But Nothing seems to work
I use p3 p4 from os
i use novarossi 5 6 7 plugs and nothing
I test the 9901 and 9853 and was a little better with the 9901 (to end)
What is wrong? I test the fuel with my other engine (ninja) and work fine
I really disapoint
What else I can test?
Thanks in advance
Never run OS plugs in a Novarossi. Taper is different; now that you have seated an OS plug into the button, you may have to buy a new button.
Use 0.80mm total head shim stack. .30/.30/.20 for 30% nitro.
Use 0.75mm for 25% or 0.70 for 20%
Use Novarossi C6TGC glowplug, or OD77T; or OD97T. C6TGC preferred; otherwise start with 77T.
I assume you meant 41029 manifold for Mugen?
Pair with 9901 pipe.
Remove fuel tank from vehicle. Pressure test the tank in a soapy water solution (submerge tank). Place finger over fuel pickup, apply pressure by blowing on the pressure line. Observe results to see if any bubbles are seen escaping the tank. Any kind of air leak will cause tuning issues.
Run all fresh pressure/fuel lines on the car.
Replace all clutch shoes and ensure they are operating properly.
The following statements are based on running the engine in a 1/8th buggy on a typical dirt-track in a racing environment...and the engine being broken in (at least 2-quarts of fuel or more).
6.5mm carb insert.
Place LSN 1/8th turn in from flush.
Place HSN 1/2 turn in from flush.
Set idle speed to have 0.50mm air gap (set with restrictor removed), or start the engine and adjust it accordingly once warmed up to operating temp on the starter box. (I'm betting it's way off).
Once running at operating temp, adjust the HSN until proper performance is achieved. With a head temp of 220F- 260F; the idle speed should be stable and fairly low.