Originally Posted by
lbz34
If we lean the LS needle it hangs even worse. It will idle all day, but off idle it is really rich. Had 3 different experienced guys try and tune it. I just don't know how much air passing through the front bearing is acceptable. My Cheapo .21 Dynamite in the RX8 responds to needle changes just fine. The HS needle (although really lean at 2.5 turns in, factory is 5) responds fine. Richening it up from 2.5 turns out, the car wont even clean out. It is just lean enough to clean out. If We run the LS at factory 2.5 turns it hangs idle really bad like an air leak.
I went through the motor today and cleaned, re-lubed everything and checked every o-ring and everything is sealed and looks great with the exception of the front bearing. I can blow smoke through the front bearing from the carb inlet. I read leaking after run oil is normal but how much air leaking is normal? This motor had about half a gallon now and still has good pinch but has come back once at 250 deg F. A bit warmer than I would like to see and its the hanging idle/lean problem that is causing this (I am new, sorry for the questions). Nobody else's car hangs the RPM's off of WOT like mine does.
It is just a stock Nova 353 steel bearing from Murnan if that makes any difference. Maybe I should have gone RB?
P.S long noob post, but want to give as much info as I can.
Thanks
Ok... here's the drill..
Note: Do not squirt the throttle more than 10% it will flood, we are trying to get the bottom tuned.
1) Ensure IDLE is closing by checking servo
2) Use a rubber band from throttle cylinder to top needle to ensure it's closed
3) Check all lines and fuel tank for leaks, head and carby too and check your plug.
4) Check the Carby BOOT (rubber has no cracks, seated properly)
5) If your top is rich, leave it like that until bottom sorted. (We need to know fuel pressure is available)
6) Warm up the engine with a hair drier
7) Start it up and let it idle for 30 seconds and then tilt the car and see if fuel is coming out of pipe. Does it start to lean up as it tilts? (Are you too rich on the bottom?)
8) If #7 is rich, lean the bottom needle 1/8th at a time and wait in between intervals for crank fuel to get used up enough for revs to come up, then drop your idle.
9) Give it a little squirt (10%) blip, does the idle drop immediately? Repeat a few times to be consistant
10) Put it on track and let it warm up with some load and tune the top.
The most common cause of a high idle after clearing the crank is your bottom needle is so rich it's bringing down your idle. Your idle gap is too large hence too much air entering the mix but your rich fuel mix brings the idle down. Once you clear the crank of fuel, the mixture entering the combustion chamber is lean with air due to the large idle gap.
Hope it helps.