lbz34

iTrader: (28)

.12 Nova 353 steel bearing. First 1/4 of a gallon ran good rich for break in. Problems started this last weekend. Stock settings are 5 turns on HS and 2.5 on low side. Motor wont clean out at all with more than 2.5 turns on the top side. The biggest problem I am having is the low side. When the motor comes off the top end the idle hangs, seems lean, took the low side out to4.5 turns and still does it. Idles fine all day, of idle it bogs like it is rich. On a 2010 worlds car with 3 races, no tank leaks, new fuel line.

Today I took the motor down and cleaned and reassembled it. Seems to have some air drawing through the front bearing. Nothing else is leaking any air, but the front bearing seems to pass a lot of air if I pull vacuum through it. Bearing is still smooth as can be but this hanging idle is chapping my ass.

I guess maybe try a new front crank bearing? Any other ideas? Ran fine first time out with the needles stock but leaned enough to get around the track. Now have the hanging RPM problem. Come off of full throttle and the RPM hangs for a long time.

Did a smoke test and only get smoke through the front bearing, very hard to blow any air out through it, but I can draw quite a bit of air through the crankshaft if I draw vacuum.

Any help is greatly appreciated.

blis

High idle off a long straight is often indicative of Faux idle. Your bottom may be too rich and idle too high.

Lean the bottom and drop the idle and see how you go.

lbz34

iTrader: (28)

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

TomB

iTrader: (10)

if the bearing feels smooth and doesn't move up or down, or in and out i wouldn't worry any more about it.

have you tried richening the bottom and top at the same time and lowering the idle?

wingracer

iTrader: (24)

That's actually what you want it to do. Lean it until it stays high for a while. Then back out the idle screw until it idles low again.

Also, I never had a 353 myself but I remember several local guys had unending tuning problems due to a bad batch of carbs. If you have a good older carb laying around, swap it out and see if that fixes it.

pegatinaman

The first thing I would check fuel lines, the fuel without any filter to the carburetor as short as possible and the air coming from the exhaust pipe to the gas tank from 15 to 17 cm in length without using any cooler type stabilizer fuel or pressure. I had the same problem with my 353 several years ago, when reviewing the installation gave me no more carburetion problems.

blis

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.

blis

Dang, I bought my younger son a 353 today. So will see how it goes!

lbz34

iTrader: (28)

I have a RB cooler on it, we took the cooler out of the loop and put a longer line prom the pipe to the tank and it seemed to help a bit. Carb is open about 1mm. I listen to the other sedans and they come off of WOT and right to idle no hanging of RPM. I am starting to wonder if I have a carb problem. I do have a Picco evo 2 i can try that carb I guess. Sucks I have to wait a couple of weeks between races to try it. On the street in front o the house the traction is so bad i can get any good load on the car to see if it still hangs the rpm. Really just want to get it sorted before I overheat this motor and hurt it. Thanks for the help and ideas so far .

brosla7

did you change glow plug after brake-in?

wingracer

iTrader: (24)

If it really is 1mm, there is your problem. .9 is about as far as you ever will need.

It's real easy. Go run it, get it good and hot. Come off the track, if it's idling high, just back out the idle screw until it comes down. Then adjust the LSN as needed to get a good idle.

lbz34

iTrader: (28)

I did

It would idle forever just a normal as any other nitro. When I would come off of the top end the RPM would hang high for 3-5 seconds then drop to a normal idle, like a really lean bottom end.

Ran it out front of the house just now after a complete tear down and cleaning and it seems to be doing better. I will just have to wait till Oct 9th to run it again at the track and see if it will run normally, with close to factory settings.

Going to take a bunch of fuel line and run short and long sections and see if that affects it. Seems the longer the line from the pipe to the cooler/tank the better it does, or it had some trash in the carb or something.

Highside20

iTrader: (2)

You got the engine from murnan right? I would give him a call or shoot him an email. I know he helps me with all the engines I bought from him.

lbz34

iTrader: (28)

I did get it from Murnan, I will hit him up. Hopefully I got it working, see ya in a few weeks.

FASRICK

Have you changed the number 5# plug out after break-in ? This will also cause throttle hanging