Running Lean on Spec Jet

viice

Member
I imagine that the answer I'll get is "It's ok."
But I'll ask for the sake of asking since I'm brand new to this engine/oval karting.
While these engines are basically disposable. I'd like to not dispose of one each weekend!

Brand new Predator 212 Hemi.
.031 Main Jet (As stated by the rules)
Removed Gov/Oil Sensor
Weenie Pipe + RLV Silencer. (As stated by the rules)
Stock Airbox, (As stated by the rules), does have hole where vent hose ran from stock tank.
3910X.
Pulsed from side cover to Walbro pulse pump.
No clearancing/tolerancing.
~2hrs of idle break in.

Considerable amount of backfiring off throttle and a nearly constant blue flame out the back. Anywhere from 2000-5000rpm under no load.
Is this typical for a set up like this?
Is there any other sort of air/fuel tuning tips and tricks that can be done without replacing pipe/airbox/filter/jets?

Thanks.
 

viice

Member
Forgot to mention: Engine was gone through after each hour of break in. Also has 10.8 Springs.
 

Kart43

Member
Are you allowed to increase pilot jet size? Where is the ignition timing? These engines don't need break in time like that, that is just a waste of fuel. Race them hard they like it.
 

DynoDon

Moderator
I just took a 212 down to the bone. It was an engine we confiscated after a prestigious "predator cup" race. The plug was a 3910 and as lean as a bone. 16 / 31 jetting
 

viice

Member
Are you allowed to increase pilot jet size? Where is the ignition timing? These engines don't need break in time like that, that is just a waste of fuel. Race them hard they like it.
It's a specified jet. Not allowed to run anything other than that jet.
Ignition timing is OEM, cannot be modified.
I'm sure I can race it hard! Put some break in time on it so I'm not having to "loosen" it up by modifying anything... A sponsor here swears by 8 hours of break in time...

Don, are you saying that's desirable?
 

viice

Member
Run real gas with no ethanol
We will run what the track provides (87). That being said the issue the post was made about was 87 pump gas from a local Caseys. Haha.
 
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viice

Member
In 8 hours you have lost lots of optimum engine time.
Keep in mind, this motor has not been clearanced/toleranced. It is as it came from the factory (aka tight).
I imagine it has quite a bit of run time to get to a decent piston/cyl wall clearance and crank journal/rod clearance...
Can always replace rings/springs etc...

Could be wrong!
 
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flattop1

Dawg 89
Not wrong , just seems unnecessary to put that many hrs on with out good reason .
Or some odd rule set .
It is after all a one hundred dollar engine .
3hrs ought to be plenty .
 

DynoDon

Moderator
It's a specified jet. Not allowed to run anything other than that jet.
Ignition timing is OEM, cannot be modified.
I'm sure I can race it hard! Put some break in time on it so I'm not having to "loosen" it up by modifying anything... A sponsor here swears by 8 hours of break in time...

Don, are you saying that's desirable?
I know the engine I teched was raced three times. It was not disassembled and clearanced as I was able to detect that it was not.
 

viice

Member
Side note. Engine seemed to have the most power out there this weekend, or we just had gearing really locked in the first time at the track...
Finished 3rd. The rest of the kart sucked... time to shift focus to actually getting it scaled and set up (as I neglected to do so in my excitement to get the "new" kart on the track)!
 

flattop1

Dawg 89
Forgot to mention: Engine was gone through after each hour of break in. Also has 10.8 Springs.
when you say this . are you simply inspecting or replacing rings , valves piston and rod or parts there of?
Congratulations 3 rd unprepared is good.
 

viice

Member
when you say this . are you simply inspecting or replacing rings , valves piston and rod or parts there of?
Congratulations 3 rd unprepared is good.

Inspecting and removing the glitter from the glitter factory on initial start up. Verifying everything is where it should be and that nothing "interesting" as far as abnormal wear has happened.

Hopefully we find consistency and stability with the set up and that will find us a few tenths (or more). Then we move on to the tire prep game... Not new to racing, but very new to ovals/dirt. Second time out and have a 1st and a 3rd locally.
 

viice

Member
What does the plug look like? Sounds like the timing is late, flame in exhaust as well as the backfire is an indication,
Timing is dead stock.
Plug always seems dry, lighter brown. Low carbon build up.

Engine was good enough at Newton for 4th out of 27 karts... so even if it's lean it's making good stock power because I certainly wasn't driving that well! Haha.
 
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