backfire

akenson16

New member
ran my sons new motor 2 days ago for 15-20 minutes runs on methanol and then after i ran premium fuel threw it afterwards like i always did on my other animal motor but today when we started the new motor for him to drive the kart around on the street there was a big backfire on the initial start up but then ran just fine. is this common? my old motor never did that so got me a little nervous that the new one did it. new to karting and don't know anything about motors. thanks for any advice.
 

Jimbo

Premium User
If it only did it once i wouldn't worry about it.
I would be more worried about someone driving over him on the street.
 

CarlsonMotorsports

Premium User
It was probably just loaded up with fuel in the cylinder. Mind you, that's not good on the rod & piston (ie hydraulic), but it's probably just fine.
The "backfire" probably didn't come "back" through the intake, but rather unburnt fuel being burnt in the exhaust. Pretty common on an over-rich cycle to fire off like that.


-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 

Deadman#73

New member
I wouldn't be using my animal to go drive on the street that's for sure unnecessary time and load on the engine. The back fire was just unburnt fuel in the exhaust. Happens whenever you flush it and whatever leftover doesn't evaporate before the next start.
 

akenson16

New member
Thanks for the response guys. Ran practice tonight and notice we had smoke coming out of the exhaust. Wasn't pouring out smoke but cuffed my hands by the muffler and noticed it. Any ideas what's causing that and should I be alarmed?
 

akenson16

New member
Probably burning oil.
Put 14 in and ran practice tonight about 28 laps and 17-17 1/2 ounces came out. Run purple plate and my son said when he floors it the kart goes but then sputters/cuts out. Lap times were 12.87 and gold plate fastest kart was a 10.37 so feel the speed is there but with the smoke coming out and cutting out fear we could be even faster.
 

Jimbo

Premium User
If you put in 14 ounces of oil and got 17 ounces out it sounds like you got a lot of methanol in the oil.
It could be a combination of things. The carb may be too rich and causing the sputtering.
The rings could be too loose causing the oil burning.
Overall this just doesn't sound good!!
 

flattop1

Dawg 89
If you put in 14 ounces of oil and got 17 ounces out it sounds like you got a lot of methanol in the oil.
It could be a combination of things. The carb may be too rich and causing the sputtering.
The rings could be too loose causing the oil burning.
Overall this just doesn't sound good!!
100% Agree with Jimbo something is wrong .
the fact you got more oil out then put in is quite odd .
 

Jimbo

Premium User
You might want to ask him what size piston and rings he put in and what the clearance is between the piston and the cylinder.
Ask him what size rings he installed?
What size top, second and oil ring?
Ask him what the ring gaps are for each ring What size did he hone the cylinder to?
What grit hone stones did he use?

Is this a PZ 22 Animal carb?
Ask him what size main and idle jet he used?
Ask him what size nozzle is in it?
What slot is the slide needle in?
How many holes and what size are they in the restrictor plate?

Get us the data and we will be able to tell you if it's built correctly or not
 
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CarlsonMotorsports

Premium User
Inlet needle is hung open, overfilling the bowl I suspect.

More oil coming out than went in is either a lack of draining all of the previously ran oil, or fuel dilution in the oil from running an extremely over-rich condition carb.
Is there any fuel running out of the carb overflow as the engine idles? That's usually a tell-tale sign that the bowl is overfilling (ie inlet needle stuck open.)
Have you pulled the bowl off the carb to take a look inside yet?
Jets are still both in place and haven't fallen out?
Float height and drop are set correctly?
Are you running your bowl overflow tube to a separate catch can than your valve cover breather line?
If they are run to the same catch can (not recommended), does it have adequate volume and ventilation?
Running them together can pressurize the bowl and cause all sorts of unintended problems.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
30 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
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