accidental flamethrower

[portedmetal]

Well i finally solved my head bolt problem. Now theres a new. I got my motor put together and this is my setup.

Gx160 head
Flat top piston
Billet rod
Billet flywheel
4 degree advance
No governor
Ar3910x spark plug
140 e-tube
A larger jet (i dont remember the size)
High flow filter
High flow exhaust
Oil sensor removed
18lb springs
Fuel pump setup

At idle this thing runs beautiful. But at steady throttle through the whole range it shoots blue flames out the exhaust. At throttle release it always backfires. Its running 93 octane. Is the fuel making it do this or is it something else?

 

[devino246]

Unless your experiencing pinging (which I doubt) theres no need to run higher octane fuel. Sounds like you may be running too rich. Have you checked your plug?

 

[kendelrk]

without your governor your increasing gas flow and somtimes un burnt gas comes into the exaughst, releasing the throttle back to an almost instant idle is going to set a bit of unburnt gas out and its going to backfire, the backfiring is normal.

 

[devino246]

without your governor your increasing gas flow and somtimes un burnt gas comes into the exaughst, releasing the throttle back to an almost instant idle is going to set a bit of unburnt gas out and its going to backfire, the backfiring is normal.

Backfiring? normal. Blue flame out exhaust at all rpm, not normal.

 

[migel101]

that sounds awsome!!! why on earth would you change it???

 

[kendelrk]

sorry interrepted it wrong, sounds way to rich, with all that i think you should be at maybe a 90 jet, and because it may be harmful to the engine

 

[devino246]

sorry interrepted it wrong, sounds way to rich, with all that i think you should be at maybe a 90 jet, and because it may be harmful to the engine

a #90 jet IS NOT a cure all solution! Especially when other mods have been made, theres a good chance it wont be right.

Do it right, or dont do it at all.

 

[kendelrk]

even tho every engine is diffrent, with all of AGK's mods, they still ended up with a 90 http://www.affordablegokarts.com/performance_basics.php

 

[devino246]

even tho every engine is diffrent, with all of AGK's mods, they still ended up with a 90 http://www.affordablegokarts.com/performance_basics.php

They rejetted BEFORE swapping flywheels, advancing timing, and increasing compression. It probably needed tweaking after those.

 

[portedmetal]

So the backfire is normal? I remembered my jet is drilled .036. At idle no flames out exhaust. I didnt do a plug reading yet because it was dark when i finished and fired it up. After work tomorrow i'll do it again and take a reading. I had a feeling that the octane Fuel was to much, so i should go back to 87?

 

[Doc Sprocket]

I don't think the high-test fuel is to blame. Do you have a simple straight pipe exhaust? Might just be a wee bit rich, with nothing in the exhaust system to quash the flame. I have seen engines that are fairly well set up shoot flames when running open headers (or none at all).

 

[portedmetal]

http://www.arcracing.com/servlet/the-453/Box-Stock-Project-ARC/Detail

Thats my exhaust setup. When i first started this project all i had was the jet i have now, that exhaust, and a high flow filter. I will eventually change the exhaust. I am thinking of a candycane header with no muffler.

 

[slideways]

You definitely need a better pipe than that. Are you running the muffler? The backfiring is normal, removing the advance key may take it away slightly. If you didn't deck the block or mill the head you shouldnt need to run high octane fuel.

I think the flame is because your pipe is too short. If you run an engine with no exhaust you will see a flame at most any rpm from the port.

 

[portedmetal]

Yea im using the muffler. At first i didnt want to dig deep into the modifications but once i started it became a sickness Haha. I'll prolly Order my candycane header tomorrow and run without a muffler.

 

[Russ2251]

It's not a backfire.

 

[portedmetal]

http://nr-racing.com/exhaust.htm

Im torn between the robertson candy cane or the mini bike dual exhaust.

 

[Russ2251]

It's not dual exhaust, but rather a "Y" pipe.
Dual exhaust in a multi-cylinder engine has advantages...but not with a single cylinder power plant.

 

[portedmetal]

Well i ordered my candycane today, should be here next week.

So the backfire or "afterfire" is normal? Will it affect the motor in any way in the long run?

I'll be doing my plug readings later today when i get home from work.

 

[devino246]

Well i ordered my candycane today, should be here next week.

So the backfire or "afterfire" is normal? Will it affect the motor in any way in the long run?

I'll be doing my plug readings later today when i get home from work.

Its fine. On larger (car) engines, a dashpot is used to slow the closing of the throttle, but theres no need on a kart. Letting off the accelerator causes a severely lean mixture, which burns slower, causing there to be a small amount of air/fuel exiting the combustion chamber, and then igniting.

 

[portedmetal]

Well i finally got a plug reading, put in a fresh plug and got this. To me it looks a little rich. But i wanna get some more input from ppl that have seen more of these than i have.