Question about loud pop when trying to start

[Sjorge450R]

I have a simple question. At the races I have heard guys on R's try to start there quad and it just makes this really loud pop. Then it takes them forever to get it started. I was just wondering if anyone knows what causes this.

My hybrid does that. I think its from running rich.
Alot of times a rich quad will make a pop after you shut it off cause of the extra gas in the cylinder.

[400exrider0004]

is it like a backfire or is it in the motor

[Johnny B]

its a back fire, mine does it when i flood it out

[tltcracing]

i know what u mean. they havent even started thier bikes yet and it lets out a big back fire as they are kicking it over. well mine did it untill i replaced the spark plug, and it hasnt done it since and it starts up really easy too.

[lumi]

bad jetting most the times or rich race jetting




-lumi

[400exrider0004]

mine does the same, i started it tonight and everytime I went to start it, it backfired. Ill check the spark plug and see what happens

[Sheepless]

Could also be leaking valves, valves out of spec or exhaust (heahpipe) leak.

[tltcracing]

header leak? ill check that. i alwase thought mine was a little off in that respect.

[Lonestar_R]

Mine does this....I think its a little rich on the jetting.....

[motox450]

This could be from a combination of things. Most common is rich jetting, leaky exhaust, or valves out of tollerance. All of these have been noted in previouse posts. Another thing to check is if your idle is set a little high. This isn't a large problem if you get it started on the first or second kick. but if it takes more kicks than that too much fuel gets into the cylinder and then into the exhaust. When it gets into the exhaust and the engine does get close to firing it ignites the fuel in the exhaust causing the loud pop. Rich jetting, as well as valves being out of tollerance can cause the same issue with exess fuel getting into the cylinder and exhaust. Another issue is the automatic decompressor could be out of tollerance. If it is set to low, ie the decompressor pushes the valve down to far it can cause similar issues and hard starting, or the reverse where the decompressor is set to high and it doesn't open the valve enough. In this case the engine should be harder to kick as the valve is not opening to allow the compession to be released.

[the predator]

check your oneway clutch and bearings if it's an e-start. backfiring is the first sign of the bearings wearing a flat spot.