LegendsRacer - Legends & Bandolero Racing Forum

LEGENDS => Engine Care & Tuning => Topic started by: Schmitt20 on May 03, 2010, 10:35:57 pm

Title: back fire
Post by: Schmitt20 on May 03, 2010, 10:35:57 pm

What causes the motor to back fire alot? Could it be a bad battery? At about 7,000 to 8,000 rpm it starts cutting out or popping alot, then when i let off it pops alot all the way down till 3,000 rpm.

Title: Re: back fire
Post by: justfreaky on May 03, 2010, 10:53:37 pm

Not battery.
Timing, carbs, valves (need shimmed?), or hitting the rev limiter.
The backfire when you let off the gas is likely caused by raw fuel still in the pipes or header igniting from the heat.
My best guess FWIW.

Steve

Title: Re: back fire
Post by: VMS Motorsports on May 04, 2010, 06:55:54 am

Are you running you old carbs with your new motor?
Maybe something is set differently with the timing with the new one so you're not burning all the fuel?
Check valves, cam timing, carbs as Steve said.

Title: Re: back fire
Post by: justfreaky on May 04, 2010, 08:37:35 am

Exchanged a few pm's with him last night.
Engine was just recently rebuilt; But carbs were not.

Steve