backfire on startup?

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Dec 14, 2011 | 10:30 AM

#11

jsbridgew

Thread Starter

Road Warrior

Joined: Nov 2007

Posts: 1,641

Likes: 4

From: south of Boston

it fired right up without a hitch....i'm used to fuel injected twinkies, so any suggestion on starting a carbed bike would be helpful

i also attached an oil pressure gauge to the case...read pretty high on startup- around 50-60psi....is this normal on a cold-start?

Dec 14, 2011 | 04:49 PM

#12

Elite HDF Member

Joined: Jan 2006

Posts: 4,344

Likes: 67

From: Hooterville, Fl.

Quote:

Originally Posted by gump305

My 97 Heritage does this also, but only after the bike is warmed up. If I ride and warmup the motor and say I have to stop and get gas. It will backfire and it is Loud, women and small children crying and running in all directions. It's embarrassing as hell. The thing is it doesn't do it every time though. I have a new rebuild kit for the carb, going to try that and see if it helps.

Mine has always done that Gump. I found that if I let it idle for about 10 seconds before I hit the kill switch, it does not do it.

Dec 14, 2011 | 08:08 PM

#13

miacycles

Elite HDF Member

Joined: Sep 2007

Posts: 4,468

Likes: 12

From: Bluffton, South Carolina

On cold startup pull the enrichner out, try to start it. If it doesn't start right away the try one twist of the throttle to put a little fuel in it. Some bikes can take up to three twists, every engine has it's own likes and dislikes. As with any HD try to avoid excessive throttle untill the engine is fully warmed up or you may get some gasket leaks. Hope this helps.

Dec 15, 2011 | 12:05 PM

#14

jsbridgew

Thread Starter

Road Warrior

Joined: Nov 2007

Posts: 1,641

Likes: 4

From: south of Boston

thanks for the tips, mia!

she starts right up on first try with enrichener all the way out...and bike sounds great

runs for a good bit, but stalls as it starts to reach operating temp....i'll push the enrichener back in, sometimes just half-way...but it won't start....then i throttle it once while trying to start it and was a small crack/backfire in carb (started smoking)

you gotta pardon my ignorance with carbed bikes, man....lol.... so used to fuel injection

Dec 15, 2011 | 07:58 PM

#15

miacycles

Elite HDF Member

Joined: Sep 2007

Posts: 4,468

Likes: 12

From: Bluffton, South Carolina

Backfiring like you describe through the carb is caused by fire exiting the cylinder and traveling through the manifold. Causes can be timing off, intake valve not closed/sealed (bent valve, poor valve seal, or tight pushrod). Also check to ensure that the vacuum hose or plug did not get blown off with all the backfiring through the carb. Hope this helps.

Apr 9, 2012 | 08:47 PM

#16

pooleo

4th Gear

Joined: Mar 2012

Posts: 8

Likes: 0

From: Michigan

I am having a similar issue. I changed my pipes. From OEM with baffles removed to SEII off-raod perfomance pipes. I get a hell of a back fire upon start up. Will the change in backpressure cause this issue...?