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Message started by DrunkenDwarf on 05/13/09 at 06:51:18

Title: Backfire + choke = ??
Post by DrunkenDwarf on 05/13/09 at 06:51:18

I definitely have an exhaust leak. The oil inspection window is covered in soot. Ignore that for now.

This morning on the way to work I noticed that when my choke was out one notch and I closed the throttle, it didn't backfire. As soon as I closed the choke it would backfire on throttle close.

Can someone explain to me the relationship?

-D. Dwarf

Title: Re: Backfire + choke = ??
Post by SavageDanny on 05/13/09 at 07:05:04

Someone might correct me on this but I think the choke is not actually a choke. It's and enricher (spelling?). Provides a little extra fuel on start up. I have heard the bike runs lean on the factory settings. If I understand it correct most of the carb mods generally make the bike run richer. When I tuned mine to run a little richer it quit most of the backfiring.

Title: Re: Backfire + choke = ??
Post by Fubar on 05/13/09 at 07:13:30

I have the same problem with mine on the oil inspection window. I can feel the exhause leak however it isn't where anything connects. Have you pulled the brass plug and adjusted the idle mixture screw to get ride of the backfire. Start at 1/4 turn at a time and give throttle to test. I recently did the white spacer mod, put a new muffler on with a stage 2 jet kit and cone filter. Very happy with the results and it sound almost like a Harley with better mid range pickup and top end speed. Still get back fire at times but I think it's cuz of the exhaust leak. :o

Title: Re: Backfire + choke = ??
Post by DrunkenDwarf on 05/13/09 at 07:26:07

Step 0) Previous owner rejetted (0.055/0.155) and installed Dyna

Step 1) Fix Exhaust leak
Step 2) Do white spacer mod
Step 3) Adjust Idle
Step 4) Ride :D

Just curious what the relationship between a richer mixture and a backfire is.

-D. Dwarf

Title: Re: Backfire + choke = ??
Post by verslagen1 on 05/13/09 at 07:30:53

444D48415B4C48290 wrote:

Just curious what the relationship between a richer mixture and a backfire is.

Title: Re: Backfire + choke = ??
Post by DrunkenDwarf on 05/13/09 at 09:29:46

6B786F6E717C7A78732C1D0 wrote:

[quote author=444D48415B4C48290 link=1242222679/0#3 date=1242224767]
Just curious what the relationship between a richer mixture and a backfire is.

Title: Re: Backfire + choke = ??
Post by marshall13 on 05/13/09 at 09:38:29

7970757C667175140 wrote:

[quote author=6B786F6E717C7A78732C1D0 link=1242222679/0#4 date=1242225053][quote author=444D48415B4C48290 link=1242222679/0#3 date=1242224767]
Just curious what the relationship between a richer mixture and a backfire is.

Same as lean mixture, except you're dumping extra fuel all the time.

With lean, a bad burn leaves extra fuel in the exhaust till it hits fresh air and kapow.
With rich, just about every burn leaves a little.[/quote]
But the relationship I noticed was that a richer mixture ("choke" out 1 notch) backfired less.

Would that imply that in some segment of the throttle I'm lean and the choke brings it up to normal?

-D. Dwarf[/quote]
kinda.... it means you get bad burns, and enrichening a bit helps at times.... only plug deposits for different throttle opening ranges can actually tell you what's happening when.... ill bet tossing in a real CDI would go a long way to eliminating backfire... yeah, i though these had CDI iggy's too, but they dont... check the wiring diagram in the clymer... batt voltage to coil (ign. hot goes to coil)... cant do that with a CDI, or you'd get a 500 volt spike back through your primary system.....