Yesterday I readjusted the carbs and balanced/sync them.I installed new plugs and gapped them to .030in.Swapped the coils from side to side.The bike rode like a dream.This morning I started it up and the back firing through the left carb is back.I went for a quick 20 minute ride.The back firing is gone but now the left exhaust valve is knocking like h377.I just did the valves when I did the carb clean and balance/sync.I guess my weekend will be spent tearing down my bike to check the valves,again.

ben2go: what ended up being the cause for the backfiring out of the carbs and slow takeoff from a stop? I'm experiencing the same problems with my newly acquired GS.

Quote from: J banning on February 10, 2013, 06:44:37 PM
ben2go: what ended up being the cause for the backfiring out of the carbs and slow takeoff from a stop? I'm experiencing the same problems with my newly acquired GS.

I had weak voltage to the coils and bad spark plug wires.The wires can be purchased at any NAPA for a few dollars.Pull the rubber boots back at the coil and the spark plug caps.Then unscrew the spark plug caps then unscrew the wires from the coils.Righty tighty,lefty loosey just like usual.I did the ignition coil relay mod and posted it. http://gstwins.com/gsboard/index.php?topic=62039.0

Ben just beat me to linking his mod thread that included his fix. A good thread it is.

- Bboy

Quote from: BockinBboy on February 10, 2013, 07:48:38 PM
Ben just beat me to linking his mod thread that included his fix. A good thread it is.

- Bboy

Thanks.

Ben, thanks for the update!

woops old thread.

Quote from: J banning on February 11, 2013, 12:46:08 PM
Ben, thanks for the update!

You're welcome.I clean one set of carbs to the point that they wouldn't stay together before I started looking at the ignition system.Also,a regulator on the verg of going bad can cause some of the same symptoms.The coils get weak voltage and causes miss fires until the engine hits peak charging output which is usually between 3000 and 5000 rpm.There is a write up around here on using a mosfet based regulator rectifier.That is the way to go.

Quote from: Funderb on February 11, 2013, 07:22:28 PM
woops old thread.

No biggie.Post up.

Ok, I know that this has been beat to death, but I am having the SAME problem with the left carb.  Along with this, my battery has been acting strange.  2009 F model:

1.  From Idle, carb will backfire on the LH side.  Only off of idle.  Jets 20/65/142.5.  Lunchbox, stock ex.  Mixture 2.5 turns.
2.  I ride year round, even when it's cold (sub 40*F).
3.  Carbs clean and just synched, valves in spec.
4.  Battery will go dead trying to crank below 30*.  Stock Yuasa YB10L-B2.  2 years old (bought bike new in 2011) Water level OK.  Jump or charge, and it's OK for a while, then will crank slower until dead.

Wonder if it's the regulator.  I have the stock one.  Time to get out the multimeter.

Quote from: jestercinti on March 14, 2013, 03:15:32 PM
Wonder if it's the regulator.  I have the stock one.  Time to get out the multimeter.

You get a Karma Korn just for using the word multimeter

My bet would be a battery not holding a charge. But with your multimeter you will be able to tell.

If you do need a regulator, I have a box of them. Or best is pay the $100 for a MosFet one. Give your baby the best.

Adidas, a Multimeter is the BEST $10 I spent at Pep Boys.  I get them free now with a coupon at Harbor Freight.

I should have a contest like John to give them away as prizes to noobs.

Quote from: adidasguy on March 14, 2013, 03:32:08 PM

Quote from: jestercinti on March 14, 2013, 03:15:32 PM
Wonder if it's the regulator.  I have the stock one.  Time to get out the multimeter.

You get a Karma Korn just for using the word multimeter

My bet would be a battery not holding a charge. But with your multimeter you will be able to tell.

If you do need a regulator, I have a box of them. Or best is pay the $100 for a MosFet one. Give your baby the best.

I agree.However,that didn't solve my problem.It helped.Check the entire charging system.It took me doing the relay mod to get rid of my problem.  http://gstwins.com/gsboard/index.php?topic=62039.0

Well, I checked my charging system using the Haynes manual, and several trusted documented methods (GSTwins, GSresources).

It's the stock Yuasa battery.  Thinking of going maintenance free this time.  My water level keeps fluctuating.  Some may say that has to do with the regulator, but I checked it 4 times, and it appears OK.  Stator is OK as well.

If I still have the issue, I'll try the relay mod.  Looking at the diagrams, it makes sense.  There are a lot of switches and connections in the circuit for sure!

I would think it is the battery going bad. Mine didn't last much beyond 2 years (2009 and stock battery).

Measure battery voltage.
Later, like next morning or in a day, measure again. It should not go down.

Riding: you're not riding for 12 hours so if the battery is going  bad, it might never get recharged. On a charger for 12 hours is more charging than when riding for a couple hours. Riding you may only be putting back 90% rather than 100% to keep it charged.

I have a voltage monitor on my bikes. It seems around 3k RPM is the tipping point between using power from the battery and charging the battery. If you do lots of short rides, you may never be at high enough RPM to fully recharge the battery. If your battery is going bad, it could take a lot more to recharge it.

Try battery. I bet that is it.

Yep. Most of my trips are 10-20 miles. Short jaunts here and there.

Battery is on my short list.

I'm going on three years on my AGM Scorpion battery from battery stuff.My bike sits in an outbuilding for three months during the winter.My bike always starts right up after sitting.I been very happy with this battery.