Backfire/stalling help please

[kacperix]

it runs fine then a loud back fire (sonds like its coming through carb) that stalls the engine (99% of the times when i apply throttle from idle). so im guessing it could be something with mixture. but have no idea how to deal with it

[Spartacus]

Originally Posted by sportsterdoc

Signing off for evening.
Based upon what you have reported, I would unplug regulator and check for corrosion inside the connector, as well as be sure that it is well grounded (no paint under star washer, etc.). Then, recheck your voltage.

I took a look at the regulator it does not unplug from the regulator end. I tried to follow the wire but couldn't find where it came out the other end... Is the connector under the seat? I tightened the ground screw and measured the resistance between it and the ground with the ohm metre was 0.

re-measured the battery:
key off: 13.06 volts
key on: 12.60
idle: 12-15
some throttle: 14-15

I may not have had a good connection last time, as they want to shake off as it throttles.

I tested the coil and with the voltmetre and it read 12.57 (s/b 12-13 by the Clymer manual) and 12.28 at each of the white and blue terminals (Clymer says 12).

What's the best way to test for good spark?

[sportsterdoc]

Originally Posted by Spartacus

I took a look at the regulator it does not unplug from the regulator end. I tried to follow the wire but couldn't find where it came out the other end... Is the connector under the seat? I tightened the ground screw and measured the resistance between it and the ground with the ohm metre was 0.

re-measured the battery:
key off: 13.06 volts
key on: 12.60
idle: 12-15
some throttle: 14-15

I may not have had a good connection last time, as they want to shake off as it throttles.

I tested the coil and with the voltmetre and it read 12.57 (s/b 12-13 by the Clymer manual) and 12.28 at each of the white and blue terminals (Clymer says 12).

What's the best way to test for good spark?

OK, your regulator is behaving. 14-15 is a whole lot better than 12.
Pull the plugs, put back in the boots, ground to the cooling fins and crank it.
You are looking for white/blue spark

[sportsterdoc]

Originally Posted by sportsterdoc

OK, your regulator is behaving. 14-15 is a whole lot better than 12.
Pull the plugs, put back in the boots, ground to the cooling fins and crank it.
You are looking for white/blue spark

You already measured about 12 volts to the primary side of the coil. If no spark...or weak spark, then measure the coil resistance. Before that, jiggle the key in the ignition switch to check for intermittent operation (from a heavy key ring), If the coil is the normal resistance, then your ignition module is the next suspect.

There should be a sticky on checking it. Work is intense, so I may not get a chance to log onto the forum, tomorrow.

[sportsterdoc]

Originally Posted by kacperix

it runs fine then a loud back fire (sonds like its coming through carb) that stalls the engine (99% of the times when i apply throttle from idle). so im guessing it could be something with mixture. but have no idea how to deal with it

Unless the timing is off, adjust the mixture screw. 2 1/2 turns out is a normal starting point.

[CoffeeGrinder]

Start with the simplest, cheapest stuff first just to rule it out..

-When it acts like it's not getting any gas and starts to stall, loosen the gas cap and see what happens (assuming you know you really aren't out of gas at that time).

-Carb farts, make sure you don't have an intake leak or exhaust leak. If all ok, then start air/fuel mixture screw at 2.5 turns out and adjust from there 1/8th to 1/4 turn at a time. (turning in should lean, turning out should richen)

-Engine, lights, everything just cuts out and starts back up sporadically. Check your negative battery cable and make sure it has a good, clean, tight connection on both ends. My '07 had these symptoms and even though the battery cable seemed ok, but 1/8 turn to really secure it solved the issue instantaly.

[Spartacus]

I scraped the ground screws. And I found the regulator wiring harness. It was loose, so I tightened it back up. She started up great and was running great but then dies like she is out of gas. Gas was looking low so I switched to reserve. She started and ran great for about two blocks then died again like she's out of gas! I noticed that it is definitely idling lower.

Any more ideas?

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[Spartacus]

Ok. I can see the inline fuel filter, it is clear, and it is empty. This is frustrating because there is gas in the tank and a brand new petcock. Guess I'll push her home and fill up from a gas can to be sure. But I can here it swoosh around...

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[Spartacus]

Filled her up, checked the filter - full of fuel. Started up and drove about a block further than last time and sputtered and died again! The filter was empty again. Pushed her home again.

I have some clear vinyl hose. I'll replace the whole fuel line this weekend and try again!

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[sportsterdoc]

Originally Posted by CoffeeGrinder

Start with the simplest, cheapest stuff first just to rule it out..

-When it acts like it's not getting any gas and starts to stall, loosen the gas cap and see what happens (assuming you know you really aren't out of gas at that time).

-Carb farts, make sure you don't have an intake leak or exhaust leak. If all ok, then start air/fuel mixture screw at 2.5 turns out and adjust from there 1/8th to 1/4 turn at a time. (turning in should lean, turning out should richen)

-Engine, lights, everything just cuts out and starts back up sporadically. Check your negative battery cable and make sure it has a good, clean, tight connection on both ends. My '07 had these symptoms and even though the battery cable seemed ok, but 1/8 turn to really secure it solved the issue instantaly.

Good basic ideas, but he already bought a new vented cap, etc.