what causes my 98 dyna wide glide to backfire out the exhaust on decell?"?

Question

Exhust are Sanson's Big Guns 3 installed in May, Did not backfire when installed. Start backfireing about a month ago. Carb rejeted to Main jet 180 (stock 170) and slow jet is a 45 (stock 42) . Plugs are whitetis. Sparyed carb cleaner on intake gaskets and motor stalled. Chofts out the carb ocasonally Thinking of installing new intake gaskets.

Answer 1

That's normal in a lot of cases. It is due to unburned fuel coming out of the exhaust port into the exhaust system. If your bike didn't used to do that then it much be running rich (too high fuel/air ratio). I have a Viper that does that when I tune it rich.

Answer 2

1. Leaks in the exhaust system (as mentioned)
2. No backpressure (open exhaust) - doesn't scavenge correctly, so there's more unburnt fuel left in there.
3. Incorrect/rich carburetion.
4. Very low possibility - cam/ignition timing.

Did you rejet to some suggested setup with some aftermarket parts, or because of plug reading?

If it was because of plug reading, do you know if the fuel you use is oxygenated? If so, the white on the plugs may not be a lean reading at all.

Also, if you did a power run, then shut down and got the lean plug reading, this would only check the main jets. So you may just need to drop those pilots back to stock.

Answer 3

If the exhaust is aftermarket,you may need to re-jet. You may have an air leak.These are not uncommon at the intake manifold. Least likely is that your timing may be too far advanced.some Backfire on decel is usually caused by a lean condition. Check you plugs there should be some color on the porcelain part of the plug. Tan- dark Tan ,if the plugs are white you are lean

Answer 4

If the engine died when you prayed the carb cleaner on the gaskets you have a vacuum leak. that will cause a lean condition wich will make the bike backfire and also cause the plugs to be white. Hope this helps

Answer 5

to much fuel lean it out by turning adjustment screw on carb to the right if it is factory set there wont be a screw this would require jetting you have three on the bike your pilot jet main jet and needle. i would try to adjust the needle first by one notch that should fix the problem your getting to much fuel on the top end of the throttle droping the needle should fix this and eliminate the backfire if the problem persists put in a smaller main jet the pilot jet would not effect your problem. also a easy fix for you if you dont know how to jet a bike or dont have enough money to take it to a shop is to put in a hotter plug to burn the extra fuel by hotter i mean more spark contact your dealer they will know what im talking about

Answer 6

Vance and Hines is my personal choice. Yours may vary, however, since it's a 2007 motorcycle you'll want to check and verify that the pipes you are buying have the bung already to facilitate reinstalling your exhaust sensor. If not, you'll need to find and buy the bungs seperately and have them installed prior to the pipes being put on the bike. In addition, checkout thunder city on the web. They make a device you can place in your exhaust in lieu of a baffle that will deepen the tone as well as add additional torque in the low end, great product.

Answer 7

Keep the 45 jet and go up to a 195 and also see if you have a leak at the heads. You also might want to try adding a hi flow air cleaner kit or look into a power commander.

Answer 8

a lean idle condition will cause excessive backfire through pipes. Will happen whenever you let go of throttle. With the engine at a steady ( warmed up ) idle spray water from a squeeze bottle all around manifold/rubbers when you hit leak idle will change drastically. If it's not leaking air it must have something limiting fuel during off throttle. been there

Answer 9

Lean fuel mixture in the carb's idle circuit.

Answer 10

the mixture of fuel to air is too rich. You need to tune it down a bit - adjust the idle a bit, or adjust the gas flow to air flow.