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Random exhaust popping - GS300

  • Thread starter Thread starter Ric
  • Start date Start date
R

Ric

Guest
Hey again! I've had fun with the 300 lately, and I'm liking the new 39-tooth rear sprocket too! But every now and then when I'm just cruising through town, the exhaust will pop like a backfire of sorts. It's not going back through the carbs I don't think, because it doesn't stammer or sputter any afterward. Just a small hiccup as though the spark plug fired a bit late, and then all is well again.

Could that mean the valves are a little tight? Or am I about to have electrical problems?
 
Could mean a lot of things but most likely is that the voltage going to your coil or coils is not where it should be. When the bike is sitting and turned off, measure the battery voltage. A charged battery will show a tad over 12.5 VDC. Now, turn the key on; power will flow from your battery to the fuse box, out of the fuse box to the ignition switch through a connector(s). Then out of the ignition switch to your kill switch (through a connector(s)) and out to your coil(s) (through at least one connector).

OK what do all those connectors and switches do? Add resistance. You will likely find you have 9-10 VDC at the coils while the bike isn't running. The amount of spark is in direct proportion to the power going to the coils. Poor voltage = poor spark and little popping backfires as you ride down the road at a steady speed.

You can clean them or add a relay so that power goes direct from battery to coils; either will mitigate the problem but the power via a separate relay is more effective as there is no way to adequately clean everything 100 percent (this is just my opinion of course).

Before anything else, making sure you have no air leaks in your intake is also a great idea... carb holders in particular but vacuum caps (if used) or the vaccum hose to your petcock are also possible culprits as are the crush washers under your pipes where they fit into your cylinder head. If re-used after removing the pipes, air can leak into the combustion chamber. Fresh air leaking into a bad gasket on your cylinder head cover (if there is one on your bike) part of the emissions stuff is also a possibility.
 
The exhaust gasket sounds most likely at the moment. I swapped exhaust bolts for studs recently, so I may have left one a little loose.

The battery is a year old, but I've read about questionable wiring that needs cleaned up on these bikes to help balance the load on the stator or something like that. I like the relay idea, thanks for that!
 
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