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I have a 1985 Honda Goldwing Interstate that will not start 98% of the time, it turns over when the starter button is pushed but about the seventh time a loud double barreled shot gun blast comes of the exhaust when it does start , again about 2% of the time it runs but sounds like its loading up . Timing ok ,coils check good, carbs ok I should also mention this happened within a matter of two days when it first didn't start I jiggled and tightened battery connections and rode it home no problems even stopping and restarting again then second day the back firing started,
Suggestions Please and Thank you
 

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Sounds like weak fire but I would check for water in the gas also. Try draining the carbs.
 

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When you say the timing is ok, do you mean ignition timing or valve timing? Something is causing a late ignition of the fuel. That's why you hear the explosion in the exhaust. It could be caused from the spark occurring just as the exhaust valve is opening or very hot exhaust is hitting raw gas in the exhaust ports. Are you getting excessive smoke or a raw gas smell? When it is running, do you still get backfire? Sorry I can't be of much help because I don't know anything about the ignition system on that particular bike. For example, I don't know how it gets it's pulse timing.
 

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When you say the timing is ok, do you mean ignition timing or valve timing? Something is causing a late ignition of the fuel. That's why you hear the explosion in the exhaust. It could be caused from the spark occurring just as the exhaust valve is opening or very hot exhaust is hitting raw gas in the exhaust ports. Are you getting excessive smoke or a raw gas smell? When it is running, do you still get backfire? Sorry I can't be of much help because I don't know anything about the ignition system on that particular bike. For example, I don't know how it gets it's pulse timing.
It would take some engineering to get the ignition timing off. It comes right off the crank just like your 1500.
 

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Perhaps a carb is draining into the combustion chamber.

I know you say the carbs are fine, but how do you know that? A very large percentage of running problems, on a GL12, are carburetor/fuel/air related. There's not much else to go wrong.
 

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Many moons ago I had a 58 Nomad. I know it's not a Goldwing, but I had a similar problem it backfired one time one the freeway that it blew the muffler wide open lol, so after fixing the exhaust system and going crazy trying to figure out the backfiring issue I asked a neighbor whom was a mechanic and he took a look at it. In about as long as it took me to start and rev it up it backfired. I shut it down and he told me to go buy an ignition switch. I did that and we changed the ignition switch out. Problem solved!!! never had a problem with it as long as I had that car.

Food for Thought...
 

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Recently I put a poor-boy kit in my buddy’s 1200. While pulling the belts off I also pulled the crank pulleys also. In between the the pulleys is the pick-up plate. It’s possible to flip it over and the timing would be way off. That could cause a backfire like you discribed.
 

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I have a 1985 Honda Goldwing Interstate that will not start 98% of the time, it turns over when the starter button is pushed but about the seventh time a loud double barreled shot gun blast comes of the exhaust when it does start , again about 2% of the time it runs but sounds like its loading up . Timing ok ,coils check good, carbs ok I should also mention this happened within a matter of two days when it first didn't start I jiggled and tightened battery connections and rode it home no problems even stopping and restarting again then second day the back firing started,
Suggestions Please and Thank you

Verify that the Rubber Isolator/s (between carb and intake manifold) are Snug... I've so often found them Loose or Cracked, in which case it Leans out the fuel mixture.
If that's happening on yours, then it may explain why it's hard to start, but then backfires (due to the exhaust system being full of wrongly-mixed air/fuel, when it does finally fire)
 

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It would take some engineering to get the ignition timing off. It comes right off the crank just like your 1500.

When I reread my post I can see that I wasn't clear at all about what I was trying to say. I know that some bikes were carbed and some had electronic fuel injection. When I said the ignition timing I wasn't only talking about the spark I was talking about the timing between the spark pulse and the injector pulse. I don't know if they both get their signal from the same source or not. That is why I can't be specific on the cause. My point was the conditions that could cause this backfire or misfire. Pre-ignition would cause it to backfire through the intake on the compression stroke and late ignition could cause it to backfire on the exhaust stroke. A very slow combustion could cause this too as in the case of the fuel still burning at the start of the exhaust stroke. As I said, I don't know very much about his engine so I was speaking in very general terms on things that could cause backfiring.
 

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At least one of the manuals out there has the firing order wrong. One coil fires front cylinders, 1-2 the other fires rear cylinders 3-4. With the wires on backward, the result is gunshot backfires.
 

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At first glance I would think it is not PG's but if you think about it a little more it very well could be. It seems when they PG's fail they have a variety of symptoms. The one thing that seems to be common is the on again off again spark to the plugs. The OP did not mention checking spark when it was not starting. I wonder if the bike is n't cranking with no spark for a while. Loading the mufflers up with air fuel mixture. At some point the spark decides it is going to start and that is your loud backfire. Maybe the "loading up" is not loading up but just weak or no spark causing misfire. I would give the entire ignition system a good look over paying extra attention to PG's and leaking secondary voltage from plug wires, coils etc. I'm wondering if you have intermittent spark some how. :)
 

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It's hard to troubleshoot when you get no feedback from the original poster. I pretty much rule out things like crossed plug wires or other mistakes because he didn't say it started after he did such and such. He also said he rode it home after it did the backfire thing and it was fine until the next day or so. To me, it sounds like the carbs are leaking and dumping raw gas into the cylinders. Cranking shoves that gas into the exhaust and the slow burning gas in the cylinders ignites the gas in the exhaust and there you have it. Just like redwing suggested. Does the 1200 have a vacuum operated petcock like the 1500? I'm gonna say his fuel is not shutting off.
 

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When my GL1200 pulse generator problem presented itself, it was like a switch turned them off. I noticed a slight sputter as I hit the highway for the ride home from work (the bike always runs like a top so a slight sputter was very noticeable) and when I stopped for an accident that had to be cleared, I turned it off and then it would not fire at all when it was time to leave. My understanding is that if one goes, the other will not work either so no spark on either set and both have to be replaced. Can the PGs have intermittent problems as well?
 

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e. My understanding is that if one goes, the other will not work either so no spark on either set and both have to be replaced. Can the PGs have intermittent problems as well?
Sometimes they will run on 2 cylinders.
 
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