Vacuum lines and backfiring - Steve Saunders Goldwing Forums

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post #1 of 13 (permalink) Old 02-10-2006, 01:34 PM Thread Starter
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Afternoon everyone, I would like to ask for some help, if I may. It’s a cold 25’ here today so naturally I thought I’d head back out to the barn and do some work on the bike. I’ve been having some trouble with it backfiring through the mufflers at idle, once it’s warmed up and the choke is backed off. It does go away at about 2,500 – 3,000 RPM. This problem wasn’t there before I removed the engine and replaced the clutch. I have checked the air cut off valve and it appears to be working; I made sure that the new o-rings for the carbs were in place, double checked the plugs and wires at the coils. I did find a cracked vacuum line from dry rot, so now I’m planning on replacing all the lines under the carbs. My question is does anyone know what the ID sizes are for these lines? My eyes aren’t focusing to well today (another sign of the times) but I can tell there are 2 different sizes. I also would be very grateful for any ideas or suggestions that would help fix this backfire problem. Thankyou.

1984 1200I Candy Cobalt Blue over Bright Silver Metallic w/ Black & Silver Marbling. Poorboy alternator. Progressive springs and a comfy gel seat.

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post #2 of 13 (permalink) Old 02-11-2006, 02:49 AM
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You might have a flooding problem, did you ckeck the colour of the plugs?


Lucky Eddie.
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post #3 of 13 (permalink) Old 02-11-2006, 08:15 AM Thread Starter
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I did recheck the gap on the plugs and they were black and had a heavy smell of gas. I just assumed that it was from running it on the choke, hoping I could "burn" the backfire away, like maybe bad fuel. I'll look into it, thanks.

1984 1200I Candy Cobalt Blue over Bright Silver Metallic w/ Black & Silver Marbling. Poorboy alternator. Progressive springs and a comfy gel seat.

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post #4 of 13 (permalink) Old 02-11-2006, 09:24 AM
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Could just be that the plugs need replaced and you need to try to run less choke, too. I fouled my GL1000 plugs a couple times until I learned to use the choke less. Thought the SE-i had a bad performance problem until I changed the plugs. Are you running a bit hotter plug this winter? Since you will tend to warm it longer and probably not run extended high speeds in winter time, going to a bit hotter plug might help prevent further problems. (hurry up Spring!) Honda's manual lists new plugs as a first step on many problems, and for some reason I think we are hesitant to take that simple step and instead look for something more dire.

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post #5 of 13 (permalink) Old 02-11-2006, 06:32 PM
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Keystone742 wrote:
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I did recheck the gap on the plugs and they were black and had a heavy smell of gas. I just assumed that it was from running it on the choke, hoping I could "burn" the backfire away, like maybe bad fuel. I'll look into it, thanks.
Highly unlikely, especially in the winter. There are bigger fish to fry there. Ive experimented with all sorts of variations of cutting, leaking and removing lines and hoses on these systems, and nothing like that happened. Id look at floats or debris in the fuel lines or needles and make sure the carbs are synchornised within 1/2 inch of vacuum before chasing anything else. Not finding anything there, electric system is next.

Backfire is from excess fuel in the exhaust. It "loads up" in the exhaust, and when its ignited by another cylinder dumping flame in the exhaust (from its being too rich) it burns abruptly and that sudden pressure increase is what you call "backfire."

Excess fuel is caused by either too much fuel in the cylinder per stroke (thus carb related problems), weak ignition (way too common on 1200s from coroded wiring) or bad spark plugs or other mechanical problems.
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post #6 of 13 (permalink) Old 02-12-2006, 03:39 PM Thread Starter
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Dave, thanks for your imput. I just sent you a PM, and I'm thinking along the same lines as you. In fact I ordered your harness about a week ago and am waiting for it to arrive. I'll let you know what the follow up is.

1984 1200I Candy Cobalt Blue over Bright Silver Metallic w/ Black & Silver Marbling. Poorboy alternator. Progressive springs and a comfy gel seat.

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post #7 of 13 (permalink) Old 02-12-2006, 04:21 PM
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OK, Im jealous, where did you get a 2006 CV PI? Weve got a 98 and its fun!
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post #8 of 13 (permalink) Old 02-12-2006, 08:13 PM Thread Starter
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LOL! It's a company car, and my office. I'm in the "bad guy" business; you know, fight crime and suppress evil. I got your PM, and you're right. All it takes sometimes is a little bumping around and a whole lot of other issues can open up. I’m looking forward to installing it and I might take you up and the visit, either on a trailer or (hopefully) I just ride up one day.

1984 1200I Candy Cobalt Blue over Bright Silver Metallic w/ Black & Silver Marbling. Poorboy alternator. Progressive springs and a comfy gel seat.

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post #9 of 13 (permalink) Old 02-13-2006, 07:54 AM
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Guess I better hide the moonshine still?

Whats the CV do 0-60? Do you want the Wing to outrun it? LOL I outran a PI one day on the 86.... but thats another story.
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post #10 of 13 (permalink) Old 02-13-2006, 08:09 AM
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Keystone742 wrote:
Quote:
Afternoon everyone, I would like to ask for some help, if I may. It’s a cold 25’ here today so naturally I thought I’d head back out to the barn and do some work on the bike. I’ve been having some trouble with it backfiring through the mufflers at idle, once it’s warmed up and the choke is backed off. It does go away at about 2,500 – 3,000 RPM. This problem wasn’t there before I removed the engine and replaced the clutch. I have checked the air cut off valve and it appears to be working; I made sure that the new o-rings for the carbs were in place, double checked the plugs and wires at the coils. I did find a cracked vacuum line from dry rot, so now I’m planning on replacing all the lines under the carbs. My question is does anyone know what the ID sizes are for these lines? My eyes aren’t focusing to well today (another sign of the times) but I can tell there are 2 different sizes. I also would be very grateful for any ideas or suggestions that would help fix this backfire problem. Thankyou.
Keystone , backfiring through a muffler (or mufflers) is usually caused by a lean condition such as a very lean fuel air mixture, a pin hole or gasket leak in an exhaust pipe to cyl head, etc (check the exhaust for pin holes or leaking gaskets to the cyl head).. It can also be caused from a cylinder firing on a partially open exhaust valve (incorrect valve lash, burnt valve, or improper cam timing)..


Honda used an air cut-off valve to richen the pilot system & therefore the exhaust mixture on decel or over-run to prevent popping in the exhsust.. Unfortunately that air cut-off valve allows a lean mixture at low RPM or idle so it won’t help on anything except decal or over-run..



Bottom line here: look for a lean mixture entering the exhaust,, OR a valve timing problem on the cyl head in question,, OR a burnt exhaust valve (do a compression test),, OR air leaks INTO the exhaust system on the side in question..



Twisty


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