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Discussion Starter #1
So I've got a 2007 VTX 1300C with HardChrome pipes and stock airbox. Had it rejetted last summer (I believe to 195) and it ran like a top.

Still does. Took it on a bunch of rides this summer with no issues.

But now, all of a sudden, I'm getting backfires on the slightest deceleration. Shift gears - backfire. Roll all the way off the throttle - backfire. LOUD backfires.

I'm seeing no symptoms of anything else - acceleration is strong through all gears, it idles just fine and starts just fine with no use of the enrichment knob.

I left it with my motorcycle repair guy and he came back with the diagnosis of: leak in the exhaust pipe (based on the old shove a rag in the end and feel underneath it with your hand. You should order new pipes. Normally I'd be like "sweet! an excuse to buy stuff!" but I really like these pipes.

So I reproduced his test at home and I think he was just feeling the exhaust getting pushed out from the opening between the pipe and the chrome. I felt no other areas along the pipe where exhaust was coming out.

I pulled the plugs and if anything they look rich. I plan on cleaning them and sticking them back in as a first step.

Any ideas would be greatly appreciated.
 

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Mine was doing the same thing I ended up buying new exhaust gaskets from the auto parts store FelPro 60569 is the gaskets you need and I put washers under the acorn nut and it solved my issue. As a side note I did the same test and did not feel a leak either.
 

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Mine was doing the same thing I ended up buying new exhaust gaskets from the auto parts store FelPro 60569 is the gaskets you need and I put washers under the acorn nut and it solved my issue. As a side note I did the same test and did not feel a leak either.
I had the same problem last year. Bought new gaskets from the stealers. Also,.... I bought some new stainless steel nuts and got rid of the acorn nuts. Never had an issue since.
 

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A exhaust leak will not make you bike run rich.
Check your choke where it is attached to you carb, and make sure it is OK.
 

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I think you are saying that you and your mechanic felt exhaust coming from the gap between the pipe and the chrome heat shield. How could the exhaust gas get into this gap if it was not leaking out of the pipe somewhere? Depending on the pipes, it may not be that hard to remove the chrome heat shields to better look for an exhaust leak.

G'day,

Vinish
 

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Take the pipes off and inspect them, but new gaskets and loose the acorn nuts if you haven't already!
There's your sign :47b20s0: Sound advise right there. Got some all metal lock nuts at the local hardware store, nice tight fit. May not look as cool as the acorn nuts, but very effective, used with a thick stainless washer too.
 

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Discussion Starter #10
Great advice, some hilarious answers (but what else would I expect from this crowd, right?)

Anyway, so before i put the plugs back in I gave them a good scrubbing and in doing so noticed that one of my plug wires had gotten a little too cozy with the front pipe and had a little melty spot on it. So I wrapped that sucker up good with electrical tape and then went for a test drive. Still backfires some but not nearly as bad.

Now, I fully intend to pull the pipes and examine/replace the crush gaskets. It appears that Honda uses 12mm acorn nuts to hold those suckers on, and has positioned them in such a way that getting them off (watch it...waaaatch iiiiit!) will take some sort of special tool. Any thoughts? If I can buy a 12mm with a built in u-joint, I'd do it in a heartbeat, because I feel like that's probably the quickest way to get them off (that's what she said).

Thanks everyone.
 

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Great advice, some hilarious answers (but what else would I expect from this crowd, right?)

Anyway, so before i put the plugs back in I gave them a good scrubbing and in doing so noticed that one of my plug wires had gotten a little too cozy with the front pipe and had a little melty spot on it. So I wrapped that sucker up good with electrical tape and then went for a test drive. Still backfires some but not nearly as bad.

Now, I fully intend to pull the pipes and examine/replace the crush gaskets. It appears that Honda uses 12mm acorn nuts to hold those suckers on, and has positioned them in such a way that getting them off (watch it...waaaatch iiiiit!) will take some sort of special tool. Any thoughts? If I can buy a 12mm with a built in u-joint, I'd do it in a heartbeat, because I feel like that's probably the quickest way to get them off (that's what she said).

Thanks everyone.
That front cylinder is a pain. I use a 1/4 drive socket set with the swivel -- carefully. :hmm2:
 

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As Sumdatx says, it is only the bottom nut on the front cylinder that is tough. I have been successful on this nut with a 3/8" drive short socket mounted onto a universal and then the universal mounted onto a 12" extension. Can't really get a good torque reading this way though.

G'day,

Vinish
 

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Discussion Starter #14
Good news. No more backfiring. I wound up putting in Glen's AF adjusting screw and backing it off two turns.

Backfiring gone.
 

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2 MORE turns, or 2 turns total?

If 2 MORE turns, then I'd check the coast enricher. It's like the accelerator pump, but in reverse. It uses the additional engine braking vacuum to open up and enrich the flow to keep the engine from going too lean or backfiring. A tiny pinhole in it can develop and cause your exact symptoms: sudden backfiring due to a lean-out during decel or when closing the throttle. It sounds like you had several issues and fixed most. If you turned the screw out 2 MORE turns, I would check this little diaphragm.
 

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Coast enricher? Where would that be found. I looked on partszilla carb diagram ,couldn'the see it...that may be something I need to check out also.
 

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Coast enricher? Where would that be found. I looked on partszilla carb diagram ,couldn'the see it...that may be something I need to check out also.
Check this link, #14. Honda calls it the air-cut. What it does is add fuel when the throttles are slammed shut suddenly. It's 'open' when you close the throttle after a rev, or when coasting clutch out while in gear. The more vacuum pulled beyond the normal idle vac level, the more 'open' it is to ensure the engine can continue operating and doesn't simply stall after the revs drop or when the throttle is reopened or when the clutch is pulled in.
 

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Check this link, #14. Honda calls it the air-cut. What it does is add fuel when the throttles are slammed shut suddenly. It's 'open' when you close the throttle after a rev, or when coasting clutch out while in gear. The more vacuum pulled beyond the normal idle vac level, the more 'open' it is to ensure the engine can continue operating and doesn't simply stall after the revs drop or when the throttle is reopened or when the clutch is pulled in.
Something for me to check as well. Appreciate todays carb lesson :mosh:
 
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