TC88 BAckfires

[Stray Dog 812]

I have an 99 FXDS Convertible, TC88, carb model. With 60000 miles It has Screaming Eagle pipes and a twin tech ign. Problem is backfire in the exhaust (?) on deceleration. Bike runs great it just backfires and pops on deceleration. Have been told it was intake leaks, changed gaskets, no help. Checked exhaust. Any advice? Thanks!

[DaFish]

You didn't say what other upgrades you have done to the bike i.e. what cams, heads and C.I.
Without any other information I would say what you are hearing is not backfire but back rapping. This is different from backfire in that the air rushes into the pipes to make up for the high rpm the engine is turning and no air (or very little) pushing OUT of the pipes. The sound of the air being sucked back into the pipe is what I THINK you hear. This is normal and should not be confused with backfire.
Backfire is when unburnt gases are introduced into the exhaust system where it is ignited and fires in the exhaust chamber or the pipes. Backfire is detrimental to the life of the engine and exhaust system. Back rapping is not.
Mine does the same thing when I roll the throttle back after a high rpm run. I think it's kinda cool and sounds great IMHO.

DaFish

[Bullwinkle_M_Esq]

Running lean maybe? What do your plugs look like? No exhaust leaks huh?

[Stray Dog 812]

Catfish, I bought the bike in Dec. 01 with app.10000 mile on it. The ignition, oil and plugs are all I've ever added to it. Sounds like maybe I am chasing my tail. But it does seam like its has gotten worse lately.

[DaFish]

Take your plugs out, take a picture of em and send it to this thread so we can see em. Then we can give you more info as to whether it's running lean or not.

DaFish

OBTW you can use photobucket to upload your pics. I found this easiest.

No need to be formal. You can call me Fish.

[OnegoodHorse]

If this is new, something changed, the most likely culprit is indeed a leak. Start it, take a spray bottle of water, some wd-40, or an unlit propane torch and spray it around the intake manifold, and where the carb meets the manifold. If the engine rpm's change, that's where your leak is. If you've put 50k miles on your bike, you can feel when something is different. Trust your gut. Also, with that many miles, check the vacuum line that goes from the intake manifold to the VOES switch and to the fuel shutoff valve. (pet**** gets censored, hehe) A lot of times those will dryrot and get pinholes that are almost impossible to detect, yet will cause the same type of problems.

[Stray Dog 812]

Fish, looks to me like my rear cylinder is running rich? I am working on this fxoxox picture. i put it in my gallery.

[OnegoodHorse]

First thing I would check is the enrichener knob. Make sure it's not sliding back out a little after you push it in. Fairly common, just tighten the tension nut behind the knob if it is. Really though, backfires on decel generally mean a lean condition, I'd do the leak test if it were me.

[freeriderogur]

Before you install the carb, try putting some lube on the intake gasket. Very very lightly with your finger and wipe it off with a dry finger. That will help the carb to slide in better without pinching or folding the gasket. I prop up the fuel tank to get a better angle on the install. Also try a new air cleaner backing plate gasket. Check for leaks like they all said, and change your spark plugs.

[gatorggg]

if you dont have leaks need to look at carb, did not check what type of carb

[Stray Dog 812]

Changed plugs and the daxn thing quit me. I cleaned the old plugs and replaced them. Ben riding all afternoon and its running better than it has for three months. Exchanged the new (bad) plugs and put them the tool box. Am sending the grimlins back to Tulsa!