Afterfiring - inconsistent but persistent

[normzone]

It does it when the weather is warm, it does it when it is cool.

It does it at high speeds, it does it at low speeds.

But it doesn't do it all the time ...

Yes, it's another episode of Bassa Talk, where I think out loud and pray for brains.

Should I be looking at exhaust pipe to muffler connections? Exhaust pipe to cylinder head gaskets? Or is there a deeper, darker, more evil explanation?

And what about Naomi?

 

[Chuck in Indiana]

Yes..

[John A]

Whats the load and throttle position?, for instance trailing throttle, steady throttle slight downhill or pulling hard third gear 6k rpm

[normzone]

On decelleration - throttle backed off.

If it's any clue, it used to do it only at low speeds, but it's willing to do it at high speeds now if it's in the mood.

 

[Chuck in Indiana]

That, combined with your terrible fuel economy, says it is running rich to me. Have you hooked up GuzziDiag yet?

[normzone]

I have a query in to my local benefactor re that, but this is not an auspicious weekend for many people ... I'll have to wait and see.

[oldbike54]

 It's either too rich , too lean , has an exhaust leak , or is broken . Hope that clears it up Norm .

 Dusty

[normzone]

I feel so much better now that I know what to look for - I'll take it all apart this weekend and fix the problem/s

[cliffrod]

On decelleration - throttle backed off.

If it's any clue, it used to do it only at low speeds, but it's willing to do it at high speeds now if it's in the mood.

 

In order for it to ignite beyond the cylinder, adequate oxygen must be present to facilitate combustion of residual fuel in exhaust gases.  If it was my bike, I would check & tighten all exhaust connections and for cracks as mentioned before chasing more complicated fuel/tuning issues.  If it's getting worse, it's probably getting more loose..   

This situation is usually caused by loose exhaust nuts/bolts/clamps/studs and bad exhaust gaskets.  Once everything is known to be properly tightened and sealed, then you can pursue other concerns.

[John A]

A new engine can stand a leaner mixture than a broken in engine. I'll look for the reference

[normzone]

I have spare exhaust collar gaskets -

Perhaps I'll start the trouble shooting by swapping out the stock Bassa instrument console for one from a Jackal.

No, seriously, I have one I've been waiting to install.

 

[Chuck in Indiana]

What Norman has failed to mention is he is getting around 25 mpg. Normally ( ) a guy would think exhaust leak, but fixing that just might be covering up the symptom rather than fixing the cause.
Obviously, for whatever reason, it's running pig rich. I would be surprised if you couldn't smell it. What say, Norman?

[RinkRat II]

      A)  Jerry Riopelle has Naomi under control.   https://www.youtube.com/watch?v=W91RrF6NLN8

      B) If it's not mechanical maybe time for a Beetle map?

       Keep us posted on Bassa Talk channel

          Paul B

[normzone]

What Norman has failed to mention is he is getting around 25 mpg. Normally ( ) a guy would think exhaust leak, but fixing that just might be covering up the symptom rather than fixing the cause.
Obviously, for whatever reason, it's running pig rich. I would be surprised if you couldn't smell it. What say, Norman?

Well, the ends of the sound reducing cans definitely have some black carbon buildup you can wipe out readily with a fingertip, but I'd expect that in anything that's not my old Eldo.

As for smelling it, the thing is that I'm above and ahead of the exhaust fumes when I go down the freeway. I guess I could ask the guy behind me 

[RinkRat II], Beetle sent me a map yesterday - I don't know how to use it yet but Aaron and I will figure it out soon.

Frankly, I would remap it if only to know for sure what it's got on it. Unless we hook up Guzzi Diag and get an identifier that makes you guys go " Oh, don't change THAT, that map is a collectors item ! "

[fotoguzzi]

When you tighten down the exhaust header use caution , everyone says make all connections tight but you don’t want to snap off one of the studs or you’ll really be in the deep sh__

[normzone]

Yeah, I imagine there's a torque spec someplace, but I'd begin with a conservative hand - as I recall I put a wrench to them once and felt no need to tighten them. Of course, that was a couple of years ago.

[kirby1923]

If running that fat (bunch) you'll smell it right in the shop sitting there running!

:-)

[Muzz]

My first thought was that you had eaten too many beans.

Then I read the thread.  Sorry.

[ohiorider]

Has the bike always gotten 25mpg?  If not (and it used to get 38-40mpg) would one want to remap the bike's ecu without knowing what (mechanically) has caused the dramatic decrease in mpg? Or first look for the mechanical issue causing low mileage?

Just asking.

[beetle]

Has the bike always gotten 25mpg?  If not (and it used to get 38-40mpg) would one want to remap the bike's ecu without knowing what (mechanically) has caused the dramatic decrease in mpg? Or first look for the mechanical issue causing low mileage?

This.
Worthy of a 'like', if only such a button existed....

[Chuck in Indiana]

Has the bike always gotten 25mpg?  If not (and it used to get 38-40mpg) would one want to remap the bike's ecu without knowing what (mechanically) has caused the dramatic decrease in mpg? Or first look for the mechanical issue causing low mileage?

Just asking.

Right. There is something basically *wrong* here. We, collectively, need to ferret it out.

[oldbike54]

Right. There is something basically *wrong* here. We, collectively, need to ferret it out.

 I agree , and using the *start with the simplest thing* concept , start with checking the spark plugs , wires , valve lash , air cleaner , etc . The stock mapping shouldn't be too off on that series .

 Dusty

[pehayes]

This is a 99?  Where does the engine heat sensor come from?  The left valve cover like the '98?  Or the right cylinder head?  If the latter, the sensor can become loose or break.  If so, the heat signal will never be adequate and the computer will always run it very rich as if startup cold.  The right side cylinder head sensor is in a plastic body and gets brittle and breaks.  There is an all-metal improved replacement.  Add some thermal paste to ensure proper heat transfer to the sensor.

Patrick Hayes
Fremont CA

[normzone]

Thank you Patrick - did that long ago, put a new sensor and the brass fitting with thermal paste and even after reading the LONG thread re the subject decided to amuse myself by making a copper spring to load the space between the end of the sensor and the bottom of the threaded hole - it had no effect.

I bought the bike and was dismayed to get forty couple mpg on the first tank leaving Tucson for San Diego, and it went down to the low thirties shortly thereafter, then settled in the high twenties where it has performed for the last couple of years.

I'll do the valves and plugs this weekend, but that's been done by the numbers since I bought the bike in early '14.

Sean Fader has set the TPS early on, and again after my clutch/drive train work.

Perhaps the fact that the chickens I'm sacrificing are free range is the problem.

[Bulldog9]

Free-range chickens will get you everytime... 

[John A]

That needs fixing, way too much fuel. What have you done to that poor machine, Norm?  It's defiantly time for a troubleshooting contest

[normzone]

My logbook says that when I do valves, plugs, and air filter this weekend I'll be doing it approximately 250 miles ahead of schedule.

I'll eval the exhaust gaskets and pipes/mufflers joints and take action as appropriate. I have spare gaskets and nuts for the pipe / head junctions.

With some luck Aaron and I will Guzzi Diag next weekend.

But you may as well keep your thinking caps on, because short of the Guzzi Diag I've done all that many times over.

Oh yeah, and ohm out the high tension wires ...

[pete roper]

I really think it's worth checking the TPS voltage and setting it from scratch with the 150mv fully closed method and then opening the butterflies to whatever the correct setting is, (450mv? Can't remember offhand.) do this with a multimeter, not Guzzidiag, it's not accurate enough. Also check for a smooth, un-stepped increase in the TPS value as the twistgrip is opened.

The suggestion about the ETS holder being cracked is also sage. No matter how rich it's running though I feel that this may be spark related, maybe it's 8/12/16 stroking? That will give symptoms similar to 'Rich' and give serious backfiring problems on the over-run. Perhaps the phase sensor gap is a bit too large and as the sensor deteriorates with age it's creating problems.

Pete

[Huzo]

That needs fixing, way too much fuel. What have you done to that poor machine, Norm?  It's defiantly time for a troubleshooting contest

Defiantly..?

[John A]

Defiantly..?

Absolutely it's the only way.  We've seen it before here, the author claimed spell check did it but we know he was lying.  I hope it wasn't me!