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There’s backfiring, and then there’s deceleration pop. Backfiring is much louder (think BANG!) and more dangerous to the motor than decel popping (“pop-pop bang pop”). Are you actually experiencing backfire?
Most of decel pop is from the O2 sensor being slower than the engine. Slower signal to ECU This is what the regional Guzzi Tech rep told me. Mainly about cost saving.
Yes tip and Bosch valve are parts of the EVAP system. There is a diagram of the system under the seat. The Bosch valve is the purge valve. It is an electronic valve that opens under certain conditions to draw intake vacuum through the charcoal canister to purge the fuel vapours so the charcoal doesn't get saturated. The thing that some people call a tipover valve is a little plastic one-way valve that closes when the purge valve is open so that you don't draw vacuum all the way back to the fuel tank.Not sure about 2021 V85, but on many later bikes you can't actually remove the purge valve or it will throw a code. You have to leave it plugged into the harness, and plug the vacuum hose that runs from the valve to the intake. Failing to do that would create a permanent vacuum leak - bad juju.FWIW my bone-stock V85 pops quite a bit on decel. Many (most?) bikes do, but it's usually not so obvious because it is well muffled by the OEM exhaust. Putting on an aftermarket exhaust sometimes makes normal decel pop annoyingly loud, even if was always there. Sometimes its really bad and needs to be dealt with. On another bike (air cooled Ducati) after adding a Zard full system, also with modified intake, the only way I could deal with the intake pop was to take *all* of the fuel out of the map in a certain rpm range on closed throttle. I chased exhaust leaks until I was losing my mind with no progress, but the fuelling adjustment was a 100% fix. Getting it in the right rpm range takes some experimentation though, otherwise you can end up with stalling when coming to a stop.
My BMW K75 pops on deceleration sometimes.
What would be the benefits of removing the tip and Bosch valve? I assume its a completely different system and not a part of the secondary air system?
....Vibration in the handlebars is driving me nuts. I've done a few "fixes" with no joy. Nowhere as smooth as my V7lll was. I wish I had never traded.kk
Good explanation of the differences between backfire and decel pop here:https://www.youtube.com/watch?v=5BKjVYAlPDUNot sure about the V85TT UpMap, but for my V7 850 the UpMap tune put the ECU into open-loop where it only reads from the fuel map and disregards o2 sensor feedback. I suspect that might be happening. End result is you're likely running richer more of the time. Check spark plugs to confirm. My bike has decel pop, even my last Ducati with a DynoJet PowerCommander and AutoTune did when well dialed in. It's not something to worry about, but backfires are... unless you're Uncle Buck.
IF I'm reading your post correctly, the bike runs fine otherwise? If this is true, I wouldn't worry about it.
Up date on my vibration. It turns out the vibration is probably more a result of the handlebar holder. Due to the nature of the newer engine I have been riding the bike quite a bit differently than my V7lll. The '26 models have a larger throttle body, 51 mm if I remember correctly. The cams have also been changed with different profiles and probably timing resulting in a larger amount of toque at lower rpm. So I have been riding it at lower rpm than the lll. I have done everything I could think of to lower the vibration level, anti-vibration risers, filled handlebars with #7 lead shot, Grip Puppies and tightened every fastener I could find especially engine mounts. Nothing changed. So yesterday I decided I would adjust my riding behavior. I rode it like I stole it. So instead of staying in the 4,000 rpm range I wound it like my my old lll liked, 5,000+. Quite an improvement,not quite lll smoothness but close. Now I have to be careful to stay in one lower gear than before to avoid a speeding ticket. Sixth gear will be like new when the rest of the drivetrain is well worn in. No 80 MPH speed limits near me. kk
Not sure if it'll help you but way back I had the same issue with my 1988 K75S and when I brought it up with Frank Stevens with BMWNA he said "when engine braking with the throttle closed be sure to close the throttle all the way". After I started doing that the occasional pops went away.
