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General Category => General Discussion => Topic started by: kevin711 on July 27, 2026, 09:29:21 AM
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I searched but could not find an answer for this.
I have a new to me 2023 v85tt with full exhaust (decat and headers) wirh zard silencer and baffles installed.
Upmap flashed for "V85 21 US ZARD FD"
The previous owner was nice enough to document all of the modifications and notes that the SAS was deleted and a K&N air filter were installed.
I am getting occasional backfiring on initial startup. Sometimes just one pop right when it starts, and also at lower rpms when decelerating coming to a stop such as a stop sign.
Im wondering if anyone else has this same setup? If so, is this normal?
I read that unless you cut fuel when the throttle is cut you will get backfiring with aftermarket exhaust but im not 100% on this. I LOVE this bike and so want to make sure im not doing any harm.
Something else ive been curious about, in the notes from the previous owner it states " removed SAS and installed smart moto block off plates and resistor. Removed tip and Bosch valve and ran vent line down left side of bike and installed resistor".
I assume this was the entire sas system that was removed off the bike but I dont understand what the tip and Bosch valve are?
Thank you in advance for any help or advice given.
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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?
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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.
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My BMW K75 pops on deceleration sometimes.
According to what I read, some seem to, and some don't.
Exhaust and vacuum leaks can contribute to both the
occurrence and strength thereof.
YMMV
I'm not too worried about mine.
-Stretch
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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?
On startup its 100% a single pop of backfire. Like a gunshot but not every single time I start the bike and when it does happen its only one loud bang right at the very start.
The decel I think is just loud because of the modified exhaust I think.
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Your map likely has a lot to do with it. It probably adds more gas on acceleration to compensate for the greater air flow.
You close the throttle and gas continues to flow for a few cycles but with less air. If its able to ignite you get a louder bang.
Pete
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The loud gunshot noise would scare me,I don’t believe in messing with stock Guzzi engineering.
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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.
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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.
I believe since it is using upmap the O2 sensors are disabled.
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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.
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?
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I have a 2022 v85tt with Arrow headers (cat and bladder delete) and stock muffler stock air filter and Upmap. I donot get backfires on start up but if I upshift from 3rd and 4th gear at 3600-3900 RPM, and only in that tight rpm range, it may "bark" but with throttle manipulation shifting above and below the above rpm's I can ride without any "barking".
With the bike stock I was getting an unacceptable amount of pinging pre-detonation and engine heat and horrible low speed fueling plus I felt the stock headers looked awful with the silly upper guards and underneath behemouth bladder.
I no longer get any "pinging" pre-detonation and the engine heat level is way down. With the Upmap 1st and 2nd gear are smooth with an added boost of torque. Maintenance is easier and looks are better.
(https://i.ibb.co/LhBYJ23L/arrow-header.jpg) (https://ibb.co/LhBYJ23L)
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I have an aftermarket “Y” pipe and stock muffler and air box. No fueling mods, and no popping. Sounds like you’re running way lean.
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My BMW K75 pops on deceleration sometimes.
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.
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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?
The EVAP system is normally removed in an attempt to address "snatchy" fuelling at low throttle angles. i.e., you roll on the throttle from a closed position and nothing happens, then with a bit more throttle the bike suddenly surges forward. It really affects low speed drivability. My V7 850 had brutal surging of this type until I removed the EVAP system. Removal was a complete (and $0) fix - it now fuels beautifully. One can easily check if their bike will benefit from this mod just by temporarily clamping the vacuum hose running from the purge valve to the intake manifold. If it has no effect, then there is no point in deleting the system.
I have no idea why the EVAP system buggers up some bikes and not others. My 2025 V85 still has the EVAP and works great. But of course, it also has a completely different throttle body (52 mm vs 38 mm in the V7), so there are a lot of differences between the bikes.
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The '26 V7 has the larger throttle body. I deleted canister and blocked the purge valve. Helped quite a bit, still surges until it gets up to full operating temperature. The throttle by wire also makes it hard to maintain a steady speed in 1st or 2nd at low speeds due to its sensitivity. I have become a bit disillusioned with mine. 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
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....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
Man I hate hearing that, I hope you find a cure Moparnut.
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At one time Rox had some AV risers. Or remove bars shove a wine cork in about 3” find a guy with a casting pot think black powder hunter and fill the end with lead. Or best yet if they still make the Bar Snake. It works.
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https://www.hvmp.com/
Works a treat.
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May or may not apply to your bike but I chased a popping with occasional loud bang on my EV for years, I thought I had it when a missing exhaust manifold gasket was found and fixed, the symptoms were more apparent when decelerating going down hill pulling a trailer and decelerating quickly with or without a trailer, the loud bang was always on the right side, the popping wasn’t noticeably different on either side. My wife was riding in the now installed side car on the right side and occasionally noticed air hitting her head associated with the popping, checking and adjusting the intake manifold to throttle body alignment seems to have fixed the problem.
Thing is the clamps were tight and it didn’t look misaligned. But so far a year later the bang is gone but I still get occasional slight popping on rapid deceleration but it’s no where near what it was.
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IF I'm reading your post correctly, the bike runs fine otherwise? If this is true, I wouldn't worry about it.
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Moparnut, sounds like something, or things are not adjusted right. Throttle on my 25" ride by wire, is not hyper sensitive as yours sounds and the engine should. If your getting excessive vibes through the bars, something is off with the engine, there is no inherent reason it should vibrate considerably more than the v7III.
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I got rid of my decel popping on my jackal by tuning the first column, throttle closed 3.6 degrees. I made the mixture 25% richer. I believe decel popping is a lean condition, which you would think because its popping its more fuel. I think because the engine is at higher rpms when coasting the throttle plate is closed thinking its closer to idling and adjust for less fuel. Adding more fuel would bring it back up to the higher rpm range it is operating at even with a closed nearly coasting throttle plate.
But this does not matter if you can't adjust your fuel map. Instead of 25% I think it only took 10-15% more on that first column.
This was awhile ago so may not have everything correct.
Wondering if the loud bang at startup is leaky injector?
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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. :thumb:
kk
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Good explanation of the differences between backfire and decel pop here:
https://www.youtube.com/watch?v=5BKjVYAlPDU
Not 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.
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Good explanation of the differences between backfire and decel pop here:
https://www.youtube.com/watch?v=5BKjVYAlPDU
Not 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.
The Upmap disregards the 02 sensors but what about the other sensors.... temperature sensor etc?
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IF I'm reading your post correctly, the bike runs fine otherwise? If this is true, I wouldn't worry about it.
Yup, ill try to upload a video of the single backfire when I first start the bike cold. Its literally one pop and the bike idles fine forever after that until it sits overnight or while I'm at work. Also doesnt do it every single time so its hard to film.
Also black soot on the exhaust baffles, so I would assume if anything im running a bit rich. Makes me even less worried. Ill check the plugs at the end of this riding season when I do all my pre winter maintenance and adjust the valves.
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Good explanation of the differences between backfire and decel pop here:
https://www.youtube.com/watch?v=5BKjVYAlPDU
Not 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.
Thank you for the link to the video. Upmap works the same on the v85, the O2 sensors are still in place but they dont do anything.
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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. :thumb:
kk
Total thread drift but...I found this really funny. I am the opposite with both my 23 V7 and my 25 V85 - I ride them in higher gears than what seems correct, specifically so I can feel that nice thrum through the bars at 3250 rpm or so. I love it! The V85 especially is so smooth that it borders on not being guzzi-ish enough, so I tend to lug it a bit to be able to feel the engine working.
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Further update. I took a long ride yesterday. I have been laid up for a few weeks due to a non motorcycle injury so I haven't been able to ride. It was really hot, 99+ so at one point while on cruise control I took my hands of the bars to unzip the sleeves on my jacket for more ventilation. To my surprise the bars started to shake, not violently but quite markedly. With my hands back on the bars it would stop as my hands would absorb the vibration. It has felt like engine vibration but is actually road connected. I recently mounted new tires so I am guessing this is the problem. So first thing is to check runout and then recheck balance. I am very happy to find where it is coming from now to find the cause. I am thinking tire because it is a back and forth vibration not an up and down and it is rapid and maybe an inch or so in amplitude. Hard to explain but I have done the best I could. I have been riding for decades and have never experienced anything like this before, something similar with a used Sportster that had a dinged wheel. I will report back when I find the cause. I am really happy to have found the problem as I was ready to trade the bike off.
kk
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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.
Early BMW K100s had the problem. By '87 BMW put a microswitch in the system to sense fully closed throttle. BMW programming shut off the injectors at fully closed throttle until RPM dropped below 2,000 RPM. That was the end of the popping on deceleration. Maybe a reprogram of the Guzzi could create a similar solution to the problem.