I still have the factory exhaust flap on my bike, it works (well it did when I checked it last year and gave it a shot of WD-40) and I've left alone for now. Apologies for my ignorance but I don't know if it meant to stay closed at low rpm's or to close at high rpm's ? I've read somewhere on this forum that if you disconnect it, ie. stays open, the bike will run a bit smoother around town, (so I assume its closed at low rpm ?) and is that really true ? The reason I ask is, I do like the bike to run as smooth as possible, but i also don't want a loud exhaust either (My termi days are long over now....) Cheers
The ‘flap’ is fitted so the bike will pass construction and use regulations, relevant to the country the bike is sold in. For the UK, that means a noise test at about 4000rpm which is the point at which the flap partially closes. Disabling it, either electronically with an add on gizmo or disconnecting the operating cable, won’t increase noise with a standard CAT fitted. There are several proprietary solutions on the market, most have been discussed and rated somewhere in posts on this forum. Andy
Think allot of the modern bikes will show a engine management light if you disconnect the servo for it so have to use something like a healtech exhaust servo eliminator to avoid that (Is plug and play). Makes next to no difference to the noise at idle only low rev's but its nothing like putting a stubby can on or anything like that Personally only done it on a track bike so not sure on rules for MOT though
Emissions and noise tests are not currently part of the UK motorcycle MoT. IME, a ‘loud’ exhaust (cough, cough) gets you an advisory. Andy
You could trick it on the old ones with a spring and some washers, to create enough resistance to make it think it's opening something.
So its open at tick over/low rpm's.. closes around 4000 rpm, and then opens up again at higher revs ?
Yes, opens at all times other than around the revs that the noise regs stipulate it should be measured. It cycles at ignition switch-on too just to verify it's working. In effect it's a cheat device to comply with the European noise emissions standards and how they're tested. As stated in the post above this is currently only tested for new motorcycles as a type approval and is the responsibility of the manufacturer, currently not as part of the MOT. Fitting aftermarket exhausts is something of a grey area but currently pretty well ignored. Disconnecting the flap is, in my experience, primarily beneficial for around town riding (I used a Healtech module, others have successfully used the spring approach). Even more so in combination with a gearing change (I've gone for 14/40T, others prefer 15/42, over the 15/40 std setup on the 1260 Multi). Another improvement to riding and slower speeds I've implemented on my 1260; is adding a throttle spacer that removes the slight slop in the throttle action when coming off a closed throttle.
Actually it is not a cheat that pass regulations..... It is there only for making lower noise and that is what is does. How it works now... It is controlled from ECU, and ECU mainly takes throttle position for its opening. Example 1: Lets say you are at 2000 rpm and go foul throttle... it will open right away at 100%. Example 2: You go from 1000 rpms to 6000 rpm with low throttle... it will remain at 20-30% closed position. As i have monitor it, it closes foul only when you are closing foul at throttle and let bike roll with gear engaged. I refer the examples for better understanding sorry for bad writing.. not good at english
When I've got a little time I'll disconnect it and just see how it runs and how much louder it seems. Don't want to cut it out fully as one day I'd like to ride through the Swiss Alps, and I hear they are super strict on noise levels !
I removed the flappy boi on my 1200 S (full termi on my 1260), it wasn't much louder, just deeper which made the sound a lot nicer. It's one of those OEM parts that really is only there for emissions tests. Chuck it ASAP.
Removed the flap on my 1260s after it got sticky and had power loss during over a few overtakes. Drilled out the rivets on the flap inside the exhaust pipe so the cable and mechanism are still there so the ECU still thinks there's a flap. No fault codes and not need to buy a healtech, or similar. I can't tell any difference in noise either. Win win.
It’s not emissions it’s for noise testing mainly. Same reason they put foam under some of the engine covers (which collects water and rusts the cases!)
just keep tension always at cable. If it remains without tension, it may unhook during first check form the other end at Servomotor and it is really hard and lucky to get it fitted without dismantle literally half the bike.
The only noise difference is at the part of the rev range where the valve closes. It just removes the additional attenuation that the valve creates at that point.
Fitting the manual spring modification without actually removing the flap valve, is a really beneficial way to go. It will eradicate the well known issue of the flap valve rusting and malfunctioning and although a slightly deeper sound, it is genuinely not that much more intrusive to the standard exhaust note. I've done it on all three Multi's I've owned and the improvements were noticeable. Never any MOT failure or indeed any 'personalised pre-MOT changes' required in order to get the bikes passed.
The most exhaustive guide to exhaust valves. They use a GS as the example - is the concept universal? They suggest it is.
Multistrada 1260 Exhaust Valve https://www.youtube.com/shorts/wjfR-sG6TWc The valve is open at idle, closes at 3500 RPM and re-opens at around 6000 RPM and above.
I deleted the flap on my Monster but opted for a Vizi-Tec Exhaust Servo Eliminator gizmo for the Multi. It's cheap and you can always disconnect it. Personally, It does smooth out the bike but you'll get used to it real fast. Not a big difference in noise if memory serves me well but my memory often does not .
