As many of you know Guzzi has been fitting recent 1400s (like my 2016 Audace) with a secondary air supply pump to help it meet Euro 4 emissions. My understanding is that this injects oxygen into the exhaust to help burn unburnt fuel when you back off the throttle making it run ultra lean. There's a picture of the pump here on the lower left side of the bike. If you grovel around you will see it connects to two rubber hoses that eventually connect to metal pipes that enter each cylinder head just to the inside of the exhaust pipe.
Having previously fitted Todd's PCV/AT300 I noticed during a recent visit to the site that he had added a comment that the hoses should be pulled and the metal pipes plugged. This topic has been discussed at length on the V7/V9 forum and Todd even has a kit to fix it (https://www.guzzitech.com/forums/threads/gtm-secondary-air-supply-sas-block-off-kit.18018/) but I was unaware of this fix for the 1400 so I thought I would give it a try and report my findings.
All I can say is what a transformation for something that is practically free, OK - about $1 for a couple of silicone based caps to fit over the 3/8" inch (1cm) metal pipes.
Idle is now much more rhythmic and stable, no sense of the throttle hunting slightly at a standstill and rocking the bike in the process, it fees more stable at the lights for example.
Throttle response is massively improved in the lower revs ranges. Twist and there's instant response from 1500 rpm onwards - any gear. No sense of a small hiccup or delay while the fuelling has a "think". Just smooth, predictable, linear response to throttle input.
Just as impressive is what happens when you back off slightly, there's no sudden deceleration like you've backed off fully or hit the brakes, just a nice smooth gentle deceleration (like you get in a car for instance) and gives me the confidence to lean the bike over in a sweeper and just make small changes to trajectory based on throttle inputs.
The transition from on/off/on with the throttle is also more predictable. I can coast down to a left or right turn/junction with the throttle closed, turn in and then apply the throttle and get a smooth predictable response that sends me where I want to go. Both of the above would previously have caused small lurches that would upset the suspension and steering geometry.
As a result of the improved throttle response, gear changes are now noticeably smoother due to the revs not dying so quickly when you pull in the clutch and back off the throttle.
The engine also sounds much smoother and more mellow, more like a growl and less rattly (see below) - Note I still have the original exhaust. Any residual pops and farts from the exhaust have completely disappeared. I didn't hear a single one today. The original factory set up ran so lean I had them everywhere. Fitting the PCV/AT300 made a huge difference, but I still used to get them, just less often and a lot quieter, but now I don't have them at all.
I've posted previously about a strange rattle from the engine at around 2500 rpm (https://www.guzzitech.com/forums/threads/strange-rattle-from-the-beast.17431/). This appears to have completely gone !! I knew I was onto something with this when I pulled the hose off the metal pipe on one cylinder and started then engine (just to see which way air was flowing). The noise coming from the exposed metal pipe was a loud "clack" which sounded just like the rattle I had before. I can only think that plugging the end caps and effectively separating the two cylinders has stopped any interaction between them.
Now my Audace has become two bikes. It's a cruiser when I'm feeling lazy and want to take in the view and a sports bike when I want to carve it up.
Any downsides - well I think there's more exhaust fumes coming out of the bike when I start it up in the Garage. If there's any changes to MPG it's not noticeable and to be honest I don't care as it's the best improvement I've made to my bike - Donation to the site coming your way Todd for this great fix.
Having previously fitted Todd's PCV/AT300 I noticed during a recent visit to the site that he had added a comment that the hoses should be pulled and the metal pipes plugged. This topic has been discussed at length on the V7/V9 forum and Todd even has a kit to fix it (https://www.guzzitech.com/forums/threads/gtm-secondary-air-supply-sas-block-off-kit.18018/) but I was unaware of this fix for the 1400 so I thought I would give it a try and report my findings.
All I can say is what a transformation for something that is practically free, OK - about $1 for a couple of silicone based caps to fit over the 3/8" inch (1cm) metal pipes.
Idle is now much more rhythmic and stable, no sense of the throttle hunting slightly at a standstill and rocking the bike in the process, it fees more stable at the lights for example.
Throttle response is massively improved in the lower revs ranges. Twist and there's instant response from 1500 rpm onwards - any gear. No sense of a small hiccup or delay while the fuelling has a "think". Just smooth, predictable, linear response to throttle input.
Just as impressive is what happens when you back off slightly, there's no sudden deceleration like you've backed off fully or hit the brakes, just a nice smooth gentle deceleration (like you get in a car for instance) and gives me the confidence to lean the bike over in a sweeper and just make small changes to trajectory based on throttle inputs.
The transition from on/off/on with the throttle is also more predictable. I can coast down to a left or right turn/junction with the throttle closed, turn in and then apply the throttle and get a smooth predictable response that sends me where I want to go. Both of the above would previously have caused small lurches that would upset the suspension and steering geometry.
As a result of the improved throttle response, gear changes are now noticeably smoother due to the revs not dying so quickly when you pull in the clutch and back off the throttle.
The engine also sounds much smoother and more mellow, more like a growl and less rattly (see below) - Note I still have the original exhaust. Any residual pops and farts from the exhaust have completely disappeared. I didn't hear a single one today. The original factory set up ran so lean I had them everywhere. Fitting the PCV/AT300 made a huge difference, but I still used to get them, just less often and a lot quieter, but now I don't have them at all.
I've posted previously about a strange rattle from the engine at around 2500 rpm (https://www.guzzitech.com/forums/threads/strange-rattle-from-the-beast.17431/). This appears to have completely gone !! I knew I was onto something with this when I pulled the hose off the metal pipe on one cylinder and started then engine (just to see which way air was flowing). The noise coming from the exposed metal pipe was a loud "clack" which sounded just like the rattle I had before. I can only think that plugging the end caps and effectively separating the two cylinders has stopped any interaction between them.
Now my Audace has become two bikes. It's a cruiser when I'm feeling lazy and want to take in the view and a sports bike when I want to carve it up.
Any downsides - well I think there's more exhaust fumes coming out of the bike when I start it up in the Garage. If there's any changes to MPG it's not noticeable and to be honest I don't care as it's the best improvement I've made to my bike - Donation to the site coming your way Todd for this great fix.
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