Exhaust pop rivet removal

Colly

Colly

fast rider
Joined
Jul 25, 2025
Messages
32
Location
Northern Ireland
Removed 401 exhaust with intention to drill out end cap rivets, remove end cap and cut out DB killer, performed this many times on other bikes without a problem but these rivets are stainless steel, ive went through 4 drill bits on 1 rivet without success, tried titanium coated without success.
Any tips?????
 
Cobalt bit.

There is no db killer in the original endcan. You can grind out the smaller pea shooter and leave an oval hole to let more air out people have used a hole saw to cut the smaller pea shooter end pipe out but the results are horrendous, visually. There are you tube vids where people bodge the endcan, most leaving no mesh over the sound packing meaning you will throw fibreglass over following traffic. This will almost certainly fail an MOT in the uk.
I would (and have) just buy an aftermarket end can.
Also if you are removing the centre muffler with a straight through pipe and chopping your endcan about, it will be too loud IMO. I also do not think the fuelx lite will cope with all your mods. You will almost definitely require an ECU re flash. Others who have done muffler delete have reported a loss of power too.
Your bike though your choice.
 
I took out the center canister and then cut my dB killer on the stock one about 4 inches shorter than stock.. So it still looks stock from the outside. Sounds good to me and not too loud. It was much to loud with just a slip on and still sounded odd. Then I removed the canister and had the slip on and that sounded amazing but was much too loud. So put the stock muffler back on and it was too quiet again although louder than stock. So finally cut 4 inches of the dB killer and now it is quiet enough but has that ripping noise to it that does not exist with the center canister.

I agree the rivets suck to remove. And it is a pain to tap the end cap off and it is on there very tight. I did not put rivets back on as I did not have any that big. I found the holes are perfect for a 6mm tap. So tapped all the holes and installed 6mm bolts with a round allen head.

No loss of power for me. I have no ECU or fuelx. I use a "booster plug" trick which in my region a simple resister works and gives me 6% more fuel. Pulls great from idle to 10k rpm.
 
Here is what it sounds like. Not perfect but I can now live with the noise at idle but still enjoy some top end exhaust sound. Anything with a slip on was too noisy for me at idle.
To view this content we will need your consent to set third party cookies.
For more detailed information, see our cookies page.
 
Zep said:
Here is what it sounds like. Not perfect but I can now live with the noise at idle but still enjoy some top end exhaust sound. Anything with a slip on was too noisy for me at idle.
To view this content we will need your consent to set third party cookies.
For more detailed information, see our cookies page.
Click to expand...
I am not an expert on modern fuelling or modern electronics of any sort so cannot comment on your feeling for the mods you have done but what I can definitely say is that is way too loud for here in the uk. It may be fine in the Philippines, or other countries. It is also disproportionately loud for a baby 400 in any country. Having said that this is just my opinion.
I would however, out of curiosity like to see your $5 airbox mod and learn more of the resistor mod you mention.
 
It is not really as loud as it might appear. I will get a video of it out of the garage later and post. Much quieter at idle than any slip on would be.

$5 airbox mod is just opening up the top of the airbox and installing a filter. Just cut mine from scrap aluminum and then added filter media from a car's airfilter I cut up.

31e9d83b-39b5-4a81-8241-a22d3387bae3.jpeg
 
As far as fueling goes their are like three ways to go.

1. Fuel-x which modifies the O2 sensor signal so it runs richer in closed-loop mode.
2. ECU piggyback that hooks to multiple sensors and controls the fuel to the injector, works in open-loop mode.
3 The Booster Plug option which modifies the IAT Intake Air Temp signal to make the ECU think the air is colder than it is so it adds more fuel (they say 6% more). Works in Open-loop mode. This is the route I went but instead of paying $150 for the Booster Plug I just added a variable resistor in series with the stock IAT sensor. Most places you would want to add a NTC thermistor ($5) instead but since I live in an area where the temp only ranges from 75f to 90f I can get by with a resistor as the sensor is fairly linear over this small range.

FYI - you can do what the Fuel-x does with a 10 cent resistor and 10 cent capacitor in the O2 signal wiring but I see no need for this in my case as the resistor in the IAT fixes all the running issues I had.
 
Zep said:
It is not really as loud as it might appear. I will get a video of it out of the garage later and post. Much quieter at idle than any slip on would be.

$5 airbox mod is just opening up the top of the airbox and installing a filter. Just cut mine from scrap aluminum and then added filter media from a car's airfilter I cut up.

View attachment 7463
Click to expand...
I did a similar mod but with much smaller holes.

IMG_0432.jpegIMG_0433.jpegIMG_0435.jpegIMG_0434.jpeg
This with fuelx lite and just an Arrow endcan.
 
  • Like
Reactions: Zep
Zep said:
As far as fueling goes their are like three ways to go.

1. Fuel-x which modifies the O2 sensor signal so it runs richer in closed-loop mode.
2. ECU piggyback that hooks to multiple sensors and controls the fuel to the injector, works in open-loop mode.
3 The Booster Plug option which modifies the IAT Intake Air Temp signal to make the ECU think the air is colder than it is so it adds more fuel (they say 6% more). Works in Open-loop mode. This is the route I went but instead of paying $150 for the Booster Plug I just added a variable resistor in series with the stock IAT sensor. Most places you would want to add a NTC thermistor ($5) instead but since I live in an area where the temp only ranges from 75f to 90f I can get by with a resistor as the sensor is fairly linear over this small range.

FYI - you can do what the Fuel-x does with a 10 cent resistor and 10 cent capacitor in the O2 signal wiring but I see no need for this in my case as the resistor in the IAT fixes all the running issues I had.
Click to expand...
Massively above my head info but it sounds like a great mod. 👍 I am more clockwork than digital as I am a 54 year old stuck in the 80s 🤣
 
Jester1971 said:
I did a similar mod but with much smaller holes.

View attachment 7464View attachment 7465View attachment 7466View attachment 7467
This with fuelx lite and just an Arrow endcan.
Click to expand...

I see you have good hands on you, as a toolmaker I can see the effort and time you have given to this fix, I used to do the same with hacksaws, files, emery paper, I did it cause back in the day I was skint and enjoyed a wee project. KTM as correctly stated have an R&D dept to produce the best airbox solution, but there arms are tied behind there backs, having to meet nearly impossible regulations, noise control, emmissions, Euro 5 tech, I believe there is a lot of maneuvering between adjustments air in and gas out by removing Euro 5 parameters.
My understanding of the air flow there is a small rectangular area below the original filter that draws the air via back pressure through the filter, you would be surprised how little air is drawn from under the seat, I bought a high flow filter which is the most important fix, but in additionI bought this (China) it arrived yesterday, thinking it was a plastic item but was shocked that it arrives in 2 pieces both CNC machined out of billet alloy, comes with high density foam (red) and medium density (yellow) + stainless steel screws.
I really dont know how they do it £14.99 with free delivery, sorry I am drifting guess what I wanted to say when you take in the cost of grinding discs, drills, materials you have a lump of I guess 3mm alloy, mesh, nuts bolts, foam etc oh forgot most importantly TIME, old men like me go China + still have original to revert back, incase next buyer unhappy and lets face it they are always unhappy
 
  • Like
Reactions: Zep
Colly said:
What is this booster plug everyone talks about, spark plug? software?
Click to expand...
It is hardware. It goes in-line with the stock Intake Air Temperature sensor. Makes the ECU think the air temp is lower than reality. So it adds more fuel.

If you search on the words KTM and booster plug you will find info. Some even run both the booster plug and the Fuel-x in combination since one works in open loop mode and the other in closed loop mode. I am not so sure this is necessary but whatever people want to do.
 
You must log in or register to reply here.
Back
Top Bottom