Exhaust flap

[Santa-2512]

Day 2

Multiple cycles of Ultrasonic cleaning at 40c gave little results , it was free but not snappy free if that makes sense

So i whacked the temp on the Ultrasonic bath up to 60c set it for 30 mins pulsed and then left it in the USC bath over night

Day 3,

Watched various YouTube videos on cleaning, lubing, destruction etc,

so i now know how/ were are the best points to lube the shit out of it

Its very clean lol

so it moves, but still sticks at the start and end points,

So i stuck a set of mole grips on the cable housing end and started to flick the unit back and forth

Drowned all the lubrication areas with GT85, and with a combination of pulling and pushing the spindle whilst rotating it

It was snapping back under the spring power

looking at the spindle there is now grey residue coming up from the blind bearing, so potentially what was gummed in there is clearing

I've drowned it in GT85, and left in the sun to bake

I'll grab some oven cleaner on the way out today, some have said its good for hitting burned on carbon (not sure about the bushes though)

If it seizes by the time it gets home i may do another over night session in the bath

 

[Santa-2512]

Well it was still free,

So as i have time , its back in the US cleaner, and will be left overnight

 

[bmstan]

i seem to recall some one had managed to get that cap off , or i may have been dreaming

either way next week

That was possibly me? I originally wrote this in April 2017 having done this a few years earlier.

On my 2010 Twin cam the flap started to stick at about 20k despite trying various cleaning solutions and high temp lubes we were using on presses running @ 980/990 deg C at work. At 24k it was seized solid. A straight ss pipe went on.

(As an aside I can recall mine also went in the ultrasonic bath more than once to no avail.)

The flap then sat in a tub of diesel, played with on occasion for a couple of months with no movement, until I knocked it over once too often. I was going to bin it but having cleaned the diesel off I decided to grind off the top of the boss on the inner side where its been rolled over to see what the bearing was like. What I found was, I think, a wire reinforced carbon brush.

I started to dig this carbon out and after about 6mm the flap suddenly snapped shut and could be easily opened by hand. I was reluctant to dig in any further because it now worked.

I decided to make a phosphor bronze bush, closed at one end, reamed to 10mm h7 to support the end of the shaft where I had taken the carbon material away. This was made as an interference fit on the o.d. and the closed end tapped 6mm so that I could put a bolt in to draw it out if necessary, as I had no idea about the shaft /bush material expansion rates and didn’t know if it would jam with the heat.

I then made an alloy sleeve cover, again closed at one end and tapped 6mm for ease of removal to go over the bush, held on by 2 grub screws, locked down onto 2 flats I made on the flap valve boss; this keeps the weather /muck out.

The bike is now on 68k and the flap is still free and working like a good un!

Apart from the cables around the pulley I have never used any type of lube on it since I did the mod.

Now in the present; April 2025.

I came to the conclusion that it IS a Carbon bush and that the problem is carbon build up between the bush and shaft. Just like I used to get on my 2t Enduro bike power valves, which could be an absolute sod if you didn’t strip and clean them on a regular basis, i.e. 40 hours at the piston change!

A couple of years ago at just over 105,000 miles when riding in the Dolomites the bike started to play up and wouldn’t pull. I found the valve was seized shut but it turned out that it was the electric valve motor that had stopped working with the flap in the virtually closed position. I released the cables and came home with it in the fully open position. It has sat like that ever since. Not turned and not lubed but still free to move under the spring pressure when I took it apart in the interest of research this afternoon. The flap doesn’t wag about either.

Mileage is now @118,000, some have been quite hard ones! I think I might have sorted mine?

I also powered up the original electric motor and the flippin thing whizzed backwards and forwards quite happily??? Seeing as I’m grounded for a few weeks I might just connect it all back up and see what happens… It might just get me to 200k?

 

[Santa-2512]

So i left it to soak after it went hard to move again,

With it soaking, i had time to think,


You have probably more chance freeing a stand alone flap assy than one in headers , so pre LC

The 1mm up/ down play in the shaft is in my opinion, a good sign. I found that the shaft walks downward with operation,

and when it bottoms it will stick at the first opportunity.

There are 3 points you can get to to lube things

The upper and lower spindle points inside the exhaust

And hidden in the return spring assy, is the exit for the spindle where the cable guide is welded to

After multiple bathing's in +60c ultrasonic solution & steeping overnight, the spindle was free enough to partially return under the power of the return spring ,

Once I'd got to this state , it hit it with GT40 & used the pull & push method whilst turning the flap via a pair of mole grips on the cable guide

then if was opening and closing under its own steam

Then i brushed Nickel antisieze into the spindle points and as the gt40 evaporated it looks like the

Nickel antisieze has run unto the space between the spindle & bearings

Reassembled and tested, all works (engine not run)

Left for 24hrs and tested again , (engine not run)

I'll put it all back tomorrow and see how it fairs

 

[widget]

I used a blow torch to heat the rolled over part and bend it out so I could get to the carbon stuff bush, machined it out, made a bush, fitted it, heated the rolled over bit to tap it down again over the little washer.

Been fine since.