Exhaust gas recirculation

[Trailbikeryder]

Hi,

I closed the Exhaust gas recirculation coming out of the cylinder and closed the spot where the exhaust gas goes back into the carburettor. Everything fine. Engine started right up... but, there were "clack clack clack" noises as if the valves needed adjustment. So I put everything back the way it was. Started up, engine came on normal. The clack clack noises were gone.

Question: why would closing the Exhaust gas recirculation cause the engine to do clack clack noises?

I wanted to try this to see if there would be any gain in power. Since the engine was making these noises though, I didn't go for a test ride.

[Krasi_BG]

I closed mine too, but haven't noticed anything different in the sound. But I also put a straight (a.k.a. loud) exhaust.

[Weldangrind]

TBR, please show us a pic of the parts you disconnected and then reconnected.

[Trailbikeryder]

I will post a picture this evening. Krasi, did you notice any gain in power?

[pete]

sound like the motor is pinking...
closing off the exhaust in to the inlet
there is now more space for air "O2"
to be sucked in so now the motor
is running leaner...

dumb ass idea...
you wouldn't run to well if yer had to eat yer own crap
so why would a motor...

SO.......
Are you sure its not a "AIS" (Air Injection System) , which makes a lot
more sence that exhaust gases going back into the motor.
My Yamaha XT660R has one... it lets air into the exhaust
to burn unburnt fuel that enters the pipe... clean air / low
exhaust exmissions etc...
Dose the motor pop/bang on a trailing/closed throttle out the exhaust pipe
as the unburnt fuel in the pipe is burnt..
on the XT closeing it off gives no more power...



.

[Trailbikeryder]

Originally Posted by pete

sound like the motor is pinking...
closing off the exhaust in to the inlet
there is now more space for air "O2"
to be sucked in so now the motor
is running leaner...

.

Maybe I didn't seal the intake on the carberrator properly and it was sucking in some extra air... Or maybe I just Need bigger jets then? Krasi, did you Change your jets?

[Weldangrind]

An air injection system makes much more sense; I think I was short on sleep when I responded last night.

Perhaps the port in the head is just not sealed properly.

Do you have a catalytic converter in the exhaust? If so, the air injection is there to benefit the cat.

[JTHSPACE]

I believe removing parts that you have will kill the cat in the exhaust - you will also have to change the exhaust or cut the existing one open and remove the cat and close it up. I believe I have seen a Highway Hawk silencer fitted which is cat-free. I found it as a youtube video when I watched one of yours, so it is out there somewhere.

This may be a vacuum operated "Air Pump" that puts air in the exhaust after the exhaust valve. It dilutes the exhaust gas mixture and introduces O2. The O2 causes the unburned hydrocarbons in the exhaust to continue burning and reduce pollutants, necessary to meet Euro exhaust restrictions.

See this article from Turner University which may be applicable.

Exhaust Gas Valve

I have seen pictures of similar 250cc engines, some with a little plate oval blocking off a hole in the right hand side of the cylinder and other pictures showing a pipe connected there and disappearing behind the engine into a unit near the starter motor. Is this what you removed?

Video of the Highway Hawk silencer . . .



Jeff

[JTHSPACE]

Just above the heat-shield on the exhaust pipe?

[JTHSPACE]

Here is a video of Overlanders modded Raptor - about 3.5 minutes in you will see the exhaust and the oval blanking plate near the exhaust pipe header. It would need rejetting, I would think . . .

[Krasi_BG]

I didn't rejet, only raised the needle as much as I could. It must be running slightly lean though, as during deceleration it pops from time to time. Which reminds me to take a look at the plug colour just in case.

I think there is a slight power gain, mainly in terms of faster revving. But I could be mistaken due to the higher noise from the open can exhaust.

How did you "plug" the port in the cylinder? I was lazy to bother with gasket cutting, so I just applied a fair amount of black sealant on the aluminium plate I made (black is the fastest colour, right?)

[JTHSPACE]

Originally Posted by Krasi_BG

(black is the fastest colour, right?)

Only if you put some go-faster lines in the sealant, at least .5mm deep and 5mm apart and horizontal to the ground. Many make the mistake of putting vertical lines in and it has the opposite effect and you lose any speed benefit.

[Trailbikeryder]

Where the two red circles are, is the places I closed. Doing this deactivates that pump or whatever that is in the green circle. This bike has the cat in the pipe where the heat shield is.
(thats not my bike on the Picture. I didn't get to take a pic of mine)

I cut a peace of 3mm sheet metal and use the original gasket to Close the Output. The Input nob I closed using a Little rubber cap I found in the garage in a junk box. It was slighly too big, but I used a Little round clamp I put over it. But maybe it still wasn't tight enough and the intake was still pulling air..

Maybe if I put some racing stripes on the front Fender the bike will be faster? The flames on the tank didn't help though.

[Trailbikeryder]

@JTHSPACE
Very interesting article. I think on These bikes its always open. because he says:
"The EGR valve does not open under heavy load" So, I think cars (or more modern engines in General) have the more intelligent System.

[JTHSPACE]

Originally Posted by Trailbikeryder

(thats not my bike on the Picture. I didn't get to take a pic of mine)

Maybe if I put some racing stripes on the front Fender the bike will be faster? The flames on the tank didn't help though.

The pic is the bike I am trying to buy (dealer response is sooooo slow) and I hope it doesn't have little red circles painted on it when I eventually take delivery.

I generally find "go faster" stripes only work if you are under the age of 25.



Is the clack-clack sound definately coming from the engine? Using the old fashioned method of holding a short piece of wood against the engine and your ear (short piece of broom handle) can you pin-point more accuratly where the sound is loudest?

If you cut 35cm off the end of the house broom, it is fun watching the next user wondering why their arms no longer work with the broom. You just have to keep a straight face . . . .

Jeff