Marble mod question

Htown Busa

I did the marble mod on my bike, started it up but now it will not stay started. Have I done something wrong?
Check to make sure when you lowered the tank nothing is pinched or came unplugged. Should't have any issues running with the marble in. I would check to make sure the marble hasn't moved also.
Check to see if anything was pinched and nothing was. Started the bike up with the tank up and it still cut off. I removed the marble and then the bike started and remained on. I am putting the marble in the first hose on this picture.

marble mod.jpg
The big hose on the left is the crankcase breather. You need to put the marble in the hose on the right.

marble mod.jpg

marble mod.jpg
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It reduces pop and backfire on shorty aftermarket exhuast. Works wonders. I used a bolt though, war more secure IMO.
What does this mod do and what after market if any parts need to be installed to do it?


When you install an aftermarket exhaust (even bolt-ons) on a GEN I, it is very common for there to be popping and backfire. This is due to the PAIR valve injecting fresh air into the exhaust system.

There are two ways to resolve the issue:

1) Remove the PAIR valve. This takes a bit of time and also requires that you block off the ports above the exhaust headers (on the head).


2) Perform the Marble Mod. The hose outlined above is responsible for delivering the fresh air to the PAIR valve to be injected into the exhaust. By stuffing a marble in the hose, one is blocking off the air supply.
It is kind of funny. I just went from the picture on the Pair mod post.

Thanks again.

Cap, please don't shut down the site again. It is obvious I need help. :laugh:
All done, thanks. Removed the marble (gave it back to the kids), and went and bought 1/2" furniture leg cap.

thanks again
Ok I am a little lost here. Where is the hose located? On the Front, Rear, Left, or Right side. On the Brocks web site, it looks like it is the hose fwd right side. Thanks in advance.