Negative Pulse

3 replies to this topic
  • thumpy

Posted November 21, 2001 - 10:20 PM


I was at my suspension guy's shop a couple months ago and noticed a brand new 426 on a stand with the top end off. I asked what was wrong with it and he said it only had 20 minutes on it, it was brand new. His first trip was out to the dunes with a Pro-circuit pipe. Evidently, the 426 has a negative pulse that sucks air into the pipe at the same time it's blowing exhaust out. This phenomina sucked sand down the pipe and into the cylinder filling it with sand. When the pipe was removed about two handfulls of sand poured out of it (where it joins the head). The moral of the story is, don't use a Pro-Circuit T-4 type of pipe if you're gonna be riding in the sand. Use a disk type ala White Bros.

p.s. The head bearings were full of sand also. Sand is real hard on mo-sicles....

  • holeshot

Posted November 21, 2001 - 10:34 PM


Well that's strange - I've had my 426 (T4 pipe) in the dunes in the middle of a sand storm with no problems. It still rips.

I wouldn't let the bike sit (not running) for a extended period with the open exhaust facing into the wind though. The pipe could fill with sand, which could be sucked in when you first kick it over.

There's no way sand can get in once it's running. A grain of sand can't be sucked from the tip of the exhaust, all the way down the length of the pipe and the into the cylinder while the engine is firing and exhaust gases are blasting out. I'll agree that sand is hard on mo'sickles though. :)

The moral of the story is, "don't p* into the wind" with an open end pipe unless you put a cork in it.

[ November 21, 2001: Message edited by: holeshot ]

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  • thumpy

Posted November 21, 2001 - 12:18 PM


I thought it sounded strange but, what do I know! It was a very bizzare deal to say the least. I'd like to talk to the owner of said sled to get the whole story. I thought I'd post this to see if anyone else had heard or experienced this same phenomina and for god's sake don't pi$$ in the wind!

  • sirthumpalot

Posted November 21, 2001 - 01:33 PM


I sure hope that your suspension guy sticks to suspension. There is no way that I see for sand to get "sucked" into the motor through the exhaust of a running bike.

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