Anybody ever hear this theory??

9 replies to this topic
  • mnovarossi

Posted July 06, 2004 - 05:02 PM


In my quest to find out why my 426 engine seems to have oiling problems, my local dealer told me if you lay the bike down (crash) and it keeps running, that no oil will be pumped through the engine. To a degree I guess this makes sense,if the oil pump cant scavenge any oil. I dont know, to me its sounds far fetched for the few seconds it lays on the ground running.

  • svotta

Posted July 06, 2004 - 07:19 PM


Easy solution. Don't lay it down. :thumbsup:

  • Hamish

Posted July 06, 2004 - 11:46 PM


The oil that gets pumped around the engine comes from the frame. Even with the bike on it's side, there will still be oil avaliable at the bottom of the frame, unless the bike is completely upside down. In my opinion, a few seconds with no oil pressure when ther bike is idleing will do no damage. The crank is a roller bearing crank and they require very little oil. The first thing to give up the ghost would be the cam journals.

  • sirthumpalot

Posted July 07, 2004 - 01:34 AM


If a 426 would die from lack of oil every time it tipped over, I would have single handedly increased the price of Yamaha stock by 2x. If you're going to run it upside down for quite some time then maybe a problem, for the short time that the bike is tipped over, oil pressure or no oil pressure, no problem. I typically fall at least once every day of moto and my bike is fine after some years of use. :thumbsup:

  • John_Lorenz

Posted July 07, 2004 - 03:22 AM


I will agree with hammish and sirthump. I will also add that the scavenging is done in the engine the frame only holds the oil and is a depository. In theory yes the bike would stop lubing it self simply because the scavenging is done from the Case level. Here is why, If the bike is on its side the sump tank or scavenging tank is dry so the oil pump simply sucks air. But the bike has to be on its side for a long time for this to happen. In theory yes, in practice :thumbsup: There is enough residual oil lubercating the system for ample time to pick your bike up.

Lets just say How many bikes do you see laying on its side running for over 5 minutes

From my point of view any person letting a bike lay down running should be Hog Tied, Horse Whipped and beaten senseless
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  • grayracer513

Posted July 07, 2004 - 02:21 PM


The preceding posts being accurate, let me say that you do a lot more damage when you cold start the engine and rev the crap out of it (ESPECIALLY after an oil change on an 03/04) than when it falls over for a few seconds.

  • mnovarossi

Posted July 07, 2004 - 03:17 PM


Easy solution. Don't lay it down. :thumbsup:

Yea, easier said than done. I end up on the ground at least once per ride. Mainly cause im too stubborn to quit trying the bigger, badder hillclimbs or rock piles, tree stumps or whatever is in my way :devil: Guess I'll just bite the bullet and spend the money on the rebuild, or mabey its time for a 450? Hmmm...

  • Hamish

Posted July 07, 2004 - 10:32 PM


I'd say that the engine would stall from flooding way before any damage occoured, unless the throttle got stuck during the fall. If the engine is doing 10,000rpm on it's side with no oil pressure expect the worst.

  • thumped50

Posted July 08, 2004 - 04:12 PM


Well said sirthumpalot,you just maid me laugh!

  • aford541

Posted July 11, 2004 - 09:16 AM


The dealer is a bullsheister, if you look at the oiling system in the owners manual you can see that the oiling system is a dry sump that means all the oil is in the frame and only a small amount is actually in the motor the bike can run horizontally laying on its side till it fills the motor with oil. If the scavenge side of the pump is not pulling that oil back in to the oil tank (frame)then you will starve the top end for oil but the motor will be full of oil and will splash oil to a certain degree.
It is hard to starve the Yamaha's of oil but I am sure it can be done.

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