" BK " question

If a person only uses thier 426 for MX ONLY and doesnt mind changing oil every race , is converting the 426 from dry to a wet sump something to consider to save weight ? or is it a major remodel to internal parts. Just wondering.


ps Just how much oil is used in a wet sump 426/250 ?

Hi, the only reason that the Pro's convert their bikes from dry to wet sump engines, is to save a little weight. about 2-3 lbs. but i beleive that you gave me the advice one time, "Dont buy carbon fibre, or Ti, buy a jump rope, it will help alot more" so, there it is. also, it HIGHLY reduces the reliability of the engines. those race teams have million dollar budgets, so replacing a 2000 dollar engine every 6 months is no biggie for them, however, for us working folks. it is... also i think it holds just over 1 quart, but you must change it about every 3 hours on the bike...and like i said, its just not a good idea for someone who doesnt have a mechanic,millions of dollars and a factory ride. but go for it if ya want. just my 2 cents.


I agree completely with Eric...for the average person, converting the YZ to a wet sump is not a good idea! I heard that when the YZ is converted to wet sump that they run over 100 degrees hotter than the dry sumps and cut their lifespan in half! But hey give it a try and let us know how long your engine lasted!



I get my kicks on a 2001' YZ426!

Friendswood, TX

" BK " you sure have alot of screen names lol, Calm down people, I have no intension of converting my 426. I was simply curious about what I read and though it might be interesting to find out some details "THATS ALL" oooooh by the way I do have a jump rope, I use it to hold my dust collection.



I don't know where these other guys get their info but converting your bike to a wet sump doesn't make your bike run 100deg. hotter! That would mean our bike would be in the 300 deg. range. No way! Also the myth that it causes more wear is also false. Agreed you must change the oil often, but shouldn't you anyway?! The weight savings is approx 4 lbs. and the engine is freed up a little because you are only turning one oil pump instead of two, and the center of gravity is lowered because you arent storing 2 qts. oil behind the stem.

The capacity is around 1000cc and the temp does go up 10-15deg.

I hope this answers your question



Have you guys considered the potential parasitic losses from windage effects at 11,000 rpm when running a wet sump engine? It's not a coincidence that nearly every successful racing engine is a dry sump design. Seems really dodgy to save a couple of pounds at the potential expense of high rpm power.

Originally posted by Rich Rohrich:

Have you guys considered the potential parasitic losses from windage effects at 11,000 rpm when running a wet sump engine?


What about Husabergs? Those things rev to the moon and they use a wet sump lube system (don’t they?).

As for the YZF/WR, there is a windage vane in the cases that protects the crank, partially separating it from oil interference from the deeper portion of the cases.

Of course you already know this don’t you? Anyway, I don’t think it is that unreasonable to expect a large increase in OIL temp (and resultant decrease in oil life) if you reduce the volume by half, but 100 degrees does seem overly pessimistic.

I wonder if the grabby clutch would go away w/ the wet sump? It seems Yamaha took a two stroke clutch and gearbox and welded it to a four stroke. A two stroke clutch is basically submerged in oil while the YZF/WR has to make-do with a relatively meager supply running out of the hollow main shaft. I wonder if the clutch issue was part of the decision to wet-sump the race motor?

I saw Tim Ferry adjust his clutch several times in Indy, the pros seem to abuse the clutch despite all that extra (factory) 426 thump.

BTW, he looked real fast on that track, didn’t he? He only missed the holeshot, coming all the way from the right side, by a few feet. I couldn’t help but root hard for the guy, another underdog on a blue four stroke…

I've never pulled the bottom end of a Berg apart so I don't know what they have done to combat the effects of windage. It would be interesting to see how much horsepower they lost on a Berg by going to the simpler lighter oiling system in the original design. Anyone want to fund the research? :)

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