alot of "bubbles" on oil dipstick...normal?

8 replies to this topic
  • bendover932

Posted May 20, 2009 - 05:27 PM


well first off let me say that for the last 14 hrs (time that ive owned the bike) ive been changing to oil incorrectly...

ive been draining the oil from the bolt on the bottom of the right side case and changing the filter...didnt know about the bolt on the left and removing the dipstick and oil fill caps..(until the thread on "proper" oil changes surfaced the other day) and then adding a liter of silver yamalube oil each time...3 times

i noticed that after riding when the bike was on the stand that there would be a discharge from the vent tube...didnt think much of it...but then the other day the bike seemed to "come uncorked"..and started to really run like a monster.. pulling alot harder on top ....and the temp/humidity were withing a couple degrees of the day before..nothing new on the bike except for a pro taper twister throttle tube..(which ive had before and not noticed any "performance" gain)

so after reading the correct oil change method i went out to the shop tonight popped out the "check bolt" i also didnt know about and a pretty good amount of oil came out...didnt measure it but was a good amount..followed the correct oil change procedure...and added a scotts ss oil filter ...when i checked the oil after running and letting it sit for a couple mins...the oil on the dipstick was almost frothy/foamy....not like milk..but when i wiped it onto my finger and let it sit for a bit the bubbles would go away and it was back to oil....when draining the oil it was normal not milky like water contiminated....radiator is full..

so my question is... is that normal since this is my first "proper oil change"..ive never run the bike then checked the oil...or is this a sign of some possible damage ive done by running too much oil..? im scared to ride it now for fear of blowing it if there is some relatively simple fix first.....i also ran the bike and sprayed carb cleaner around the carb boot/head/cylinder base gasket/center case areas to try and rule out pulling air and causing a lean situation..and nothing....advice/opinions anyone?...

  • grayracer513

Posted May 20, 2009 - 07:23 PM


On the '06+ models, the return oil from the sump is routed back to the reservoir so that it flows across the dip stick as it enters the "tank". In all dry sump systems, the return pump has roughly double the volume capacity of the feed side so that it can always pump the oil back to the tank faster than the feed pump can deliver it to the engine. This results in the return pump "running out of oil" as it picks up oil faster than it shows up in the sump, and because of this, it slurps a lot, blowing bubbles into the return oil line, and onto the dip stick, where you see it.

  • bendover932

Posted May 21, 2009 - 02:31 AM


thanks gray! its nothing to be worried about then?..i was concerned that by running too much oil all this time that it might have blown some seals or gaskets and that was why it was that like a kinda poor all the oil foamy or just what the dipstick contacts?...i checked it 15 mins after running and i still had foam...wouldnt the air bubbles take up space making what reads as in the cross hatches actually be low without the bubbles?....or am i just over thinking this all?...hahaha...just dont want to blow this thing

  • grayracer513

Posted May 21, 2009 - 06:33 AM


The air is coming from the crankcase, and is blowing ON to the feed oil in the reservoir, not IN to it, so it won't raise the level.

Also, because the YZ is a true dry sump, excess oil may cause smoke or oil discharge at the breather, or messiness in general, but it won't interfere with the engine oiling.

If you use this oil drain procedure, including the filter, and always fill with exactly one liter, you won't have too much oil in it, ever.

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  • bendover932

Posted May 21, 2009 - 04:00 PM


gotcha...thats the thread i read that made me realize i was screwing it

one last question...does the oil drain down/away from the dipstick area after sitting say ..overnight?...i followed the method you linked to last night discovered the air bubbles but the level was in the cross hatches... and tonight i just pulled the dipstick without starting and the oil is maybe 1/8th on the bottom of the that normal .....since when i was not removing the left side drain bolt ,fill bolt or dipstick....and still adding 1000 cc's and i would check the dipstick without starting and it was always in the cross hatches...just want to make sure its ok prior to racing this weekend...thanks a ton gray!

  • grayracer513

Posted May 21, 2009 - 05:55 PM


The feed oil in all dry sump systems tends to drain down to the sump over time. The Gen2 450's ('06+) have a much lower tendency toward this than the older YZF's simply because the feed oil supply is so much lower, and nearly at sump level already.

By not draining the left plug, you were leaving the feed oil supply nearly full. When you read the stick without starting it, it showed up. It would not have ever reflected the grossly overfilled state it was in because there is almost no room for more than a full normal charge of oil. When the return pump tried to pump an extra 800cc into the tank, the excess was force out through the pressure balance vent (external hose) and back to the sump.

  • bendover932

Posted May 22, 2009 - 02:29 AM


Well my bike is an 07 yz 450... I drained all bolts per the proper method...installed a scotts ss filter...1000 ccs of yamalube 15-40.... Ran for a minute checked the oil the level was fine...just foamy... Just about 24 hrs later I checked the level again without running the motor and it was maybe an eighth of an inch on the very bottom of the said days for it to drain out of the I have a problem?....Or do you need to run the motor then let it rest a minute to get the proper reading?

  • grayracer513

Posted May 22, 2009 - 05:05 AM


No, you don't have a problem. As I said, ALL dry sump engines will drain the feed oil back to the sump as they sit. The steel frame bikes will drain all of it back eventually. The Gen2 engines will stop at the point where the level in both volumes matches, but they still do it.

And yes, once again, you have to run the engine for a minute or so, shut it off, and wait 30~60 seconds in order to get an accurate read.

  • bendover932

Posted May 22, 2009 - 11:22 AM


Ok great, thanks for all your help!

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