whole engine rebuilt - no oil on dipstick...?


I`ve got a strange problem. I rebuilt the bottom end of the engine - new crank, bearings, clutch plates and springs, of course new oil filter. I also checked the oil pump and it is in v.good condition.

I filled the engine with +- 1L of oil and when I checked the oil dipstick it was dry.... I`ve checked the engine oil level a milion of times and never had such an issue. I filled the engine with more and more oil and there was still no oil on the dipstick.....

What could be wrong?
I must admit that I didn`t check the piston rings... my fault, I know... The piston and rings have 30 hours already, but it could be worn... I burnded the clutch and all the crap from the friction plates were in my engine...

Afther the rebuilt the engine was washed throughly with brake cleaner and all the dirt removed. Next I filled the engine with oil, ran it for a couple of minutes and flushed the oil. Nextly new oil was poured in

I followed every step mentioned here http://www.thumpertalk.com/topic/756844-oil-change-procedure-for-06-09-model-yz450s/

Edited by thefex

You ran the engine again after you refilled it, yes? 

Yes. I even rode the bike for about 1h until, after that I tried to check the oil and there was no sign of it on the dipstick... tried both just after stopping the engine and waiting 30 minutes.. no difference. it all happened yesterdy.. I will check the dipstick again this evening when I get to the garage

And this is in fact a 2006-2009 model?


Is the dip stick getting wet while the engine runs, but does not show oil when wiped off and dipped?

yes, this is a 2006-2009 model (2008 built year)

its hard to say if the dipstick is getting wet. it gets slightly wet while the engine runs, just on the tip (one drop). when dipstick is screwed into the engine and pulled out it is usually dry.. when the motorcycle is on a stand and I tilt it left about 30* the oil is leaking out of the oil filling hole, so it definiately has oil!


I tested where the oil level is using a ziptie that I put through the hole where the dipstick is screwed in. The oil level was about 10 cm below the dipstick hole in the crankcase

I also unscrewed the oil pressure check screw (the one with a copper washer, just below the carb intake port), the oil is pumping out through it while the engine runs, so the oil pump is ok..

I also unplugged the hose which is connected to the PIPE, BREATHER (5XC-15373-00-00) - number 3 on the diagram - and no oil is leaking out through them (both the hose or the breather pipe #3). I ran the cold engine with the hose unplugged for about 15 seconds and no oil appeared, didn`t want to run the engine for a longer peroid of time though. The hose was unplugged in the place where the #3 breather pipe is located


besides I noticed grey smoke comming out of the exhaust while the engine is gassed. when it`s working on idle or on constant RPM no or very little (hard to say) smoke is comming out... So I assume that the piston rings may not have a proper sealing. But as I said, I raced the motorcycle for about 1-2 hours before I noticed this fault and it worked fine, had power, kept the RPMs on idle and so on


the cylinder head was rebuilt in a professional machine shop, new titanium valves+springs+seals were installed


what could I check to determine what`s happening with the engine? honestly it`s a real mystery to me...

As I said, the cause of the engine overhaul were burned friction plates on Red Bull 111 MegaWatt.. The particles from the clutch friction plates were everywhere in the engine.. I cleaned it as good as I could....

Edited by thefex

One of two things is happening.  Either the oil is not being returned to the tank section of the crankcase, or there is a hole in the case allowing it to flow back to the crankcase instead of staying separated. 


The hose you mention is an air pressure balancing hose, there to keep pressure equal between the oil tank and crankcases.  Shouldn't move oil through that in either direction under normal conditions.


The first thing to look at is the return, or scavenging oil pump.  That's the rotor set that gets installed in the crankcase before you bolt the other oil pump on over it.  Check to see if the pin that locks the inner rotor is sheared or missing.  Also look into the crankcase and be sure there isn't something really dumb, like a rag sucked under the pickup screen.  The dip stick should become covered with oil from the return port running back to the tank, since the port points directly at the stick.


If nothing is wrong with any of that, have a look at the crankcase in the area in front of and below the balancer shaft on the left side, under the flywheel cover.  Occasionally, one finds a dime sized hole in the partition between the oil tank and crankcase in this area due to an unusually thin casting.  This lets oil run back to the crankcase on its own.  If there was damage to the wall between the crank and the oil tank from whatever went wrong with things before you rebuilt it, that could also be the cause.


The oil smoke is most likely due to the incorrectly high oil level in the crankcase causing the crank to sling extra oil up the cylinder.  The rings can do only so much.

thank you Grey for all the help so far!
here are some pictures that I made during the rebuild, maybe you will look something up

http://www.bikepics.com/members/thefex/08yz450f/default.asp?i=2667798&s=0 (scroll to the bottom of the page)

could you please show me which one is the scavenging oil pump?
is it visible on this diagram? http://yamaha-sklep.pl/content/oryginalparts/index/diagrams/323/diagram/10632 ?
 I always thought that this '06-09 YZ  has only 1 oil pump
if you are talking about the pin #3, then I definiately remember putting it in while assembling the oil pump. But I`ll double check on that once I have some time to waste in my garage

so the next thing I should do is disassembling the entire engine once again?
and could any damage have occured to some parts of the engine due to this oil problem that I have?

btw. which way normaly the oil returns to the tank section?

Edited by thefex

now I`m not sure.. but there is a possibility that I didn`t apply sealing in the pink marked area....


That may be the whole problem.  When you apply sealant to the cases, it will physically keep the two halves very slightly separated.  If there is none along the area you marked, oil would then leak out of the "tank" area in front, back into the crankcase. 


In the parts diagram, number 1 is the feed oil pump. It pumps oil under pressure from the tank to the engine and trans parts.  Number 2 is the return oil pump. #3 is the drive pin.




Oil is picked up by the return pump through the sump screen, then sent to the left side crankcase at the ignition cover...





...where it is routed from the lower rear of the cover up to the top of the crankcase near the dip stick...




...where it enters the reservoir, or "tank".  You can see the dip stick is positioned so that oil coming from the return port will splash directly onto the stick (thus, my earlier question about the stick getting wet).  The thin casting holes, if they develop, are usually in the area directly in front of or just below the balancer shaft on the left case shown here.





The lack of sealer is a possibility I hadn't considered, but would certainly cause a problem of this kind.  As you can see from the picture of the right case, oil would have to be extremely low in the engine to actually starve the feed pump, and even with a leak in any of the areas discussed, as long as both pumps were functional, the engine should lube at least adequately.  Given that the return pump moves oil out much faster than it comes in, and that your oil pressure check was good, you probably haven't hurt anything.

great pictures and info, I am very grateful !!

ok, I'll dissasemble the engine once more and pay extreme attention to the oil routes and will post progress

Edited by thefex

I dissasembled the engine and I must say, that we both were right... I didn`t apply sealing on the mentioned surface.. and there was a thorn to little pieces rag in the engine ;)
fortunately no harm to the engine was done, the crank and cams are fine

I also need to replace cylinder and piston. Which is better? Oryginal Yamaha or Cylinder Works? The price is very similar in my country - about $500 for a set

The Yamaha cylinder is a new factory part.  The Cylinder Works product is reconditioned.  Very nicely, but reconditioned.  If they're close at all, go with Yamaha.

 thx for the info! I`ll go with a factory set then
Are the Cylinder Works made in USA?

I have only experience with reconditioned cylinders in England.. they last 1 year of riding, then the nicasil coating is worn to bare aluminum...

Edited by thefex

Cylinder Works is a US company, yes.

Grey, could you also tell me your opinion about Psychic, Nachman and Athena cylinders? They are about 10-20% cheaper

got the pricing from my Yamaha dealer:

- cylinder WORKS - $247
- piston set VERTEX - $170

- cylinder YAMAHA - $290
- piston set YAMAHA - $170

I might have better prices for the piston in a different motorcycle shop

Edited by thefex

Athena makes a good product.  No info on the other two.


Unless you're racing this bike at a pretty high level, avoid using aftermarket pistons with a single compression ring instead of two.  The single ring piston wears faster because it's less stable in the bore, and the ring itself will start loosing significant sealing ability sooner.  The best choice for most people is the stock piston.

The Yamaha cylinder is a new factory part.  The Cylinder Works product is reconditioned.  Very nicely, but reconditioned.  If they're close at all, go with Yamaha.

Gray, just a slight correction the Cylinder Works cylinders are new cylinders and not reconditioned. Thank you.

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