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Yamaha Tech Originally the Yamaha XT600 Tech Forum, due to demand it now includes all Yamaha's technical / mechanical / repair / preparation questions.
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  #1  
Old 10 Jul 2007
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XTZ 660 Dry sump has become wet sump!

I've just aquired this 96 bike and oil is pissing out of the breather pipe into the air box. It seems some oil is returning to the frame/tank, but not enough and the crank is filling with oil. So it seems there is a problem on the scavenging side of the oil system.
I don't have a manual yet so is there anything obvious anyone can suggest to check?
Thanks.
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  #2  
Old 10 Jul 2007
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Well, I don't know your bike/engine but you could start by reading here;-

http://www.horizonsunlimited.com/hub...al-stuff-27640

for general advice. Someone more qualified will come along to tell you more.
In the meantime, you don't say anything about the history of the bike; mileage, general condition etc etc and that is relevant, very relevant.

Welcome to here by the way!!

Dave
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  #3  
Old 11 Jul 2007
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Well

assuming you rode it for a while; if insufficient oil is returned to the tank the result is that the primary oil pump will eventually get no oil, with the related stop in lubrication of crankshaft, piston, camshaft etc. This in turn would have been noticeable immediately :-).
How do you know the oil accumulates in the crankcase?

First check that the engine has not been overfilled. Checking oil level on these bikes has a certain wizardry to it, and you would not be the first getting it wrong and overfilling. -> see other posts.

Auke
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  #4  
Old 11 Jul 2007
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Thanks and thanks for the welcome.
I am pretty well versed on motorcycle mechanics but in the absence of a manual I thought I would try here first in case anyone else had had the same problem.
This is not a minor case of fluctuating oil levels. When oil is added and the engine started the oil level drops very quickly and starts blowing out of the breather so it is obviously flooding the cranckcase. Some oil is returning top the tank but not enough. I suspect a stuck return valve or pressure release valve or broken internal pipe. The return pipe is located under the starter motor. Is there a seperate oil scavenge pump here to return oil to the tank?

Does anyone know where I can get a manual. It is a 1996 XTZ660

Thanks.
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  #5  
Old 12 Jul 2007
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Mmmm ...

In order really to be 'pumped' (as opposed to being taking into the gas stream from increased blow by) through the breather hose you would have to fill the crankcase with oil up to about the level of the oil filter. Would be (guess) something like 12 liters, unlikely.
The oil pump is actually two pumps, no. 1 lubricating crankshaft and highly critical parts, no. 2 scavenging and lubricating gearbox, clutch etc. No. 1 has a non-return valve, no. 2 does not.

My order of checks would be:
1 - Check oil level -> see earlier posts
2 - Check for increased blow-by or other sources of combustion gas entering in the crankcase: worn valve seals, rings, head or base gasket blown

for pump no. 1 scheme is (german):www.xt600.de Ölkreislauf - Special

for pump no. 2 scheme is
www.xt600.de Ölkreislauf - Special

The case ventilation goes through the balancer shaft (on the level of the oil filter) where the gases cool off, oil vapour is separated and supposed to run back into the crankcase. Only, if the gas flows increase with a worn engine, oil droplets will be taken into the flwo and exit through breather hose.

Auke
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  #6  
Old 13 Jul 2007
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Thanks Auke

The schematics were very helpful, although my German is not good.
Your posting prompted me to drain the cranckcase and out drained an amazing 6 litres from the 'dry' sump. I then topped up the tank and ran the engine on tickover for 3 minutes, then drained the tank of another 2 litres of oil. During this time there was, at least, no oil discharging from the breather, so I think blow by can be ruled out. So at least I know it's a scavenge system problem. I've managed to find a manual on ebay so will look further when that arrives.

bob
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  #7  
Old 14 Jul 2007
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Pardon

my disagreement, but having 8 litres (6+2) of oil in your system does not indicate a scavenging problem but an overfilling problem!
Just fill up with the correct amount of oil and she'll be allright.

Or I miss something?

Auke
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  #8  
Old 15 Jul 2007
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Auke

The 6 litres came out of the cranckcase alone. I didn't drain the tank so that was more or less full after draining the crankcase, so 12 litres plus in total!
I've got the manual now and it looks like a staight return of the oil from the pump to the tank on the xtz660, with the gears being pressure lubricated from the feed circuit. Will try and get at the oil pump today.

Bob
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  #9  
Old 15 Jul 2007
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Hi,
What Auke is saying is just fill it correctly, as per your manual - there has been way too much oil in there and that is probably why it has been coming out of the breather - it has to go somewhere when the engine is running!!
That will be the problem (and if it isn't, after getting the quantity of oil to the right level, you can always take the engine apart after that)

Dave
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  #10  
Old 15 Jul 2007
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ps Hman, have you read the other threads on here about checking the oil level on XTs, and the related filling technique? - just do a search for those keywords.

Cheers,

Dave
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  #11  
Old 15 Jul 2007
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Hi Dave
Thanks for the post.
Yeah, I've read most of the topping up subjects. look at my 3rd last post and you'll see that I drained the crank, ran it for 3 minutes and accumulated 2 litres of oil in the sump. The oil is just not returning to the tank fast enough.
I've now removed the oil pump. I can blow down the return pipe at the top of the tank and air will come out of the scavenge oil pump port. If I stick my finger over the port and blow, the air goes into the crankcase, so I think there is an internal leak or crack that is allowing oil back to the crankcase.

bob
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  #12  
Old 17 Jul 2007
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Well, I've looked at everything now. The oil pump seems fine. The scavenged oil goes from the pump through an oilway to the other side of the engine. That is fine. It then goes through an oilway running inside the lower LH engine cover and exits out the top. That is fine. It then goes into an oilway in the LH crankcase about 4 inches and exits through the return pipe junction and is taken back to the tank. Here I think is the problem, because just before the pipe junction there is hole that allows oil back to the cranckcase. One would think that this might be a splash feed to lubricate the gears, but the gears are pressure fed from the feed circuit. The manual shows that the oil returns directly from the pump with no exits, so this hole is allowing oil to return directly to the sump and not enough oil is getting back to the tank.
So what is this hole here for? Please anybody!

bob
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  #13  
Old 26 Jul 2007
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Cool Scavenged Oil - XTZ660

Hi Bob,

My lube diagram from a 94 XTZ660 manuel shows the scavenged oil from the 'hole' you mention delivers oil to the main axle and the drive axle within the gearbox.The gears take their feed from the other side of the pump on the feed side via the filter and oil pipe on the outside of the right hand crankcase.

Best of luck

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  #14  
Old 30 Jul 2007
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Thanks Alec

That's strange. My lube chart for a XTZ660 (3YF) shows a direct return from the scavenge pump to the tank, with the feed pump supplying oil to the shift fork shaft, main axle, and drive axle. From the fork shaft and axle it splashes to the clutch and gears.
My theory is that I have this type and that a blanking plug or screw has detached, and the only way to find out is to split the crankcases. Instead I've reamed out the oil passage and installed a brass sleeve with a small hole to line up with the other (just in case) and the problem has been cured.
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