# YT660 - Engine oil bubbling out of filler neck



## Lunta

I changed the engine oil towards the end of last season, topping it up to bring it level with the filler neck hole (as per instructions).


In early autumn I drove the machine outside and gave it a general lube, brush-up and treated a couple of rust patches. When I unscrewed the filler cap, I noticed some engine oil overflow out of the filler neck. I thought this must be because the oil had expanded a bit during the summer and didn't think much about it.


The machine wasn't used until today. It was around -5°C (23°F) in the store. The blower was parked on a level surface and I checked the oil level before start-up. Again oil glugged out of the filler hole. 



Any ideas?


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## gibbs296

If she is "making oil" it has to be from fuel getting into the oil. Carb needle/seat issues if its an air cooled carbureted machine.


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## Lunta

Oh dear, that sounds serious.


The machine is <1 year old. Any pointers on how I can confirm that it's the carb/needle seating? And whether this is an "easy DIY fix" or whether it should go in for service?


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## gibbs296

I assume it still has warranty on it and even if it doesn't a machine as nice as that should go to the dealer so factory quality parts are used for the repair. It may be something that they have seen before and should know the correct procedure to repair it.


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## Lunta

I collected some of the overflowing oil and it didn't smell like fuel.


But I will still be contacting the local Yamaha dealer to get her booked in. Not the best time of year though.


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## Coby7

I doubt there's anything wrong with your engine. I think you just overfilled it when you did the oil change. Engine has to be level when you fill it to the mark on the dip stick. It is easy to overfill if the auger mouth is lifted a bit.


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## Lunta

@Coby7 I appreciate your comment but I'm pretty sure I was level when I did the oil change.


I have read some boating forum information and it seems Yamaha has had issues with "making oil", at least on those marine engines. It seems the rings were not seating properly. No idea if that could be a similar problem here, or whether it's as Mr Gibbs originally suggested.


For one reason and another, I'm wondering whether I should try a fresh oil change and monitor the unit closely over a few hours running. The local Yamaha dealer isn't exactly the best there is (couldn't be bothered to even quote for a new machine which meant I bought elsewhere, and later when I visisted the service desk they refused to order the "Yamalube" specified in the manual, on the basis that he would need to order "a pack of 12"). So I'm not exactly enthusiastic about dealing with them..


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## gibbs296

A cellphone is your best friend. Find another dealer or use the web to contact Yamaha customer support. Hopefully they can provide some answers.


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## skutflut

It may be that your machine is not completely broken in yet and rings have not seated completely, but rings are not going to create more oil in the engine. 

Did you store your machine with gas in the tank over the summer? Was there any gas left in the tank when you started it during your maintenance work or had the gas mysteriously disappeared from the tank. Does your machine have a fuel shutoff valve? If it does was it closed? If it does not have a shutoff valve, I would suggest you install one.

You might want to try changing the oil again, and making sure that you close off the fuel valve so that in case the needle in the carb is leaking, the leak will be prevented with the fuel valve closed. I always close the valve on my machine, and then let it run until the gas in the carb is used up and it stops by itself. 

You also want to used conventional oil for the full amount of time specified in the manual for the break in period. Do not use synthetic until the engine is fully broken in.

If you have a warranty on the machine that is still in effect, then you need to refer the problem to the dealer to be corrected. If you tamper too much with the machine trying to diagnose the problem, your dealer might decline to do warranty work due to the tampering.


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## 1132le

It's over filled
Change it again and add manually until full not the amount the spec calls for and see how much it takes


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## foggysail

Coby7 said:


> I doubt there's anything wrong with your engine. I think you just overfilled it when you did the oil change. Engine has to be level when you fill it to the mark on the dip stick. It is easy to overfill if the auger mouth is lifted a bit.


Yeah....I agree, too much oil. But go back to the OP's thread where he states:

''I changed the engine oil towards the end of last season, *topping it up to bring it level with the filler neck hole *(as per instructions).''


I have never ever seen that much oil required in an engine. Maybe he has an engine that has such requirements but...


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## Lunta

@skutflut Thanks for super advice.


_Did you store your machine with gas in the tank over the summer?_ _Was there any gas left in the tank when you started it during your maintenance work or had the gas mysteriously disappeared from the tank._



Actually I thought I stored it full but it wasn't full when I checked in autumn. That was puzzling me and I was doubting my memory...



_Does your machine have a fuel shutoff valve? If it does was it closed?_

Yes and yes


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## Coby7

foggysail said:


> I have never ever seen that much oil required in an engine. Maybe he has an engine that has such requirements but...


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## Lunta

foggysail said:


> Yeah....I agree, too much oil. But go back to the OP's thread where he states:
> 
> ''I changed the engine oil towards the end of last season, *topping it up to bring it level with the filler neck hole *(as per instructions).''
> 
> 
> I have never ever seen that much oil required in an engine.



Page 45 of the user manual. Feel free to expand your own knowledge by checking out the picture above the text, "Correct engine oil level".


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## Lunta

Aha, Coby7 seems to be helping you out


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## Coby7

I believe the problem lies with one phrase in that picture. "Warm up the engine for several minutes" 
Now if I remember correctly oil expands with heat, so if you fill it to the line with cold oil and then start the engine to check it you can be sure of one thing oil is going to flow out of the crank case no question. When I filled mine with this in mind I didn't fill to the top, I just filled to the first mark on the dip stick which is about a ½" from the top and after running it, it still flowed oil from the filler neck. Let it flow out, you now have the right amount in the crankcase.


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## 1132le

what he said coby7 said
kinda hard to over fill that style plug mine is right to the brim on the414cc its fine
notice no difference cold or warm other then complete drain back cold
if you have no gas leaking in your set


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## Lunta

Coby7 said:


> I believe the problem lies with one phrase in that picture. "Warm up the engine for several minutes"
> Now if I remember correctly oil expands with heat, so if you fill it to the line with cold oil and then start the engine to check it you can be sure of one thing oil is going to flow out of the crank case no question.



The "warm up the engine for several minutes" does not appear in my user manual. It instructs an oil check before start-up, and shows that same picture to indicate that the level should be in line with the filling spout lip.


The picture you're showing is from the workshop manual and I think they've screwed up the descriptions on that page. The two main mistakes they have made are:


1. No need to warm up engine before checking oil level.
2. No need to replace O-ring and filler cap when you've simply been checking the oil level.


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## 1132le

it should be right to the brim pretty easy


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## tadawson

Pretty much the same fill procedure that was used on L head Tecumsehs pretty much forever . . .and almost impossible to get wrong without significant effort . . .


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## skutflut

I think the only thing you can get wrong with that filling/level plug method is to forget to put new oil in after draining the old oil. Had a neighbour who did that one year, drained the oil in spring, didn't refill it right away. I guess he forgot to check it before start up the following winter and guess what happened...

I have a Honda engine on my Toro lawn mower with the same fill/level system and your can' mess that up, unless you end up pouring in too much which promptly drains out all over the mower deck and makes a mess, but the correct amount is still in the crankcase.


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## foggysail

Coby7 said:


>




Thanks Coby :smile2:


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## Lunta

Daylight finally came and brought some snow. Oil change is now done (non-synthetic, thanks Mr Gibbs) and I closed the fuel tap and let it die out itself (thanks SkutFlut  )


I'll monitor the situation and update results/solutions in case it helps someone else out.


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## DriverRider

Lunta said:


> I changed the engine oil towards the end of last season, topping it up to bring it level with the filler neck hole (as per instructions).
> In early autumn I drove the machine outside and gave it a general lube, brush-up and treated a couple of rust patches. When I unscrewed the filler cap, I noticed some engine oil overflow out of the filler neck. I thought this must be because the oil had expanded a bit during the summer and didn't think much about it.
> The machine wasn't used until today. It was around -5°C (23°F) in the store. The blower was parked on a level surface and I checked the oil level before start-up. Again oil glugged out of the filler hole.
> Any ideas?



Simple explanation.:smile2: As the crankshaft turns various parts of rod, crank and slinger will contact oil in sump displacing it.
As evidence, remove oil fill cap and very slowly rotate crankshaft one turn and watch the oil level rise and fall.:grin:


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## Lunta

Thanks DriverRider for the reply.  I understand the principle but I fear there is another cause. I've seen an increased oil level on three different occasions in the last 3 months, but the oil level was steady before the 15-20 times I used it last season.


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## RIT333

Sounds like you may be adding gasoline to your crankcase from a leaky carb. needle valve.


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## foggysail

RIT333 said:


> Sounds like you may be adding gasoline to your crankcase from a leaky carb. needle valve.


Would you explain how that can happen? I would think a leaking carburetor would leak external to the engine proper


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## RIT333

foggysail said:


> Would you explain how that can happen? I would think a leaking carburetor would leak external to the engine proper



I have had a spec of dirt between the needle valve and the n.v. seat, and the gas will fill up and then enter into the crankcase thru the intake manifold. This was on a B&S 14 HP Intek engine - not sure what exact carburetor. 



Take a sample of your oil and see if it has any gasoline smell to it.


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## JnC

No need to worry, Honda GX motors are the same way, fill them to the brim as per the owners manual, check it later and it overflows. The first time it happened I had checked the oil right after running it for a while, one thing I did notice was that the oil had a lot of bubbles in it. The oil gets agitated due to the elbow/arm stuck to the piston rod causing the bubbles; also, when you checked the oil the protruding arm may be in the down position dipping in the level oil causing it to come up a bit.


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## 132619

foggysail said:


> Would you explain how that can happen? I would think a leaking carburetor would leak external to the engine proper


just had the same issue on a troy bilt, leaked internally into the manifold into the bore via the intake valve,past the rings into the crankcase, the needle was gone, 
new carbs seem to be unlike the olders for epa/carb gas vapor rules,


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## foggysail

33 woodie said:


> just had the same issue on a troy bilt, leaked internally into the manifold into the bore via the intake valve,past the rings into the crankcase, the needle was gone,
> new carbs seem to be unlike the olders for epa/carb gas vapor rules,




You fellows have made me a believer.


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## Lunta

Lunta said:


> Daylight finally came and brought some snow. Oil change is now done (non-synthetic, thanks Mr Gibbs) and I closed the fuel tap and let it die out itself (thanks SkutFlut  )
> 
> I'll monitor the situation and update results/solutions in case it helps someone else out.



No further problems encountered, everything is exactly like it was last winter.


I have been turning the fuel supply off and letting the motor die on its own.


Also... another Yamaha owner told me that they had engine oil bubbling out of the filler hole at the beginning of this season. So maybe it is a feature.... Certainly hearing that made me slightly less concerned.


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