Breather hose breathing too much... or not?

[mg94]

Hello guys, I need a bit of help understanding a possible issue with my 2000 SM 610 S. About 5000 kms ago i bought and installed a HTM Hi-comp piston (claimed 12.5:1 compression ratio), along with that i replaced the cylinder because it had deep marks on one side (could feel them with fingers) with a used one that had the normal signs of wear. A trustworthy mechanic told me it was usuable without having to polish it and that it fit piston tolerances, so i installed both the new piston (with new compression ring and oil ring) and the used cylinder. I did about 1000 kms of breaking in, then I changed the oil and filter and started using the bike normally.

I did overfill it a bit - not much, just above the two white marks on the left side - in fact when I first noticed that oil was dripping down and out of my airbox i thought that was the reason, so I removed the necessary amount with a small tube, checked oil level, cleaned the airbox and called it a day. After a while the problem was back, so I decided to unplug the breather hose from the airbox and leave the oil vapours puffing freely in the atmosphere.
Thing is, when I open the throttle there's quite the vapour jet coming out of the hose, though no liquid oil is ejected. Worrying thing though: the oil deposits smell a bit of combustion, and that's not a very good sign...

Now, the bike doesn't seem to eat oil, but i have some oil leaks from the stator cover so I can't be 100% sure about that - we'll see when i fix those.
So i was thinking piston rings, even if that doesn't make that much sense considering that I don't feel her down on power and the piston is pretty much new. If a member would be so kind to film their motorbike's breather hose gasses I would really appreciate it; in the meantime I will do the same, though can't be sure when

Whaddya guys think?

 

[PawPaw]

I am not sure about your ride, but I know that modifying the OEM breather set up on my 2013 TC 449 cured this issue. This type of mod may do the same for you.

Paw Paw

 

[mg94]

I am not sure about your ride, but I know that modifying the OEM breather set up on my 2013 TC 449 cured this issue. This type of mod may do the same for you.

Paw Paw

What did you do exatcly? Thanks for the response!

 

[Spice Weasel]

If a member would be so kind to film their motorbike's breather hose gasses I would really appreciate it; in the meantime I will do the same, though can't be sure when

Whaddya guys think?

I recorded this with my phone. 08 fuel injected 610 with 10900 miles. I let it idle until the fan came on (about 10 mins) then made the vid. Hope this helps
> Click for link to video <

 

[Theo]

Thank you for the video, it's interesting.

 

[Spice Weasel]

Thank you for the video, it's interesting.

I didnt think it was very interesting, its exactly what i expected to see. I would bet if i took it out for a 15 minute thrashing, that the vapours would probably double. mg94 seems like a decent guy, so thought it wasnt too much trouble to try and help.
Thats insulation tape on the hose, to make it a tight fit, i was just too lazy to trim it.

 

[mg94]

Sorry for the late reply, but really appreciate your effort spice weasel. Something might be up with mine, you seem to get barely any vapour when idling, but so do I.. The problem gets more severe when I open the throttle. I will try to post a video. Anyway, thanks SW and the others

 

[mg94]

Sorry for DP but I apparently can't edit my posts.
I watched SW's video on my pc with greater detail today and noticed the vapours, and TBH it looks exactly what my motorbike does... So at this point I may get my compression checked but I guess it's just crappy airbox design, since on my model it's open on the lower end and any deposited oil drips down pretty easily.

 

[Spice Weasel]

Sorry for DP but I apparently can't edit my posts.
I watched SW's video on my pc with greater detail today and noticed the vapours, and TBH it looks exactly what my motorbike does... So at this point I may get my compression checked but I guess it's just crappy airbox design, since on my model it's open on the lower end and any deposited oil drips down pretty easily.

You could see the pooled oil in the bottom of my airbox in the vid, i think it must soak into the foam filter, because i havent noticed it dripping.
I tried to get the best recording i could with my phone, i used an inspection lamp to try and show the vapours. Its the best i could do.I dont have anything else to record with.
Just keep checking your oil level and keep riding it. As long as its not using lots of oil, dont worry.

 

[mg94]

Since things about my bike evolved a lot lately, I thought i could update you guys about the issues that I had.
I recently had to redo my top end because the bike was smoking white from the exhausts, and it was eating plenty of oil. I discovered that the lower ring of the oil ring assembly dislocated itself from the its seat and broke in half. But that only happened when the bike started smoking (recently), becuase I found some pieces of it in the RH oil screen when i disassembled the bike to fix the top end. But since i checked the oil screen about 1000 km before the troubles, it couldn't be the culprit of the oil-in-airbox nightmare.
Took out the piston and the rings, which were both covered in burned oil. Brought both to the mechanic, who told me that he had big troubles with those kind of oil rings because they simply wouldnt do their job and oil would get into the combustion chamber super quickly.
He told me that he had similar problems with a CRF 450 and Athena Pistons - he had to remake the top end 2 times before he realized that it was the rings' fault. Symptoms were similar - after 300-400 kms the bike would smoke white from the exhaust.

Unfortunately, I can't seem to find the oil ring to take a picture, but in layman's terms it differs from most oil rings because its 'S' shape is rotated 90° compared to stock Husky oil rings. I will look into providing a picture, deeply sorry for the lousy description.

TL; DR: I highly discourage anyone to buy an aftermarket piston with the aforementioned oil ring desing. Mechanic told me that since the rings are manufactured separately from the piston, any manufacturer could potentially use them, for any motorcycle model.

 

[Raaron12]

Here is the best info on the breather hose modification. http://rickramsey.net/TE610mods.htm Did the mechanic check the clearances on the piston and cylinder? If the clearance was too great and out of spec that could have been why the oil ring unseated. Are the husky cylinders not serviceable, can you not bore them or resleeve them? I am just curios as to why you rebuilt the top end in the way you did?

 

[mg94]

The piston/cylinder clearances were measured beforehand and after the disassembly and both times they were in spec (the cylinder measured 97.99-98.00 and the piston measured 97.95). Yes, you can "resleeve" them but it's cost prohibitive since it can't just be bored out but the nikasil sleeve has to be removed and then redone in spec. The cost of the operation ranges from 150 to 200 € depending on cyl size. On the other hand, the nikasil cylinders are much more durable and do not wear out like cast iron ones.
Thanks for the link, but if the source of that problem was the faulty piston ring, I'm going to keep the hose plugged into the airbox, since the fumes expelled are EXTREMELY cancerous.