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Topic-icon R 90 S Updated Breather Valve/Engine now farts

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1 week 5 days ago - 2 days 13 hours ago #5951 by bremoit
25K on bike
Just installed new oil pump seal, rear main seal, push rod tube seals
Bike running fine.

Then, decided to update the old type fiber breather disc to the newer metal version.

Now, when I shut the engine off, I am hearing, sorry for the term, a fart of air. I understand this is most likely being air sucked in thru the rear main seal.
No oil leaks at pan, push rod tubes or else where. Oil level is 3/4 full.
No blow by from the rings, that I can see. No smoke at start up. Rings were in good shape and inspected when push rod tubes were installed.

Questions
1) Why did installing the new disc type breather introduce this new noise?
2) What should I check to see if there is an other issues causing this?
3) Is it something to be concerned about.
Last edit: 2 days 13 hours ago by bremoit. Reason: new title

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1 week 5 days ago #5953 by Wobbly
What is making the noise I can't say, but obviously the new flapper valve is sealing VERY well. The old one was probably allowing some air back into the engine, so there was no noise. Now, with the stronger seal, there's a greater vacuum inside the engine.... which is what you want.

Don't hide 'em, Ride 'em !!
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1 week 5 days ago #5954 by bremoit
Wobs,

Thanks for the reply. Your comments echo my thoughts, exactly. Just trying to get some feedback if there was any reason for concern.

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2 days 14 hours ago #6048 by bremoit
Update:

After a 2 day 500 mile ride, I've got a sheen of engine oil on the transmission shelf. Most likely from the Rear Main Seal, less likely from the oil pump. Both seals were replaced in the past two months.

Issue started with the "fart" after the engine was shut off then worsened to now seeing oil on the shelf.

I did a leak down test, both hot and cold and found R side blowing air thru the oil filler and a 20% leak down. No air thru intake or exhaust.

L side showed less than 5% leak down, no air thru intake or exhaust but some hissing thru the oil filler hole.

Thinking I have blow by at the rings causing excessive pressure and the RMS to weep.

All this happened after I replaced the breather valve with the updated version about 3 weeks ago. RMS and oil pump seal are new and were replaced about 2 months ago.

Questions

1) Should I also do a compression test?

2) Replacing rings, I would do both or just the one side? I would err on the side of both

3) Rear main seal or oil seal compromised and need replacing? I would err, again, on the replacing.

4) Breather installed incorrectly? New breather valve was installed just below flush with the crank case and with the reed opening at 5:30 to line up w. the vent hole on the housing. Used existing housing and a new gasket. Not sure this is the culprit but after I installed it, this is when the farting and oil leak appeared. Normal oil flowing thru the breather and vent hose on the R side. Not too much, seems normal from my experience.

I have not opened up the engine to see where the oil leak is coming from but the shelf reveals a sheen of engine oil.
That plus the farting and air movement from the engine when it is shut off seems to indicate the oil leak is coming from the RMS and a result of bad rings and excess crankcase pressure from the right cylinder.

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2 days 6 hours ago #6053 by Wobbly
1) and 2).....
I would certainly do a compression test before I tore the top end off to replace rings "on a whim". Meaning low compression would be positive evidence that the rings actually needed replacing.

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2 days 4 hours ago #6054 by bremoit
Thanks for the note Wobs. I concur with your comments. Turns out the oil was from the trans input seal. Just changed the trans oil so it was clear/clean and appeared to be from the engine. There is a small nick in the seal housing. Going to dress that up and install a new seal, carefully. I may have cocked it on install.

I did use a puller to remove the old one but may have compromised the housing?

Either way, I know where the oil is coming from. RMS and OP are dry.

Still have the air suction at the RMS to figure out.

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