R90S Breather Valve

[RPGR90s]

I've had the updated reed style breather valve installed in my '74 R90s for about 10 years. But it's retained that idle speed honking that I thought I would eliminate over the stock spring/disc system.

The bike retains it's stock oil pan so it only holds 2.4 quarts. So I keep it pretty near the full mark and it doesn't use any amount of oil.

Symptoms are that once the bike is fully warm, it does the turkey gobble chorus only at idle. Anything above that and it goes away.

Seems like it's finally irking me and I would like to solve it.

Appreciate any guidance.

RPGR90s

 

[jad01]

Ted Porter told me once that the sound you are describing can also be a sign of the rear main seal failing. Do you have any oil on the "shelf" under the transmission?

 

[pglaves]

I had an R90/6 that honked like a Canada Goose. Replacing the orange bobber button with the leaf spring valve did not cure it. The sound was air being drawn in, not pushed out, past the rear crankshaft seal. Replacing the seal cured the problem.

 

[RPGR90s]

Breather

thank Paul and jad01 for your response.

I did replace the rear main seal (to the latest design) when I updated the breather valve to the reed style and there is no weeping, seeping from that area (no oil on the little shelf below the tranny).

If I recall, the new rear main that I installed was a sharper edge style and I had to pre-form it on the flywheel for a set time before installing into the crankcase.
Is there a later design that would work better.

Would there be any advantage in changing the amount that the reed valve opens? IOW, reduce the amount that the reed opens by bending the metal stop that sits atop the reed.

RPGR90s

 

[pglaves]

thank Paul and jad01 for your response.

I did replace the rear main seal (to the latest design) when I updated the breather valve to the reed style and there is no weeping, seeping from that area (no oil on the little shelf below the tranny).

If I recall, the new rear main that I installed was a sharper edge style and I had to pre-form it on the flywheel for a set time before installing into the crankcase.
Is there a later design that would work better.

Would there be any advantage in changing the amount that the reed valve opens? IOW, reduce the amount that the reed opens by bending the metal stop that sits atop the reed.

RPGR90s

I don't think altering the opening of the valve will make a difference. As the two pistons retreat together from top-dead-center the valve is pushed open preventing excess pressure in the crankcase. As the two pistons move together back toward top-dead-center the valve closes and there is negative pressure in the crankcase. This can allow air to be pulled in past a seal. The usual culprit is the rear main seal but in theory a different seal might be causing the noise.

It has been way too long since I have done much with Airhead engines and I don't know the progression of seal changes.

 

[20774]

Does the R90S have a bigger oil pan? My /7 only holds right at 2 liters/quarts (whichever...it takes two bottles!) Anton's website shows the part 11 31 1 262 723 '76-80 and RealOEM says it's the part for the R90S and the /7. Maybe try dropping the amount of oil down to 2 quarts to free up more air space inside the case.

 

[RPGR90s]

Does the R90S have a bigger oil pan? My /7 only holds right at 2 liters/quarts (whichever...it takes two bottles!) Anton's website shows the part 11 31 1 262 723 '76-80 and RealOEM says it's the part for the R90S and the /7. Maybe try dropping the amount of oil down to 2 quarts to free up more air space inside the case.

I l

I believe the stock pan on all /6's was 2.4 quarts. Mine is stock. Both the R90/6 and R90s could have this issue, because of the larger pistons moving more air, than the R75, R60 or R50 (same crankcase).

I think I'll take your suggestion in removing about 1/2 quart of oil and go from there. I know many people updated their oil pans to move the quantity lower (to allow more air space), so that may be an option, but I'd like to keep the bike stock if possible because I still ride it alot. (140k).

Thanks,

RPG

 

[20774]

Easy enough to know what volume of oil you need. Provided you have the stock dipstick, if you pour in 2.4 quarts and it registers full on the stick, then Bob's Your Uncle!

Update...I checked my Haynes and it says for /5 thru /7 up to 1980 without cooler, it takes 2.38 qts or 2.25 liters, so I didn't realize my /7 took that much. For the past number of years, I've been using two 1 liter (1.056 quart) bottles of Spectro oil after I drain the sump and replace the filter. When I recheck oil level after running the engine, the oil is right at the max mark on the dipstick. So, I don't know where the extra 0.38 quarts could possibly go. Are you putting in 2.4 quarts and calling it good? If so, you might be over filling. Again, not sure what your process is for changing oil and checking level on the dipstick. I wouldn't go less than 2 liters of oil in any case for a stock pan setup.

 

[dwalter]

New-to-me '76 R90S. First oil change surprisingly took 2.75L to reach the dipstick Full mark. Blow-by immediately down to ~2.5L (w/filter) to dipstick mark between "2 Ltr" and "Full" marks. I've read where blow-by is common if topped off (R90's) and to just fill to the "engines preferred level". So I must have the deeper sump that was intended to provide some head space above the oil, not intended to increase oil capacity per se.
I too get a few honks at idle.

 

[20774]

Welcome to the forum! How does your oil pan compare to those shown by Anton on his page...any pictures you have from the side?

http://largiader.com/tech/oilpan/

My /7 pan is the -723 pan that Anton mentions, but without the baffles. When I drain, I refill with two 1-liter bottles...the oil is at the full mark on the dipstick

 

[PAS]

Make sure the fill plug is tight! I put an o-ring on mine to seal it good.

 

[dwalter]

Looks like I have the MAC pan. Correction on dipstick ACTUALLY full level, with ~2.5L is between the "2" and "Ltr" marks. Includes filter change of course. Thanks for the oil pan reference.

 

[RPGR90s]

Oil Breather

I removed about 1/2 quart of oil and will do some testing and report back. My theory is that the stock crankcase and the huge 900cc pistons needs just a bit more room to reduce/eliminate/soften the infamous turkey gobble.

RPGR90s

 

[20774]

It will be interesting to hear the results. But my 1000cc engine has even bigger pistons and AFAIK it has essentially the same case as your R90S.

I know I've mentioned this earlier, but I don't remember what the situation was. Are you running the stock oil pan? RealOEM indicates that the /6 including the R90S as well as the /7 have the same part number for the oil pan. I've stated before that on my /7, I drain and put in two liters and the oil is at the full mark. In a /6 owner's manual (as well as my own /7 manual) it says that the oil capacity is 2 liters or 2.25 liters if the filter is changed. I'm not sure where your reference to 2.4 liters is coming from. I would say that is too much.

 

[RPGR90s]

Oil Breather

It will be interesting to hear the results. But my 1000cc engine has even bigger pistons and AFAIK it has essentially the same case as your R90S.

I know I've mentioned this earlier, but I don't remember what the situation was. Are you running the stock oil pan? RealOEM indicates that the /6 including the R90S as well as the /7 have the same part number for the oil pan. I've stated before that on my /7, I drain and put in two liters and the oil is at the full mark. In a /6 owner's manual (as well as my own /7 manual) it says that the oil capacity is 2 liters or 2.25 liters if the filter is changed. I'm not sure where your reference to 2.4 liters is coming from. I would say that is too much.

Yes, I'm running the stock pan.

When doing an oil change, (with filter), I put in two liters, start the engine and run for awhile and check the level after letting it sit overnight. Oil level will be about 1/2 way between the full mark (max/2 ltr) and the lower 1/mm mark. It's always taken another .4 liters to top off to the full mark on the dipstick. (which I assume is stock). So I assumed full capacity was 2.4 liters.

Looking at my original Owner's manual, I see it says it takes 2 liters (as you mentioned), but if changing the filter, add another .25 liters. So it looks like I might be over-filling.

My dipstick measures 10 7/8" (10.857" or 276.225mm) from the bottom of the threads to the tip. I'm assuming that's the stock length? Length to the full mark is 247mm, as outlined in:
http://largiader.com/tech/oilpan/
11 43 1 252 661 metal dipstick with 247mm MAX mark for early bikes (now obsolete)

I've added photos for reference. I'm going to test ride it and see if there's any change. Thanks!

RPGR90s

 

[20774]

I guess we have different dipsticks. Anton indicates that your '74 has a different one than my '78. Indeed, the distance from the underside of the threads to the full mark is 260mm for me. Last time I filled, I put in the 2 liters and went on my way. I just checked and I'm maybe 1/4 to 1/3 down the stick from the full mark. Maybe that's the filter amount called out. But I've never bothered to top it off. It's been said here on the forum that Airheads don't like running with oil at the full mark. Typically what happens is the additives and other misting tends to burn off some amount and the engine settles in to it's "happy" spot. Maybe that's where my bike is at. Hopefully you will find a happy medium as well!

 

[RPGR90s]

I guess we have different dipsticks. Anton indicates that your '74 has a different one than my '78. Indeed, the distance from the underside of the threads to the full mark is 260mm for me. Last time I filled, I put in the 2 liters and went on my way. I just checked and I'm maybe 1/4 to 1/3 down the stick from the full mark. Maybe that's the filter amount called out. But I've never bothered to top it off. It's been said here on the forum that Airheads don't like running with oil at the full mark. Typically what happens is the additives and other misting tends to burn off some amount and the engine settles in to it's "happy" spot. Maybe that's where my bike is at. Hopefully you will find a happy medium as well!

Thanks Steve for sharing that measurement. I'll report back what I find. Can't do it today though. It's snowing here in southern MI.


RPGR90s

 

[RPGR90s]

Breather Valve

After draining and re-filling the crankcase on my R90s with just 2 liters of oil, the turkey gobble noise is totally gone at idle.

I had been overfilling it. I'll use 2 liters as my new capacity.

Thanks everyone.

RPGR90s

 

[20774]

Nice report! Go forth and do good!