What oil for rotary valve?

16 posts in this topic

Posted

What oil have people used successfully for their rotary valve reservoir. I have been using the same synthetic 2-stroke TC oil that I use for the fuel. My Avid has not flown in over a year and a half due to some repairs and then more repairs/replacements after the main gear was underwater during Hurricane Harvey. I think I may have rotary valve oil leaking past the internal crank seals now. I have done several ground runs and the oil level has dropped in the reservoir after each run. There are no external signs of an oil leak. I was wondering if a slightly thicker oil could be used to slow the leak. The engine is running great and I hate to send it for a complete overhaul for just a seal leaking. I am going to try a few more ground runs to see if the oil level will stabilize.

Thanks, Dan

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Posted

I think most people use the same oil as they use for the fuel.  That's what I've always done.  If it sits for a while, do you notice any oil in the carbs?  (looking in with the airfilter off)   JImChuk

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Posted

If the RV seals are leaking its only a matter of time before you find yourself in a really bad situation (and a really quiet engine).  Its pretty easy to pull the shaft and replace the seals yourself.  

:BC:

 

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Posted

Those seals were replaced a couple years ago. No issues with those. I am thinking I might have an issue with the crankshaft seals and the oil being sucked into the crankcase.

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Posted

even worse... do a leak down on the engine and you will know for sure.

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Posted

A leak down test on the crankcase? Wouldn't that require plugs for the intakes and exhaust ports? How would I know what air pressure those seals should be good for? If air goes past the seals there will be air bubbles in the rotary valve reservoir.

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Posted

Rotax Rick ships with regular 30 w oil, since the rotary valve lube doesn't get burned. Says it is better lubrication, and not compromised by the need to burn clean.

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Posted (edited)

A leak down test on the crankcase? Wouldn't that require plugs for the intakes and exhaust ports? How would I know what air pressure those seals should be good for? If air goes past the seals there will be air bubbles in the rotary valve reservoir.

You don't want very much pressure.  5 lbs at the most.  I built on once that used a blood pressure bulb to pump the air in.  That was all you needed.  Mike Stratman, who used to own California Power Systems  (CPS catalog) wrote a nice article years ago about pressure testing two stroke crankcases like that.  I'll try to dig it up.  JImChuk

Not the article I was thinking about, but I found this right away.  https://www.motorcycleclassics.com/mc-how-to/pressure-check-a-2-stroke-engine

Again, not the article I wanted but another one Mike did.  https://www.cps-parts.com/cps/pdf/Part59.pdf
 

Edited by 1avidflyer

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Posted

Rotax Rick ships with regular 30 w oil, since the rotary valve lube doesn't get burned. Says it is better lubrication, and not compromised by the need to burn clean.

I just read that somewhere. I am thinking about changing the oil to 30w to see if it makes a difference. I guess if I see a change in smoke from the exhaust that might confirm the leak as well.

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Posted

You don't want very much pressure.  5 lbs at the most.  I built on once that used a blood pressure bulb to pump the air in.  That was all you needed.  Mike Stratman, who used to own California Power Systems  (CPS catalog) wrote a nice article years ago about pressure testing two stroke crankcases like that.  I'll try to dig it up.  JImChuk

Not the article I was thinking about, but I found this right away.  https://www.motorcycleclassics.com/mc-how-to/pressure-check-a-2-stroke-engine

Again, not the article I wanted but another one Mike did.  https://www.cps-parts.com/cps/pdf/Part59.pdf
 

Thanks for the interesting articles. I would have to fabricate and order some parts to run the CPS test. He was checking for air leaks into the combustion chamber. Would the same test work for the oil leak? Maybe it would need to hold vacuum longer? If changing to 30w oil doesn't change anything I might try to set up for the CPS test.

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Posted

Rotax Rick ships with regular 30 w oil, since the rotary valve lube doesn't get burned. Says it is better lubrication, and not compromised by the need to burn clean.

I just read that somewhere. I am thinking about changing the oil to 30w to see if it makes a difference. I guess if I see a change in smoke from the exhaust that might confirm the leak as well.

I should have added that Rick said to watch the oil level in the small reservoir. If it starts going down, that says you are burning the oil, so then switch to the 2-stroke oil (Amsoil) to prevent any dirty burning. I have about 10 hours so far, the oil level hasn't budged. My old 582 (using Lucas 2 stroke oil) never showed any level change in 160 hours.

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Posted

Dan:

 

Use the same oil as used in the fuel and make sure you have no air in the rotary reservoir a nd associated lines.

It's been a while since I drove a 582, but I seem to remember the Rotax manual describing how to fill the rotry valve reservour to prevent air in the lines.

John M

 

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Posted

The oil loss is erratic. I filled the reservoir above the full line this afternoon then Made 2 take offs and landings. With taxiing and runup that was about a half hour of run time with no oil loss in the reservoir. Then I flew to the neighboring airport made 2 more landings and returned to home airport for just under 1 hour of run time. After that the reservoir was down at least 1/2 inch. It is not air in the system. It has not been drained and refilled recently. I will be tearing down the motor soon to take a look and decide what to do from there.

It's too bad. The engine performance is great right now. My home airport has a 600' pattern altitude and it gets there quick

Dan

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Posted

I tried SAE 30 oil in the rotary valve reservoir with the same problem. It was definitely burning the oil.

I have now pulled the 582 off the Avid. I was going to put my piston/cylinders on another 582 that was sitting in the hangar with piston issues but nixed that plan when I pulled those cylinders off and found a lot of play in the rod bearings at the crankshaft.

Is there any alternative to buying a new crankshaft just to replace the inner seals? Is there anyone that can rebuild this crankshaft successfully and at a reasonable cost? It kind of sucks to have to go through $2000 worth of parts for a rebuild just to replace 2 seals.

Dan

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Posted

I tried SAE 30 oil in the rotary valve reservoir with the same problem. It was definitely burning the oil.

I have now pulled the 582 off the Avid. I was going to put my piston/cylinders on another 582 that was sitting in the hangar with piston issues but nixed that plan when I pulled those cylinders off and found a lot of play in the rod bearings at the crankshaft.

Is there any alternative to buying a new crankshaft just to replace the inner seals? Is there anyone that can rebuild this crankshaft successfully and at a reasonable cost? It kind of sucks to have to go through $2000 worth of parts for a rebuild just to replace 2 seals.

Dan

Is this a pressed together crankshaft? I have a Yamaha engine in my jet ski that was a two piece crank. I purchased just the half I needed replaced and my local snowmobile repair shop took the old one apart and pressed the new part in place. It's common practice in many of the sled engines.

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Posted (edited)

PS  after I posted this, I went back and reread the start of your thread.  Still wouldn't hurt to be sure the shaft seals aren't leaking.

 All of these 2 stroke Rotax crankshafts are pressed together.  Are you sure the crank seals are leaking.  There are also seals on the rotary shaft that keep the oil from being pulled through to the rotary valve and then get sucked into the crankcase.  Look at these links.  JImChuk  https://www.cps-parts.com/cps/pdf/Part50.pdf
https://www.cps-parts.com/catalog/rtxpages/582crankcase99.php
 

Edited by 1avidflyer

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