Balance Shaft Gears/Oil

Richard Thoms · Posted: Tue Jul 10, 2012 6:17 pm Post subject: Balance Shaft Gears/Oil

I recently broke the plastic balance shaft gears. The case was dry when I opened it but there was so much shaved and oil-soaked plastic in there I thought maybe it was just absorbed into that stuff. I changed all the gears and very carefully filled the case till the oil runs out the check hole. The very next race (after maybe 1.5 hours runtime) I break the gears again and the case looks dry again (with oil soaked shavings). I did not notice any oil leaks. The seal on the crank looks OK but how to test it? There is no seal on the balance shaft bearing. Could the oil be going in there? Any advice appreciated.
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Ray Chiappe · Posted: Tue Jul 10, 2012 7:03 pm Post subject:

I have never had your specific problem, but I have broke gears before. Once from over reving due to a thrown chain. There is steel main gears avail now that you have to run with the new clutch. With the plastice gears I change the oil everytime I road race. With the steel ones you have to run double the oil (approx.) About 4oz Did you replace all of the gears??

Richard Thoms · Posted: Tue Jul 10, 2012 8:02 pm Post subject:

Yes I replaced all the gears. I've had the engine for 3 years now and only changed the oil at the beginning of the seasons (maybe 10 hours between change). Now I really think I'm losing oil somewhere that has caused the two recent failures. It could be worse - I thought this last one was a lower con-rod bearing. I'll happily pay $50 for a couple more gears but need to fix this issue. I still run the old clutch and not looking forward to $500 upgrade.
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Nick Weil · Posted: Wed Jul 11, 2012 12:59 am Post subject:

Sounds like your oil seals are leaking and the oil is getting sucked into the motor. By any chance do you run somewhat different jetting than everyone else to get your Rotax to run right?
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Nick Weil
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Richard Thoms · Posted: Wed Jul 11, 2012 11:51 am Post subject:

I was running 1-2 jets bigger than I thought I should for the weather but this was also my first time road racing the rotax with big gear and I thought that was the reason why. I'll go ahead and replace the seal and keep an eye on the oil level next time out. Is that as simple as pulling the seal out and putting a new one in or does it take any special tools?

There is no seal on the balance shaft bearing. That is much higher in the case but what's to keep oil from going in there?
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Nick Weil · Posted: Thu Jul 12, 2012 11:04 am Post subject:

Unless your a service center, or not racing by Rotax rules, you cannot replace the seals yourself. A service center must do that for you. Just an FYI.
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Nick Weil
Authorized Rotax Service Center and Dealer since 2002
2004 Team USA Rotax Worlds Finals DD-2 Driver

Want to save money AND grow the economy? www.fairtax.org

stephen barthelmass · Joined: 13 Dec 2010 Posts: 8

10 hours between oil change is excessive. Rotax recommends 2 hours max before changing oil.

Richard Thoms · Posted: Thu Jul 12, 2012 12:38 pm Post subject:

Nick - You need a service center to replace the crank bearing seals?? Can't those just be pulled out and new ones popped in? Do you need a special tool? I'm not talking about the RMAX/passport anti-tamper seals.

stephen - you're right and I've learned my lesson. 2 hours from now on.
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