Saito 82 oil leak

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Saito 82 oil leak

Postby oldsapper » Wed Sep 15, 2010 1:48 am

I have bought the above engine second hand. Have mounted it inverted in a 1/6 scale Bristol M1 (Balsa USA kit). Motor runs fine on test, but appears to be leaking some fuel from around the prop shaft, which is, I think, the cause of the spinner backplate slipping. The spinner is scale for the model, (bigger than half a tennis ball), aluminum, the backplate is thin brass and doesn't seem to have much grip on the drive flange. So my questions are:
a) do I replace the prop shaft bearing, or
b) could I drill thro the backplate and into the drive flange and tap the two holes for short M4 cap head bolts?

Would appreciate any suggestions, thanks.
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Re: Saito 82 oil leak

Postby RCModelReviews » Wed Sep 15, 2010 3:39 am

A slipping spinner backplate should not cause an oil leak.

The 82 has a sealed front bearing which should stop all but the smallest amount of oil leaking out the front bearing.

Check that the vent-nipple (on the crankcase) and any drain tube you have connected to it is not blocked -- otherwise the oil will have no option but to force its way past the seals.

If you are experiencing slippage of the spinner backplate on the prop-driver then you may want to fit a flexible washer of some-kind in there to provide a greater coefficient of friction than you get from metal on metal. A fiber washer of some kind may be the answer - but you'll need to keep checking the torque on the prop-nuts to make sure it hasn't compressed -- or the prop prop/spinner will slip.

I'd be surprised if the backplate of your spinner was "thin brass". 4-stroke engines like the Saito are hard on spinners so you really ought to be using something more substantial.

I don't think I'd go drilling holes in the Saito prop-driver and using bolts to attach anything -- there's not actually a lot of meat in there.

So... first-up, I'd check that the breather nipple/pipe isn't blocked.

If you don't have a pipe on the breather than put one on -- they do spew a lot of oil out here aid it is always possible that in a cowled engine, that oil is being sucked forward onto the spinner backplate anyway. Use a piece of fuel tubing to carry the breather oil outside of the cowling.

If the prop *is* slipping then try a thin fiber washer between the driver and the spinner backplate (make sure you get everything totally degreased (oil-free) first and re-torque regularly for the first few outings.

If there's still a lot of oil coming out then it may also be some blow-back from the carby. The 82s (like most Saitos) have a very short carb-intake which means that at some RPMs, the overlap in the valve-opening causes some air/fuel to be blown out of the carby intake. Fitting a velocity stack will fix that.

If none of that solves the problem then new bearings will help., just the facts.
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Re: Saito 82 oil leak

Postby oldsapper » Sun Sep 19, 2010 11:59 am

Thank you, Bruce. I have fitted a fibre washer cut from a new Fordson Major head gasket.
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Re: Saito 82 oil leak

Postby Spacewalker » Wed Jan 05, 2011 7:03 am

For slipping spinner back plates and props to spinner back plates, especially plastic ones, I make up a washer by gluing two pieces of wet and dry sand paper back to back and make a washer. This has workrd 100% for me.
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