bohelle

I bought an old well used saito 65 with the air bleed carb off of eBay and put new bearings in it. I have about 30 minutes of run time on this engine and at idle it had a noise in it. I took it back apart and found that the cam was completely dry and one of the plastic washers between the cam and housing was worn out and in the bottom of the case. The rear bearing has a shield and not a seal just like the bearing that was removed. Also there is some oil in the bottom of the case between the front and rear bearing so I know oil is getting through the back bearing. My question is how does the cam supposed to get oil to it?

Thanks
Bob

Flyboy Dave

My Feedback: (21)

Usually it doesn't get any oil....especially if you engine has the normal
vent fitting in the backplate. Almost all the residual oil from the blowby
lubrication system blows out the rear of the engine. Like most engines
of this type, it must be lubricated manually as well as the rockers.

I oil my rockers periodically, and run plenty of oil down the pushrod tubes
to get some oil into the cambox....usually about every two hours of running.

FBD.

XJet

It's worth noting that some of Saito's later designs (the 82 for example) no longer have the vent nipple in the backplate but opposite the cambox instead. This promotes the flow of oil past the rear bearing and into the important cambox area.

On my backplate-nippled Saitos I still make sure I give this area a good dose of oil by hand because they *do* run rather dry otherwise.

And dribbling oil down the pushrod tubes isn't always enough because the lifters seal pretty good, thus stopping that oil from reaching the cambox.

liquid_TR

I was frustrated with this issue on my saito 100, so I put alot of quality, high temp bearing grease on the entire cam drive. I will see how it held up next week when I open it up for inspection.

Next time when changing my bearing, I will use a sealed type on the back as well, which holds up much better and longer than an open type - in my experience, and stuff alot of bearing grease on the cam drive to help prevent it from wear, tear and corrosion.

XJet

I don't think that grease will hold-up too well to the high RPMs encountered on the crankshaft/camshaft.

The gears themselves don't actually need a whole lot of lubrication. A proper involute gearset has no sliding motion involved, simply rolling so lubrication can be quite minimal without wear occurring.

It's the lifter/camshaft interface that has a whole lot of sliding going on so needs the lube.

I fear that if you try to put grease in here, it'll get flung away and simply stick to the walls of the cambox where it does no good at all.

For best lubrication, I suspect that 4-stroke engines should be mounted inverted to help promote the flow of oil through the cambox and into the rocker covers.

w8ye

My Feedback: (16)

I packed a 56 cam box with grease and it really slowed the engine down until the grease go out of the way.

Bone

This is how I solved the (potential) problem on my Saito 45. The usual rear backplate nipple is still in place but capped by a short piece of fuel tubing with a small bolt in the end. The main bearing is not sealed so the oil laden air in the crankcase forces its way through into the cam box lubricating all the bits before escaping out the breather nipple [8D]

Jezmo

The 91 I converted to Gasoline wasn't getting much if any oil to the rocker boxes so I trimmed the gaskets in order to create a tiny leak and now it gets plenty of oil up to the rockers. I am thinking that this oil must be passing by the cam/lifter area in order to reach the pushrod tubes and on up to the rocker boxes. The area around the rocker boxes is pretty oily after each flight so I just dry it off with a towel. (I'd rather do that than have it run dry)

rajul

My Feedback: (58)

That's a pretty neat idea

Bone

Thanks Rajul - but I shouldn't really take credit for the idea coz our dear friend Bill Robison inspired me to do it.

Anyway, the system works very well with a nice stream of oily air coming from the new vent. I do, as FBD suggested, manually oil the top end & pushrod tubes from time to time.

Also, I obtained a 2nd cam cover so that if need be, I can "convert" the engine back to standard configuration [8D]

rajul

My Feedback: (58)

Yes, Bill is kinda of a legend here. His Saito notes are a must have for all Saito owners

Flyboy Dave

My Feedback: (21)

....I didn't mention it in this post, but I have said it many times before,
I thin the oil that I run down down the pushrods tubes. This allows the
oil (straight castor oil, what else ?) to get past the cam followers, and
get on the cam between the cam and the followers where it needs to be.

Bill Robison used to lube his beloved Saito rockers on every flying day.

The rockers, in most instances, need to be lubed manually, no matter what.

FBD.

bohelle

Thanks guy's for the replies. I like the idea of the vent in the cam box so the blowby lubes the cam on the way out. The only thing I wonder about is if the crankcase will eventually build up oil because the vent is so high and can not just run out. I think I will use a little grease instead of oil this time when I reassemble it.

Bob

XJet

I don't think so...

On my Saitos, the seal between the lifters and camshaft is so good that nothing gets past, not even air.

Dribbling oil down the tubes will oil the lifter/pushrod interface and the top of the lifters but it won't get through to the camshaft.

Flyboy Dave

My Feedback: (21)

....OK XJet....if you say so.

FBD.

Jezmo

Somehow it's getting past the lifters because I'm getting oil up to my rocker boxes now that I trimmed the gaskets to leak. It ain't much but some is definitely getting through. It's a slightly different oil (Redline synthetic) because it's mixed with gas instead of methanol but that shouldn't make a difference.

buzzingb

My Feedback: (2)

The needle valves greatly have an effect on the oil that is blown by the piston. When the needles are very lean there will be little oil blown by the piston. I observed this once while flying a 180 that needed a rocker cover gasket. When the needles were very rick the oil blown out the rocker cover was all over the engine and front of the plane, then when the needles were leaned down there was hardly any oil at all. I made me a new sasket after this but it did show me that blowby is affected by needle and fuel mixture. So if you aren't getting any oil at all you may be too lean. Just a thought.