42etus

My Feedback: (2)

My Saito 115 took a dump today. I opened it up and the camshaft supports had both broken. The cam jamed up and really screwed up the crankshaft, crankcase and of course the cam. The cam and surrounding area seemed quite dry of oil, not completely dry, but not wet with oil either. This engine was only 5 months old and has used about 2 gallons of Coolpower 15% fuel. It appears that the failure was due to a lack of lubrication in the cam bearings, even though the crankcase was literally dripping oil when I removed the back plate. I'm wondering if anyone else has seen this type of failure on this engine. I talked to Horizon Hobby and they said to send it in and they'd look at it. I'm hopeing that this isn't some kind of a design problem as I just got another 115 that hasn't even been started yet. So has anyone seen this before, or do you think it was just a fluke happening?
Paul

Hobbsy

My Feedback: (102)

What prop were you running when this happenned, is it possible it over revved and jammed a valve. I seriously doubt that lack of lube would be the problem, I have about 20 Saitos both rear vent and front vent and no problems ever. Thanks, Dave

PS, also what fuel?

XJet

I keep telling people that you should pre-lube the cambox area of those Saitos with a backplate-mounted crankcase breather nipple.

There's simply nothing to push the oil past the rear bearing and into the cambox area beacuse all the excess oil just vents out the back of the engine.

I've outlined the process I use at the start of each flying season before and I've never had an issue but I've heard of quite a few other folks who've ended up with dry camshaft bushes because they perform no manual lubrication or think that oil dripped down the pushrod tubes will make its way into the cambox (which it wont).

42etus

My Feedback: (2)

XJet, what is the process that you're speaking of? I know that dripping oil down the pushrod tubes won't make it to the cam, but on the other hand one shouldn't have to perform a lubrication ritual to keep the cam lubed. The engine should do that through it's design.


Hobbsy, The prop was a 14x8 which tachs at 9900 at my altitude (4300 ft), so I know it didn't over rev. Besides, this is the same prop I've always used on it. Fuel was Coolpower 15%. I'm quite sure the failure was due to lack of lubrication as the cam housing was quite dry of oil.

We'll see what Horizon Hobby has to say.
Paul

w8ye

My Feedback: (16)

Most new Saitos come from the factory with black Molybdenum grease in the cam and rocker arm areas

However I just took an older 100T twin apart that had never been run and there was nothing but just some light machine oil in it.

XJet

I fill the crankcase with oil (via the breather hole) then stand the engine (or model) at a 45-degree nose-down angle, with the cylinder inverted.

This allows the oil to trickle past the rear bearing and pool in the cambox.

Put a rag under the front of the engine because much of the oil will seep out the front bearing.

I leave my engines/models like this overnight to be absolutely sure that the cambox is bathed in oil.

As soon as you start the engine up, any excess will be blown out the breather but this "dose" of lubrication seems to last the whole season long if you use the engine regularly. I have a feeling it also helps prevent rust.

Ram Jet

Xjet, I have been consternating over the question of how four cycles get adequate lubrication to the cam lobes and big end con rod bearing. Ring blow by? I'm conjuring up a cotrivance in my little brain where I employ a Perry Pump injecting ATF oil into the cam drive box powered by muffler pressure to insure adequate lubrication and venting crankcase pressure/blowby directly into the intake manifold. I haven't acted upon this for fear I will be escorted to a padded room somewhere.

Bill

DarZeelon

Paul,


Even if this only happened in *your* engine, this is what the warranty is for.

The damage you describe seems to be quite extensive; justifying a replacement, rather than a repair of the engine...

With labor and parts, it will cost more to repair...


Send your engine back to Horizon Hobbies, without wasting any time.

If you ran it according to the instructions, they will replace it.


Just make sure you ask them to send you a replacement engine from a different production run, just to make sure...

Hobbsy

My Feedback: (102)

Dar, my thinking is that if the failure was due to lack of lube the damage would only be stripped teeth on the cam, the catastrophic breaking of the cam supports had to come from severe down force from the cam pushing against a jammed valve or other.

ChrisAttebery

My Feedback: (15)

Hmmm, I submitted this post last night and it seems to have disappeared.

Get a pump oiler. Fill it with ARO. Attach it to the breather and pump the crankcase FULL of oil. Clamp off the breather. Turn the motor over by hand several times. This will pump the oil past the rear bearing. Unclamp the breather and turn the motor over until the breather quits spitting oil. DONE.

w8ye

My Feedback: (16)

Cris,

I cannot see that your post was ever on here. If it was deleted, I would have a notation of it

ChrisAttebery

My Feedback: (15)

I may have killed the session too quickly?

42etus

My Feedback: (2)

I agree, I think Horizon should replace the engine rather than just repair it, but I suppose it's their call in the end. I sent it to them yesterday afternoon USPS and insured. I should be hearing from them next week some time. I'll post back when I do.
Paul

42etus

My Feedback: (2)

Follow up:

Horizon called me today. They had no explanation for the failure, but said that it shouldn't have happened. They agreed to repair the engine under warranty and return it to me. Fair enough.

In my first post I mentioned that I had a 2nd new, never run 115. Well I took the cam cover off and was shocked. There appeared to be no lube of any kind in there. No grease and no oil, absolutely bone dry. Needless to say, I pre-lubed the thing with Xjet's method. In the future, I'm going to store all my Saito equipped planes in a nose down attitude, the idea being that any residual oil in the engine will drain down to the cam. Any comments?

Paul

w8ye

My Feedback: (16)

Sounds like a winner. I guess they quit putting the moly grease in the new ones

Bone

I can report that the cam box on my Saito 45 with rear mounted breather also runs very dry. In fact the last time I pulled the cam box off, I was alarmed by how dry it actually was. Even the conrod big end was dry []

As for fuel, I'm using home brew of 5% castor, 15% red Klotz, 10% nitro & the balance methanol. As you can see, there is ample oil in the fuel. I think I need to switch back to my other cam box cover with the breather mounted on the cover itself, the vent on the backplate being plugged.

I also like X-Jet's idea about pre-lubing the engine as earlier described in these posts [8D]

Ernie Misner

>>>I've heard of quite a few other folks who've ended up with dry camshaft bushes because they perform no manual lubrication or think that oil dripped down the pushrod tubes will make its way into the cambox (which it wont). >>>

If the pushrod tubes go down to the lifters, how could the oil not reach the cam? There must be a tiny bit of clearance around the lifters ... ? granted it wouldn't get there too fast though, but overnight?

Thanks,

Ernie

XJet

The lifter/cambox seal is a very good one. On all my Saitos it's gas-tight and won't allow oil to get past.

Ernie Misner

Thanks XJet. What kind of trouble could I get into by pulling the cambox cover off (Saito 82) to take a peek in there? Wreck the gasket.... or?

Also, I am blanking at the moment. How does oil get up to the top end (rockers) if not past the lifters?

Thank you,

Ernie

NM2K

My Feedback: (14)

Making the cam box seal unsealed would attract oil mist into the cambox, thus lubricating the cam, cam bushings and lifter bottoms. Of course, the whiners complaining about oil leaks would drive the folks at Saito USA nuts. Gaskets are for sissies, unless you absolutely need a pressurized crankcase. [&o]


Ed Cregger

Hobbsy

My Feedback: (102)

Ed, here is the 18 year old cam out of my 1.50, I thought it was worn out but low and behold the new one is identical. I thought it was worn because the exhust cam is kinda pointy, so is the new one. apparently the exhaust valve opens very quickly, the intake is more rounded.

Waco Driver

I recently rebuilt a crash damaged Saito 72 with reportedly less than 5 hours running time total. Both cam followers had the outer edges worn on opposing sides giving the appearance of a slightly peaked roof, with the worn areas having a scuffed appearance. The cam lobes showed no appreciable wear. This is obviously a lubrication failure problem. I suspect that the engine had never been treated to an after run oil. This engine has the breather nipple at the bottom of the front case which should ensure proper lubrication to the cam box area. The cam followers in this engine are significantly smaller diameter than those used in OS engines and are therefore more highly loaded.

I have never seen this type of wear before in rebuilding many 4 stroke engines.

w8ye

My Feedback: (16)

Almost any tear down of a Saito medium engine actually requires refacing/replacement of the cam followers

DarZeelon

It seems like nearly all manufacturers of model four-stroke engine, either think that all modelers are suckers... Or that none of the manufacturers ever studied mechanical engineering...

The camshaft and lifter lubrication, in most four-stroke engine, can at best be considered rudimentary/borderline.


I am surprised they even last as long as they do... And some manufacturers even do worse, by making mistakes; such as the one OS made, but using a fully sealed rear bearing in the now defunct .70FL, which made the availability of fresh oil to the camshaft/cam-gear/lifters, even less copious than none at all...[sm=disappointed.gif]

Also; if you look at the cams and at the lifters/tappets/cam-followers, you will see another moot design consideration...

The lifters in a full-size engine had a rather large diameter (or are 'mushroomed') and a have convex bottom, so they only contact the cam-lobe with their bottom and are actually rotated, as the rotating cam-lobe slides against it.

This rule does not appear to be followed by model four-stroke engine manufacturers... It appears the cam lobes could ride on the edges of the rather small diameter lifter; which can damage both the lobe and the lifter.

...It appears engine longevity was never paramount, on their requirements list...

For a long time I was quite reluctant to purchase any four-stroke engine; because of these, among the reasons.


I own just one such engine, which I traded for a used one with another prominent member of this forum.


Despite any fear I had, this Saito .72 has so far given me no trouble at all.

But from all I have read here, I think perhaps I am lucky...

w8ye

My Feedback: (16)

Dar,
I was with him when he bought that engine at a small hobby shop about 30 miles north of here in Berlin Heights. It was a consignment so we don't know anything about the original history of the engine.