Author Topic: Broken saito .56 (Read 6719 times)

Joe Yau · « **on:** January 24, 2013, 12:20:45 PM »

not sure exactly what caused it.. but just about 3 laps after the 4 leaf clover maneuver, my Saito started making a clicking noise, it just kept going for about 2-3 laps then stopped with the prop still spinning away.. like it was an electric motor or something. when I got home, I strip the engine down and found the cam gear was missing a few teeth, basically it's striped and frozen tight. I haven't pull the gear off yet.. but what would cause that? as it ran fine right through the whole pattern.

Bob Reeves · « **Reply #1 on:** January 24, 2013, 02:29:48 PM »

Not quite enough info.. Exactly what prop and fuel were you running?
Even with that info not sure we can figure out what happened. A valve would almost have had to get stuck to shear off the teeth but am pretty sure you are not running any castor, are you?

Joe Yau · « **Reply #2 on:** January 24, 2013, 02:34:05 PM »

Hi Bob,

I'm running a Xoar 13x6 Electric wood prop, and Byron 20/20 fuel with no castor. I have the cam gear off now, and seems one of the lifter was quite tight. Would running the valve gap on the loose side cause this?

Bob Reeves · « **Reply #3 on:** January 24, 2013, 02:42:47 PM »

I was editing my above post when you were posting. Don't think Bryon has any castor but not sure.

Bob Reeves · « **Reply #4 on:** January 24, 2013, 02:50:03 PM »

Reread your origional post, Is the cam gear stuck on the shaft, as in won't turn?

BTW: If you plan on going back with a stock cam gear I have a couple laying around. Email me your address and I'll stick one in the mail.

Bob Reeves · « **Reply #5 on:** January 24, 2013, 02:52:41 PM »

Nother question, did you ever do the oil content test on the fuel we talked about some time ago?

Joe Yau · « **Reply #6 on:** January 24, 2013, 03:34:44 PM »

Quote from: Bob Reeves on January 24, 2013, 02:50:03 PM

Reread your origional post, Is the cam gear stuck on the shaft, as in won't turn?

BTW: If you plan on going back with a stock cam gear I have a couple laying around. Email me your address and I'll stick one in the mail.

good question.. I removed the cam gear and push up on the lifters, and one seems tight while the other one was nice and free. not sure how far it was out or if that is enough to cause a teeth to break off the gear tho.

Much appreciate the cam offer. I'm thinking of trying a CCW cam now I need to replace one. would you have a spare one you wouldn't mind selling? and maybe a 13x6 Jxf pusher prop?

Joe Yau · « **Reply #7 on:** January 24, 2013, 03:47:43 PM »

Quote from: Bob Reeves on January 24, 2013, 02:52:41 PM

Nother question, did you ever do the oil content test on the fuel we talked about some time ago?

Gee, I totally forgot all about it. as I was getting good and consistent runs with the fuel. I will try to do the test next week.

Bob Reeves · « **Reply #8 on:** January 24, 2013, 04:26:33 PM »

Sorry, no extra reverse cams..

You can speed up the oil test by lighting the fuel and letting it burn off the alcohol and nitro but it might not give accurate results as I think if it gets too hot some of the oil may also burn off. Hope you still have some Powermaster fuel you can compair to the Bryon, maybe using fire with both will normalize the test?. Tuna fish cans work real well, use two or three ounces of fuel so you will have enough oil left to measure.

Hope we can figure out what happened, might save me and others from the same issue.

ash · « **Reply #9 on:** January 24, 2013, 05:26:24 PM »

Can you give us a large super-close-up of the broken surfaces? That might enable us to determine if it was a fatigue failure (built up over a long time) or brittle fracture (caused in an instant by some massive load).

Joe Yau · « **Reply #10 on:** January 25, 2013, 10:15:14 AM »

Quote from: Bob Reeves on January 24, 2013, 04:26:33 PM

You can speed up the oil test by lighting the fuel and letting it burn off the alcohol and nitro but it might not give accurate results as I think if it gets too hot some of the oil may also burn off. Hope you still have some Powermaster fuel you can compair to the Bryon, maybe using fire with both will normalize the test?. Tuna fish cans work real well, use two or three ounces of fuel so you will have enough oil left to measure.

Hope we can figure out what happened, might save me and others from the same issue.

sounds like a good idea.. I do have some Powermaster YS20/20 for comparison.

Joe Yau · « **Reply #11 on:** January 25, 2013, 10:17:50 AM »

Quote from: ash on January 24, 2013, 05:26:24 PM

Can you give us a large super-close-up of the broken surfaces? That might enable us to determine if it was a fatigue failure (built up over a long time) or brittle fracture (caused in an instant by some massive load).

I'll try to take some close up pics later today.

Joe Yau · « **Reply #12 on:** January 25, 2013, 03:14:42 PM »

O.k. I tried to light it on fire.. but it wont stay lit. guess I'll let it evaporate.

Bob Reeves · « **Reply #13 on:** January 26, 2013, 06:03:00 AM »

Did you use the jars shown when you tried to light it? First I don't think using glass jars is a good idea if you are trying to burn off the alcohol. I'm thinking you would just end up with broken jars.

Also thinking the way the jars are shaped the oxygen is getting consumed and the restricted mouth isn't letting enough in to substain the fire. Also thinking the mouth restriction will slow down the evaporation rate and it will take much longer to see the end result.

I like the jars, can think of many uses for them just not what you are using them for. Buy a couple cans of tuna fish, eat the tuna or feed it to your cat and use the cans for your fuel test.

BTW: I have this neat little USB microscope that would take great close up images of that cam gear. If you want to send it to me I'll do the photos.

Martin Quartim · « **Reply #14 on:** January 27, 2013, 07:03:57 PM »

I think Byron 20/20 is an excelent fuel. I have used nothing but Byron 20/20 for many many years.

Martin

Bob Reeves · « **Reply #15 on:** February 03, 2013, 05:34:54 AM »

Quote from: Martin Quartim on January 27, 2013, 07:03:57 PM

I think Byron 20/20 is an excelent fuel. I have used nothing but Byron 20/20 for many many years.

Martin

No one is trying to knock Bryon fuel, just trying to eliminate one variable from the mystery.

Any updates?

Douglas Ames · « **Reply #16 on:** February 04, 2013, 05:36:28 PM »

Looks like the cam seized and the teeth let go at the mesh point of the crank gear. With the valve(s) partially open it allowed the prop/ crank to freewheel with an airload.
I agree with you Bob, my first thought was "lack of lube".
Not sure if a Saito has valve clearance at TDC, that depends on cam timing and lift. I'd definitely check the pushrods and valves for damage.

Joe Yau · « **Reply #17 on:** February 05, 2013, 11:41:03 AM »

Quote from: Bob Reeves on February 03, 2013, 05:34:54 AM

No one is trying to knock Bryon fuel, just trying to eliminate one variable from the mystery.

Any updates?

It's getting close..

I don't know the history on this engine as I got this one used, but it sure seems to have a lot of rust in the oil that's left on the parts. maybe from the bearings? I notice that when I set the valve gap on it a while back too, and thought it might clear up by it self.

Bob Reeves · « **Reply #18 on:** February 06, 2013, 10:49:57 AM »

I think your fuel test has gone far enough to tell us it isn't a fuel issue and we can mark that off the list.

Rust could for sure create all kinds of issues.

Joe Yau · « **Reply #19 on:** February 06, 2013, 10:27:28 PM »

Quote from: Bob Reeves on February 06, 2013, 10:49:57 AM

Rust could for sure create all kinds of issues.

I guess I should of strip it down to find where the source of rust came from before this happened.. I'll be replacing the rear bearing, tappets, pinion gear as well.

Jim Kraft · « **Reply #20 on:** February 22, 2013, 02:16:25 PM »

Many times the ball cages come apart and will do that kind of damage. I would not be surprised if the ball cage on the front bearing is not coming apart. It could also be a small particle of the race or a ball. Once it gets in the teeth something has to give and usually does.

Douglas Ames · « **Reply #21 on:** February 23, 2013, 08:54:02 PM »

<snip >"I don't know the history on this engine as I got this one used, but it sure seems to have a lot of rust in the oil that's left on the parts. maybe from the bearings?"

Yes, from the bearings.
The steel in the bearings is rusting from the Methanol and water in the fuel (Alcohol is hygroscopic). This the very reason they sell "After-run oil" - to coat the bare steel and prevent corrosion.