Ys200s
 

Hi all,

Has anyone had a failure of the Conrod big end bearing on one of these engines?

Is the factory aware of the issue and is anything been done ?

Many Thanks

Yep, my 200S did the same.

Big end failures are nothing new. All the DZ engines have had a failure somewhere, sometime, it's not only the 200S.

My first 170 did. I've been using YS for 20 years with 1000's of flights and only had the 2 failures, so that's not too bad.

Thanks drac1,
Do you think its oil content / quality related?

I doubt it's oil content related.

From the 170 onwards, all my engines are cdi and I've always used 10% oil. If it was oil %, I would have had more than the 2 failures.

If anything, I would say it may be that the bearing was a bit tight? But that's only a theory.

Previously, I've run a couple of tanks through on the test stand. Now I give the engine a really good break in with the break in needle open. I run at least 2 litres through at a very rich setting on the test stand, then close the break in needle and fly it.

It would be interesting to know what factory clearance should be, but not much chance of finding that out. Lol.

I brake in my engines using 20 % oil and the valve open for 3-4 tanks on the ground with a very rich mixture ......3-4 turns out.
I occasionally check the temperature and don't allow more than 40 deg C during the break in process.

Once I run a tankful through I lean the engine and advance the throttle up but not maximum rpm.I then richen the mixture and keep the process for the next 3 tankful.

When I am happy that the engine responds and transitions I close the valve ....not fully and lean the high speed to about 1 1/2 turns .
At this point I fly the engine and change the fuel to 10% multi viscosity CP and 30 % Nitro.

I always check the engine and regulator temperature after each flight ......I get around 30-40 deg C in the winter and a little higher during hot weather ops.
If I get a high reading I richen the engine ....only one click is enough on the high speed.

I keep the break in valve a little open for at least 40-50 flights .

That also indicates to me it isn't a oil % problem.

Just one of those things 😬

I do beleive is break in needle valve and oil related, I did the same as FBW, broke in the engine with 23% oil, but 2.5Lts of fuel, then break in needle still open fly.
I have to try the YS fuel I got when weather colaborates, and that has 10% oil, that´s why I burned so much 23% first. I have seen the same issue with a 185 Red that had the break in needle valve closed, and failed around 40 flights, as I investigated the motor, found the bushing rotated due to heat closing the lubrication orifice causing it to melt on the cranckshaft pin.

Will see how mine does on low oil.

I've always run 10% oil, for break in and flying. I fully close the break in needle after bench running for break in.
If it was oil % related, I would think I would have had more than 2 failures in around 10 years and 1000's of flights.

Yes, but if it doesn´t fail on the first flights I do not think it will fail at all, that´s why I think is a problem only during break in, and engine with 100 flights will not have this failure unles is too lean, and actually, the bushing that failed was kind of silver in color not bronze, when I reported back to Richard on the findings, he said the conecting rod was the same, so I was never able to figure out the color change, unless heat?

I agree that if it does not fail early it will be OK.

My theory is that occasionally the clearance may be a bit tight.

I might check mine now that we even have snow and most roads are closed, I will compare to my 185’s as it is the same conrod.

I’ll let you know what I find.

ok 🙂

Just as a matter of interest how many flights did you have on your 200S before the failure ? And what temperatures do you get after flight ?

Also probably not related but has anyone noticed that the front bearing is now different on the 200S........

kind regards

The 200 and 200S have a different front bearing part number to the previous engines.

From what I can tell, it's the seals that are different.

So when you think you know the YS this happens....

I am in the process of braking in my YS 200S and I noticed that there was a lot of oil on the rocker cover after running the engine for a few minutes.The engine was very difficult to start and throttle response was very poor . Initially I thought this was normal as the engine was new and running very rich.
However on closer examination I noticed that oil was pouring under pressure from the rear bolt that holds the rocker cover ....*** ???
Is this normal and can anyone give an explanation as to where is this oil coming from ??

Thank you in advance

Use some fine wet and dry on something flat and sand the bottom of the valve cover until all the paint is gone.

Check the muffler's rubber band
Maybe that's where the leak comes from

Done all that ....you won't believe this but the oil is actually coming from inside the hole where the bolt screw into ....
You can actually see it when you flick the prop with the cover off.....WT$

Hello

I had the same problem on my 200 CDI with a leak at the cylinder head due to porosity.
Yamada sent me a new cylinder head as a guarantee.
Claude

A quick Question ........
How does the oil/fuel get into the valve area ??

Hi Claude,
I think porosity is a plausible explanation which explains the oil coming out of the bolt hole under pressure....probably a fault in the alluminium head casting !!!

regards

If the parts of the gasket (circled in red) don't seal, then the bolt threads are exposed to the pressure/vacuum in the valve cover depending on the throttle percentage. That's one pathway to leak air/oil in and out of the intake system because the bolt isn't sealed in the valve cover. A crack in the valve cover at that point (can occur from reusing gaskets or overtightening) would also cause a leak. I had that happen on a motorcycle gearbox cover.

https://cimg1.ibsrv.net/gimg/www.rcu...8ea417a597.jpg
Valve cover gasket

As an aside, there's a company in Australia manufacturing TZ750 crankcases and they perform a process called vacuum impregnation on their cases to "seal up" any porosity in the finished article. It's an interesting process.

Point taken and thank you for the reply.
My issue is that oil is pouring out of the actual hole that the cover bolt screws into.........by removing the cover and flicking the prop you can see the oil coming out.
Surely this is not normal on a brand new engine ??

regards

Does anyone know how does the oil get into the valve cover on the YS200S engine......

many thanks

Through the push rod tubes.