It happened again. My first flight lasted 3 minutes when the engine quit. After landing i noticed that the damper in YS mount had broken and further inspection found that the conrod had sheared. I replaced the conrod and restarted the engine, she ran well for a minute and then again the conrod failed. This time it didn't break apart but seems to have elongated around the crankpin. My fuel is 10% Klotz oil and 20% nitro. Can't quite figure it out. This time when I opened the back plate the engine parts seemed to be well lubricated. Due to the elongation of the con rod, it had scored the crank case in some areas. I now feel a certain roughness from the bearings as well. Quite a mess. I have cleaned all the parts and plan to get new bearings and also con rod to give it another go. Could there be something else that I need to look into? The crank pin looks smooth and doesn't seem bent.
Your thoughts please?
Thanks

Gyri:

Wow, never saw or experienced anything like that. At this point I suspect your fuel at 10%, should be 20-20 for the YS. Has the engine been backfiring or other indications of detonation? Frankly I would send the engine into a YS service center to be rebuilt. My experience has been that the centers do a outstanding job at a very reasonable price. Am sure other help will chime in.

Gyri, I hate to say it but your ploblem is self inflicted, you have used the wrong conrod and/or put it in the wrong way.
Nt all of the 160/170/170 spark rods are the same.

Send it in for service, I don't know who there is in India, but either back to Japan, or to the United States or to me here in Australia.

YS SERVICE DOWN UNDER

It's a possibility XMANS,...can't deny. The reason I went at it myself is the enormous procedure of sending out an engine and collecting it back in India, without suffering import duty all over again. The paper work and shipping charges are too ridiculous. Hindsight I could have been a bit patient and had it taken to Singapore during my next visit. But again , in the past I successfully recondition two YS110s quite well with parts from Central hobbies and this looked just as well.

The part# on the spare conrod packing matched what is in the 170CDI manual (parts diagram). I am unaware of the orientation I fixed it in, the part looked very symmetrical and I assumed it goes both ways without mattering. Thinking back I did notice two punch marks on the brass bushing (big end of con rod). I assumed that punch was done to secure the brass/phosphor bronze bush to the aluminum casting. Not sure anymore, possible an oil groove that requires some orientation to function well.

However, with the replaced Conrod, it ran 20secs very smoothly at mid throttle and then suddendly died out. I am concerned if the issue is more than the conrod. possibly a bent crankpin/crankshaft. After the first conrod failure when I inspected the crankpin it looked perfectly fine to me. The engine has overall run barely 20 minutes from the intial flick.

Can I get anymore thoughts from you guys? I wish I could send it across, would save me a lot of anxiety.

Thanks for the replies so far

The big end of the conrod has a shamfer on one side and not the other, when installed backwards the big end nips up tight, not enough clearance between rod and counter balance of crankshaft, and you know the rest. well thats my theory.

Thanks Xman,

I don't know how I missed that. When I checked and both sides had chamfered edges, only 2 punch marks at one side. May be it's not so prominent. If so, I guess the chamfered end faces the counter mass and the not so chamfered side faces the back plate. After the second damage, I didn't notice any wear on the counter mass, only on the crank case. Meanwhile I spoke to Singapore hobby supplies about the problem I have and they suggested that I bring it over in my next trip so that it could be sent to YS. What was interesting in my coversation with Mr.Johnny (of Singapore Hobby Supplies) is that the ASian F3A pilots use nothing less than 20%oil in the 170CDi. Also there is a preferance for 20 size prop to keep the revs below 7000. This is quite the contrast to all that I have read on RCU. Most of the pilots on RCU claim they fly 5-12% oil on the 170cdi.

Ofcourse when I attended Singapore NAts last year most pilots where on 170CDI (or electric) and where very happy with it. I myself am a big fan of the YS and have a few YS110s. In fact I might buy another 170cdi to get back to flying while my current engine is sorted out. I just want to make sure that I don't have a repeat of the same issue.

XMAN, what sort of fuel mix do u reccommend?

I myself run 12% oil and 25% nitro with the APC 4 blade, has done lot and lots of flights.
Why do I run 12% cool power, just to be on the safe side, and I don't need all the power that this engine can produce
and I feel this will run forever, well nothing is forever.

YS SERVICE DOWNUNDER

There are seasons in Australia where the temperatures soars as well. Do you increase the oil percentage then? That seems to be the reason I got for 20% oil content in Singapore where they have typical tropical climate. The days I ran my engine weren't really all that hot 37 degree cel max. I am not sure which way to go now.

I don't worry about the weather, but I do run 20% oil in my glo versions.
A comment, if your CDI is a kit conversion then keep running 20 % oil, if it is a proper 170 CDI then you can use lower oil,
these 2 engines are not the same internally, they have differant cranks, conrods, cam follers, carb housing.
A simple way to tell is to look at the cam followers, if they don't have spiral groves around them then it is a kit build,
and the carb housing don't have a bleed screw on it.

I bought mine as a 170cdi engine. Not a kit build as the box itself says 170cdi. Now I am totally lost on the oil front. As mentioned it's more to protect my engine in future, this piece as well as the next one I am eager to buy.

I have run them with 10, 15, 20, and 23% oil. I am very happy sticking with the 20% oil as the engine runs cooler and seems to be much happier long term. After talking to Richard at YS, the lower oil engines definitely wear faster (which is to be expected). The smoke trail with the Low Smoke series fuels are minimal anyway, so I don't see a major advantage to the 10% oil.

Arch

Thanks for your input rcpattern. I have been advice by Singapore Hobby supplies to send the engine to YS Japan. Going to do that. I hope I read from many other 170cdi users about what percentage oil they use and arrive at some consenses. Agreed that everyone would have their personal fav, but there is got to be some sensible range, hopefully. I am very tempted to go lower on the oil, for number of reasons. One, its easier to clean , 2 oil is in our concern more expensive at this point than Nitro, as we have to import Klotz for our requirement. It's also the reason I waited for the 170cdi. It's not so big a loss now. I would definitely prefer reliability over some loss of power or gain in goop.

Hope to hear from other regulars on their fuel percentages.