YS120SR started running hot

[mc_clean_david]

I bought a 120SR with my Whiplash back in October. I have ran 5 tanks through it and the mixture is still rich. It started and ran perfect for 4 tanks then on tank 5 it cut while doing a slow circuit and there was smoke coming from the head, now it cuts every time I start it. I haven't taken it out of the Whiplash yet but I suspect a engine fault. Anyone else had any issues?

[rapidgaz]

YS120SR started running hot

Check ur non return valve.

[mc_clean_david]

Check Valve working - loads of pressure in tank or how do you test it?

[rapidgaz]

YS120SR started running hot

Blow down it.

[Delarado]

make sure you can blow one way but not the other

[jamiem]

YS120SR started running hot

If it now won't idle, it's probably very low on compression. Will it idle with higher throttle position? Just put the starter wand in and try turning it by hand, it should be very very hard to turn, if not, you need to find why it has low compression. Possibly broken/cracked ring or piston, possibly scored liner.

[mc_clean_david]

Check Valve definately working. Head tight and plug is fine. Will remove the engine and take off the head as I've just found the following thread on helifreak
YS120 suddenly running hot - HeliFreak

[mc_clean_david]

It is still hard to turn over - infact my Align starter will only just turn it over with a fully charged battery

[Guest]

As my old comp mate from when we flew in the states said. "If something has change its not right" I wouldn't turn over the engine anymore, drop it out and take it apart to inspect. At very least take exhaust off and check piston through port for damage.

MJ

[jwatts007]

Sounds like you have not damaged it...make sure the fuel lines are as short as possible and do away with the in line filter...the pressure pipe needs to be a 100mm to the valve with no tight bends in it...the weekend mine needed to be run richer must have been the misty conditions.....

[tonystevens]

+1 on keeping the fuel tube as short as poss with the 120.

Another thing to check is the two black o rings in your pipe header, if they are split it can cause a lean run. These days im covering mine with grease now and that keeps them from going dry and brittle and also stops them becoming stuck to the pipe and split when you remove the pipe.

[jwatts007]

just changing a bearing in mine...I am impressed how clean the engine is not a mark or stain on the piston...running it on opti 20....120 003.jpg120 004.jpg120 005.jpg

[tonystevens]

Any chance we can see the bearing jon, while your in there?

[Steve]

Was the weather cold (like 1-2 deg C or lower) when it started playing up?

If so, then the check valve probably seized in flight due to the oil in it getting so thick that it's stuck shut (or open). Then you take it home and check it, and it appears that there's nothing wrong with it because it's warmed up.

It's been a perennial problem with YS engines that the check valve gums up in very cold weather. The solution is to route the line from the back plate in such a way that the check valve is touching the inside edge of the silencer on it's way to the fuel tank. The muffler then keeps the check valve warm in flight and stops this happening.

[jwatts007]

bearing is not so good...it is not notchy but the centre ring has some play in it and is rocking about this was a SKF bearing a SNR one is going back in...I did notice the SKF bearings do have a bit of play...this SNR bearing has none....bearings 002.jpgbearings 003.jpgbearings 005.jpgbearings 006.jpg