OK. Prop is probably a bit small for the 200.

Hey Claude,

How many flights have you had before overhaul ?

Hello Mavros

The engine has about sixty 15-minute flights. It worked very well with an APC 21.5 x 10.5 PNC propeller, very powerful.
Then I saw traces of fuel at the cylinder head.
The one was porous and YS replaced it with a new one under warranty.
Since the engine has less power while I only changed the cylinder head.
I have done a lot of checking but the problem still persists.
It's very very weird.
Claude

Sixty Flights !!!!!!

I think you should send it back to YS and demand a rebuild.

Hello
Yes I did.
Engine was very powerfull until I changed cylinder head.
With the new cylinder head, the engine runs very well but lacked power.
Of course I want a powerful engine like the original but I would like to know the cause
Claude

It would be good to know what the problem is. YS usually won't say what is wrong. Just fix it and send it back.

Hi Claude
I can help you with your problem, I have been rebuilding YS Engines for 8 years.
If you want information on why your engine is loosing power i will be glad to help you.
Let me know.
Fran Ferrante
[email protected]

Hello Fran

I red your MP about YS repair.
Thank you very much for yours advices.
claude

Do you mind sharing any information ??

regards

Be glad to give any info you and your friends need. I was in your spot a long while back.
If you received my private message you can post it.
If not I will post a new one.
Fran

Hello
YS Repair From Fran FerranteHi
I have been rebuilding my YS engines for over 10 years.
I can tell you from my experience when you lose RPM the first place to go is the Piston Ring & Sleeve.
If you take the ring out of the piston and put it back in the sleeve measure the gap. if it is bigger than 15,000 that is part of your problem.
Also hold the sleeve up to the light and see if there are any deep scores in it. Also notice if the coating is worn off the inside of the sleeve.
I normally change both Ring and sleeve with the run time you have on it.
Also when you put a new head on the engine you should lap the head to the sleeve with some light compound.
The rear Bearing is a big problem. when you have the engine apart put your finger in the rear bearing and move the inner race see if it is rough.
Check the rotor it should have a little drag on it. If it is loose or really free this could cause a drop in RPM.
I can go on and on.
Any questions feel free to contact me.
Fran Ferrante
[email protected]

Another area that you should also look at is the back plate assembly. If you are down on power, sometime it's because there is oil residue built up between the disc valve & the back plate. Disassemble the disc valve from the back plate & clean the parts with denatured alcohol. After re-assembled, there should be slight friction between the parts.

Do a search on You tube, there are three links on Naruke showing how to clean the back plates on a 170DZ at a local Japanese flying field.

Adrian

I've never removed the disc to just clean it. A film of oil doesn't hurt, as it lubricates and seals. If there is no drag, I tighten it up a bit.

I agree you do not haft to take apart the rotor to clean it.
I put all my parts in a sonic cleaner with Dawn dish washing detergent . For 4 Minutes.
Then I wash them out one by one with water, I blow them off with air pressure and soak them with oil.
The oil i use is from Cool Power. The same oil they use in their fuel with Rust inhibiters.
One other thing you should look out for, when checking the rotor.
Hold the rotor in one hand and put pressure on each side of the face of the rotor with your other hand.
If you feel any play side to side it should be replaced.
Fran

Hi Fran,
There is always a bit of sideways movement withe disc even with a new engine.
Do you have to change the whole unit or just the Brass bit?

regards

Sorry I did not explain it right. Yes their is a slight bit of play if you put pressure on the sides of the disk, that is OK.
But what I meant is on the face of the disk if you can rock it by pushing down on each side, the brass bit is worn and should be replaced.
I have purchased them from Yamada.
You may not see them listed.
I E mailed him and explained what I wanted, when I ordered the brass shafts.
Fran

I've been using the DZ's for 18 years and never had to replace the brass screw.
If the rotary valve rocks when pushing down on each side, either the back plate face or the rotary valve face is not flat. I can't see how that would happen though 🤔

Dont want to get into a debate with you.
I have ran across 2 of them over the years, & repaired them.
From engines that were giving to me for repair.
Just thought you should check the Rotor while you have the engine apart.
Fran

Hello

I received answer from Yamada. I'm surprise by the speed of their delivery., very quick !

"We will send DZ200 tomorrow. I test it on the bench, power was no problem. 21x10.5. 6,800 rpm 15% nitro. As the pomp bracket was broken, I changed it.
Best Regards"

I'm not totally satisfied because I will not know the cause of lack power.
claude

He never says what was wrong.

part of the YS 'mystique' :-)

Sort of reminds me of this scene... there's a longer version out there for context but this couple of seconds sums it up.

ARGHHH, can't watch it here: 'NBC Universal has blocked it here in the USA on copyright grounds'. For 8 seconds. Really...

The YS USA representative/distributor, Rich Verano, is happy to discuss YS problems in detail. He always returned repair engines with all the old parts that were replaced, too (or used to)

Hello

After having received the engine 200CDI from Yamada I was a little apprehensive because according to their statements the engine had nothing and worked well which was not the case before I send it to them.
I flew last week and the engine is as powerful as it was at the start.
I know these engines well because it has been about 30 years that I have revised them but there I understand nothing !
Claude

Good news it's OK again.