jeeper80

I picked up a YS .61 LS that was all gummed up. I freed the piston by soaking the engine in lacquer thinner. The problem I have now is that the backplate won't budge. Any tricks for removing the backplate?

NoOneFlysAtMyClub

My Feedback: (32)

Warm it up with a heat gun then tap it with a plastic screwdriver handle.
Works great.

DRC1

My Feedback: (10)

speedracerntrixie

My Feedback: (29)

I hope you didn't expose the diaphram to laquer thinner.

doxilia

My Feedback: (3)

Mmm...

Yea, a complete break down and replacement of silicon parts might be in order. No petroleum based products or chemicals that attack silicone should be used in these puppies!

David

jeeper80

Oops, yeah, very possible that lacquer thinner got to the diaphragm. Anyone know where I can get a new one?

doxilia

My Feedback: (3)

YS engines USA or the auction site. Possibly here via request.

Did the backplate come off?

David

jeeper80

Yup, I guess the lacquer thinner softened up some of the crud and I gently removed the plate off by wedging a sharp chisel between each screw lugs and the case. No damage and the gasket is reusable. I was able to remove the liner and piston. The wristpin was very stiff but some good old lacquer thinner and WD40 loosened things up. Put the engine back together and it has excellent compression. I bought some Boca bearings for it. Don't really know if it needs it. Feels pretty smooth but theres a lot of black gum build up on the bearings and don't know if that will be harmfull if it llosens up and starts floating around.

doxilia

My Feedback: (3)

It's not worth the risk IMO. If there is something black and hard, get the new bearings in.

If you soaked the entire engine, there's a good chance the silicon parts are shot. It's best to disassemble the carb parts from the engine first and then, once there is only metal and a backplate gasket, you can go to task. Heat works very well especially when it comes to freeing a sleeve from a case or the crankshaft from the bearings. New tricks I learned here. You often have to handle the engine with gloves after it comes out if the oven and work quickly as the metals cool down quickly and the differential expansion is short lived.

While the engine is disassembled, take advantage and make sure the carb air and fuel conduits are clean and free from residue. YS engines have a very different "injection" type fuel feed mechanism than ordinary carb engines. Replace the needle o-rings and the diaphragm and reassemble. If the piston and sleeve are in good shape, it should deliver impressive performance. Prop it with a 12x10 or so.

Don't put any typical after run oil in the engine. Use synthetic Mobil or the like.

Rear exhaust or side?

David

jeeper80

It's a rear exhaust engine. I wonwhat looks like a Hatori .60 size tuned pipe on aEbay bid. Hasn't gotten here yet.Looks like alater 650 or a 700 with the baffle corrugations. According to the ad specs though, it sounds like it's a 650.

flywilly

My Feedback: (121)

Performance Specialties makes an after run oil formulated specifically for YS use called Ultra Oil. Check their website.

DRC1

My Feedback: (10)

Many Pattern guys used Mobile 1 Synthetic Oil if I'm not mistaken. It won't attack the silicon...

Dean Pappas

Yes, Mobil 1 definitely: it does not affect the silicone parts and is the best anti-corrosive you'll find for alchohol fueled engines.
Regards,
Dean Pappas

Jim Johns

Ah, my brother from another mother. Good to see you post, Dino! Gentlemen, this man has forgotten more about airplane design and engines than most of us will ever know! Not to mention that he's a great guy to boot.