ys 91 4 stroke
 

My YS has fuel dripping from the vent line during operation can you suggest what might be done to correct this?
Thanks for your help.

RE: ys 91 4 stroke
 

YS does NOT have a vent line. It's a pressurized fuel system. There are NO connections to the muffler.


http://www.smilexpress.net/photo/alb...1_plumbing.png

RE: ys 91 4 stroke
 

My ys has a nipple located on the rear left [as you are facing the engine], lower 1/2 of engine which drips fuel. I called it a vent, it is probably something else.
Any thoughts or suggestions?
Thanks for looking and best wishes.

RE: ys 91 4 stroke
 

Like this one?

http://www.smilexpress.net/photo/alb...0_plumbing.png

RE: ys 91 4 stroke
 

Thumb.....thanks for hanging there with me. Turns out the nipple is on the carburator. There are two nipples at the very front of the engine and the one on the carb. The supply and pressure come off the front of the engine. It is labled OS 91 AC.
It is the nipple off the carb that drips fuel.
Best to you.

RE: ys 91 4 stroke
 

The nipple at the carb gets plumbed to the regulator just under the cam on the side of the engine like on the bottom image.
The rest of the plumbing is like the top picture. The top image is from the 91AC manual.
Replace that line with new tubing.

RE: ys 91 4 stroke
 

Here is a picture of a YS 91AC at this [link=http://www.geistware.com/rcmodeling/images/91ac_newl.jpg]LINK[/link]

If you are dripping fuel from the carb nipple it is either loose, the washer is missing or the fuel tubing has lost its elasticity.

RE: ys 91 4 stroke
 

I was finally able to get the cowel off and get a closer look. What I thought wa a nipple appears to be a set screw or adjusting screw on the other side of the engine. It is not a niopple. My guess is the carb is dripping fuel. It was dripping off the set screw so I thought it was some kind of nippole.
Any thoughts on why the darb would drip fuel?
Thanks to you bogh for looking.

RE: ys 91 4 stroke
 

Yep. if the regulator gets some crap in it and it doesn't close you will get a drip from the carb. If the engine is inverted you will get a little drip every now and then just from fuel giving in to gravity but a constant drip is the regulator not sealing shut.

RE: ys 91 4 stroke
 

good deal that 91 is a beast i run a 16 x 6 on mine

RE: ys 91 4 stroke
 

Thanks guys so much for your help. Now if I can just figure out how to clean that regulator.
Best wishes.

RE: ys 91 4 stroke
 

The regulator is pretty straightforward, before you begin take note of where the regulator is set. Pull the housing off the engine, back the regulator screw the whole way out and remove it and the spring, noting which way the conical spring points, and flush it out with raw fuel while exercising the plunger. Make sure you do all this in a clean environment as any dirt in the area will find its way into your regulator and cause you grief.

If you are not comfortable doing this you can box it up and send it in to YS for repair. Given the age of the 91 it might prove prudent to have it gone through.

RE: ys 91 4 stroke
 

Pete; thank you. I was trying to find a drawing of the parts assembly. Your description help a lot.
Best wishes.

RE: ys 91 4 stroke
 

http://www.centralhobbies.com/Engine.../YS91ACEX.html

Exploded diagram of 91AC.

RE: ys 91 4 stroke
 

Thank you sir, working on it now.

RE: ys 91 4 stroke
 

Fullload<div>I know it's been a few months since your last post on the YS 91, was wondering if you got your engine running yet. I have a YS-91A and when you have trouble with this engine, it can be frustrating, even the plumbing can be confusing. But once you get it running right, it's a powerhouse!! I've had my YS-91 since 97 and it's still going strong! </div><div>
</div><div>Just wanted to throw my two cents in!..Enjoy!</div><div>Gerry</div>

RE: ys 91 4 stroke
 

Hey Gerry;
Thanks for checking up on me. I have not gotten into the 91 yet. Busyness keeps getting in the way. I have however put the plane on my hobby table 3 days ago to begin.
I have the detail breakdown right next to it and planned to make it the next project.
If I run into problems, can I come back to you?
By the way, you are right, the YS 91 has more power than should be allowed. I am really surprised at what it is capable of putting out. I have a Saito 90 for comparison and although the Saito runs well, there is no comparison relative to power.
Thanks again for the check back and best wishes.

RE: ys 91 4 stroke
 

Petre
Bit the bullet, and took the time to pull the 91 apart. Pretty straight forward, may have been a tiny peice of metal in it, but otherwise looked pretty clean.
I do have 1 questionm; How far in do I turn the large pring regulator screw? It appears to have a pretty wide adjustment range. Can you give me any tips for that?
Thanks again, and best wishes.

RE: ys 91 4 stroke
 

Flush with the regulator body to start.

RE: ys 91 4 stroke
 

Yep start with the brass screw flush with the regulator body and go from there. Do NOT screw it down the whole way or you risk the little spring taking a set and not functioning properly. Also make your adjustments 1/8th turn at a time and allow the engine to catch up to the changes so you don't keep chasing the regulator.

RE: ys 91 4 stroke
 

OK, I've got a dumb question. I make 1/8 turn adjustments with the screw, what am I looking for to determine when I have the setting correct? Will the engine just not run if it is too tight?
Thanks and best wishes.

RE: ys 91 4 stroke
 

Check out this link:

http://www.julton.net/Fact%20Sheet%20YS%20Engines.html

It will answer a lot of questions.