Question #1: Flew my Funtana 90 powered by a new YS1.10 for the first time this Saturday. I am flying at 4700 ft. I had the engine running great on top end, idle (2200) and transition. However, after running in the midrange for any amount of time, the engine would sputter and die when I would open the throttle. One thing I noticed was that the engine would leak fuel out of the carb when it wasn't running until I relieved the pressure in the tank. The engine is mounted horizontally. I'm running an APC 16X6 prop and 20/20 fuel.

Question #2: What is the correct idle speed for tuning and running? Mark Fuess (see link below) suggests that the idle speed must be 2000 RPM or below to correctly adjust the idle. He states that the reason for this is that 2000 RPM ensures transition from fuel injection to carburetion has taken place. Any comments?
http://home.comcast.net/~mark.fuess/ys110.htm

Question #3: How is the bottom end of a YS1.10 lubricated? I've read that fuel is injected only into the air chamber. My understanding is that other nitro 4-strokes depend on blow-by to lubricate the bottom end. With the YS, the crankcase is typically under pressure so I would expect this to reduce the amount of blow-by.

I never try to idle any YS at 2000. I like to be slightly into the regulator at 2200 to 2400. It's personal preference, but it works for me, and a whole lot of other flyers as well.

I think your only problem is the regulator is set too rich for your altitude. Start screwing it in 1/4 turn at a time until it works properly.

The 110 runs fuel through the lower case just like all YS engines other than the DZ's. The DZ's depend on blowby for bottom end lube.

Thanks Dave, I'll give it a shot.

Is it normal when the fuel system is under pressure for fuel to leak out of the carb when the engine is not running?

They will dribble sometimes, but if fuel is gushing out, the plunger is either stuck or there will be some debris holding it open. Relieving the tank pressure after a flight is a good thing to do, and will help with the dribbling problem.
Are you using fuel dots, or some other type of fueling arrangement?

It's just dribbling.

I'm using fuel dots. The "fill" fuel dot is tied in to the fuel supply line, so starting at the tank there is a "T" for the fill fuel dot line, a filter, then the engine fuel inlet barb. The "vent" fuel dot is tied in to the pressurization line, so starting at the tank there is "T" for the vent fuel dot line, a checkvalve, a filter, then the engine pressurization barb.

I'm curious about the where and when the fuel is injected. Where is a good detailed description of the YS air and fuel induction process?

The fuel isn't INJECTED anywhere in the normal YS engine such as yours. It has a common carburetor which feeds a disc valve in the backplate. The engine intakes on the upstroke and fuel/air is forced into the combustion chamber on the downstroke, much like a 2 stroke engine The YS 91/110 and the old 120AC used what they call an "air chamber", the box behind the head. In reality it's just a plenum, or storage box for the fuel/air coming in from the bottom end. It increases the volume of the fuel/air charge when the intake valve opens.

Your fuel system sounds fine.

Hi Dave,

Ran another 1.5 tanks (16 oz tank) of fuel through my new YS1.10 tonight with the engine mounted in my Funtana 90 and the cowl off. This makes a total of 3 tanks of fuel through this engine.

I did as you suggested, and turned the regulator adjustment screw in 1/4 turn at a time. I experimented only with regulator screw settings that were clockwise (lean) of the regulator screw being flush with the regulator housing. I would make the regulator adjustment, take it wide open and set the high end needle about 300 RPM down from peak (plenty of smoke), set the idle screw as best I could, then test transients and midrange performance. In every case, the top end and transient performance were great, the idle was so-so, and the engine would never run properly from just above idle to about 3/4 throttle. If you tried to hold a constant speed in that range, the engine would start hunting, then die. Hooking the glow starter up made a substantial improvement to this midrange problem. Even with the regulator screwed all the way clockwise, transient performance was still great? Doesn't make sense to me.

Tomorrow I'm going to reset everything back to factory recommended initial settings, then go from there.

Any other suggestions?

This thing pulls like a horse (16x6 APC @ 9200 RPM at 4700 feet on 20/20!) and has great throttle response. I can't wait to get this mid-range problem fixed.

You never mentioned glow plug. I'm assuming either YS#4 or OS-F. The engine is looking for HEAT. At your altitude (just like mine) you can do one of the following: Increase nitro to 30%(use 30% heli fuel), or try pulling the element up out of the plug about 1/32" with the tip of an exacto #11 blade. It will make the plug run hotter. Hooking up the starting battery should have been the clue.

You really haven't run much fuel through this thing, I would suggest at least a couple more tanks through it at a slightly rich full throttle setting without trying to set any of the other adjustments.

Reset the valves to .003" just for drill.

Hi Dave,

The glowplug is an OS-F. I take it you are having to make the glowplug mod and/or run 30% nitro in your YS's? What is your altitude?

4800 feet. Some engines need it, some don't. What brand of 20/20 are you using? Maybe a switch to another brand of fuel will fix the problem. I've seen it before. All fuels are not created equally, no matter what the mfg. tells you.

Dave,

A buddy of mine was flying my Funtana 90, and without too many details, the plane ended up slamming in to the ground nose first. Externally visible damage to the engine is a bent crank and destroyed muffler. Any idea what it might cost to get this fixed if I sent it in to you guys?

I had switched to Cool Power 30/20 fuel and the engine ran better, but I was still never able to get the mid-range to clean up to my satisfaction.

Impossible to say without seeing the crashed engine. Send it to service and ask for an estimate.

As far as your goes, wait until the season is over and send it to us, we can make it perfect.

Hello Again Dave,

I have just finished installing a new crankshaft, crankshaft bearings and shaft seal in the YS110 I mentioned earlier in this thread. I am currently in the process of trying to install the camshaft.

The instructions state "Turn drive washer so the piston is at top dead center. This can be accomplished by aligning the "I" mark on the drive washer to the top of the mold line on the engine front case. ...cam...should also be mounted with the point mark located towards the top of the engine just below the cam followers." I have a couple of issues/questions regarding these instructions.

I haven't yet mounted the drive washer, it does not have an "I" mark, and doesn't have any kind of key aligning it with the crankshaft anyway. How would I possibly use it to obtain TDC?

I have set the engine at top dead center by aligning the rod pin on the crankshaft with the casting line on the case. I measured the casting line to ensure it represented the center of the case. With the crankshaft aligned with the casting line, I installed the cam. The problem here is that the mark on the cam is not exactly at the top (w/ cam seated in its innermost bearing). In fact, it's almost exactly 1/2 tooth off, so I don't know whether to install it 1/2° retarded or 1/2° advanced?

Thanks in advance for any answers you can give me on these issues.

P.S. I just read through some other 1.10 related threads on the YS Engines Support Forum. Sounds like others are having mid-range problems similar to what I mentioned earlier in this thread. Can you give me some details on what you are finding as the cause for this problem?

The newer engines have gone to a collet on the crank rather than a keyed driver, so there is no mark.
The alignment mark on the cam gear should be as close to vertical as you can get. Since it is off slightly, run it to the advance side and you should be OK.

The mid range problems are either regulator, throttle barrel or both. Depends on the particular engine. It has been a problem on a small percentage, I'm glad for that at least.

Dave,

Thanks for all the help. It would be great if the manual could be updated so that other YS1.10 owners won't suffer through the same confusion.

If the midrange of this engine doesn't improve after a couple of gallons of fuel, it'll send it your way.

Keep me posted.

Hi Dave,

I've given up and am sending this engine to YS Performance. I have about 20 flights on it now, and the mid-range is not improving. With the regulator set for optimal throttle response, the engine still still surges badly in the mid-range and at some point usually ends up dying.

I've going to follow the service instructions on YS Performance for returning the unit. I'm also going to include a letter with details about how the engine has been running. Please let me know if there is anything specific I should include in this letter.

Just your contact info. Sorry for the hassle, we'll get it fixed.

Dave,

The engine was shipped out yesterday and should get to you in 2-3 days. Are you involved with the actual repair?

I included a letter explaining my history with the engine. I didn't include that I have been running a 16 x 4 APC prop. You guys might also want to verify the cam timing.

Actually I don't work in service, but I pass along info to them daily.

A 16x4 is a little light for the 110, we've been using a 16x6 with better results.

Service will run the engine before shipping it back, so there should be no problems when you get it, barring snow on your end of course.

I'm using the 16x4 to keep the speed down on the Funtana 90. This plane has reputation for aileron fluttering if you fly it too fast. This is actually what brought down my first Funtana 90. I would like to run a 17x4 APC, but there isn't one on the market yet that I know of.

All you have to do is throttle back in level flight or when diving. The 16x4 is too small for a 110.

There is an APC 17x4, I will try it tomorrow, will let you know.

Yeah, unfortunately I wasn't the one flying it when the incident occurred. I will certainly move up to a 17" prop if one is available.