Wow!!!!!!!!!

Heck, I got my first 4-stroke last year and love it. Have purchased 3 more but they're still in their boxes. Bought a tach too...just 'cause I wanted one. And they're nice. Especially when you can see rpm changes that your ears don't reveal. Don't believe me? Just point one at a flourescent light!

The good thing about the flourescent light is it demonstrates just how accurate that tach is. My engines-2-stroke and 4-stroke all vary rpm's some, but not that light. (Be sure to turn light off before taching your engines.)

I can't say that I need a tach but I sure like it and I know I can use all the help I can get. Now to figure out why I can't keep a prop on an engine that's not running lean and as best I can tell not backfiring either!



Clay

I use a tad of thread lock and a cresent wrench to tighten up the nut.

seems to hold the prop on a little better

Wow,,,,hope you guys aren't in the same club. If you are, I bet club meetings are a real treat!!!

I would suggest that whoever wants to use a tach,,,,use a tach. Whoever doesn't,,,,don't. Pretty simple. Just double nut the prop and go to tuning. Whenever it gets to lean,,,,it'll die.

Have a great day![8D]

The only real problem ive had with four stroke is it pulling my birds straight up out of sight there a get engine to have

I sometimes work on other people's two strokes but I don't own any two strokes

I just got my first YS, a .63, and fired it up for the first time this afternoon. all I could say was HOLY S***! It fired right up and adjusted very easily. I've always felt the throttle response on OS and Saitos was great but this little YS is unbelievable. Not only that, it sat and idled beautifully.

I forgot about the pressurized fuel system though and pulled the line off, squirting myself with fuel.

I can't wait to get it in the air. Hopefully it doesn't make a liar out of me.

Nothing runs better than a new Y-S

I cannot wait to fire up my nice new YS FZ110s!!! You guys are getting me awfully excited; just over two months and it will be time Fortunately or unfortunately I've been concentrating much more on school this semester and haven't really touched a plane since January; still have a little work to do to all 3 planes before they are flight ready, but that's what Spring Break is for!

To tie it to the thread, I've got one season of flying RC - all two strokes. I took the plunge for a 4 stroke, and I think the OP should, too!

Now I don't have any first hand experience tuning a four stroke (other than holding a plane and blasting my instructor with questions while he tuned his), so I plan on bringing along my tachometer, leaning out in small increments, and listening by ear and watching my tach for the first sign of a drop in RPM. Maybe I'll hear it, maybe I won't...
I remember the excitement of starting my first RC plane engine last summer. I was extremely excited and nervous and didn't really know what I was listening for. Even with a bunch of hours flying, I still think I'll feel the same with the YS, and having the tach is at the very least an extra safeguard against nasty lean conditions.

Well 8, after all this time I thought you were a strict Saito guy. I am impressed!!!! Chuckles, nice to see you made it away from the dark side!!![8D]
Joe, see what I said, they are great right out of the box. Most people never have to touch the low end at all, even that big scarry brass screw is factory set. [8D]

I won't give up on the OS 4-strokes just yet but I've been impressed so far. A summer of flying will be the real test. Actually I finally broke down and bought a couple gassers and I almost contemplated ditching the glow engines all together.

Same here. I have my 30% Extra up and flying. Just starting to work on the trim and get all the little bugs worked out. I have my RCS 1.40 mounted onto an old 120 size Kaos but it has taken a back seat to a build I'm working on. Maybe get it up and running again this summer? I keep saying that. I have a Brison 2.4 doing nothing and I keep looking at my old Boeing Bipe thinking it would be a nice home for the Brison. Just a pain to haul out to the field. Then I look at my glow planes and I can't see myself retiring them but the gassers are just so easy and you don't need all the support gear. I just can't put them away.[&o] I may just get another set of plans and build another Sukhoi around the Brison, that was an outstanding combo!! Just too many choices!!!

gaRCField,

Bet you'll still be amazed. Last year when I decided to get back to RC modeling I decided to spring for a 4-stroke. When I fooled with RC 20yrs ago the 4-strokes sounded good but seemed cantankerous yet I still recall telling myself back then that I wanted one.

Due to the cost I purchased a Magnum XL 91 RFS instead of a YS or Saito and to be honest, I was a little worried about it. I purchased a Jtec engine stand and mounted it to a small table in my garage (that is on wheels) that I'd been using to run some .049's on.

Now, I knew a larger engine would pull the table some so I made sure I mounted it over the end that didn't castor at right angles to the direction the wheels turned. Not knowing which direction of the throttle arm was off or full throttle (and not looking in the barrel of the carb to check ) I was caught by complete surprise when the engine fired immediately when I hit it with a starter.

Keep in mind this was the first time I'd used any of this stuff in approximately 20yrs too and to say I was rusty is an understatement. Something flew off and hit my forehead, I had to stiff arm the table to keep the engine from chewing me up and it took a second to regain my composure, wrestle myself to a position where I could hold the table with one arm and reach around and shut the dang thing off! Thank goodness the prop stayed on!

Turns out the cheap plastic spinner disintegrated when the engine fired and flew all around the garage in a gazillion pieces. That's what nicked my forehead and as it turns out my arm and back of my hand. Lucky I wear eyeglasses. That will also be my last plastic spinner (held together with sheetmetal screws at that).

I followed the instructions on breakin and ran a half-gallon thru it before mounting it in my plane. I also rigged up a throttle linkage on my test bench so I wouldn't have any more runaways I can't manage.

The power of that engine still impresses me and I can only imagine how strong these gassers folks use nowadays are. I was very fortunate to not have been seriously hurt and atleast had some familiarity with it so I was able to react fast enough to the situation I so foolishly had gotten myself into. I was also shocked to discover how much castor a half gallon of fuel could deposit on my car windshield when it was parked all the way at the end of my driveway while the engine and test stand were up inside the garage with the propwash directed outside!

The fuel residue running around the engine was black at first but cleared up significantly halfway thru the first tank. The idle improved remarkably after the 3rd tank and the engine has had about 1 1/2 gal thru it now. I pulled it and installed a ST 75 2stroke on my trainer so I could put the 4-stroke on my T-28.

Its been a few months now, I'm still assembling another ARF and have yet to maiden the T-28 successfully so I'm just about as excited to get back at it as I was this time last year.

Sorry for the long post. Your excitement about your new engine got my wheels a'goin.

Clay

Many of the posts here are people saying how much they love the 4s better than 2s. Seems kinds weird to me really. Don't get me wrong I have 2 4s in my fleet right now and I love them. I have a old OS 91 Surpass that has some serious miles on it, (25-30 gal) and it still runs great. I also have a fairly new Saito 82 which is a sweet little motor. For me though I don't like my 4 strokes any better that my 2 strokes. My other three planes are 2 strokes. I have one TT Pro 46 which in my mind is the best 46 on the market hands down. My other two planes have OS 55AX's on them. Now that is one awesome little motor. As much as I love the Pro 46 it just can't hang with the power of the 55AX. One of my 55's has a tuned pipe on it and i love the sound. A 2 stroke engine screaming by at 15k rpm sounds just as cool to me as a big 4 stroke roaring by. For me a good balance of both types of engines is best. As far as tuning goes I really do not think one is any easier than the other, they are just different. I can tune by ear on both sides but I have a tach for seeing the difference between props. I like to do alot of experimenting with props and seeing how the changes made in RPM affect both speed and transition. When it comes to experiementing with props you can't "hear" a certain RPM.

tonight was engine check out time for me on my OS 91Surpass thats mounted in my Hangar-9 P-40.
the usual engine mount bolts,one was slightly loose now tight.
clean and inspect engine area.
check fueler for proper operation, good to go.
fuel lines for wear and potential leaks, looking good there.

and last but not least the rockers,the engine was new when it went into the plane and passed the adjustment test last time I opened it up but was on the loose end of the spectrum, since the engine was nice and cold and the house was quiet I went for it.
flipped the plane over and after wiping the engine down I unscrewed the valve cover engine looks good nice and oily makes me happy
after finding the neutral point where both valves were closed OS engines have a mark on the thrust plate I pulled out the OS valve adjustment kit and checked the gap.
well what do you know a little sloppy on my clearances over.014 the thickness of both feeler gauges put together a .004 and .010 this is over the recomended clearance.

FYI the engine will run with this gap mine was running, but might not have full power or rpm's with a little slop in the rockers, I started to notice a small drop in the RPM's and smoothness of this engine last time I flew it so I had a feeling the rockers needed looking at.

so time for a adjustment, this is a fairly easy job but I will go over it for the new 4strokers out there to eliminate the mystery around this task.

in the adjustment kit which includes instructions for doing this job if you lost your booklet that comes with the engine, there is a small wrench for the lock nut its about 4mm or so and a allen key to fit in the tappet adjustment screw, loosen the lock nut just a little and slide the smaller gauge between the rocker and the top of the valvethen with a light touch tighten the screw so it snugs down on the gauge then back it off so it slides freely, and holding the allen key tighten the lock nut.

then check the gap with the thicker gauge I go with tight for this gauge, flip the prop at least 2-3 revolutions and recheck the gap, if it checks out, repeat on the other one, and its done.

this is the one bugaboo with 4strokes and it really isn't that big of a deal,it can affect the quality of the engines performance but a once a ayear check is all that needs to be done.

I just got a new set of electric retracts,and struts, for this plane so now its ready for our new field, hope this clears up any questions about this little job, figured since I was doing it I might as well take some pics to post.

This means nothing at all but I will pass on a little secret. These four strokes will run very well as long as the valves are opening at all. Anything is about enough. They aren't putting out peak power but they will run. That's why I check mine every year. If you think about the valve lash or gap it's a low of .004mm to .010mm, that's a bunch of slop to play with. Anyone should be able to adjust them if you just read the instructions. When I was building VWs the gap was .006in set cold. Just kinda giving you an idea of what you can get away with. These engines are very user friendly!!

The clearance ramps on our model four strokes are set up for the .002"-.004" range

Running .010" long term will show up on the cam and lifters as wear at the beginning of the cam ramps and edges of the lifters

thats why you set them at .004 cold when adjusting them to get the slop out, the 91 was running but had lost a bit of peak rpm, and wasn't purring like it usualy did I have had this engine for close to 4 years and this was the first time having to touch the valves at all.