MAVROS

Once again i find myself on a forum trying to understand why this YS brand is so unreliable
Here it goes brand new YS 70 DZ new fuel new plug read the instructions 2 turns out.
No way it will start trouble shoot yes you guessed it no fuel going into the engine.
What am i suppose to do send it back to the shop and ask for my money back I have send another YS 70 back and they exchanged it with new.However i don't think the new one will be any better

The pont i am trying to make is why do we bother with such unreliable engines that will not even start when they are straight out of the box.

Electric will have a great laugh i know

regards

Mavros

bjr_93tz

So this is the 2nd 70dz that's had an iffy pump like the one you wrote about in October last year?

You are right. There's no excuses for a pump not to pump straight out of the box, however when I fill my plane for the first flight of the day I pressurise the tank a bit with the last few cranks of the handle so the pump doesn't have to suck the fuel through and it's clears any little bubbles quicker. Once it's primed through to the injector it's one prod of the starter.

For general information, when I was having ignition problems a few years back I messed with the pump by stretching the little springs to increase the teflon valve pressure, but all it did was prevent any little bubbles from clearing the pump because the very short stroke of the piston wouldn't generated enough suction to pull the valve open if there was any air in the cylinder. Drove me mad because it would work perfectly when stroked manually on the bench but wouldn't pull fuel when stroked by the intake pushrod. I shortend the springs to a specific length to reduce the teflon valve preloads to absolute minimum and it worked like a charm again.

MAVROS

Thanks mate,
As a matter of interest is the fuel line from the tank on your YS70DZ connected to the top nipple of the regulator or the bottom one?

regards

Jetdesign

My Feedback: (8)

I think people 'bother' because once you develop a good understanding of YS engines, you are rewarded with amazing power and a sweet sound. Most of the 'issues' with YS engines are due to people not fully understanding them, and therefore not knowing how to troubleshoot them.

I had a YS and I struggled with it. It was absolutely amazing when I could get it to run right. I was not interested in spending the time to really get to know it and suffer through the learning curve, so I sold it. I am sure someone else appreciates my lack of patience.

Nothing is perfect - sometimes there is a bad design or a bad part, but most of the time that is not the case with brands like YS.

I see myself owning one again in the future, if/when I make even more time for RC.

speedracerntrixie

My Feedback: (29)

I have owned 3 YS engines over a period of 20 years. All have worked flawless. They are different and you need to learn what the need just as Joe has stated. There is a reason why no other engines are used worldwide for pattern, simply put its because they work. That being said, if you no longer want your 70 I would be more then happy to send you an OS 91 surpass and 100.00 in exchange for it LOL

MTK

The smaller YS's usually worked well. I still have 120FZ and the 63DZ. Well mannered little mills. I had a 140L that was an absolute bear and after factory repairs it was sold.

The new 185 really really sounds interesting. Just may have to get one of them.

Gasoline 2 stroke engines that work well in Pattern are finally emerging over the past couple years. Light and powerful mills. One needs to experience the simplicity and easy field manners, and surprising torque in mid range to appreciate these latest developments. Some people world-wide are experimenting with them, notably the French and a several of us here in the states. These are more reliable than any glow powerplant I've yet seen. They just work and work, for years with practically no maintenance..... not one season and then overhaul.....As always your milage may vary.

bjr_93tz

Sorry Mavros, I forgot to mention mine was a 170dz but from the pics they look identical? On mine and the pictures on the net of the 70dz the fuel line goes on the bottom nipple, and the top nipple heads off to the throttle body. You should be able to pump fuel into the bottom one and it will come out the top but not the other way around.

Also when priming I have the throttle wide open so it pushes the fuel to the injector through faster, then close it back to idle for starting. I NEVER try to get the engine "wet", it's really just making sure the lines from pump-throttle-inejctor are primed. and only for the first start of the day.

I'll agree it was a learning curve and still is and there're some things I won't do with the engine eg. couple of laps flat out then pull to an upline with rolls on high rates at the end of the flight. It's quit twice over the years doing that for some reason so I don't do it anymore. Maybe the prop unloads a bit too much and it gets bubbles in the line during the rolls (I don't know) but it runs flawlessly during the schedule I have to fly so I'm not changing prop/fuel/needles just for some flat out hot dogging at the end of the day.. A downwind pass over the strip at full noise with an F3A ship tends to take the guys by surprise that're only used to seeing it nearly 200m away chugging around almost silently at constant speed..

kenh3497

My first YS was a 53 FZ that had a factory fault. It passed through two previous owners who failed to find the issue. My finding it was almost an accident. It had a TINY hole in the carb under the throttle plate so it would suck air. The engine was years out of warrenty so I fixed it with a little JB Weld. It is the sweetest engine I've ever had. It ran all summer long with only two adjustments to the high speed mix. ( three clicks each way) That was only necessary because of large temperature fluctuations. I've since purchased a second YS, an older but barely run, 120 NZ. I also ran flawlessly on the test stand. It awaits an airframe to stretch it's legs in. I intend to purchase more YS's as the need comes up.

Ken

speedracerntrixie

My Feedback: (29)

My current YS, a 115 WS runs great. It currently has 8 runs on it and has been flawless to the point of motivating this pylon airplane to a third place finish. The series is pretty much a local one in Northern California but we do draw guys as far away as Utah and Nevada including Mr. Yamaha himself that attended one race last season. I am currently bringing an old MK Aurora pattern airplane that would be a perfect candidate for the 7O

drac1

My Feedback: (4)

I've owned 14 YS's from the 63FZ, to my current 185cdi's and every one has ran straight out of the box.

With a new engine, I open the needle 2 - 2 1/2 turns. Full throttle and turn it over untill i hear the engine speed up.(indicating that there is fuel in the engine).
Back to idle and connect glow or turn the ignition on. Starts immediately. Run about 1/2 a tank through and make sure it will idle and throttle OK. 2 or 3 flights then lean it off to where i want it and don't touch it again.
From then on, the starting procedure is the same as already mentioned. I've never had any problems running my engines this way.

I use a bladder tank and have never had any issues with air in the fuel. The engines run perfect from an inverted low pass just above idle to a full throttle pass. Speed, roll rate, attitude of the plane, aggressive manoeuvres on high rates or any combination of these doesn't affect the engine.

It's strange, but It seems that some people have alot of trouble with YS's and others have little or none.

I've been using YS's for 14 years and love 'em. I wouldn't hesitate to buy another one, which will most likely be a DZ70cdi.

bjr_93tz

I use the K&S tank with the YS foam clunk and flying the shedule it works fine. The YS manual clearly states the foam clunk in a normal tank isn't going to work well if part of it becomes exposed so it's hardly a hanging offense (for YS) if I'm chucking the plane about with no fuel left in the tank at full power and it decides to stop twice in 3 years. I suspect it's really only there to stop air getting into the fule line while you're at idle on a downline. I run a bladder tank in one of my other sport planes, backwards with a foam clunk on a stumpy bit of tubing (because I can't be bothered to get all the air out of it) and it works fine. Bladder tanks aren't light though.

I've been lucky (?) to experience "great engine"->"terrible engine">-"fantastic engine" all with the same engine, and the "terrible engine" part of it's life was finally cured when all the little bits giving me problems were replaced about 3 years ago and I've been a happy camper with it ever since.

Rumour has it Matthew didn't have a flash run with YS at the Masters or was Painey winding me up?

drac1

My Feedback: (4)

Yeah Matt had a few issues, but got it sorted in the end. Onda helped out alot.

I'm more than happy to sacrifice a little extra weight for the bladder tank to ensure trouble free running.

MAVROS

Thanks to everyone for your replies.Sorry I haven't been on internet for a while but busy with work.
My YS 70DZ had the fuel line connected back to front straight from the factory and If you care to check the YS schematic diagram supplied it does show the fuel line in the wrong position as well hence it will not start.
Amazing that a manufacturer would miss this.
I have owned a feu YS engines now and personally the YS175CDI is the best so far but it is very disappointing when you don't get what you paid for

regards

drac1

My Feedback: (4)

If you are impressed with the 175cdi, wait 'till you get the 185cdi. Much better than the 175cdi.

bjr_93tz

Not sure what schematic they put in the box for your motor but the .pdf manual (english and japanese versions) on the YS site shows the fuel lines in the correct position.

I guess yours must have been one of the first ones out the door before they realised the mistake?

It does make you wonder about the training or culture because if I were on the production line and was told to put the outlet line on the bottom of the pump after years of putting the outlet line on the top of the 170/175/185, I'd ask my supervisor if he were sure..

drac1

My Feedback: (4)

It goes way back to around 2001 when the DZ140 was released. I would think the schematic in the manual is the same from then, with small changes as the engines were developed. The side view in particular appears to be the same, with the check valve added from the 160 and later the addition of the super mount from the 170cdi on.

I would think the pdf is what they use to print the manuals from. After so many years it is strange that some would be wrong. But then again, stranger things have happened.

I hope that you get your 70 running OK Mavros.

JRgraham

My Feedback: (1)

Ive had quite a few YS engines too, always ran flawless for me until my Dad got the 110. It would dead stick on him until finally the firewall broke off the plane last dead stick landing. He had even sent it in to YS and received it back claiming perfectly fine. I took it over from him, fixed the plane and went on with it.. ran great for about 5 tanks, and started running erratic and dead sticking again.. I found that the gaskets were getting eaten up somehow, no matter what I did. they are nearly just paper as it is.. I rebuilt it 3 times with new gaskets, same scenario.. about 5 tanks and problems started with gaskets leaking being eaten away.
I still have it in pieces, but unless I find a better quality gasket set.. it will remain in pieces.. its too bad for that one, because I have always had flawless running YS motors otherwise. Maybe just something out of play with that one causing extra vibes that eat the gaskets.. I dont know.

triumphman49

My Feedback: (149)

Speed,

That's sure a good looking plane. Love the yelo and red checker box. Looks like a great build and clean lines - sure is a big ol' canopy sticking up there.

Don't own any YS's yet, They sure seem to hold their value on the used market, as I've watched quite a few. That and tuning "fears" have probably held me back. Something in the 50 to 1.00 sz is probably in the cards for me tho.

Have a good one

T-man49 in Al
Club Saito 723
Glo Bro 33

bjr_93tz

That's a tough one, I'd expect the gaskets are the victim and not the cause. Gaskets tend to die if the clamping pressure is incorrect or uneven, or if they are lubricated before they are installed.

Two things to check would be are the mating surfaces flat? and is everything dry when you assemble it? I wipe all my surfaces with methanol or isopropyl alcohol to make sure they are lubricant free. Considering this engine has done this from new and from a factory rebuild I'd be really tempted to bet on uneven mating surfaces.

After a full rebuild I do tend to pull the engine after a handfull of flights and nip things up once the gaskets settle but I can't remember anything ever really needing tightening up. Valve cover is a bit hit and miss though, I'm tempted to pull the gasket on that, use a sealant as it only ever comes off about 2-3 times a year..

JRgraham

My Feedback: (1)

You know, funny thing adding to the 110 I mention.. it started when I noticed the valve cover gasket would go first. I surfaced the cover (like most YS engines really need) and solved that. But, then all the sudden after the valve cover was seated really well, the other gaskets started blowing out. First the backplate, then to another one I forget now.. I think around the carb area. been long enough now, I dont remember certain. I rebuilt it with new gaskets twice, but same thing both times, backplate gasket then the next. All within about 5 tanks. One side of the gasket would be nearly eaten away completely.

Pretty certain I surfaced those areas as well as I could too while i had it apart, thinking the same thing. It ran SO well though, for those few tanks it was amazing.. but just wouldnt hold. even transition was a bit more crisp than most I have had.
I do intend on playing with it again sometime near future when I have time to kill.. just wish I could find some high quality gaskets... because cutting them out is a serious challenge!

flywilly

My Feedback: (121)

I would give Rich Verano, The YS importer a call. He really knows the engines and may be able to help with the gaskets (there have been after market gaskets available in the past, though I haven't seen an ad in the K-Factor for them in several years. Since the DZs use a different fuel delivery system, demand for quality gaskets (in the pattern market) has significantly diminished. You might try your local 'speed' shop or check online. I also remember seeing an ad for laser cut gaskets somewhere.
Good Luck. YS engines are great when they run right, but can be a PITA when you are chasing a problem...

JRgraham

My Feedback: (1)

My next step on it was to find the best gasket material I could, and just cut some myself. I have just not began looking for the material yet.

Thanks

*oh, and yea. I was told that the higher quality gaskets that use to be avaliable were no longer made, like you said.. the demand faded away.

bjr_93tz

I've had the valve cover weep a bit but never enough to affect the running, but actually blowing bits of gasket out? That seriously sounds like the gasket itsn't being clamped into place evenly all around. I know I have had to touch up the phenolic (or whatever material it is) spacer between the throttle body and crankcase as it doesn't stay particularly flat.

If you get the motivation in the future, chuck it back together, give it a couple of runs then pull the back off it and see where the gasket is or isn't seating. Other than that you're sort of stuck with finding a reinforced gasket material.

JRgraham

My Feedback: (1)

I agree, it is out of the ordinary. And I have had it apart and new gaskets 3 times. The back plate would be disintegrated on the one side every time, so it is consistent. After that third rebuilt with same results, I put it in the box until I both regained the desire to do it again and seek out better gasket material. Because I am almost certain I will have to find the materiel and cut them, (and did cut a set once) its a real pain in the rear.. but I will eventually. Might just be in the near future, since I have some new ideas too.. (like welding the thing together! just kidding)

bjr_93tz

Put it back together with some JBweld, then after 500 flights sell it to somebody you don't like