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YS user seeking sympathetic ears :(

Old 03-13-2017, 03:37 PM
  #26  
bjr_93tz
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Off the top of my head ~40 US gal, based on the number of empty 20L methanol drums I think I have in the shed.

That number does seem a fraction low, given I ran the 600cc fuel tank for a few years before switching to the 360cc fuel tank and clocked up a few hundred flights (full tanks, not schedules) per year.

New head just turned up in this morning's mail, so I've got something to do when I get home from work this afternoon, if it's not pouring rain like it is now...

Quick Update: New head assembly installed, lawn fertilised and had 20mm of rain to water it in. At least the lawn mower runs ok, touch wood...

Last edited by bjr_93tz; 03-14-2017 at 02:00 PM.
Old 03-15-2017, 08:45 PM
  #27  
bjr_93tz
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New head assembly arrived, new check valve fitted, valve clearance set in the middle of the range (about 0.05mm) to allow for some settling in and out to the field I went.

First impressions were a bit of extra oomph at lower throttle settings but no spectacular change on the tacho at full noise. 5 minutes in the air later I'm creeping up the throttle position a little more each pass as the power is dropping off, then the misfiring starts all over again. Land it, shut it down, spinner back plate is cool and the cylinder is cool enough to hold for a few seconds without burning yourself. Bit more needle and reg tweaking and a few more ups and downs and nothing is getting better so called it quits for the afternoon. Odd thing is that the leaner I went the more responsive the engine became, and the earlier it began to misfire..

Pulled it apart last night to replace the ring seeing as I had one in stock, and the crankcase and valve lifters were full of fuel. Had a real close look at the throttle body and butterfly seal and couldn't see/feel anything obvious. Pressurised it underwater and nothing leaked where it shouldn't, and reassembled it all with new o-rings, gaskets and carb insulator.

Took it out at lunch today and same thing, cruising around to bed in the ring, with the occasional upline to clear things out and 5 minutes later, I'm inching up on the throttle as the power starts dropping off, then the misfiring starts again.

The oil underneath the plane is as clean as it went in, usually it's lightly speckled (running 10% coolpower) under there with slightly darkened (but not burnt) oil.

I'm stumped how an engine that can run so well for so many years, can become unreliable within the space of 1/2 dozen flights with nothing obviously broken.

I've got some choice words I'd like to use to describe my feelings on the matter, but "very disappointed" is close enough for now.

Last edited by bjr_93tz; 03-15-2017 at 08:49 PM.
Old 03-15-2017, 09:25 PM
  #28  
Dave Harmon
 
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Just for kicks....try installing a glo plug and have another go.
You'll have to retune it though...richer on the needle and mebby richer on the pump.
Back on the CDI....experiment with different spark plug gaps and different plugs.
Is this engine a conversion from the glow model?
YS sold a mod kit with a different head etc along with the CDI box to convert the original engine to spark.
Old 03-15-2017, 10:19 PM
  #29  
bjr_93tz
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It's a factory cdi, not a conversion.

I'm really tempted to go the glow plug route, however I've heard the horror stories of backfires and kickbacks and I'm very reluctant to tempt fate. I've replaced the sensor, module and plug with no change to the problem, even running it directly off a battery instead of through the regulator to isolate that.

If I had an old workhorse to mount this into I might not be so concerned but as it is my Oxai ship is getting pounded left and right at the moment. It's turned out to be a good thing it was one of their more "solid" airframes.
Old 03-16-2017, 12:19 AM
  #30  
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Originally Posted by bjr_93tz
It's a factory cdi, not a conversion.

I'm really tempted to go the glow plug route, however I've heard the horror stories of backfires and kickbacks and I'm very reluctant to tempt fate. I've replaced the sensor, module and plug with no change to the problem, even running it directly off a battery instead of through the regulator to isolate that.

If I had an old workhorse to mount this into I might not be so concerned but as it is my Oxai ship is getting pounded left and right at the moment. It's turned out to be a good thing it was one of their more "solid" airframes.
I would run it on a glow plug Brett. It will prove whether it is actually an ignition problem or not.
You will have to richen both needle and reg, but you are using a large tank so will be able to fly the whole pattern OK.

Not sure what stories you have heard, but shouldn't be any different from a normal glow engine. Using a delay on the glow driver is a good idea though.
Old 03-16-2017, 01:13 AM
  #31  
bjr_93tz
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Thanks Scott, I'll have to go through my stash of goodies to find a suitable glow plug.

I have an OS "F" plug on hand, but I'm sure I've got a YS 4 stroke plug hiding around. I'm not keen on drilling holes in the belly pan but I'll sort out something.

But stuff me, I've got 3 cdi modules, 3 cdi sensors and a bag full of new and used spark plugs to swap around, how many do I need!!!

Cheers
Old 03-16-2017, 02:25 AM
  #32  
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Originally Posted by bjr_93tz
Thanks Scott, I'll have to go through my stash of goodies to find a suitable glow plug.

I have an OS "F" plug on hand, but I'm sure I've got a YS 4 stroke plug hiding around. I'm not keen on drilling holes in the belly pan but I'll sort out something.

But stuff me, I've got 3 cdi modules, 3 cdi sensors and a bag full of new and used spark plugs to swap around, how many do I need!!!

Cheers
Either a OS or YS plug will be fine.

Fly it with the cowl off. If it runs OK, then fly it with the cowl on.

You could do that using ignition as well. A couple of more things eliminated.
Old 03-16-2017, 10:48 AM
  #33  
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Did you run it on a stand?
Running without - with the engine cowling might indicate a cooling problem.
Old 03-16-2017, 11:33 AM
  #34  
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The fuel pump has it ever been replaced or has all the 40 US gal of fuel gone through that particular pump.
It might be the problem, there are some wear parts in it along with a dynamic seal (O-ring).
You said there is a lot of fuel in the crankcase and valve lifters.

Regards,

Arnstein
Old 03-16-2017, 02:52 PM
  #35  
bjr_93tz
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Hi Arnstein, the fuel pump was one of the first things I changed when the problem started. I replaced the original pump during the horror nine months that occurred not long after I purchased the engine, so the 2nd pump (with the seat inserts) had done quite a bit of work by the time this problem reared it's head.

I haven't found a regulator position I'm happy with yet, but 2 or more turns out from flush seems to be where the engine is reasonable.

As it sits in the plane today, the only original parts left are:
Crankcase
Crankshaft
Cam, cam cover and valve lifters
Valve rockers and exhaust pushrod
Valve cover
Throttle body, butterfly and main needle valve

Seriously, that's all that is left from the original engine I purchased in 2009. Talk about getting nickled and dimed!

I am tempted to bolt it to a bench and flog it...
Old 03-16-2017, 05:39 PM
  #36  
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I had terrible trouble with the 170 pump piston wearing out....take a look at it and you'll see.
Low oil content make this worse.
Old 03-16-2017, 08:01 PM
  #37  
bjr_93tz
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Thanks Dave, I re-read my previous post and it didn't read very clear. I replaced the 2nd pump with a new pump not long after the problem started so it's on it's 3rd pump now, and it hasn't seen much work yet. I did disassemble it and flush it between flights while the plane was charging but it made little difference.

There was fuel in both valve lifters and fuel pooling in the crankcase when I pulled it apart the other night. In a perfect world, fuel goes in at the intake valve (I've got the sub needle closed at the moment), is burned, then shot out the exhaust. There shouldn't be raw fuel in the crankcase or cam area unless it's leaking from the throttle assembly, pump or the intake valve isn't sealing. Surely the old (2nd) pump wasn't leaking into the cam area and the new (3rd) pump is doing exactly the same?

It wouldn't surprise me, I had to send back a brand new back plate assembly because it was faulty out of the packet. Imagine my frustration to fit a new back plate assembly, turn it over by hand to check the spark, head out to the field and then not a single pop when I tried to start it. It'd spark when turned by hand, but no spark when turned by the starter. How does that happen???

If the weather holds I'm heading out this afternoon with the valve clearance set to the full 0.1mm, and a new spark plug set to 0.35mm. Fingers crossed...
Old 03-17-2017, 12:52 AM
  #38  
bjr_93tz
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Quick update re this afternoon's shenanigans.

With the valve clearances loosened out to ~0.1mm and tweaking the mixtures in the starting gate with the tacho to get a baseline setting, I just had 3 x 20 minute flights with hardly a beat skipped.

Considering the new ring has about 10 minutes and the mixtures were "about right" I'm not complaining at how it ran.

There still may be an issue that requires the valve clearance to be set so loose, and I may tighten them back up to about 0.06mm if I have some more sucessful flights but usually I set the valve clearances ~0.025mm. The is some small wear under the rocker and maybe the rocker is shifting causing the valve to ride or maybe the lifter isn't always going all the way back down if there's a lip where it rides??

Still more speculation but fingers crossed it seems to be running fine.

What valve clearances are others running???
Old 03-17-2017, 05:36 AM
  #39  
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Originally Posted by bjr_93tz
Quick update re this afternoon's shenanigans.

With the valve clearances loosened out to ~0.1mm and tweaking the mixtures in the starting gate with the tacho to get a baseline setting, I just had 3 x 20 minute flights with hardly a beat skipped.

Considering the new ring has about 10 minutes and the mixtures were "about right" I'm not complaining at how it ran.

There still may be an issue that requires the valve clearance to be set so loose, and I may tighten them back up to about 0.06mm if I have some more sucessful flights but usually I set the valve clearances ~0.025mm. The is some small wear under the rocker and maybe the rocker is shifting causing the valve to ride or maybe the lifter isn't always going all the way back down if there's a lip where it rides??

Still more speculation but fingers crossed it seems to be running fine.

What valve clearances are others running???
0.001" / 0.025mm

Have you checked the rotary disc clearance? It should have a slight resistance to turn it. If it becomes loose that will affect power.
Old 03-17-2017, 07:18 AM
  #40  
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Brett....because there is wear on the rocker as you mentioned....I never used a gauge to set the valve lash....I always set them by feel.....just a very small movement.
Using a gauge always results in the lash being too loose due to the dimple(s) in the rocker arm.
Rich Verano mentioned this to me years ago when we started using 4 strokes.
That's right about the disc clearance....wash it in lacquer thinner to cut the oil and there should not be any wobble.
Turning the disc should be dead free without any oil drag. If you feel any snags as it turns look for any rough spots or grooves on the backplate.
Using two .001" or .025mm feeler gauge under the disc 180 degrees from each other should be a fairly tight fit.
Using two gauges will remove any wobble and give a good indication of the real clearance.
If you have to reset this clearance....remove the disc and true the aluminum face on glass with some 600 grit with oil....then reset everything.

edit...I just remembered....
Look closely up into the plug cap.....there is a spring in there that the center conductor of the spark cable should be inserted.
Make sure that it is fully inserted into the side of that spring or misfire definitely will occur.
This was a major problem with the first version of the sparkbox but I would check it regardless which box you have.

Last edited by Dave Harmon; 03-17-2017 at 07:22 AM.
Old 03-17-2017, 01:30 PM
  #41  
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Hi Guys,
This has been very interesting bit of reading. As a long time YS user, though not the big stuff lately (the largest YS I currently run is the 115), it seems that they have become progressively more complex. When they run great a YS is awesome, but when things go awry and it won't run properly, they can be difficult to diagnose and repair. Considering that the number of YS users flying pattern has shrunk significantly over the past several years (electric power is pretty easy to use) shouldn't YS consider doing a 'Hanno' and produce a much simpler engine with same power and throttle capabilities (the Magic to Calypso transformation). Maybe reduce the price and attract more users. I fear that pattern will become completely electric in the near future.
Back when the YS 120AC pretty much was the only engine to run in pattern (25 years ago or so) the belief then was that you needed 3 engines: one in the airplane; one ready to go in the airplane; and one being rebuilt. I know of pilots who had 1,000 flights on their AC with little or no maintenance, but they were running 15% nitro. As the nitro % went up; so did the maintenance requirements.
I think YS could come up with a new design, but is there enough motivation (engine sales)?
Old 03-17-2017, 03:23 PM
  #42  
bjr_93tz
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Hi Dave, that dimple under the rocker is definitely noticeable as you can kick it off to one side a bit and feel the clearance change.

According to the dial gauge on the back of the rocker, there's about 0.03mm between the loosest and tightest position.

Right now I'm going to let sleeping dogs lie and keep my fingers crossed it keeps running well. It was weird to actually hear the TX countdown timer go off for a change, it's been a long time since I've heard that when flying this plane.

When the ring is bedded in and I'm happy the engine is "sorted" I'll look at the valve issue a bit closer. Maybe the bottom of the lifters aren't flat anymore and if they rotate to a different position my clearance disappears?? Could be any number of stupid things happening..
Old 03-17-2017, 04:04 PM
  #43  
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Brett.....ahhh...I see what you are doing. I assumed you were using a flat feeler gauge.
edit....Brett....I added a 1oz header tank and that improved fuel feed considerably and virtually eliminated air in the line getting to the pump. This might help eliminate your misfire.

Will....I agree.
Truthfully....I have always questioned the "500" flights one or two well known individuals have claimed before problems occur.
Other than that....I never had much trouble until I started using the DZ series of engines. The rest of the engine is virtually unbreakable.

I had good use and reliability with the FZ pressure tank versions of 2 stroke and 4 stroke engines however I never tried the FZ175.
http://www.yspower.co.jp/en/engine/plane/fz175s.html
Has anyone tried the big FZ engines?
I might try one.

Last edited by Dave Harmon; 03-17-2017 at 04:08 PM.
Old 03-17-2017, 04:59 PM
  #44  
bjr_93tz
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Thanks Dave, in my frustration I've used many different ways to check the valve clearance. The consensus on the 'net seems to be "tight is best" and that's sort of always how I've set them.

Just thinking out loud, but although I've changed the cam bearings in the past, I wonder if they have worn a bit again? My thinking is that I set the clearance at TDC where the cam is unloaded and thus settled as far away from the rockers as it can be, but the crankshaft will try to push it upwards towards the rockers under load. The camshaft may also be rocking a bit along its axis if one side is driving a valve. I'm just wondering if there's enough slop in there to take some clearance away when it's running??

I've also never checked the clearance at anywhere other than TDC. I'll check the clearances at different points on their respective base circles next time the valve cover is off.
Old 03-17-2017, 05:20 PM
  #45  
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Brett....I tell ya....you are making me remember a lot of stuff!!

Let me mention a couple of things....
I used a 'right sized' wood dowel to insert into the cam bearings and then pulled back and forth to see if there was much slop in the bearing.
As the balls wear down the 'in and out' clearance would increase.
Comparing with a new set of bearings would help.

The next thing is the wear in the spiral cut on the cam. You can use a tool and move the point of it back and forth across the wear mark to see how much it is worn.
Same thing on the shaft.
Still another place I had trouble with is the face of the cam that contacts the lifter.
The ramp on the lifter was pitted and wearing away causing some problems. The actual lifter was ok though.
You might try increasing the oil content to perhaps 15% total or perhaps 1% castor to help out with wear for a total of 16%.
Also...I used 1oz of acetone to help with the idle.
Old 03-19-2017, 12:45 AM
  #46  
bjr_93tz
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Being a quiet day, I decided to run the dial gauge on the valve rockers at various positions.

Both rockers/tappets had dimples from the valves so I ground them flat again, only needing to take off about 0.04mm.

I'm pretty sure I put new cam bearings 6 months before the problem started, making them ~ 2 years old now but not having done much work. The dial gauge tossed up some interesting results. When the cam was loaded ie during a valve lifting part of the cycle, the clearance on the other valve dropped quite a bit.

0.06mm of clearance (at TDC) on the exhaust valve reduced to 0.01mm when the intake valve was being opened.
0.07mm of clearance (at TDC) on the intake valve reduced to 0.02mm when the exhaust valve was being opened.

Not sure why this is happening but I'm guessing this isn't "normal" for a new engine otherwise YS wouldn't specify the clearance to be set between 0.0mm-0.1mm. It might be something that creeps into an older engine like mine. This is something I'll review when I change the cam gear bearings. I'm guessing the bearings have been letting the cam shift when under load, unseating the other valve and allowing it to leak.

Anyone else out there notice their valve clearances change like this?
Old 03-19-2017, 03:12 AM
  #47  
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Originally Posted by bjr_93tz
Being a quiet day, I decided to run the dial gauge on the valve rockers at various positions.

Both rockers/tappets had dimples from the valves so I ground them flat again, only needing to take off about 0.04mm.

I'm pretty sure I put new cam bearings 6 months before the problem started, making them ~ 2 years old now but not having done much work. The dial gauge tossed up some interesting results. When the cam was loaded ie during a valve lifting part of the cycle, the clearance on the other valve dropped quite a bit.

0.06mm of clearance (at TDC) on the exhaust valve reduced to 0.01mm when the intake valve was being opened.
0.07mm of clearance (at TDC) on the intake valve reduced to 0.02mm when the exhaust valve was being opened.

Not sure why this is happening but I'm guessing this isn't "normal" for a new engine otherwise YS wouldn't specify the clearance to be set between 0.0mm-0.1mm. It might be something that creeps into an older engine like mine. This is something I'll review when I change the cam gear bearings. I'm guessing the bearings have been letting the cam shift when under load, unseating the other valve and allowing it to leak.

Anyone else out there notice their valve clearances change like this?
I would think that when the engine is running, the valve would seat in the dimples as that is where they want to naturally sit, so I wouldn't think it would cause any issues.

I've never replaced cam bearings in any of my engines. I check them when I replace bearings, but never felt one that seemed loose or rough. Being so small, they would have to be extremely worn to cause any problems. Even then, I suspect they would fail before affecting engine running. As for the clearance variation, with everything being solid, not sure how that would happen. I've never felt the need to check with a dial guage - Just set and forget. Never had any problems doing it this way. Might have to check mine during the next rebuild if I remember.
Old 03-19-2017, 06:20 AM
  #48  
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Brett....it sounds like the cam is rocking from side to side across the shaft.
Worn/egg shaped cam bearings or rocker shaft holes allowing vertical play.
Old 03-19-2017, 04:33 PM
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Interesting read on the YS power website regarding valve clearance.

It turns out that not only were there differences in the cam timing instructions between the English and Japanese language instructions on certain models, but the valve clearance procedure is also different.

The English instructions tend to say 0-0.1mm clearance at TDC
The Japanesese language instructions roughly say 0-0.1mm at one full crank rotation (180deg on the cam) from full lift of the respective valve.

In a perfect world both methods "should" yield the same result, but with a worn cam and crank who knows?
Old 03-25-2017, 07:32 PM
  #50  
bjr_93tz
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The last few trips to the flying field have not been particularly rewarding. I just can't find a needle and regulator setting that gives me a consistent run. I've had glimmers of hope where the engine has had that nice smooth drive off the bottom end with every throttle position meaning something, only to have it start running like a hairy goat 3-4 minutes into the schedule later.

The odd thing is that not matter how lean I've run this engine (I've tried rich and lean) while having problems, the oil under the plane has never been dark. Way back when it was a reliable engine you could see changes in the oil coverage and colour depending on the mixture setting.

So I'm committed to one more trip to the field before I go on holidays for 2 weeks to make a decision about the engines' future, either it stays or it goes...

DZ185cdi or DZ185cdi ZERO ????

The ZERO would be pretty much be a drop in replacement for the 170cdi power wise and a bit cheaper to run fuel wise, although the Aries 07 would probably benefit from the extra power of the 185cdi given the airframe wasn't' one of Oxai's lightest.

I was looking at it between flights yesterday while topping up the batteries, then looked at the club fire extinguisher and almost wished the Li-Po pack would catch on fire and put an end to the problems..

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