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YS user seeking sympathetic ears :(

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Old 02-27-2017, 02:50 PM
  #1
bjr_93tz
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Default YS user seeking sympathetic ears :(

I've really wanted to hold off on this until the engine got sorted but it's just dragging on with no end in sight.

After a horror 9 months months with my nice new DZ170cdi back in late 2010 - mid 2011, things went really well for years with the resulting combination of new and original parts, feeding it 20% nitro 10% oil, bearings, rings, o-rings and gaskets, taking me from our Advanced class through to F3A over a period of four years.

In late 2015, the idle got a little lumpy the weekend before a comp and the 1500ft drop in elevation didn't help tuning matters, getting worse each round before it backfired to a stop in the 6th round pushing over the Golf Ball in P-15. It wasn't the first time it'd backfired to a stop over the years, as for some reason it's always needed to be set super lean. Full power strip beat-ups with vertical rolling climb-outs to 1000ft were something I'd learned not to do with this engine, but for F3A work it was as perfect as it could get..

It's fair to say my interest in Pattern had been waning, there are four motorcycles of various types in the shed, so sorting out my DZ170cdi wasn't high on the list of things to do but 1.5 years later, countless trips to the flying field, gallons of fuel, almost enough parts to build a whole new engine I'm still no closer to getting this thing running right again.

The other thing I've found during this journey is YS's habit of revising parts but keeping the same numbers means not everything fits together as it used to..

A smarter man probably would have just replaced it with a DZ185cdi by now but it's sort of becoming a battle of wills, although finding the problem and fixing it is now a matter of principle, it's probably just a losing battle.

Anyway, shameless appeal for sympathy over, wish me luck.....
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Old 02-28-2017, 04:47 AM
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Hi,
Did you check valve timing? Timing, not lash
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Old 02-28-2017, 02:46 PM
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Quote:
Originally Posted by naftali View Post
Hi,
Did you check valve timing? Timing, not lash
Surprisingly enough I was looking at that last night. I pulled the valve cover off and poured some oil down the plug hole (to seal the piston and ring) and was turning it over backwards and forward to listen for valve leaks and the intake valve did seem to close rather late. I've checked it a couple of times before now, lining up the dot on the crankweb with the case seam, and the dot on the cam facing down.

I replaced the intake valve when I rebuilt it and it ran normally after the rebuild, but did start playing up a few months after.

I tried lapping the valves a few days ago but it didn't make it run better or worse.

The valve I changed out looked like this, it was running fine but changed it out anyway...
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Old 03-01-2017, 12:53 PM
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You did not mention the status of the valve guides. Low oil content since 2010 might contribute to rocking and dancing valves due to enlarged guides.
I enjoyed a similar phenomenom years back with my YS 140. after a long fight and parts replacement of all kinds I solved the problem by switching to a YS 160.
Wish you find the culprit and share it with us.
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Old 03-01-2017, 02:41 PM
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Thanks Naftali, I had a weak moment yesterday and ordered a new head assembly along with some other bits and pieces which should turn up in a few weeks.
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Old 03-01-2017, 04:52 PM
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With the looks of that valve I would suspect the head/valve seats. I think the new head you ordered is a good thing.

Ken
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Old 03-01-2017, 09:29 PM
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Quote:
Originally Posted by bjr_93tz View Post
Surprisingly enough I was looking at that last night. I pulled the valve cover off and poured some oil down the plug hole (to seal the piston and ring) and was turning it over backwards and forward to listen for valve leaks and the intake valve did seem to close rather late. I've checked it a couple of times before now, lining up the dot on the crankweb with the case seam, and the dot on the cam facing down.

I replaced the intake valve when I rebuilt it and it ran normally after the rebuild, but did start playing up a few months after.

I tried lapping the valves a few days ago but it didn't make it run better or worse.

The valve I changed out looked like this, it was running fine but changed it out anyway...
I find the dot on the cam always ends up slightly to the left.
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Old 03-02-2017, 10:52 AM
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Slightly might be OK. I have found once the gear was way to the right by the factory: Too advanced for the 160. Put it back correctly and the idle improved significantly
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Old 03-03-2017, 08:09 PM
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With a quiet Saturday morning on the cards, I decided to strip the engine completely and see if I'd done anything silly like leave out the crank sealing ring.

After sucking and blowing on the port which supplies the vacuum signal to the regulator, I found it's also ported to the intake side of the crank web via the crank pin and the holes in the con rod big end which line up with that port at different positions depending which way around you have the conrod. The old conrod had two big punch marks in the big end bush for orientation, the new rod has a tiny radius that really isn't noticeable so you don't need two guesses which way around I had the conrod on.

So with a new rear bearing fitted, conrod flipped, cam timing double checked, and engine back together with a stroke of luck I can get out to the filed some time this afternoon....

.
My YS seems to dress slightly to the left as well..
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Old 03-04-2017, 02:07 AM
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Quote:
Originally Posted by bjr_93tz View Post
With a quiet Saturday morning on the cards, I decided to strip the engine completely and see if I'd done anything silly like leave out the crank sealing ring.

After sucking and blowing on the port which supplies the vacuum signal to the regulator, I found it's also ported to the intake side of the crank web via the crank pin and the holes in the con rod big end which line up with that port at different positions depending which way around you have the conrod. The old conrod had two big punch marks in the big end bush for orientation, the new rod has a tiny radius that really isn't noticeable so you don't need two guesses which way around I had the conrod on.

So with a new rear bearing fitted, conrod flipped, cam timing double checked, and engine back together with a stroke of luck I can get out to the filed some time this afternoon....

.
My YS seems to dress slightly to the left as well..

Yep, that's how all mine line up.

I'm surprised it wasn't tight to turn over with the con rod back to front. It would be jamming on the pin radius. Probably lucky it didn't pick up and sieze.
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Old 03-04-2017, 05:51 AM
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Question my 140 and 115 the dot on the cam is directly up right under the case opening 180 degrees of yours.

Last edited by computermonkey; 03-04-2017 at 05:55 AM.
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Old 03-04-2017, 05:56 AM
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I found the manual is it is opposite of the 140 and 115 engines.
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Old 03-04-2017, 12:50 PM
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Quote:
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Question my 140 and 115 the dot on the cam is directly up right under the case opening 180 degrees of yours.
That's correct.

The dot position changed to the bottom with the 175.
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Old 03-04-2017, 05:57 PM
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Ha, Dot bottom/Dot top, makes no difference in the grand scheme of things as it swaps from bottom to top every 360 deg rotation of the crank, but the book (for a 170cdi) says bottom so to the bottom it goes.

After 1.5 flights yesterday, I'm sort of back where I started the whole saga. It'll do a schedule but the reg and needle needs to be super lean that it won't load up but it still will if you don't clear it out every now and then. Needle is set about 2 clicks to the lean side of peak rpm, which isn't the safest way to run it.

Time to put the thing away until the new head assembly arrives. I'll post back when it does..

Edit: With the V8 supercars putting on their usual boring show and the MX track a muddy slop it was off to the shed to turn up a dummy cylinder to bolt the head to, so as to test the sealing of the valve seats.

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Old 03-04-2017, 08:15 PM
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Quote:
Originally Posted by bjr_93tz View Post
Ha, Dot bottom/Dot top, makes no difference in the grand scheme of things as it swaps from bottom to top every 360 deg rotation of the crank, but the book (for a 170cdi) says bottom so to the bottom it goes.

After 1.5 flights yesterday, I'm sort of back where I started the whole saga. It'll do a schedule but the reg and needle needs to be super lean that it won't load up but it still will if you don't clear it out every now and then. Needle is set about 2 clicks to the lean side of peak rpm, which isn't the safest way to run it.

Time to put the thing away until the new head assembly arrives. I'll post back when it does..
This is from the 170cdi manual on the YS website.
The dot should be pointing straight up when cam is fully installed.
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Old 03-06-2017, 12:48 PM
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First, following the manual could be a good start and help in the trouble shooting.
Because it's an old engine, with a lot of history problems I would personally send it back to the factory.
This has been proven most of the time to be faster and cheaper than trying to solve the problem himself, purchasing and changing unnecessarily, sometimes, good parts
.

CAM GEAR TIMING

http://www.yspower.co.jp/en/data/pdf/dz170.pdf

If for some reason you have to disassemble your engine, please followthese important steps on reassembling the cam gear.
1- Remove the carburetor and backplate assembly. Notice the im
pression mark or dot opposite the rod journal on the crankshaft.This mark is to point straight down or lined up with the outercase seam line at the bottom.
2 - Reinstall the cam with the dot facing you and pointing slightly to the left. This will allow the cam to turn to the right when properly installed. The dot should be pointing straight up when cam is fully installed. Reinstall cam cover and timing is now set.
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Old 03-06-2017, 01:44 PM
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Hi J-P,
yes these engines seem very difficult to diagnose the cause as many different causes seem to produce the same running problems. Having the tools to test each part is working properly would have saved much time and money. Once it's running well again, I'll hopefully have some good spares..

That being said, this engine did go back to YS factory early in it's life for a warranty repair during the first "horror 9 months" I described in my opening post. The failed rear bearing was easy for YS to diagnose and replace, but the failing cdi sensor was missed and caused me much grief. I was on a steep learning curve with this engine and I had the impression YS didn't want to see it (under warranty) again.

On the subject of the cam timing dot, for some reason the English DZ170cdi manual isn't available on the YS Japan website, but the ones available elsewhere on the 'net (and which came in the engine box) says dot pointing down. Dot up/ Dot Down, it swaps position every complete rotation of the crank so it isn't too important which we chose.

However our Japanese friends must laugh at the confusion, because in the Japanese language manuals their position for the dot hasn't changed since the DZ140.

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Old 03-06-2017, 02:06 PM
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Quote:
Originally Posted by bjr_93tz View Post
Hi J-P,
yes these engines seem very difficult to diagnose the cause as many different causes seem to produce the same running problems. Having the tools to test each part is working properly would have saved much time and money. Once it's running well again, I'll hopefully have some good spares..

That being said, this engine did go back to YS factory early in it's life for a warranty repair during the first "horror 9 months" I described in my opening post. The failed rear bearing was easy for YS to diagnose and replace, but the failing cdi sensor was missed and caused me much grief. I was on a steep learning curve with this engine and I had the impression YS didn't want to see it (under warranty) again.

1. On the subject of the cam timing dot, for some reason the English DZ170cdi manual isn't available on the YS Japan website, but the ones available elsewhere on the 'net (and which came in the engine box) says dot pointing down. Dot up/ Dot Down, it swaps position every complete rotation of the crank so it isn't too important which we chose.

However our Japanese friends must laugh at the confusion, because in the Japanese language manuals their position for the dot hasn't changed since the DZ140.
1. http://www.yspower.co.jp/en/data/pdf/dz170.pdf

There's no confusion. It's clear from the manuals that up to and including the 170, the dot is to point up and the 175 and 185 the dot points down.

As to whether it really matters or not according to your 360 degree theory, it still would be a good start to point the dot up as the manual says. Won't hurt and another potential problem avoided.
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Old 03-06-2017, 03:09 PM
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You're not going to make me scan in my DZ170cdi manual are you Scott?

I wonder if there are different versions of the english manuals for the 170cdi floating around?
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Old 03-06-2017, 04:33 PM
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Quote:
Originally Posted by bjr_93tz View Post
You're not going to make me scan in my DZ170cdi manual are you Scott?

I wonder if there are different versions of the english manuals for the 170cdi floating around?
Could be Brett. That one is a YS Japan online manual though. Don't know why they would be different though??
I'm not home, so can't look at the hard copy manual with my 170.
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Old 03-06-2017, 07:24 PM
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Seeing as the new head is still many days away, I thought I would throw up some light reading.

I gather it was published around the 5th month 2009, but I'm not sure why the http://www.yspower.co.jp/ website hasn't got it available in english?
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Old 03-11-2017, 01:14 AM
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I finished off my head testing thingy today (see photos) and the short story is that both valves leak like sieves.

It was a bit of a surprise as I would have bet money on the exhaust being still ok as the valve face looks ok, the valve seat looks clean and even, but the air just pours out.

The intake valve was the one I replaced and under magnification the valve seat looks trashed, but it wasn't leaking much worse than the exhaust valve.

There really doesn't look like there's much meat left to have a go at re-cutting the seats, so it may be time to bin it.

Fingers crossed with the new head when it arrives..
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Old 03-11-2017, 12:39 PM
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That's a great bit of kit!

BTW just checked my 175CDi and 185 CDi manuals and they do say both dots pointing down

Keith
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Old 03-11-2017, 07:52 PM
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Thanks Keith,
It's an overkill for what it does and a piece of flat plate with an appropriate sized o-ring would do the job just as well.

I don't mind making a mess on that lathe/mill on occasion, I just hate cleaning up after.

Ken suggested in an earlier post the seat could be shot for the intake valve, glad this proved him correct but I was surprised the exhaust was no better..
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Old 03-13-2017, 10:18 AM
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Quote:
Originally Posted by bjr_93tz View Post

Ken suggested in an earlier post the seat could be shot for the intake valve, glad this proved him correct but I was surprised the exhaust was no better..
Sometimes you get lucky on a diagnosis. How many gallons of fuel though that engine?

Ken
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