[NSRCA-discussion] Question - YS140DZ

Mon Jun 2 17:14:02 AKDT 2008

Sounds like the prop slipped on the thrust washer like Adrian stated. This can happen. Try one of the Central Hobbies large diameter thrust washers...I used these when we ran the 140DZ's

The 160s and 170s changed the the thrust washer to make it more aggressive bite on the spinner. The slip will happen then the aggressive bite that is there gets smoothed off and then its tough to get it to bite properly again.

Another little trick is to tighten the prop...run the engine a little and get everything heated up...then stop it...Tighten the prop up again and lock the double jam nut down onto it. Your collet behind the thrust washer can get compressed a little and it will actually slip if the engine backfires. Its because the collet is compressed X number of times and the grip on the taper is not as good. This is usually only a  problem when the  when you have had the thrust washer off the engine and the first time you tighten it back up. If the thrust washer has not been removed from the collet then its probably not the issue...

We did the Central Hobbies thrust washer in order to give a bigger diameter to bite the spinner.

http://www.centralhobbies.com/engines/ys/biggrip.html

It works well. Not trying to pimp the product but it was designed to solve this problem and also the bigger hub 3D props had this problem too. The 160's and 170's don't tend to suffer from this as much. The 140DZ has a good bit of compression and tends to have a bigger kick....so the it can throw the spinners loose more that the others. 

Another issue could be a little lean on the pump....this would make it detonate a little on the throttle up. Try richen the pump just a  little bit 1/8th of a turn or so CW or (IN) if the engine is sounding a little harsh or hollow when throttling up. 

Your choice of prop is good in that its not loading the engine too hard. The higher loaded props will tend to spit harder when you run it out of fuel or the engine starves and goes lean.

Check you fuel filters..if they are clogged up then you can get reduced fuel flow and it will make the engine go lean for a split second on the throttle up. Its amazing what a small piece of lint can do. If your fuel filter is the screw together type check it to make sure its tight and not pinching the o-ring to allow an air leak.

Fuel lines or tank can have a small air leak and get an air bubble in the line causing the burp....If it burps in the air..check the prop for tight the next you fly it. Chances are it might have slipped a little.

I have used about 60grit cloth backing sandpaper like Adrian stated, Put two pieces back to back and CA them with thin CA and it makes a good surface area grip. Another option is a small disk of aircraft ply like 1/8th soaked in thin CA with the sand paper on both sides. Tighten it to compressed the wood then CA it again and then tighten the prop back up.

Like I said the 160's and 170's are lower compression engines and don't tend to suffer from this kickback issue as bad. In fact I have not had any problem with it the last few years. 

You can reduce the kick on the 140DZ by removing the crank shaft ring. This will reduce the power a little but makes the engine run smoother less vibration and less kick if it gets an air bubble.

Also are you running the YS Bubbless tank pickup (Foam clunk) you should be if you are not already. Talked to a buddy today that was running a 140 Sport and put a 140DZ in his model. The foam clunk seems light but when it gets fuel in it the weight is proper to keep it in the fuel all the time.

As always check screws, on the carb, head bolts, backplate, valve cover and so on. An air leak from a loose screw will make the engine go lean. Not always kickback...but it could and be causing the problem.

I hope this helps.

Troy Newman

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From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Lisa & Larry
Sent: Monday, June 02, 2008 4:41 PM
To: 'General pattern discussion'
Subject: [NSRCA-discussion] Question - YS140DZ

Ran the engine at home about three weeks ago and perfect idle, midrange, and full throttle... 

I went to the field Sunday to maiden my Titan...Started as it usually does, and while it was at idle I adjusted the transmitter to get it dialed in after my Tx repair / reprogramming. This took about 15 to 20 seconds...Let it warm up a little longer and then slowly increased rpm...About ½ throttle on the stick, somewhere between 5,000 and 7,000 RPM I heard a low freq buzz (sounded like an electric motor burning up...vbg)...shut it down and found that the spinner loose (new spinner, new prop APC 16 x 11). This is the set up I have flown with this engine for 3 years...

Tightened up the spinner making sure the prop was tight and started again and got a DZ bump...nicked spinner, not bad...Tightened everything up again, started nice idled well, then transitioned to full throttle. Again at half throttle, it popped, quit, and shavings of prop flew every where. It was violent. The spinner is bent worse than I ever saw before by anyone...The prop was intact except for the missing chunks at the hub where it hit the spinner.

Starting procedures and equipment:

Radio South Starter with on/off switch in the off position, using a Kavan starter turn the prop and then turn on the Ni-starter. Temperature was about 20 degree warmer on Sunday than the initial test run. Used the same fuel from the same can, Power Master 30% DZ

Three weeks ago it was running a bit on the rich side and I didn't touch anything until Sunday when I intended to lean it out...Never got that far.

What did I do wrong if anything? What can I look for in the engine to repair or correct myself or looking at?

Or do I just send it in to YS Performance?

I have a back up 140DZ and bought the last FAI 3-¼ TT spinner w/ light backplate at Central...vbg...

If I made a mistake, I don't want to repeat it.

Your thoughts? Troy you out there?

Larry Diamond

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