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HelicopterEngines Plugs Mufflers Fuel › YS91 crank shaft breakage, I had enough
12-21-2003 12:25 AM  13 years agoPost 1
rappyfly

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Toronto, ONT

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Hi all

I have second crank shaft destroyed on my newest engine which has 50 flight at bought on Oct 6th. Does this become common thing or this is unique individual experience ?

Why i had enough? 3 crack crank cases, 2 crank shaft and I connecting rod failure, caused completely destroy engine plus bearings...

I am very confused.

D

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12-21-2003 12:50 AM  13 years agoPost 2
rickc

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Creve Coeur IL. (Peoria Area)

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Wow, your hard on engines. Either super bad luck or possibly a user issue? Do you try to get 110% out of the engine? What fuel without starting a fuel war? What engine temp? What gear ratio and head speed?

Rick

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12-21-2003 01:03 AM  13 years agoPost 3
spincycl

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Marietta, GA

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I second what RickC said. There must be something wrong here. I know that some YS's have a problem now and then, but that many failures is totally unreasonable. Hmm, what's going on here, Yamada?

I even ported+polished my YS80 and ran it at VERY high rpms, and it still ran for a year+. (put out incredible power for an 80) Now, I have one of the very first 91's and it's still perfect. (yes, its one of the non-US ones) I have always LOVED the way YS runs, but let's not start having problems now, Please....

There are a few others that have had the rear bearings fail in the 91 as well. Perhaps they are using cheap bearings, but even with that the crank should not ever fail in normal service. The crankcase issue has been resolved for the most part by moving the regulator a little. I have never heard of con-rod failures in a YS...

What fuel are you using? What engine speed? (headspeed x gear ratio) Fuel mixture? How is the temperature? ?????

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12-21-2003 01:44 AM  13 years agoPost 4
rappyfly

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Toronto, ONT

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Hi

Now I feel no anger when I saw something wrong with my engine, even no increase in heartbeat. I get used to it.

It sounds a lot failures, but I have 4 91's on 2 furys 1 milli with 80G of fuel this year. I think the failure has little to do with fuel, rpm etc but for your info:cp 30 with 8.45. 1850 3D &1600 quiet 3D.

D

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12-21-2003 02:43 AM  13 years agoPost 5
rickc

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Creve Coeur IL. (Peoria Area)

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Hmmm, sounds like your no harder on your engines than anyone else, unless your running them lean and hot. 1850 at 8.45 is getting everything out of it you want though. My CS was at 8.4. I flew at 1750 most of the time and 1850 for short periods on some maneuvers with a GV-1. I always use PowerMaster, but I'm almost sure that it's not fuel related. To many fly Morgan fuels, a red flag would have popped up long ago. I think you just have a grey cloud following you or your just running lean. Bummer..... I hope you find an answer.

Rick

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12-21-2003 12:31 PM  13 years agoPost 6
Vinnie

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Miami Beach, Florida

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hmm

Just asking a dumb question here but what method did you use to immobilize the crankshaft while tightening the prop nut?

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12-21-2003 01:37 PM  13 years agoPost 7
sluggo

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Kitchener Ont

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Time to try a C-spec David!!!

I have had 3 bearing failures and 1 case crack.

Chris

Teambob00

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12-21-2003 01:41 PM  13 years agoPost 8
Andi G

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Switzerland

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Hi,

I wonder how long a C-Spec will survive at 8.45 and 1850rpm...

Andi

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12-21-2003 04:07 PM  13 years agoPost 9
Al Magaloff

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12,199 Posts- Enough Time Wasted. See Ya!

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I have had many OS engines, and recently decided to try YS. I now own two YS91's. Comparing quality of machine work, the YS is really crude. The intake hole through the crank, looks to be machined with some kind of chisle, or possibly an axe. If I were the peeps at YS, I'd be plenty ashamed of that craftsmanship. I spent MUCH time "fixing" that hole, smoothing over the axe marks. I'm not surprised that some have broken. Also, that keyway has to go. Rappyfly, where did your cranks break?

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12-21-2003 04:15 PM  13 years agoPost 10
capebob

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Cape Coral, FL

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Al,

The crank pin broke off my 91. It is due back from YS performance tomorrow. At least they back them up with prompt warranty service.

Bob

Success is the ability to go from one failure to another with no loss of enthusiasm. Churchill

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12-21-2003 04:39 PM  13 years agoPost 11
Al Magaloff

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That's pretty unusual Bob!

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12-21-2003 06:13 PM  13 years agoPost 12
G.Man

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Bristol

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Hmmm

Have all the YS91 breakages been at 8.45 gear ratio?

If so it does not surprise me as its not a gear ratio YS actually recommend...

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12-21-2003 06:15 PM  13 years agoPost 13
rappyfly

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Toronto, ONT

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This is my first broken crankshaft. I am not going to take photo on the second one, but it always break here. Just insert a tooth brush to get the fan out. if it break at other side, oh well....

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12-21-2003 06:16 PM  13 years agoPost 14
G.Man

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Bristol

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Yikes look at those rust spots...

so glad I dont run coolpower anymore...

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12-21-2003 06:30 PM  13 years agoPost 15
Al Magaloff

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12,199 Posts- Enough Time Wasted. See Ya!

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Rappyfly. That is where the two cutters meet, and leave that ugly line. One of mine actually had a step there. That is where I would expect it to break.

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12-21-2003 07:55 PM  13 years agoPost 16
spincycl

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Marietta, GA

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I agree totally that the machine work on the YS cranks is just crap. All of those tool marks can cause stress concentrations too. I also suspect that the hardening/tempering is done improperly.

The rest of the engine OK, so why can't they make cranks anywhere near as well as OS?

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12-21-2003 07:59 PM  13 years agoPost 17
sluggo

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Kitchener Ont

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Galifrey the 8.18 is what ys says to use but JK and ToddB say for 3D to use 8.45 ratio.

http://www.freestyle3d.com/

Look under ys tunning

Chris

Teambob00

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12-21-2003 08:35 PM  13 years agoPost 18
spincycl

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Marietta, GA

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Thats good thinking, David, but heck if YS says that their engine is happy at 1000 revs more than OS, then it should run that without falling apart. Now, I have heard various numbers here and there, but I answered them just by calling YS-usa. The tech there said that 16K is it's designed top side of the power band. He said not to run over that, but 15-16K rpm is ideal.

It is a short stroke engine, so it should allow slightly more revs then the OS.

OF course, if they just didn't cut the crankshafts with a jackhammer, then this thread wouldn't be here!

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12-21-2003 10:29 PM  13 years agoPost 19
Vinnie

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Miami Beach, Florida

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ah

DavidH what do you recommend as max head speed for a YS .91 ST on 8.18 gear ratio? This is with the Muscle Pipe II.

Also what is the highest recommended head speed with an OS .91 C-Spec PS on 7.75 gear ratio with SB-16?

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12-22-2003 07:50 AM  13 years agoPost 20
G.Man

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Bristol

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Chris

Thats because they use an SB16 which works better at that gear ratio...

The MP2 delivers more power at lower revs and is better at 8.18..

http://www.curtisyoungblood.com/heliproducts.html

Muscle Pipe 2 vs. Hatori SB-16

I finally had a chance to test the MP2 80/90 vs. the SB-16 this week on a YS 91. The MP2 had a higher peak power level, 0.3HP higher (MP2 2.58hp, sb16 2.27hp, Note: these numbers are relative so the absolute amount is not important and will not match engine company power ratings). The MP2 also created power at a lower RPM (more torque) so you can run a lower gear ratio and the engine is quieter.

The ideal gear ratio for the MP2/ys91 combination is 8 to 1. If you run the MP2 at 8.4 it will work but you are starting to get out of its peak power range.

If you run the MP2 at the 8 to 1 gear ratio you will have a very quiet system that is more powerful than the SB16 at it's ideal setup ( the ideal gear ratio for the SB16 appears to the 8.4 to 1).

Don't Email me as I wont reply - PM Only (spam countermeasures)

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