R U using Polaris Woodruff keys???

 

Yes, they are genuine Polaris Parts...

 

I don't know where the issue is at this point.
I'm just trying to find the solution and in order to do that I want you guys to have all the information that I have re: this problem.

Here's Muzzy's response to my email to them about it:

Chris,
I have spoke to Mr.Muzzy himself about this and he has never seen this with any of our engines or have even heard of this problem of yours. First of all we have sold many kits and second of all you would think it would shear the key on the first start if the compression was to high, plus our racing engines have much higher compression than you.

It must be some kind of timing issue on the firing order is all I can think of.

I have to agree with their response. It doesn't make ANY sense whatsoever.

 

Chris is the key still tight in the shaft after replacing it ? Sounds like one of those thing you could pull your hair out with I would think those guys that build them regularly would have seen this !! Anyway good luck

 

Yes, it fits in there real nice; no wobble; tight as can be... torqued to factory specs.

 

very strange.
I wonder if you got a bad batch of keys.
is there a heat treated aftermarket option? LOL
sounds like you need a grade 8 key, if there is such a thing.

 

There are higher and lower grade Woodruff Keys available...

 

Maybe the taper is off on the crank and doesnt let the mag tighten up good? To me it doesnt seen like the key is to keep it from spinning it seems like it would be more to index the mag so it fires at the right time. Just a theory.

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X2..bolt torque and taper fit keeps the flywheel from turning on the crank. Key is only intended to index the wheel during install imo abd may provide a little help keeping it lined up but that in my mind is the main job of the taper fit. Id inspect the flywheel bore, crank taper, hardware fit ect JMO

 

I have my theory but on record for knowing nothing about an engine.
However.
you have a failed key in your hands. Put it to a bench grinder. Look at the spark coming off it. Take a photo of the spark shooting off. Post photo. Compare to "spark test" on internet. Make sense?
May have your answer.

 

It would tell by the sparks if it's pot metal or a good quality metal...

 

do your test with as little shop light as possible...to differentiate color and see in general.

(hold with vise grips....)
(set camera on timer...)

BTW Hog, you wanted to be Chief Engineer or similar on the fantasy Polaris job thread.
yellow face rolling fingers....

 

Chris don't know if spark test would be a lot of help .you know that their are a lot of different keys.The question is do you want to try a harder stronger key. The cons of this you take the chance of the shaft being the weakest point and messing the slots up . The pro is if it works you got it made. My (guess is the polaris and or local parts store is cheap quality.

Hope you can read the pic they call out a stock key at 1035 standard cold roll stel is 1020 so it's barely above that

 

hmm....Machinery's Handbook, interesting reading - class 1, class 2, class 3 fit with different top and side tolerances. 10 pages of dimensions and charts but they all have one thing in common. no Harbor Freight back then. All were made with Detroit hack iron where the eagle sh!$ on Friday.

Good luck hog. I'm out.

 

Here's my response from HotRods re: the crank:

Chris,

I am sorry to hear of your technical difficulties, I have heard stories of people having issues with woodruff keys after install any new crankshaft. There was one solution that was told to me by a shop:

Apply grinding paste to the crank’s taper. Hand press the flywheel onto the crank and turn it back and forth for five minutes. This will hone down the high spots on the surfaces of each part so the flywheel won’t ever loosen up and shear the woodruff key.

Now I have something to do...

My nephew is going to come over tonight and help me pull the engine out again. I should have it out and possibly polished up tonight.
My wife has to work late so it'll give me something to do...

 

Here's my response from HotRods re: the crank:

Chris,
I am sorry to hear of your technical difficulties, I have heard stories of people having issues with woodruff keys after install any new crankshaft. There was one solution that was told to me by a shop:

Apply grinding paste to the crank’s taper. Hand press the flywheel onto the crank and turn it back and forth for five minutes. This will hone down the high spots on the surfaces of each part so the flywheel won’t ever loosen up and shear the woodruff key.

Now I have something to do...

I'll be lapping it later today....
Thanks for the help guys.
You'll know when I have it fixed.

Make sure to remove any burrs on the keyway in the crank and on the key itself, a good file will do this no problem.
Make sure the key is seated fully in its slot in the crank with no burrs holding it up not letting it seat fully.

Keep in mind, the interference fit of the flywheel to crank only comes into play after the crank bolt is torqued fully, and the flywheel is pulled into is final position on the crank. "Hand pressing the flywheel" and Lapping it before it is pulled into its interference fit final position could remove small burrs or high areas from poor machining on the flywheel or crank snout, but not in the key-way or key. After the crank bolt is torqued, flywheel is pulled maybe .100+ thousand's of an inch farther up on the crank snout, so lapping it in the non torqued position really does not improve the interference fit. Not that you could possibly lap it in the torqued position. The proper machining on the crank snout taper and the flywheel bore's taper, is what makes the correct interference fit, not lapping.

IMO, don't go over board on the lapping, as you don't want to remove much/any of the interference fit. Or make a ridge that will hurt the fit once the flywheel is torqued farther onto the crank into its final position.

Sounds like the guy you got the response from at Hotrods was not a tech engineer, but more of a customer service guy just trying to help by relaying some info he heard from a shop.

I would lap it back and forth for maybe 20-30 seconds and then check for shinny spots on the crank snout and flywheel bore taper to see what you are actually doing/accomplishing.
I would never lap it for 5 minutes, ever.

jmo

 

I'll have to find one...

Thanks...
I'm gonna go work on it now

 

Well; the engine is out...
I'll start working on it tomorrow.....

 

Chris, I think Hotrod's advice will solve your problem. Waaaay back when I raced 4-cycle karts running B&S motors we would remove the flywheel key so we could set the ignition timing different from stock. My engine builder would lap the Morse taper of the crank/flywheel with valve lapping compound as described by Hotrods. The interference fit of the taper is what retains the wheel and the key is just to index timing (as already described). Periodically, even though the tapers "looked" good the timing would "slip" and we would re-lap the tapers and it would solve the problem. Very quick and easy to do...at least on a Briggs motor.

 

I'll be lapping it later today....

Thanks for the help guys.

You'll know when I have it fixed.

 

Are you having any hard starting issues? maybe tuning at startup/idle is off? If it kicks back or back fires you will have a ton of shear force against the key.

or tac weld it! lol

 

No starting issues whatsoever.

Yes! I'm pissed enough to tack it. But I know better

 

Just looked at your picture of the key...
Is it just me, or is that keyway look like it has cancer pits. Was there rust on it that was cleaned off ?

That has to be the worst looking key I've ever seen, its terrible. Wondering if it fit all the way down into its keyway slot in the crank and or flywheel...???

 

The taper on both the crankshaft stub AND the hole in the flywheel are machined/reamed to what is known as a Morse-Taper. Both MUST have an almost perfectly smooth finish in order to work properly. Also, sometimes the key-slot in the flywheel flange will crack and open-up, generally due to over-torquing. Suggest you examine corners at the base of the key-slot in the flywheel under bright light and magnification, looking for a tell-tale crack. A little heat, some Zyglo and a black-light would be optimal. FWIW, a properly machined and torqued Morse-Taper is almost impossible to rotate/spin; The Woodruff key is just there for proper indexing: I'd be looking for damage/expansion in the flywheel-flange. My two-bits.........

Cheers

 

^^^ Excellent point about minute crack in the flywheel. It would certainly cause a failure of the interference fit. A dye penetration test would be advised.

 

I agree with the inspection for cracks but,
Dye penetrant is "old school" have some one do a magnetic particle test on it it will show the smallest indications. If not done correctly you could miss more with the dye test. It will definatly "bleed" in the key way with the dye.
Just my .02.

 

Didnt have time to read every post, so I am just going to throw this out there:
Absolutely NO OIL, or any kind of lubricant on the tapers. NONE! This will cause a woodruff or a small profile key of any kind to fail almost instantly.
Second, if whatever is on the other end of the crankshaft is either loose or missing, you will also shear a key. Most small engine makers rely heavilly on the load end of the crankshaft to add the needed weight to make the engine run smoothly. The ring gear side of the engine is kept as light as possible so more HP can be realized at the PTO end.

 

Yep; got the "NO OIL" thing. It was dry as a bone; cleaned it off with TB Cleaner; wiped it down and cleaned it off again.

So are you saying that I have to have the primary clutch on in order to run it without snapping the woodruff key?

If that's the case; then why does it only snap when I'm starting the engine not when I'm running it.

Any ideas?

 

Chris, there are several factors included in keeping an engine in forward rotation, esp during start up. If the timing is very close to TDC, then, if the engine begins to crank and immediately hits the compression cycle, there is a very good possibility that it is kicking back and shearing the key. If the cranking begins on the power stroke, exhaust stoke, or intake stroke, then there is time for the crankshaft to get it's mind right and head in the right rotation, and of course maintain that direction. Is your primary clutch in place right now?

 

I'm an engineer, so I understand the concept behind your point.

No, the Primary is NOT (and has NOT) been in place.

I just don't see anything in the service manual about it being a requirement to be in place.

 

How quick can you bolt on the primary and try it again?

 

I'm not sure.
A few days.

 

I was in the power equipment business for 25 years, and I learned this at an early age. You cannot start a lawnmower without the blade securely attached. If you do get it started, you will run around the yard for an hour trying to get away from the pain inflicted by shearing off your right nipple!

 

There's your sign............

You made me laugh

 

Im not saying that its not bad for the engine but me and I know someone else I know has ran the engine without the clutch on and neither of us had any problems.

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Don't see it now but I thought I read this wasn't stock compression? I've not seen a stock RZR engine shear a key because of it but I've seen them not idle without the primary. I don't know if I'd bet the bank on it being his problem but would'nt be surprised either especially if it's not stock compression and/or cam

 

UPDATE: !!!!!
I took the engine apart; the crank and the flywheel still look good.
I put a new woodruff key in and put it back together.
The engine is installed and started right up.

I used an air impact wrench to install the flywheel nut.
It torques out just fine...

I'll know more as the next 10 days go by...
If I can get the entire buggy together tomorrow I'll be riding it.
Otherwise it will probably won't be until I'm at Carolina Adventure World next Thursday.

Thanks for all the help guys

 

Any chance to run her hard yet?

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X2 interested in the outcome as well.