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PostPosted: Wed Mar 16, 2005 5:54 pm 
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Joined: Mon Dec 22, 2003 3:44 pm
Posts: 32
Location: Texas
I removed the Pilot Engine today and split the cases. The main seal on the clutch side showed signs of leakage and the clutch could be moved ever so slightly by hand in a radial direction(bad news). Sure enough, the Nachi main bearing on the clutch side spit out it's little rivets in 4 spots, exactly 1/2 of them BTW.

This is not the 1st time I have seen a bearing failure in one of my motors, not even the 2nd. Several others have seen the same exact thing.

I have wondered in the past if the seal went out and the bearing got contaminated or if the bearing went south 1st and then wrecked the seal. Now I am confident in saying the bearings are going 1st. The seal was in perfect shape and there was no grit in the bearing.

Some have suggested that there are some unbalanced PowerBloc clutches out there contributed to this problem. I have never seen either of mine show signs of out of balance but there is no way for me to 100% say that. I have also heard of problems with off center PBs and again, I have not experienced that one either.

I use quality gas and oil at 32:1, run my Pilot very hard, and know how to build a bottom end correctly....

So.....

What does eveyone think is the problem is for the bearings to fail?

Bad batch of Nachi bearings from Honda?
Undersize bearing for this application?
Lesser quality than needed?
Too much power/abuse for this bearing to handle?
Clutches vibrating the rivets out?
All of us with problems terribly underqualified mechanics?

And, if you have a reason for failure, what is the solution?

I personally think these bearings are too weak for the horsepower these motors are making and the abuse we give them. I am going to talk to a bearing shop tomorrow to ask for some guidence. Maybe there is a stronger bearing with the same clearances that will beef up things. The bearing rolls along with 8 little balls, maybe one with 10 or 12 balls with even out the load and last longer....

:shock:


Attachments:
File comment: Whats missing here?
rivet1.jpg
rivet1.jpg [ 37.34 KiB | Viewed 3239 times ]
File comment: Another view. Looks familiar...
rivet4.jpg
rivet4.jpg [ 32.39 KiB | Viewed 3239 times ]
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PostPosted: Wed Mar 16, 2005 6:05 pm 
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Joined: Mon Dec 15, 2003 2:40 pm
Posts: 22077
Location: Chicago
I can feel for you buddy been their done that and it sucks.

Its the exact same size bearing as the FL250 used, they had problems with them
on the mod and full mod engines, answer was Marv's super cases with the extra
bearing, they also made a bearing holder you could weld on to the outside of
the cases...

I don't see their being enough room to add one on the Pilot I think you could bore the case out
press in a new bearing holder then weld it to the case, then machine the hole out
to ensure it was perfect after all the welding and heat, then press in a dual row bearing,
or perhaps one with a larger OD that has a few more balls?


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PostPosted: Wed Mar 16, 2005 6:48 pm 
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Joined: Sun Dec 21, 2003 11:30 pm
Posts: 476
Location: Nebraska
Doesn't this have to be a bad batch of bearings issue ?

Most all of these machines have run flawlessly for 10+ years on the original bearings
Now all of a sudden when they are replaced they are not lasting 1 year ?

The rivets appear to be completely inadequate...

If we rule out lubrication and contamination issues all I see left is bearing or possibly clutch balance issues ?

Has anyone NOT running a PowerBloc Clutch lost a lower unit ?


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PostPosted: Wed Mar 16, 2005 7:01 pm 
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Joined: Mon Dec 15, 2003 2:40 pm
Posts: 22077
Location: Chicago
FL670R wrote:
Doesn't this have to be a bad batch of bearings issue ?

Most all of these machines have run flawlessly for 10+ years on the original bearings
Now all of a sudden when they are replaced they are not lasting 1 year ?

The rivets appear to be completely inadequate...

If we rule out lubrication and contamination issues all I see left is bearing or possibly clutch balance issues ?

Has anyone NOT running a PowerBloc Clutch lost a lower unit ?



How do you test the balance of the clutch?

The crank bearings on my Rotax crank have a plastic ball seperator, don't know
what the brand of the bearing is I just know it is a German mfg.

The Pilot the exact same size bearing as the FL250 used, they had problems with them
on the mod and full mod engines, answer was Marv's super cases with the extra
bearing, they also made a bearing holder you could weld on to the outside of
the cases...


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 Post subject:
PostPosted: Wed Mar 16, 2005 8:51 pm 
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Joined: Mon Dec 22, 2003 9:04 am
Posts: 465
Location: Springfield Ohio
Take a good look at the bearing races. The bearings Hoser sent me to look at have spalling on the outer race (looks like a small area where the surface has flaked off). I would not think so many could have bearings from one bad batch. Don’t know for sure what the problem is but I would rule that one out just from the volume of problems.

My pet theory is that the spalling caused vibration in the bearing that lead to the rivits comming apart. I still vote for lack of oil. Not a one time melt down lack of oil but less oil = more wear.


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PostPosted: Wed Mar 16, 2005 9:02 pm 
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Joined: Mon Dec 15, 2003 2:40 pm
Posts: 22077
Location: Chicago
My pet theory is that the spalling was caused by the bearing seperator no longer
keeping the balls seperated so they bounced off each other they also bunched
up and left part of the crank unsupported on one side....


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 Post subject:
PostPosted: Wed Mar 16, 2005 9:24 pm 
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Joined: Wed Jan 14, 2004 8:45 pm
Posts: 2238
There has to be some sort of machine to check the balance of a spinning clutch. Maybe like a smaller version of a digital tire balancer. A little weight imbalance would significantly magnify at a high RPM possibly causing bearing failure over time. Anyone actually use a rifle reloading scale or other precision scale to check the weight of each stack of pucks? Just my 2 cents again, Gary


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 Post subject:
PostPosted: Thu Mar 17, 2005 8:40 am 
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Joined: Tue Sep 21, 2004 3:58 pm
Posts: 67
Location: CT
I'm a newb who don't know jack, especially about pilots since I only own FL350s, but are the missing rivets always on one side or the other, top or bottom, front or back?

If the missing rivets are always on the front top (northeast so to speak), could it be just a matter of the crank flexing, in other words, the first bearings lasted 19 years, but the replacement bearings only last a year because something else is worn and causing problems?

Spalling, if I recall correctly, is due to excessive heat....

Just a thought or 2.


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PostPosted: Thu Mar 17, 2005 9:13 am 
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Joined: Mon Dec 15, 2003 2:40 pm
Posts: 22077
Location: Chicago
PChiarizio wrote:
I'm a newb who don't know jack, especially about pilots since I only own FL350s, but are the missing rivets always on one side or the other, top or bottom, front or back?

If the missing rivets are always on the front top (northeast so to speak), could it be just a matter of the crank flexing, in other words, the first bearings lasted 19 years, but the replacement bearings only last a year because something else is worn and causing problems?

Spalling, if I recall correctly, is due to excessive heat....

Just a thought or 2.


The bearing seperator rotates with the bearing so it is never in the same place
when the bearing is in use.

The missing rivets seems to be random, look at Pilotnuts bearing.


Attachments:
pnut-bearing.jpg
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 Post subject:
PostPosted: Thu Mar 17, 2005 10:09 am 
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Joined: Fri Dec 19, 2003 9:37 pm
Posts: 824
Location: Howell, New Jersey
Is there someone at Honda that might be willing to do a little research on this? Or are we just to small a group (and our machines to old) for them to really give a hoot about??

Hoser - when you install my new crank bearings, put a dab of Super Duper Glue on each rivet - thanks!!


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PostPosted: Thu Mar 17, 2005 10:29 am 
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Joined: Sun Dec 21, 2003 10:04 am
Posts: 477
Location: wallace,sc
lmao,super duper glue :shock:

wasn't lee looking into some of the bearing issues ?

anyone running a comet clutch or stock clutch having the same problems with the bearings?

Tom is there a way you can test the rivets for strength ?

say if you put the bearing in a vise and try to see just how easy the peened end of the rivets comes off.


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 Post subject:
PostPosted: Thu Mar 17, 2005 11:15 am 
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Joined: Mon Dec 15, 2003 2:40 pm
Posts: 22077
Location: Chicago
Here is Pilotnuts bearing after I took a screwdrive and pried the ball seperator
up so I could see inside.


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MVC-011F.JPG
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 Post subject:
PostPosted: Thu Mar 17, 2005 11:16 am 
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Joined: Mon Dec 15, 2003 2:40 pm
Posts: 22077
Location: Chicago
Here is the other side, the seperator was already broke.


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 Post subject:
PostPosted: Thu Mar 17, 2005 11:17 am 
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Joined: Mon Dec 15, 2003 2:40 pm
Posts: 22077
Location: Chicago
The bearings on my Rotax Engine have plastic


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 Post subject:
PostPosted: Thu Mar 17, 2005 11:18 am 
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Joined: Mon Dec 15, 2003 2:40 pm
Posts: 22077
Location: Chicago
It also has 2 crank bearings like the Pilot should have had.


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 Post subject:
PostPosted: Thu Mar 17, 2005 11:23 am 
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Joined: Mon Dec 15, 2003 2:40 pm
Posts: 22077
Location: Chicago
tsutton44 wrote:

wasn't lee looking into some of the bearing issues ?

.


Yeah he said lack of oil, if it was lack of oil it has to be an intermittent problem
I always find plenty of oil after a bearing failure.

I say it is the fact we have in most cases doubled the HP of the stock Engine
but nobody seems to want to listen, the FL250 uses the same
bearing back in the racing days then they more than doubled the HP (17hp
to 40-55 HP) they suffered bearing failures on the clutch side, the fix was
to install the second bearing on the clutch side, Marv at 4x4 Tuff had
"super cases" built with the dual bearing setup by Calvin Pollet
http://www.cpindinc.com/

Some are wanting to blame the clutch, like having no spark first thing to get the
blame is the CDI (Capacitor Discharge Ignition) box, people want to chane it, think it is the clutch then the answer
is simple enough, rebuild the Engine and install your stock clutch or go buy a
comet clutch and run it for a few years let us know what you think, keep in mind that
Power Bloc has been making clutches since the late 60's I doubt they would
not balance them but you never know, I have tried to contact them with no
luck, Rudedude has purchased stuff from them you would think since they
took his money (our money) and sent him a product he could maintain some
sort of verbal contact with them and ask some simple quesions, again I could be
wrong.

Also keep in mind that my two last Engine failures had NOTHING to do with the
bearing faiures your talking about here so take them off your mental list of
failures I keep reading and hearing statements like "with all these recent failures"
ensure you have your focus on the right failures.


Attachments:
plenty of oil.jpg
plenty of oil.jpg [ 51.29 KiB | Viewed 3173 times ]
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 Post subject: Update
PostPosted: Thu Mar 17, 2005 11:37 am 
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Joined: Mon Dec 22, 2003 3:44 pm
Posts: 32
Location: Texas
Ok, I called Nachi directly and talked to a bearing engineer that has been building/designing bearings for many years. He says the cage rivets do not fail in normal use. The seperators do not do any work other than loosely hold the balls in place. He said there was 2 things that cause the balls to expand and push on the cage or cause the cage to spread:

1- too much/too thick of lube. He said thicker lube in a ball bearing causes drag on the ball. Think of driving the truck trhough mud. I doubt this is an issue.

2- too tight of fit on the ID AND OD. He was suprised when I told him that both rings had a press fit. Anyone have the actual tolerances? The crank or cases could be out of round causing the bearing to bind and spit out the rivets.

I also asked him about a 5 lbs clutch hanging off the end, being possibly unbalanced. He stated that would do it too.

So, he recomended checking these things out and possibly running a "looser" clearance bearing, say a 6306 C4 instead.

I also asked about a heavier duty bearing. He said they produce ball bearings with larger balls that significantly increase the load capacity. The drawback is the cages get too big if they use a really large one and actually stick out past the races themselfs, not good for us.

Food for thought.

Hoser and others- save those bearings! I want to send a couple of them to the engineer directly so he can offer insight to the failure. Box em up and send em to the folks who made them. Why did we not think of this 1st instead of making assumptions and questioning a Honda guy who is not a bearing specialist? Duh.


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 Post subject:
PostPosted: Thu Mar 17, 2005 11:45 am 
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Joined: Mon Dec 15, 2003 2:40 pm
Posts: 22077
Location: Chicago
Tom you have a address I was going to send Pilotnuts bearing to Lee but
can send to nachi if they want to look at it.

Too thick of oil haha guess I better quit greasing my wheel bearings..


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 Post subject: Clutch differences
PostPosted: Thu Mar 17, 2005 12:45 pm 
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Joined: Wed Dec 24, 2003 12:06 pm
Posts: 1412
Location: San Diego
Ok, I'm no pilot expert, my main area of interest here is the 250 so correct me if I'm wrong.

The stock pilot drive clutch and the comet clutch both use a spring/roller type of mechanism whereas the powerbloc uses loose fitting pucks. Putting the balance of the clutches aside is it possible that the vibration of the pucks is causing an harmonic issue that would be missing in the spring/roller design.

As the engineer stated the bearing separators do not normally carry a load, so other than being tweaked by torsional forces the only real factors left are harmonics, lubrication and then lastly heat (which is usually induced by one of the three previous factors).

Like all the others reading these bearing failure posts I'm left wondering why all of these failures are happening to powerbloc equipped machines and not the stock or comet equipped machines.

As far as the 250's experiencing bearing failures in racing machines, almost everyone that was raced used a powerbloc clutch. Coincidence? I doubt it. They are infinitely more adjustable hence their popularity.

Do all sled engines have dual bearings or is it more common on machines that come equipped from the factory with powerbloc clutches?


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 Post subject:
PostPosted: Thu Mar 17, 2005 1:34 pm 
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Joined: Wed Jan 14, 2004 8:45 pm
Posts: 2238
Does anyone have access to a precision scale, such as a rifle reloading scale, to weigh each stack of pucks on a power block clutch? Just to see how much variation in total weight there is on each stack. Just another suggestion.


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 Post subject: Re: Clutch differences
PostPosted: Thu Mar 17, 2005 2:50 pm 
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Joined: Mon Dec 15, 2003 2:40 pm
Posts: 22077
Location: Chicago
Ody_Stable wrote:

The stock pilot drive clutch and the comet clutch both use a spring/roller type of mechanism whereas the powerbloc uses loose fitting pucks. Putting the balance of the clutches aside is it possible that the vibration of the pucks is causing an harmonic issue that would be missing in the spring/roller design.



The pucks are under tension when in use just like the rollers on a roller clutch.

I have no access to a gram scale to weigh anything. I don't think balance is
or vibration from the clutch is a issue I don't worry about it any more than the
added vibration you get when using worn Engine mounts or switching to a wiseco
piston or adding a aftermarket exhaust system, becides if it was vibration why
don't the bearing on the other side of the crank fail the same way it is located
5" away from the other bearing on the same shaft, how come the vibration
don't affect the balancer bearings or rod bearings?

Try this start a stock Pilot and a modified one and rev them up, put your hand on
each one in the same location like the head, you tell me what you feel.


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 Post subject: Harmonics
PostPosted: Thu Mar 17, 2005 3:39 pm 
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Joined: Wed Dec 24, 2003 12:06 pm
Posts: 1412
Location: San Diego
At idle the pucks are not under tension and will be vibrating. These harmonics may be at just the right frequency to cause the damage.

In this case low speed may be more damaging than high speed. Being closer to the source of the vibration may also be the sole reason it's always the output side since the crank is not continuous from one side to the other.

I'm not laying blame on anything, just throwing out some options since no one has yet to find an exact cause.


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 Post subject:
PostPosted: Thu Mar 17, 2005 5:25 pm 
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Joined: Mon Dec 15, 2003 2:40 pm
Posts: 22077
Location: Chicago
The 350 clutch side bearing is bigger its a 6307 I wonder how much stronger that is than
the Pilot 6306?


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 Post subject:
PostPosted: Fri Mar 18, 2005 4:58 pm 
It seems like modification of the rev limiter and a big increase in horsepower would be suspect to me. This makes sense if an extra bearing were added at one time to a 250 to handle the extra power! More performance = Less reliability.


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 Post subject: Bearing Failures
PostPosted: Fri Mar 18, 2005 6:39 pm 
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Joined: Sat Dec 20, 2003 2:11 pm
Posts: 61
Location: Lewiston New York
Correct me if I'm wrong but spalling is a form of fatigue failure. I don't think that it has to do so much with heat (however I'm sure this happens simultaneously), but you are overloading the surface of the material......what would cause this? I like Hosers idea of the the rivets working loose and causing balls to bunch up....?

Another thing to consider is how the bearing is treated. I was taught that if you ever drop a ball bearing on the floor..........THROW IT OUT! When you drop a bearing it is subject to impact.....they aren't designed to absorb impact, the result is an indentation on a ball or race....or both. Now I'm not saying that the people who do their own bottom ends don't know how to handle bearings, but what about the 10 other people that handled it before.......I wouldn't consider the packaging of the bearings we get to be great, or good for that matter......who knows?

After reading all the discussion about clutch imbalance I think it holds some merit. I see no signs of any balancing marks on either of my PB clutches, or the pucks, or any part of them. There is no way in hell that they are perfectly balanced in there as cast forms. The way I see it, its alot like working on cars.....if you are going to build a hot motor (( Internal Combustion Engine ? )) that you are going to spin faster and harder, you always have it race balanced. They balance everything from your rotating assembly to your flywheel....why would a pilot clutch be any different!


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