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Aermacchi cam failure

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Aermacchi cam failure

davidfallon441
Hi;

I got the 350 Aermacchi, Harley Sprint, on the track in October for
the last Roadrace weekend of the year.  This was a build from scratch
project.  The engine had to be taken down to all its little parts.  I
cleaned the crank pin and checked the BE rod bearing rollers.  All
looked well.  The transmission was good.  I put fresh bearings on all
the shafts.  It needed an OS piston and fresh bore.  

During the race weekend, it ran well for 50 laps over two days.  I got
out in four practice sessions and two races.  It never missed a beat.

When I got home Sunday night, I drained the oil.  It had lots of very
tiny metal flake which responded to the magnet; that means iron.  I
suspected the cam, so I pulled the cam and lifters.  The intake lobe
has  some very light scuffing.  The lifter has the good circular
pattern, but it also has the deep scratches and one galled spot, so it
is toast.  I can save the cam with a little stone work.  The cam was
NOS, it looked as new when it was installed.  I used a moly coat prior
to installation.  I could not find new lifters, so I found lifters
that were used that looked OK.  I did polish the bottom with finer
grades of sandpaper to get a mirror finish.

I used 20-50 Castol as it still has the SH rating and all sources
recommended 50 weight for this motor (that seems heavy to me).  I did
get about 40 heat/cool cycles before I ran it on the track, so I felt
it was stable and ready for full speed action.

I need advice on why such a failure occurs.  What is a good way to
proceed now.

A machinist at work suggested that the hardening on the lifters could
have been very shallow and between wear and my sanding, it was gone.

Any advice would be appreciated.

David Fallon
WMRRA 441

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Re: Aermacchi cam failure

hans_o_man
Hi David,
tell me more about the cam-material. I guess it isn't cast-iron, but
steel? After having a steel-cam case hardened or nitrided, parkerizing
is a good surface treatment, but it always is difficult to break in
steel cams the right way.
Take a look there:
http://yarchive.net/car/cam_break_in.html (thanks to hoodrewoodre)
The article contains lots of useful information.

Here you can see a pair of XT500-rockers(kind of
ferro-titanit-hardblocks inserted), ran on case-hardened steel cams
for about 300km. Main reason of failure might have been a wrong break-in.
There was no lubrication fault, not even in the first few revolutions.
http://www.nefo.med.uni-muenchen.de/~hiha/bilder/rijeka05_1024/PICT3192.JPG

Good luck,
Hans

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Re: Aermacchi cam failure

Grog
In reply to this post by davidfallon441
David,
I've only had abnormal cam'follower wear failure on race engines once.
That was the result of ignorant-me tying to run cams with lift rates
that were too high for the diameter of the round flat followers...the
cams were simply running off the edge of the followers, wiping oil from
the contact surfaces and having almost point contact with resultant high
contact pressures per area and no oil to speak of. Elementary, but not
obvious to me until I wrecked two sets of cams and followers!

Not saying this is the problem here though, but I have seen a set of
rockers that were second hand, previously used with standard cams, but
were pressed into service with a new hot cam.
Fortunately(!) the engine had another failure and was stripped down but
bad war was evident and the cam and rocker contact area. THe old rocker
had worn the edges of its contact area to the std cam but was only
running on it's edge for the first and last part of the lift with the
new cam.

All I am saying here is to ensure that you do not perhaps have a mix of
parts that run to the edge of contact surfaces......as possibly the
XT500 Yam pic might be showing? That insert has a sharp edge with no
real lead in at the unworn end....?
But of course we cannot see the starting shape of the edge of the rocker
inserts on the leading edge anymore.

I also raced 500 Yams. Mine were raced in English-style dirt track and
long track. They ran huge lift cams, had big valves, hairy springs and
ran a full 14:1 CR on meths and were a match for the early Jawa and
Weslake 4 valvers, unless they were ridden by the top few riders....
I have seen bad cam and follower wear on Yams with an oil flow fault,
but never experienced catastrophic wear on my engines.
I lubed new cams with the tube of moly-stuff that came with the cams
when new, but did not do this always.
But then of course I ran castor oil 40w in EVERY alky engine I've ever
raced.
That stuff is good.
When Castrol here in Oz stoppedselling it I rang their techo guy and
asked what was the recommended replacement.
He talked a bit and mentioned product, but I asked if any of it has the
same load bearing capability (or whatever the correct technical term is)
and he told me that none of what they supply can match the castor oil.
I thanked him.
I now use Rock Oil Castor 40w.

I don't know if that is the full story on oils, but after Castrol
admitted that, why would I use anything else?
My experience seems to bear this out, I've had good wear rates in all my
race engines over the years.
I would never run any highly loaded old non-Jap race engine on anything
else.

I guess I've lit the oil-fuse now.....lol...hope not.
So check the fit of the follower to the cam and make sure it is not
running right to the edge of contact before you go too far.
Greg


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Re: Aermacchi cam failure

davidfallon441
In reply to this post by hans_o_man
--- In [hidden email], "hans_o_man" <der_hiha@...> wrote:
>
> Hi David,
> tell me more about the cam-material. I guess it isn't cast-iron, but
> steel?

Hans;

I guessed it was cast iron in the form of Ductile which I know some
call cast steel.  It is an exact match for the original stock cam, so
I assume it was made in the mother country of Italy.  It was an NOS
part still in the factory packing too.  This is just the plain old
street motor with modest power.

The info about the cams and lifter is good.  I did not know that the
lifters require a radius ground into the contact surface.  That could
be what the problem is.  I used sandpaper on a flat granite plate to
get the contact surface flat, smooth and shiney.  That sounds like the
wrong thing to do.

Crane also has lot of good info about cams and startup, though they
never mentioned about the radius on the lifter contact point.

It hurts my wallet to see the picture of the Yam 500 cam and lifters.

I did use the Bel Ray moly cote for engine building.  I know moly is
your friend when it comes to high pressure.  I also could and did
prime the whole oil system backwards by using a handy external line
that goes up to the cylinder head.  The engine got a push start and
started right up to, so I got all those parts right.

I'm not acquainted with Parkerizing.  Is it the do it yourself option?

David Fallon
WMRRA 441

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Re: Aermacchi cam failure

davidfallon441
In reply to this post by Grog
--- In [hidden email], Greg Summerton <gregss@...> wrote:

>
> I guess I've lit the oil-fuse now.....lol...hope not.
> So check the fit of the follower to the cam and make sure it is not
> running right to the edge of contact before you go too far.
> Greg
>
Thanks Greg;

Even though this is a stock set up, I need to look at the contact
point too.  With this bike it is very out in the open and easy to see,
so I'll check that.  

Oil wars, there always interesting, and I hesitated to mention what I
had used.

David Fallon
WMRRA 441

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Re: Aermacchi cam failure

hans_o_man
In reply to this post by davidfallon441
Hi David,
>
> It hurts my wallet to see the picture of the Yam 500 cam and lifters.
>
Don't bother, the worst work was cleaning the engine from debris :-)
The cam was built by myself, and the rockers are repaired by grinding
off the hardblock, hardwelding and regrinding. For I can do that
myself, ist's not a wallet-, but a time problem...

For pre-lubrication I use the redline assembly lube
http://www.racerpartswholesale.com/redline10.htm
>
> I'm not acquainted with Parkerizing.  Is it the do it yourself option?
>
I didn't try to parkerize myself, but galvanic shops(?) do that.
Its also called manganese-phosphating and many OEM-cams are treated
that way.

Gruss
Hans

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Re: Aermacchi cam failure

Michael Moore-3
In reply to this post by davidfallon441
David, another thing you can do to prime the engine is before
starting it (in the bike) remove the plugs and engage low gear and
push it around until you see signs of  oil circulation.  You probably
only really need to do that before the first start of the day.

I've heard the people at Megacycle Cams refer to "Italian mystery
cam steel" and they seemed unenthusiastic about hard-welding on
OEM Italian camshafts due to problems with (I think) cracking.

cheers,
Michael
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Re: Aermacchi cam failure

davidfallon441
--- In [hidden email], "Michael Moore" <mmoore@...> wrote:

>
> David, another thing you can do to prime the engine is before
> starting it (in the bike) remove the plugs and engage low gear and
> push it around until you see signs of  oil circulation.  You probably
> only really need to do that before the first start of the day.
>
> I've heard the people at Megacycle Cams refer to "Italian mystery
> cam steel" and they seemed unenthusiastic about hard-welding on
> OEM Italian camshafts due to problems with (I think) cracking.
>
> cheers,
> Michael
>
Thanks Michael;

The note about the mystery steel is very interesting as the Megacycle
folks would have lots of experience with that sort of issue.

David Fallon
WMRRA 441

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Re: Aermacchi cam failure

Ian D-2
In reply to this post by hans_o_man

>For pre-lubrication I use the redline assembly lube
><http://www.racerpartswholesale.com/redline10.htm>http://www.racerpartswholesale.com/redline10.htm


There is always arguments over what oil to use, the next hottest
subject to get into an argument over is whether to use a
"pre-lube" during assembly.   The best engine builders I know
are divided on this, and if they can't agree then I'm not going to
express an opinion.



Cheers          IAN


See www.drysdalev8.com for :
- Drysdale 750-V8 Sports & 1000-V8 Cruiser
- DRYVTECH 2x2x2 Experimental
- Carberry Enfield 1000cc V-Twin
- Drysdale Hillclimb Open Wheeler


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Re: Aermacchi cam failure

davidfallon441
--- In [hidden email], Ian <iwd@...> wrote:

>
>
> >For pre-lubrication I use the redline assembly lube
>
><http://www.racerpartswholesale.com/redline10.htm>http://www.racerpartswholesale.com/redline10.htm
>
>
> There is always arguments over what oil to use, the next hottest
> subject to get into an argument over is whether to use a
> "pre-lube" during assembly.   The best engine builders I know
> are divided on this, and if they can't agree then I'm not going to
> express an opinion.
>
>
>
> Cheers          IAN

Ian;  

I do love a heated discussion as long as it sheds a few grains on
knowledge on the subject.  I usually do not participate myself, but I
love to observe.

David Fallon
WMRRA 441

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Re: Aermacchi cam failure

hans_o_man
In reply to this post by Ian D-2

I only wanted to say: [Redline-lube] It worx for me...:-)

>
> There is always arguments over what oil to use, the next hottest
> subject to get into an argument over is whether to use a
> "pre-lube" during assembly.   The best engine builders I know
> are divided on this, and if they can't agree then I'm not going to
> express an opinion.
>
>
>
> Cheers          IAN


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crankshaft balance

bateman147
In reply to this post by davidfallon441
Another question -

Has anyone experimented with crankshaft balance factors other than 50% for
the SV650?  And - in figuring the bobweights are you including an amount for
the oil in the crank or are you ignoring it?

Also -

Is there any reason why a pressed together crank with captured rods (ie
Honda 160 etc) can't be balanced statically with the rods in place by
hanging appropriate weights from the rod ends while on either a knife edge
fixture or a nice fabricated low friction balance rig?  I'm sure all of this
was figured out in the '40s and I'm just now catching up...  :-)  Based on
my reading of Honda's tech papers from the '60s we tend to relearn an awful
lot of stuff that's been known for years.

Cheers!

Michael

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Re: crankshaft balance

Ian D-2

>Has anyone experimented with crankshaft balance factors other than 50% for
>the SV650?


A 90 deg vee twin has zero primary vibe at 50% BF, why
would you want anything else ?


>Is there any reason why a pressed together crank with captured rods (ie
>Honda 160 etc) can't be balanced statically with the rods in place by
>hanging appropriate weights from the rod ends while on either a knife edge
>fixture or a nice fabricated low friction balance rig?


No reason, you can get them pretty close with a bit a
practice.



Cheers          IAN



See www.drysdalev8.com for :
- Drysdale 750-V8 Sports & 1000-V8 Cruiser
- DRYVTECH 2x2x2 Experimental
- Carberry Enfield 1000cc V-Twin
- Drysdale Hillclimb Open Wheeler


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RE: crankshaft balance

bateman147
>A 90 deg vee twin has zero primary vibe at 50% BF, why
>would you want anything else ?

Thanks Ian - I guess a better way to ask that question would have been
whether or not there's any reason to think of a balance factor other than
50%.  I have heard tuners that seem to know their stuff talking about
balancing over 50% of recip by several percent.  

>>fixture or a nice fabricated low friction balance rig?

>No reason, you can get them pretty close with a bit a
>practice.

Thanks again - much appreciated.  Didn't think I was missing anything, but
the more I learn the less I think I know, so it's nice to have confirmation.

Cheers -

Michael

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RE: crankshaft balance

Ian D-2

>I have heard tuners that seem to know their stuff talking about
>balancing over 50% of recip by several percent.


OK, I thought you were talking about changing it to 35% or
65% BF.

Yes, I have heard this 48% to 52% BF argument for Ducati's
but I have never ridden one set up like this so I can't comment.
All I can say is that physics says 50% BF gives you zero
primary vibe in a 90 deg V twin.

The secondary vibe can't be altered by changing the BF, but
it is partially cancelled anyway, and not usually too annoying
on a 90 deg V twin.

What is possibly going on is that introducing a small amount
of primary vibe counteracts some of the secondary vibe ?



Cheers           IAN


See www.drysdalev8.com for :
- Drysdale 750-V8 Sports & 1000-V8 Cruiser
- DRYVTECH 2x2x2 Experimental
- Carberry Enfield 1000cc V-Twin
- Drysdale Hillclimb Open Wheeler


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RE: crankshaft balance

bateman147
>Yes, I have heard this 48% to 52% BF argument for Ducati's
>but I have never ridden one set up like this so I can't comment.
>All I can say is that physics says 50% BF gives you zero
>primary vibe in a 90 deg V twin.

>The secondary vibe can't be altered by changing the BF, but
>it is partially cancelled anyway, and not usually too annoying
>on a 90 deg V twin.

>What is possibly going on is that introducing a small amount
>of primary vibe counteracts some of the secondary vibe ?

Interesting thought.  Perhaps that's it.  For myself I'm more interested in
engine life rather than perception at this point.  Race SV-650s have a
terrible reputation for broken cranks and I'm hoping to put a dent in it.
I've got several guys here that I've been building (sort of building - to a
real tight budget) race motors for that always seem to not be able to afford
time or money to do things right the first time, but just gotta have that
broken motor back together for the next race weekend.  And it's gotta make
boatloads of power too of course.  

This season I'm insisting on carefully balanced cranks and flywheels at a
minimum, and I want to make sure that I insist on the right thing
balance-factor wise.  Some of the v-8 tuners say that the cranks need to be
overbalanced for high revs, and I've talked to a couple of Ducati tuners who
seemed to be thinking along the same lines.

It seems to me though that at least for 90 and 180 degree motors it
shouldn't depend on revs, unless something is incorrect in the balancing -
IE you didn't achieve 50% through an error in measurement or something like
that.  But that's only how it seems to me - I've certainly not got enough
experience to know.

Cheers -

Michael

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Re: crankshaft balance

Brent Prindle
----- Original Message -----
From: "Michael Bateman" <[hidden email]>
...

> Interesting thought.  Perhaps that's it.  For myself I'm more
> interested in
> engine life rather than perception at this point.  Race SV-650s have a
> terrible reputation for broken cranks and I'm hoping to put a dent in
> it.
> I've got several guys here that I've been building (sort of building -
> to a
> real tight budget) race motors for that always seem to not be able to
> afford
> time or money to do things right the first time, but just gotta have
> that
> broken motor back together for the next race weekend.  And it's gotta
> make
> boatloads of power too of course.
>
> This season I'm insisting on carefully balanced cranks and flywheels
> at a
> minimum, and I want to make sure that I insist on the right thing
> balance-factor wise.  Some of the v-8 tuners say that the cranks need
> to be
> overbalanced for high revs, and I've talked to a couple of Ducati
> tuners who
> seemed to be thinking along the same lines.

The major breaking point on the SV crank is between the main bearing and
the rotor.  Every one I have seen has been a torsional break in this
area.  Sometimes from the oil hole and sometimes from the keyway.  Both
good stress risers at the wrong place.

Lightening up the rotor/flywheel, and keeping a high ratio between web
and rotor mass seems to help.  The crank inertial "absorbs" some of the
shocks from the power pulses and there is less twisting of the crank
behind the rotor.  I think some of the overbalance is actually adding
weight to the crank and helping the ratio.

Talk to Lanigan (local guy) and he seems to swear by sending the cranks
to Falicon for balance, true, and polish.  He says that he has not seen
a crank fail that has had this treatment.  Perhaps there are some
grinding issues from Suzuki that are being polished out, eliminating the
stress risers from aggressive/coarse grinding.


-oo
Brent Prindle
[hidden email]



 
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Re: crankshaft balance

john fisher-4
In reply to this post by bateman147
Zoran would know too, especially if you are in the Bay area.
He's on here or the chassis list or both.

.... Race SV-650s have a
> terrible reputation for broken cranks and I'm hoping to put a dent in it.
... ...
>
> Cheers -
>
> Michael
>
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RE: crankshaft balance

Ian D-2
In reply to this post by bateman147

>Some of the v-8 tuners say that the cranks need to be
>overbalanced for high revs,



But most V8's have no balance webs on the centre throws
at all, which they compensate for by twisting the webs on
the end throws by 13 deg. or so.

This means that the middle throws have ( effectively ) a BF
of negative 200-300%.   It creates massive stresses in the
crank and main bearings, but cast iron blocks seem to
stand up to it OK.

You will see ongoing arguments as to the need ( or lack of )
to fully counterweight V8 racing cranks.  I'd be VERY
nervous about running big revs in a alloy block V8 with an
"end weighed" crank.



Cheers        IAN


See www.drysdalev8.com for :
- Drysdale 750-V8 Sports & 1000-V8 Cruiser
- DRYVTECH 2x2x2 Experimental
- Carberry Enfield 1000cc V-Twin
- Drysdale Hillclimb Open Wheeler


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RE: crankshaft balance

bateman147
In reply to this post by Brent Prindle
> The major breaking point on the SV crank is between the main bearing and
> the rotor.  Every one I have seen has been a torsional break in this
> area.  Sometimes from the oil hole and sometimes from the keyway.  Both
> good stress risers at the wrong place.

Hi Brent!  Good to hear from you.

Yes - two of the four breakages were the end of the crank breaking off.
Both appeared to start at the end of the keyway.  I'll be balancing all of
the flywheels, and lightening the total-loss flywheels as much as possible
before balancing.  I'm thinking I'll also try to reduce the stress riser at
the end of the keyway by careful grinding to remove the sharp corners.
Interestingly enough Dan Zlock pointed out to me that the later model cranks
have the keyway moved entirely under the flywheel taper, where earlier ones
were only partially under the taper.  I've also noticed that the end of the
flywheel bolt corresponds almost exactly with the end of the keyway.  I'm
thinking that a slightly shorter bolt may also be in order.

> Talk to Lanigan (local guy) and he seems to swear by sending the cranks
> to Falicon for balance, true, and polish.  He says that he has not seen
> a crank fail that has had this treatment.  Perhaps there are some
> grinding issues from Suzuki that are being polished out, eliminating the
> stress risers from aggressive/coarse grinding.

I tried to get these guys to send the cranks to Falicon last year.  Of
course there "wasn't enough time" and they didn't want to spend the extra
dough.  I talked to Falicon quite a bit and they said that they polish and
balance, and also recommend cryo treatment as well, and still find that the
cranks may not last the season (but are much improved).  I see now that they
are offering a billet crank for the SV.  Same with balancing the flywheels -
no time or money.

Two of the cranks however were broken at the crankpin on the inside of the
flywheel side web.  Right at the radius.  Also, in almost all of the motors
the flywheel side main bearing is walking around - the lower half is walking
toward the crank.  On the early motors it is retained by a plate, but on the
later motor they (Suzuki) left that plate out and the main bearing just
walks right out into the crank.  Even on the early ones the bearing walks
enough to bend the plate out almost a full mm toward the crank.

In talking to Dan Z it appears that almost all of the high hp SV's do this -
but I suspect that it's much worse in the ones with inadequately balanced
cranks.  Especially since two of the cranks broke at the web - looks like
the crank is flexing a lot - probably really exaggerated by imbalance.  I
pinned one in place with a roll pin in the oil groove, and it appears to be
staying in place, but that's a band-aid.  

I'm also guessing that these guys don't exactly operate the bikes with the
most mechanical sympathy.  I wouldn't be surprised to find they'd been
bouncing off the rev limiter all the way around the track, and mechanically
forcing it past the rev limiter on downshifts.  Perhaps a slipper clutch is
in order...  :-)

Cheers -


Michael

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