Seized motor

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King
Posts: 387
Joined: Fri Apr 02, 2004 5:05 pm

Seized motor

#1

Post by King » Tue Nov 29, 2005 1:38 pm

Description: Without any warning the back end locks up and I skid to a halt

Hi All

On Saturday I was on a ride, weather fine though cool in the 40’s, the bike (a 51FL) running strong, when without any warning the back end locks up and I skid to a halt. I try a restart but the kick pedal won't budge, not a millimeter, even with all 220 lbs of me standing on it. Clutch disengaged it spun so we ruled out the tranny. I waited till the motor cooled a bit, thinking heat seized piston, and tried again but still no movement.

Back in the barn I took off the primary cover and tried to turn the motor over with a socket on the engine sprocket nut. Counterclockwise (direction of rotation) all I did was unscrew the nut but clockwise it moved. It took a bit of effort to get it moving but I was able to rotate it clockwise freely for a couple of revolutions. Then I tried counterclockwise again and it was perfectly free! It rotates normally now with the kicker. There is no grinding, clicking, or any other sounds when it is rotated. Also it seems to have good compression using the thumb over the spark plug hole test but I'm not ruling anything out at this stage.

Has anyone had or heard of a similar happening? I'm not going to attempt to start it with out a complete tear-down but would like to know where to look first.

Thanks

King



Jack_Hester
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Re: Seized motor

#2

Post by Jack_Hester » Tue Nov 29, 2005 2:29 pm

King -

I'm not sure there is anything that anyone can say about what happened, other than maybe a seized piston. But, it's all speculation, until you pull the top end. After you pull the heads, squirt a bit of oil on the cylinder walls before you turn it over. Not that you will leave it this way. Just making sure no further damage can occur when you pull the cylinders. Scarring of the piston skirts and cylinder walls it the first thing to look for. Broken rings and missing wristpin keepers are others. Give us the details of your inspection. Pictures if you can. Sorry for your misfortune. Wish I was close enough to help.

Jack

Cotten
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Re: Seized motor

#3

Post by Cotten » Tue Nov 29, 2005 3:21 pm

Although top end woes are most common, I have encountered others...

The directional bind suggests to me an endplay problem.
I would place a bet upon the crank screwing sideways, galling upon the thrustwashers, either at the crank or a main race.

King
Posts: 387
Joined: Fri Apr 02, 2004 5:05 pm

Re: Seized motor

#4

Post by King » Wed Nov 30, 2005 12:56 pm

Jack and Cotten

Thanks for your replies and insights. I started the strip down last night and will post the results as they are reveled.

King

King
Posts: 387
Joined: Fri Apr 02, 2004 5:05 pm

Re: Seized motor

#5

Post by King » Mon Jan 02, 2006 2:05 pm

Happy New year to all!!

Well the Pan seizure mystery has been revealed. I finally got back home during the Christmas break and was able to strip her down. Removal of the heads showed no problems with pistons or cylinders although fairly heavy "coking" indicates oil is getting in somehow, so it was time to look deeper down.

I removed motor from frame set it up on the bench and began the serious stuff. I first moved into the gear case where all was well, no sign of bindings etc., no excessive wear on the cam, tappets, or gear bushings, and happily no metal flakes . Then I removed the oil pump. Every thing was fine there also, good and tight, with no sheared keys. So on to splitting the cases.

The actual "split" occurred easily with the removal of the case bolts but the split was only about ¼”. With a bit of gentle wood block tapping the right (pinion) side came off easily having just the amount of bind one would expect from a good set of bearings. All looked good except for a bit of galling of the thrust washer. But the left (sprocket) side was a totally different story. It was tighter than the proverbial amphibian's orifice. However, a bit of judicious tapping with the light hammer/wood bloc routine reveled that it would move. So for about an hour I moved the case along the sprocket shaft micron by micron till off it came.

Here is what I found. The sprocket shaft bearing is fried and bound into the race. It also had put a fairly good bind on the shaft but does not seem to have galled it What probably caused the actual seizure was the inner portion of the bearing cage appears to have either "walked" up the shaft or expanded to come in contact with the trust washer on the flywheel and put on the binders. The thrust washer and the bearing shell are galled and the thrust washer heat "blued".

Cotten, you were spot on with your prognosis!!

I suspect a lubrication problem but will let more experienced diagnosticians make the call.

So it's off for the rebuild.

King

Cotten
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Re: Seized motor

#6

Post by Cotten » Mon Jan 02, 2006 2:15 pm

We feel your pain.

I must ask: was there a Colony seal/retainer installed upon the sprocket shaft?
(Just a concern, not a "smoking gun".)

...Cotten

King
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Re: Seized motor

#7

Post by King » Tue Jan 03, 2006 1:11 pm

Hi Cotten

I kind of doubt that the retainer/seal is a Colony product. The last time the cases were split was in 1976 when Red at Fast Harry's in Sparks NV (anybody remember that scene?) did a rebuild and I'm not sure Colony was around then. This Saturday one of my AMCA buddies will give it the eye and I'll post the results.

For reference, is there a problem with the Colony seal/retainers?

King

Cotten
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Re: Seized motor

#8

Post by Cotten » Tue Jan 03, 2006 3:59 pm

I cannot remember anyone making seal kits before Colony, but I only started riding Pans in '75...

First it must be said that there are great many machines out there running seals just fine. I've assembled more than a few myself.
However the design raises a few concerns.

A minor concern is when a motor frequently sumps full of oil from sitting. The original slinger retainer was an escape valve. The bearing pack was not designed to run submerged, and hydraulic pressures when put into immediate service may well force things in directions that aren't desireable. After repeated incidents, a 'fuse may ignite'.
(This would be aggravated if the machine leans heavily toward the kickstand, and is left there running for extended periods,... or 'rapped' often: accellerated while not under load.
And particularly if an unduly heavy of grade of oil is used.)

Primary concern: the bearing pack needs oil flow, and we all know that the slinger allowed some! It is possible that a seal reduces the volume to pass through the pack, as well as preventing any damaging particles from purging into the primary.

Questions that I have:
How many miles were on the motor before it seized?
How true were the flywheels after you removed them?

mbskeam
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Re: Seized motor

#9

Post by mbskeam » Wed Jan 04, 2006 5:41 am

just a ?....
is the oil feed (drip) hole in the case right at the V.
this collects oil and puts it into the race to oil the bearings is it plugged up with goo or some thing? just a thought. can you push a pipe cleaner into hole and see what comes out?

can this race spin, and block this hole? any body...

as for the colony seal I had over 18,500 before I went thru engine....just can leave things alone. and got 6,000 more since rebuild. . I only think unless you pushed it way up into the race and took all the crank end play out, now that would help fry things....

mbskeam

King
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Re: Seized motor

#10

Post by King » Wed Jan 04, 2006 6:10 pm

Cotten

I think there is about 20,000 on it (odometer is sketchy). This Sat. I'll try to check out the true.

Mbskeam

I am suspicious of that oil passage but I have left it "as is" for the time being. This Sat a bro who has a lot more diagnostic experience than me is going to give the whole motor a good look. I will let you know what we find when we probe it.

I too have wondered if the race could turn and block the passage?? Anybody know??

King

Cotten
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Re: Seized motor

#11

Post by Cotten » Thu Jan 05, 2006 2:23 am

Blowing air through the oilhole will quickly tell you if it is blocked..and of course you would see the notch on the shoulder of the race would have moved from 12 o'clock if the race had begun to move.

Races will spin in their bore if severely overheated. Just like welding a bead around a wheelbearing race will make it fall out, motor mainraces will shrink if they reach their critical temperature (as do valve seat inserts, rod races, etc.)

Normally these sort of 'catastrophic' seizures occur in fresh, tight motors; for it to happen to a motor with over 15G miles on it is most curious indeed. As I posted before, we feel your grief!

King
Posts: 387
Joined: Fri Apr 02, 2004 5:05 pm

Re: Seized motor

#12

Post by King » Mon Jan 09, 2006 1:40 pm

Hi All
Well my bro Fast George and I went through the wreckage on Sat. All in all things are OK. The damage was restricted to the sprocket shaft bearing and the thrust washers on the flywheel. The pinion shaft bearing is worn but everything else down stairs miced out fine. Up stairs, the cylinders are a bit egged but all in the heads was OK.

The weird part is there was no apparent cause for the failure, the oil was clean and the oil supply hole to the bearing was clear and wide open (no rotation of the bearing race). Thus some mystery remains.

Now its time to start collecting parts to begin the rebuild. I'm sure I will have a torrent of questions and here are the first ones:
  • * What brand of pistons is recommended?
  • * Who is a good supplier of bearings and other lower end parts?
Thanks

King

Cotten: There were no seals installed. Unfortunately we forgot to check the true before we borke down the wheels. But it was running quite smooth (as judged by some who should know) right up to the time of failure. However, it would have been interesting to see if the failure process "untrued" the wheels.

King

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