Author Topic: Possible cause for seizing  (Read 1082 times)

Online ironhead

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Re: Possible cause for seizing
« Reply #15 on: 29.08. 2019 00:02 »
To check little end bush's I have a shaft the same size of the pin about 10 inches long. It should pass through both rods.


Hi Tinu,  As Musky's suggestion above.   This pin must be the same size as the gudgeon pins ( not a loose or rattle fit)

If it slides through smoothly ,both rods should be straight. After this I always set 2 parallels, 1 on each side of the crankcase flange & rotate crank forward gently until the checking pin(mandrel) lightly rests on the parallels. If both touch the same, all good. Then I do the same rotating the crank backwards. If not , the case flange is not parallel to the crankshaft. If good rotating one way & not the other, there is a crank problem.

  These are 2 ways of quickly checking if everything usable. Looking again at your right piston, there is heavy scuffing from the top ring to crown on the right side & none or very little on the left. The piston has been running heavily to the right side of the cylinder wall ( bent rod. Mis aligned  bush) 
The left side piston looks like as others have said to be a normal heat / clearance  seizure, there wear & markings look similar all the way round.
You mentioned a damaged bush , was it on the right side?
Hope this helps.
Ironhead.
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Offline tinu

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Re: Possible cause for seizing
« Reply #16 on: 29.08. 2019 08:38 »
I have made a few piccies yesterday: both pistons from all sides plus one from the damaged pin hole.
I will check the rods and make the parallel test asap.
Musky, I think I don't reuse that Piston again... *eek*
Left hand side in this post.
Cheers tinu
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Offline tinu

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Re: Possible cause for seizing
« Reply #17 on: 29.08. 2019 08:38 »
Right hand side...
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Offline tinu

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Re: Possible cause for seizing
« Reply #18 on: 29.08. 2019 08:40 »
Damaged gudgeon pin hole...
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Online BSA_54A10

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Re: Possible cause for seizing
« Reply #19 on: 29.08. 2019 09:33 »
Thanks for the photos

Because we all interpret things differently. This is what & see and why
1) The outside tops of the pistons were clean while the underside is heavily oxidized and shows burned oil , =  both cylinders way too hot ( lean burn)
2) burnt oil between the rings adds to the above & indicates that the cylinders were in fact getting oil
3) oil under pistons again shows plenty of oil in the bores
4) Both pistons showing more damage on one side than the other,
a)  if this was the inside of both pistons = overheating  because the outside cools better than the inside
b) if it is the same side on both pistons = crank not true to the bore ( usually because bore is not true to crankcase mouth or the bores are off set with respect to the journals )
Car cylinders are generally indexed off the head but motorcycle cylinders must be indexed off the base flange.
5) no scuffing on the thrust face so the clearance looks to be OK

What do the little ends look like ?
nice & silver or stained brown ?
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Online ironhead

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Re: Possible cause for seizing
« Reply #20 on: 29.08. 2019 10:18 »
Hi Tinu.
Could you post some pics of the top part of the rods?
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Offline tinu

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Re: Possible cause for seizing
« Reply #21 on: 29.08. 2019 12:27 »
Short lunch at home, take some pictures, back to work...
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Online ironhead

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Re: Possible cause for seizing
« Reply #22 on: 29.08. 2019 23:28 »
Hi Tinu.
Many problems there, A few things that stand out at a quick look to me are
* Right hand rod has bash marks around the hole.
* Same rod has been running hot.
* Left bush hasn't been reamed properly ( not supporting the bush full length)
* Rods have a lot of schrapnel damage.
This alone would have me pull the engine completely down & start from scratch.

A couple of other things, one of your cam lobes has wear marks. Also looks like the crankcase flange may have been machined at some stage. ( never seen those stamp marks on any cases I've seen over here but may be different overthere) . A few studs look like there starting to pull as well.
Others will probably see other things but there is a start.
Have you tried the mandrel tests yet?
Ironhead.
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Re: Possible cause for seizing
« Reply #23 on: 30.08. 2019 05:53 »
Thanks for the pickies.
Basically doubleing up on Iron Heads posts
Pull it back apart
Some one has bashed the RH gudgeon pin with a 10lb hammer without aligning the piston properly resulting in that nice big divot.
IT will have to be removed or the rod is likely to let go along the dent line
In fact both rods will need a clean up. All those nicks have to go or you are riding a time bomb.
Neither little end bush looks good, I would replace both and ream them to the pins.
If you don't have a reamer most engine rebuilders will do it for you .
Car pins are tight on the rod & loose on the piston.
Bike engines are tight on the piston & loose on the rod.
With those divots in both rods I seriously doubt either one will be strait.
They can take a pounding up & down but sideways they bend really easy.

Not good news but neither is a big blow up.
Anyway is it coming into winter up there so shed time .
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Offline Swarfcut

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Re: Possible cause for seizing
« Reply #24 on: 30.08. 2019 08:44 »
tinu, You have come, as we say, to a fork in the road.  The bike ran OK for you up until being subject to some really hard work, overheated and seized. So you could just put in your new pistons and things would be just fine. Maybe.....

 Looking at what you have, for any serious fast riding or long distance reliability I would be inclined to strip it to the last nut and bolt. This engine has signs of heavy handed abuse in the past, such as bruising to the small end eyes, burred crankcase join where the breather passage runs. Previous posts mention important tell tale signs that all is not as good as it could be. All signs that whoever built it was not as good a builder as you would like...smacking pistons with a big hammer is not a recommended workshop practice.  Stripping it will allow you to check every part and replace or refurbish as necessary.

 The camshaft is also showing signs of wear, so easily replaced or  gently stoned smooth, depending on your budget or future plans, while all is apart. Cam followers will also be wearing, so again, check here. The crankshaft sludge trap can also be checked, this is a well known failing.

 The con rods need to be checked by your machinist. If they are bent, replacement is the only sensible option. Big end eyes need checking for ovality, and if they are found to be at fault, they can usually be reworked. Have the small end bushes replaced and accurately sized to match the new piston pins. A good firm hand push fitting at room temperature is about right. With the pistons warmed up with a heat gun, the pins will slide into place, needing just a little hand pressure. No need for violence or big hammers. Have the rods polished to remove nicks and burrs, and matched for weight.

 Check the crank cases are a matched pair. With the engine removed you should find matching numbers stamped on the front faces of the cases, below the dynamo mounting, hidden by the front engine mounting plates. Mis-matched cases are not the end of the world, but could possibly be a factor in your problems.

 Compared to modern machines, this engine is relatively simple to work on, but requires attention to detail, extensively covered by the thousands of posts on this forum.

 At the end of the day it is your choice, depending on your budget and how much reliable use you want from the bike.

 Swarfy.
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Offline tinu

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Re: Possible cause for seizing
« Reply #25 on: 30.08. 2019 09:05 »
Thank you guys for all your advice given! I was expecting to abuse my family and work all night in the shed one time...  *work*
Although I am not racing with my A10, there are various steep hills in our country that are a joy to ride. Therefore I will take the long way.
More question (and pics) will pop up, definitely!  *smile*
Cheers Tinu
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Offline muskrat

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Re: Possible cause for seizing
« Reply #26 on: 30.08. 2019 10:24 »
G'day tinu.
Wise choice mate. We are all here to help, not trying to give you work or spend your money. In the long run if done right you will have a bike that will eat those hills without trouble.
The only reason Pommy bikes had a bit of a bad reputation was the back yard, ham fisted morons who worked on them.
Cheers
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Re: Possible cause for seizing
« Reply #27 on: 31.08. 2019 10:18 »
And you can never tell.
Shane bought Doug's old A10  as a spare  loaner bike for the 55th international.
Doug had run it for 15 years with few problems
On the test run up the Snowy Mountians a little end let go.
Had we have known what the bike was like inside it would have had a full strip down
'Both rods were unservicable having been bodged at both ends and they were not a pair
Every bush inside the engine was mashed from being fitted with a pin punch and horror, the crank was cracked full circumference.
Bolts had been drilled out and tapped randomly in random profiles from metric to AF dowel pins were missing oil pump was loose.

Preso Pete bought a rocket that another member had spent 5 years rebuilding .
HE sold the bike because he hurt his back & was no longer able to ride.
The DPO thrashed the bike when he rode it so again we thought it would be a good buy at the price.
$ 6000 latter is replacement parts the ideas are a bit different and how the DPO did not kill himself is beyond belief.

Winter is coming up so some time in the shed will not distract from possible road time.
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Re: Possible cause for seizing
« Reply #28 on: 31.08. 2019 13:21 »
" ham fisted morons who worked on them" YEP that's meeee musky when I was trying to get the front wheel spindle out as a young one does and my dad was working on his lathe and heard this click - bang sound and shouted ITS LEFT HAND THREAD. he had to make a new spindle a bit longer with a nut to fit as well for safeness as I had also slightly damaged the leg . still on the bike today--- cheers dad *thanks*
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Offline BigJim

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Re: Possible cause for seizing
« Reply #29 on: 31.08. 2019 19:55 »
" ham fisted morons who worked on them" YEP that's meeee musky quote)
I'm still learning and pleased to have a vice!
Generally try to improve it and often make it worse.
Someone has to be last when it comes to toolwork.
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