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Author Topic: A7 Barrel needed - Short Stroke  (Read 1553 times)

Offline Bsa Nut

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A7 Barrel needed - Short Stroke
« on: 05.12. 2013 02:12 »
I went to cleaning/blasting my A7 barrel today and discovered a very nasty crack,
two inch up, and two inches around, just to where the fins start. Junk.

I need a replacement. A good usable replacement. I can bore it, not a problem.
No broken fins, please.

Let me know if you have an extra.
-Luke
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Offline WozzA

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Re: A7 Barrel needed - Short Stroke
« Reply #1 on: 05.12. 2013 05:21 »
can it be welded & re-sleeved?   *eek*
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Offline Bsa Nut

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Re: A7 Barrel needed - Short Stroke
« Reply #2 on: 05.12. 2013 10:16 »
I'm not sure of the limitations of that repair...
If anyone out there has experience with this sort of thing, let me know.
If it was a small vertical crack, I would consider that option.
It is a semi-circular crack that follows along the base of the first fin,
after coming from the very bottom of the flange.
Someone before me, pried between the cylinders too hard,
the crack is pushed from the outside to the inside.
I would be afraid of a major failure...but after a sleeve installation
it may be as good as new. (I really have no experience, other than tractors on sleeving cylinders.)
I typically keep looking for a new cylinder.
I'll try to get a picture tonight.
-Luke
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Offline muskrat

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Re: A7 Barrel needed - Short Stroke
« Reply #3 on: 05.12. 2013 10:45 »
G'day Luke.
The A7's are a bit thicker in that region than the A10's but I would still be worried with a sleeve job. The interference fit of a sleeve may push the crack further. Welding/brazing from the inside before boring for the sleeve may help but it's still a risk.
Is yours a big or small fin? I'll have a dig around in the shed.
Cheers
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'51 A7 plunger, '57 A7SS racer now a A10CR, '78 XT500, '83 CB1100F, 88 HD FXST, 2000 CBR929RR ex Honda Australia Superbike .
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Offline Bsa Nut

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Re: A7 Barrel needed - Short Stroke
« Reply #4 on: 05.12. 2013 22:12 »
http://www.flickr.com/photos/89103304@N07/11227554206/

Here is a picture of the crack. A major repair would have to take place prior to sleeving...
just don't think it's usable.

Enlighten me on the variation of the big fin vs. small fin.
This is from a '53 B7S prefix engine, and the only number I can find on the barrel is  PAT. 56-7029.
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Offline a10 gf

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Re: A7 Barrel needed - Short Stroke
« Reply #5 on: 05.12. 2013 22:23 »
^^^ nasty damage. If that was an airplane engine, I'd never fly with it whatever anyone tried as a fix! On 2 wheels, after some (expensive) attempts at repairs, it may hold 10 miles or 1000, who wants to ride it to see how it goes...  *smile*
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Offline WozzA

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Re: A7 Barrel needed - Short Stroke
« Reply #6 on: 05.12. 2013 23:50 »
I have seen damage like this done when a bike was washed with cold water while the motor was still hot.. *doh*

IF that is the only crack / damage, & there is no damage to the outer casting ???
I'd be looking into having it re-sleeved..  & have BOTH sleeves machined to suit your pistons..
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Offline Bsa Nut

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Re: A7 Barrel needed - Short Stroke
« Reply #7 on: 06.12. 2013 01:23 »
Quote from: WozzA on 05.12. 2013 23:50
I have seen damage like this done when a bike was washed with cold water while the motor was still hot.. *doh*

IF that is the only crack / damage, & there is no damage to the outer casting ???
I'd be looking into having it re-sleeved..  & have BOTH sleeves machined to suit your pistons..

Yeah...this was caused by a bit more than cold water. LOL
The crack in completely though to the outer surface, and upon closer inspection,
the bore is distorted (slight flat spot) where prying occurred.
This thing was seized big time, yet the barrel was unbolted from the cases and raised about 1/2".
And oddly enough, the lifter block screws were removed on the sides, and missing. LOL
It then sat 'open' like this for long enough to seize the lower end as well. Someone gave up at some point...
I pushed it apart using grease, and much caution...to no avail. ;(
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Offline WozzA

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Re: A7 Barrel needed - Short Stroke
« Reply #8 on: 06.12. 2013 01:52 »
In that case I suggest you buy a length of rope, tie a 1/2 hitch between the left & right pot
& use it as a boat anchor... *eek*
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'51 Golden Flash Plunger
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Offline Bsa Nut

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Re: A7 Barrel needed - Short Stroke
« Reply #9 on: 06.12. 2013 02:20 »
Quote from: WozzA on 06.12. 2013 01:52
In that case I suggest you buy a length of rope, tie a 1/2 hitch between the left & right pot
& use it as a boat anchor... *eek*

Right on!!

Or a BSA Parachute...for when the 7"ers don't stop ya!
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Offline RichardL

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Re: A7 Barrel needed - Short Stroke
« Reply #10 on: 06.12. 2013 12:22 »
Clearly, e, you haven't seen enough movies, like "Flight of the Phoenix". If you could sleeve the cylinder to fly out of the middle of the Sahara, you would do it. However, I happen to know that Luke is not located in North Africa.

Luke, maybe this was what made one of those sounds you heard while using the grease plate. I know, it's an awful thought. Maybe the opinion of the shop we've discussed would help. I am guessing that they have had to weld-up cast iron diesel blocks in the past. I'm not saying it's salvageable, only that hearing a variety of opinions makes decision making easier (sometimes).

Richard L.

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Offline A10Boy

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Re: A7 Barrel needed - Short Stroke
« Reply #11 on: 06.12. 2013 16:53 »
Is this for the early small fin A7 or the later jobbie? I think I have an early barrel somewhere.

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Offline Rocket Racer

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Re: A7 Barrel needed - Short Stroke
« Reply #12 on: 13.01. 2014 23:49 »
Quote from: WozzA on 06.12. 2013 01:52
In that case I suggest you buy a length of rope, tie a 1/2 hitch between the left & right pot
& use it as a boat anchor... *eek*

Old barrels make good fin donors, so should be put under the bench.
I was given a thin flange barrel that had blown the flanges off (running 10.5:1 on +100 by the evidence), the fins have come in very useful!
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