Author Topic: Constipated Crankcases  (Read 820 times)

Online trevinoz

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Constipated Crankcases
« on: 11.12. 2012 20:56 »
Yesterday I started cleaning up a set of AA7 cases for a future project.
All of the usual, clean out 30 odd years of grease, dirt and sludge. Run a tap through the threads. Repair the damaged ones. Drill out the broken stud.
Pretty basic stuff.
Then I came to the oil galleries.
They were OK between the tank feed/return ports, just dirty.
The scavenge pick up was blocked.
This will be easy, just wriggle a bit of wire through it!
The 2 right angle bends tended to stop this.
Maybe a bit of 100 psi air?
Might as well use my mouth.
Remove said pick up from the case.
Still no joy.
Wave lit oxy torch at the whole thing until hot.
Flames from the pipe but still blocked.
Next I unsweated the pick up ball housing from the pipe. With a bit of effort i managed to wriggle a piece of wire into the elbow and cleared the blockage.
Just a quick silver solder job to put the pipe together and re-install.
Now for the relief gallery.
As most of you know, this runs from the relief valve to the cam tunnel with a drilling to lubricate the timing gears.
Another total blockage!
So I pushed a wire through the gear drilling while running solvent through the relief.
I managed to clear this bit but there was nothing reaching the cam tunnel.
I managed to wriggle a piece of copper wire from the relief to the bend at the end of the tunnel and again from the tunnel to the bend but even high pressure air wouldn't budge the muck.
I then drilled out the plug in the end of the gallery, not all cases have one.
I still couldn't budge the blockage with a straight run at it, it was probably in the bend and the wire would not go around.
Finally I filled the gallery with solvent and quickly pushed a close fitting rod down it.
Solvent in my hair but enough pressure to force the obstruction back through the bend and it was then washed out.
And people wonder why it takes so long to restore a bike!


Offline Beezageezauk

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Re: Constipated Crankcases
« Reply #1 on: 12.12. 2012 10:01 »
Yes Trev.  But if a job's worth's worth doing properly and attention to detail makes a big difference.


Offline terryk

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Re: Constipated Crankcases
« Reply #2 on: 13.12. 2012 00:32 »
Wrap them in plastic now cause up here in Nth Queensland we get wasps and hornets building nest in those crankcase holes. I dont know what its like in your neck of the woods Trev probably cockroaches lol.
I had a set of cases nicely vapour blasted and looking great with a nice clean rag over them sitting on the work bench then a few days later wasps built nests in the oil holes they got under the rag.
1950-53 A10 rigid/plungers, 1958-61 A10 super rockets, 1947-50 A7 longstrokes, 1949 Star twin,
1951-54 A7 plungers, 1940s M21, WDM20s,
1948-50s B33s rigid/plunger/swingarm, 1948-50s b31s rigid/plunger/swingarm

Offline Brian

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Re: Constipated Crankcases
« Reply #3 on: 13.12. 2012 05:20 »
Where Trev lives he might get one of those big black orrible airy bitey things take up residence in his cases, or dont they travel that far North ?

Offline shuswapkev

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Re: Constipated Crankcases
« Reply #4 on: 02.01. 2013 09:36 »
i had to clean out a oil pickup pipe on a set of cases that had sat for a lonnnng time...

then i sandblasted them...and then thought for a much of what could be in that pipe...anyway..stripped off a bit of control cable inner and chucked in a cordless drill and i had the bsa equiv of a plumbers rat...worked like a charm..all sorts of disgusting stuff came out...

Offline cus

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Re: Constipated Crankcases
« Reply #5 on: 07.01. 2013 20:40 »
Now thats a great idea!!
56 G/Flash project

Offline LJ.

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Re: Constipated Crankcases
« Reply #6 on: 08.01. 2013 09:08 »
I'm wondering how that engine managed to run with so much stubborn muck. Do you have the crankshaft for that engine? the sludge trap will be interesting.
Ride Safely Lads! LJ.
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red