Author Topic: Crankcase problems - repair or replace?  (Read 2925 times)

Offline Brummie1960

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Crankcase problems - repair or replace?
« on: 09.06. 2009 13:33 »
Hi,

My Dad and I managed to strip the engine down on Sunday last and it was easier than
I thought it would be once we got the puller to work on a couple of the pinions.

Having checked the state of the engine bottom end in a general way it looks like the crank
is good with no up/down play at either end, no feelable play up/down on the con-rods,
the camshaft rotated smoothly with no discernable play although the cam faces are a bit marked.
The magneto pinion has a chipped tooth and the advance mechanism has been welded for use with
the Lucas Rita ignition that was fitted. The dynamo drive pinion is also missing a couple of teeth, which
was handy as I could get a puller behind it through the gap. It wouldn't budge just by drifting it as per
the book.

It has 356 cams and flat-topped pistons. Are these the 7.25:1 variety preferred for a touring
type engine tune?

The crankcase looks to have been already welded on the lower part, judging by the smooth metal
that does not look like the cast finish on the rest. That seems to be a sound repair.

It also has 3 areas around the barrel studs broken away which need to be repaired.

So I need to make a decision or two - do I get this crankcase repaired, which seems to have good
bearings/bushes and be in decent condition apart from the broken areas or buy a replacement pair of cases.

As I dont know any of the history of this engine and its getting on a bit, I guess it would be wise at this stage to have the crank checked/balanced, replace the con-rods, the pistons will probably need replacing as my new barrel will most likely need a rebore to clean it up, and get the bearings and bushes checked.

Seems I would have to do all of this anyway if I bought replacement crankcases with maybe the extra expense of replacing bearings and bushes, but that may need doing on the existing cases when they are checked properly.

I would be glad of the group's thoughts as to advantages/disadvantages of each approach.

Andy - I no longer live in Birmingham, but am now in north Coventry about a mile from Corley Services
on the M6.

Thanks,

Nigel.

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Offline MikeN

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Re: Crankcase problems - repair or replace?
« Reply #1 on: 09.06. 2009 14:04 »
Nigel,
The problem with having parts that are missing from an alloy casting built up with weld is that the welding material that is deposited onto the casting will probably be very soft .ie softer than the original casting . I would be reluctant to thread it for barrel base studs.
 I think i would look for a good set of cases.
 Also ,Now you have it down this far you must dismantle ,clean and measure the crankshaft . Just because it feels good it may not be so.
  If previous owners have managed to break lumps off the cases and  teeth off pinions i would assume it has had rather a hard life so you need to go through every component part and check for wear and alignment .
  I would not be planning on using any of the rolling or plain bearings again.
 Definately heve the rods checked for alignment,scoring on the oil pump body .end float in the oil pump gears etc.etc.
Mike
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Online RichardL

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Re: Crankcase problems - repair or replace?
« Reply #2 on: 09.06. 2009 14:28 »
At the risk of finding out that MikeN teaches heliarc welding at the local trade school, I, having no heliarc experience, am going to venture that the hardness and quality of welds to cast aluminum are dependent on the quality of the welding service employed. If I recall correctly, there is some welded area around one or two of my base studs and those welds are holding fine (I need to "go to film" to cofirm, however).

If your case numbers are already mismatched to your frame, no big deal. However, if they match the frame, and better yet, concur with the original dispatch documents, you would certainly be better off repairing the cases. I know this from experience, now sorely regretting having discarded my original bent frame in an effort to save a piddling $300 in frame straightening cost. I learned too late that the difference in dollar value of the bike is probably close to 10 times that amount.

All this said, MikeN has given you very good advice on the other aspects, even if we slightly disagree on the cases. Filling in one of Mike's unsaid points, cleanout that sludge trap.

Richard L.
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Offline MikeN

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Re: Crankcase problems - repair or replace?
« Reply #3 on: 09.06. 2009 15:56 »
No ,Im not a welding teacher,im not even a proper welder (although I have been TIG welding Stainless steel regularly for the last 25 years) .
  However,in the spitit of (not very scientific) experimentation I have just grabbed a couple of peices of 10mm thick 5083 alloy plate which is quite a hard alloy which does not bend easily and TIG'd it together using an
alu 5% Mag rod.
  Afterwards I put it in the vice and heaved and it bent very easily at the weld and the parent alloy in the region of the weld (which I assume it has now anealed).Unfortunately I dont have any cast alloy to hand to try.
  I then built up a blob of weld on the edge of the plate to simulate a built-up lug and took it over to the Bridgeport and milled it flat and drilled and tapped a 10mm hole.
   Actually ,that went better than I was expecting.The few times  Ive machined alloy weld in the past its been like machining chewing gum.This time it looked quite good,But i still wouldnt want to use it for stressed parts.Thats just a personal view .Im always interested to hear other peoples opinions.
  Time to bring on the coded welder!
Mike
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Offline 69Bonni

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Re: Crankcase problems - repair or replace?
« Reply #4 on: 09.06. 2009 16:24 »
I was trying to get my Primary case welded and talking to a welder, he was telling me about the problems associated with welding old Ali castings. One thing was the amount of silicon in the alloy used to get the alloy to flow into the cast and the mix and quality of the alloy. Apparently there can be tendancies to blow holes in the casings and cause even more damage.

I guess Mike knows all about this, Id really like to get my Primary case welded but now im worried about going there! (its a Late casing with the clutch adjusting bung)

Ali welding a skill way beyond my meager welding skills!
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Offline MikeN

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Re: Crankcase problems - repair or replace?
« Reply #5 on: 09.06. 2009 17:02 »
No, I dont know all about this at all.
  Although  youve just reminded me, a few years ago I wanted one of those nice rev-counter drive covers for my pre-unit Triumph,but I couldnt afford one. So i made one by welding on a block of alloy to simulate the blister on the side of a standard one. When filing it to shape I had a lot of trouble with small blow-holes that kept appearing in the welds which I had to keep going over. I got it to look like the  proper thing eventually.
  I put that down to at the time.it being an old casting,with maybe oil impregnation(?).
 A proper welder will tell us, Im sure
Mike
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Offline shabashow

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Re: Crankcase problems - repair or replace?
« Reply #6 on: 09.06. 2009 19:48 »
I'm not a welder, but have had a few bits and pieces repaired, by welding, on my cases. The guy who did the job says it's a difficult weld, mainly because of impregnated oil spluttering out of the metal as it's heated.
John
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Offline A10Boy

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Re: Crankcase problems - repair or replace?
« Reply #7 on: 09.06. 2009 22:06 »
Brummie

There is a company called "Bropel" in Aldridge that I would highly recommend. They have done Alloy welding for me on several occasions and do a first class job. It would be worth contacting them to get their opinion on this.

The last time I was there, I had a BSA/Triumph Twin Leading Shoe Brake plate built up with ally weld around the fork lug slot area which I fettled back down to shape, the alloy used was hard and solid, and filed / machined like the original metal. That was done with a TIG, and they will do it while you wait.

Website below.

http://www.bropel.co.uk/
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Re: Crankcase problems - repair or replace?
« Reply #8 on: 10.06. 2009 11:08 »
The quality of the weld will be dependent upon the quality of the cases , the strength of the rods and the skill of the welder.
You can , (and some times need to) make the weld harder & stronger than the parent or visa versa.
A weld is basically just a fancy casting, and the cases are cast in the first place.
Find a specialist aluminium welder they will have a larger variety of sticks and naturally more experience.

Cleaning is the real hard bit . And a couple of cycles of  degreaser , rinse, bake ( in oven) will help greatly and a light blasting with an abrasive like soda, glass beads, walnut shells etc would not hurt either.

I am a bit funny with welds I favour torch on castings and sticks on wrought where possible.

If you are going to pull the rank right out ( and you should now that you are this far) get the crank carbo nitrided ( or nitro carburized if you preffer) should cost about £ 20.00 and will substantially toughen your crank and markedly reduce it's notch sensativity.

Both the crank & the rods should be crack tested.
You can do this yourself with a dye penetrant kit sold by Turco worldwide about £ 30.00 but will do about 100 tests.
Then check the rods for ovality and stretch.
Naturally the sludge trap will come out.
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Offline Goldy

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Re: Crankcase problems - repair or replace?
« Reply #9 on: 10.06. 2009 21:20 »
If you are near Coventry have a word with GPD Welding, Veasey Close, Attleborough, Nuneaton Tel 02476351134
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Offline Brummie1960

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Re: Crankcase problems - repair or replace?
« Reply #10 on: 10.06. 2009 23:27 »
Thanks for all of the suggestions and the insights into the problems with welding cast alloy.
I sent some photos to SRM and they reckon they can repair it, about £60 for the welding, re-drilling and tapping the holes and another £80 to jig and re-skim the top of the crankcase flat.

If I can find some good crankcases for less than the £140 repair bill I think I'd rather go with that
and have solid original metal to secure the barrel to.

Either way, I will want to have the crank, rods, camshaft and all bearings and bushes checked out/replaced. I cant really afford to have SRM fix it all at the moment, though that would be nice, so are there any recommendations on engineers (Midlands preferably) familiar with these engines who could give it the once over and give me a solid bottom end?  *eek* 

Regards,

Nigel.
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Online RichardL

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Re: Crankcase problems - repair or replace?
« Reply #11 on: 11.06. 2009 02:23 »
I thinhk if SRM can do all that for 140 GBP you are doing quite well, referring back to my earlier post, especially if your crankcase and frame numbers already match. Furthermore, you will be getting back something you can be rather certain was done with care, which could well be better than "a pig in a poke." (or, if you prefer, "the devil you know is better than the devil you don't know").

Richard L.
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Offline A10Boy

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Re: Crankcase problems - repair or replace?
« Reply #12 on: 12.06. 2009 18:36 »
Quote
Either way, I will want to have the crank, rods, camshaft and all bearings and bushes checked out/replaced. I cant really afford to have SRM fix it all at the moment, though that would be nice, so are there any recommendations on engineers (Midlands preferably) familiar with these engines who could give it the once over and give me a solid bottom end

I've been speaking to a company called T&L Engineering from Beds. [no connection].

They will check over your crank, grind as required, fit a new timing side bush and line bore it, check over the cam bushes etc, set the end float and if you need them to, they will also rebuild it for you @ £50 per hour.

Prices are roughly as follows.

Grind crank £38 for all journals
Fit a phosphor bronze bush £35, line bore £30.

I asked them if they would fit a LB bush from elsewhere and they will. They even said that they could make up a white metal bush for about £60.

I know beds isn't Mids, but its only a trip down the M1 from Coventry. They are highly recommended, the AJS / Matchless owners club don't use anyone else for crank work. I will be taking my A10 bottom end there when I do my engine re-build.

If you phone, ask for Derek he's the bike man.

http://www.vintage-engine.net/

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Offline Brummie1960

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Re: Crankcase problems - repair or replace?
« Reply #13 on: 15.06. 2009 16:07 »
Andy,

Thanks very much for the link to T & L.

Their website says they also do alloy welding so they may be able to tackle the whole bottom end for me.
I have some time off in a couple of weeks so hope I can take the engine down to them then for an assessment.

Nigel.
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Offline A10Boy

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Re: Crankcase problems - repair or replace?
« Reply #14 on: 15.06. 2009 18:31 »
Let me know, I will be taking my crank and cases for a new T/S bush shortly, maybe we could share the transport cost if the timing works out.
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Andy

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