Welding cracked heads.

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rossguzzi
Posts: 433
Joined: 23 Jan 2019 14:21
Location: Perth W/Australia

Welding cracked heads.

Post by rossguzzi »

Hi,
Unfortunately I have a small crack in one head between the valve seats. That area is slightly raised as well. I have a guy that said he could weld it but thought I would ask here, how successful is welding these heads. (500 Camel) Is it a short or long time fix ? I also need the exhaust thread fixed. Read story in my Off Road Bikes thread.
Also, I don't seem to be able to find a source for valve guides. Mdina don't seem to have any. Anyone know where to get some ?

Alternately, I could be in the market for a good 2nd hand head.

Cheers.
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rossguzzi
Posts: 433
Joined: 23 Jan 2019 14:21
Location: Perth W/Australia

Re: Welding cracked heads.

Post by rossguzzi »

One more thing, can the rear head be removed without tilting the motor ? I might check the rear while I'm at it.

Cheers.
morini_tom
Posts: 920
Joined: 05 May 2006 13:47
Location: Northampton

Re: Welding cracked heads.

Post by morini_tom »

Cracking between the valves on the 500 heads is unfortunately common.

One method is to create oversized valve seat inserts and overlap them, but have seen them successfully welded too.

A couple of (sorry not very good) pictures of mine on this post:

viewtopic.php?f=34&t=2499

Regarding guides, Alex Lussi had new stock: alexluzzi@gmail.com
EVguru
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Re: Welding cracked heads.

Post by EVguru »

Mdina have them, search for 'valve guide'
Paul Compton
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
harrymuffin
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Joined: 07 Apr 2014 16:06
Location: west midlands

Re: Welding cracked heads.

Post by harrymuffin »

Have a rumage around at lazer welding, it is very unintrusive and the depth of weld can be varied and the heads do not need to be stuck in an oven to reduce distortion. It is now the chosen method for delicate die molds and other delicate work. There is another method that is now coming into use which is cold welding that along with lazer is becoming the norm in proper engine repairs for aluminium alloys and cast iron.
rossguzzi
Posts: 433
Joined: 23 Jan 2019 14:21
Location: Perth W/Australia

Re: Welding cracked heads.

Post by rossguzzi »

Thanks Paul, I found the guides.
Harry, I will look into Lazer welding down here.
Tom, thanks for that info. I may suggest to the engine rebuilder to do a valve overlap. I will see what he says.
I spoke to Brook Henry from VeeTwo (Ducati expert, look it up) and he said overlapping the valves could work.

I want to take the rear head off this weekend to check that one. Is there enough room without tilting the engine to get it off ?

Cheers.
rossguzzi
Posts: 433
Joined: 23 Jan 2019 14:21
Location: Perth W/Australia

Re: Welding cracked heads.

Post by rossguzzi »

I got the rear off without having to move the motor in the frame. Just cleared. Looks like the rear has not cracked. But won't know for sure till the guy cleans them up. So At this stage, front will need welding and new seats, guides and exhaust thread. Rear, seats guides. Hopefully the valves can be cleaned up and just faced.
Disappointed as this is a great time of the year for riding. Before the heat of summer hits.
Oh well after this there shouldn't be too many hiccups for a while. Hopefully another 30 plus years ! Hmmm that would make me 90.
rossguzzi
Posts: 433
Joined: 23 Jan 2019 14:21
Location: Perth W/Australia

Re: Welding cracked heads.

Post by rossguzzi »

Think I will remove the barrels and check the bores ect. There is a ring of carbon at the top of the bore. One of the base gaskets was weeping slightly so this is the time to look at the whole top end. Will probably give the bore a slight hone after checking for wear. New rings, guides, seats etc.

I can't remember reading anywhere what the ring gaps should be. Or for that matter the piston gap and how/where to measure that. Can anyone point me to where that info would be ? Or do I just buy some rings from Mdina and install them ?

In the 40+ years of riding and working on my bikes, I have never had to remove heads/barrels before ! So this is another learning step for me.
rossguzzi
Posts: 433
Joined: 23 Jan 2019 14:21
Location: Perth W/Australia

Re: Welding cracked heads.

Post by rossguzzi »

Ok, found the info.
Cheers.
Steve Brown
Posts: 1390
Joined: 12 Nov 2007 23:44
Location: Leicestershire

Re: Welding cracked heads.

Post by Steve Brown »

rossguzzi wrote:Ok, found the info.
Cheers.
Glad you found it, I was about to say it's in the blue book but haven't actually checked. As it's your first time taking heads and barrels off don't be too tempted to rebore/regrind/recondition everything in sight! If it wasn't using oil and there isn't any obvious damage or wear, then just clean and re-seal everything. A lot of people jump in with both feet and shorten the life of cranks or barrels by getting them done.
There is a good case for cleaning out the sludge trap in the crankshaft if you go as far as splitting the crankcases-but as I recall yours is very low mileage I doubt you need to worry too much there. Taking the barrels off in this instance is well worth it as having removed the heads you will have released the compression on the base gasket. If it's weeping already then...
Good luck with it and don't go fixing what isn't broke!
Even as a regular trail rider you will find it a challenge to get enough miles on the old bike to justify the expense of regrinds/rebores etc. I'm prepared to bet even the rings will be worth putting back in! OK, I'll bet you a pint :wink:
All donations to the rest home for old Camels, Leicestershire.
rossguzzi
Posts: 433
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Re: Welding cracked heads.

Post by rossguzzi »

A mechanic mate recons light hone and new rings. It doesn't have Nicasal bores, so a light hone I believe is ok.

Blue book recommends Mollycote A for head and base gaskets. Another Guzzi mechanic of 40 odd years suggested spraying silver spray paint onto both sides of the gaskets before install instead of Mollycote. Anyone herd of this as a sealant ?? He used to do it on old Guzzi racing bikes with success. New one to me.
Steve, unless I feel play in the big end, I don't want to split the cases.

With all the advise you guys are giving me, I owe the pints ! :D
EVguru
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Re: Welding cracked heads.

Post by EVguru »

rossguzzi wrote:Blue book recommends Mollycote A for head and base gaskets.


You might want to read the Blue Book again.

Mollycote A is recommended for the valve stems. For head and base gaskets it says; Arexons "Motosil D".

Not all that easy to get, I found you could get it in the UK from a competition Yo-Yo specialist!

Cagiva era manual says Threebond 1215, which is easily obtained and not expensive. I use Threebond.
Paul Compton
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
rossguzzi
Posts: 433
Joined: 23 Jan 2019 14:21
Location: Perth W/Australia

Re: Welding cracked heads.

Post by rossguzzi »

Ah,yep, your right !
I was going by memory. I would have double checked before actually doing it. Thanks Paul.
I did read that the 500`s are meant to have dowels between head and barrel. Mine does not ?? Is this a worry ?
I got the front barrel off tonight before running out of time. I does not look scored. But I have not had a good look. Had to make up a gudgeon pin removal tool. How do you guys think the front piston looks ??
I have a feeling I may need to tilt the motor to get the rear off. :(
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EVguru
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Re: Welding cracked heads.

Post by EVguru »

Gilardoni barrels/heads have dowels.
Paul Compton
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
rossguzzi
Posts: 433
Joined: 23 Jan 2019 14:21
Location: Perth W/Australia

Re: Welding cracked heads.

Post by rossguzzi »

Finally got time to get the motor out and remove the rear head. Things I have found. Feels like a step in the bore of both so am guessing bore with 1st oversize pistons rings etc. Rear base gasket was broken at the back of the barrel. Front gudgeon pin a bit loose in the con rod.

I am now contemplating whilst the motor is getting refreshed;
Stripping the frame and getting the crack in the rear engine mount fixed properly the getting the frame painted.
Painting the motor silver/alloy VHT Brake Caliper paint.
New nickel plated bolts for motor and mounts.
Making a nice alloy bash plate.

Question.
Both wrist pin bushes show strange wear marks. Front one has play where as the rear feels snug. Both have this marking. See pic.
When reinstalling the new bush in the con rod, is there a need to ream it for the new wrist pin to slide in ? Or should they be good from new parts ?
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