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V50 MK II: Nicasil (or chrome?) bore lining failure

i24

i24

Just got it firing!
Joined
Aug 1, 2017
Messages
3
Location
Cape Town
Hi All

I just joined the forum. I have a V50 MKII that has been sitting in my garage for 15 years. Before life got in the way I rode 80000 km on it. It is a 1978 or 79 model and bought it 2nd hand in 1982. My son has started riding bikes and I have finally got the urge to get the Guzzi going again, with his able assistance.

We discovered the engine had ceased - the right hand piston had frozen. We stripped that cylinder head and knocked the piston down with a hammer and block of wood and eventually got the cylinder off. What we found is the bore lining has started to separate off the cylinder at the top near the cylinder head. Most of the damage is above the highest level of the top ring, but at one point it looks to go 5mm below. I presume this is due to corrosion as the bike was running fine when I lost rode it. Also there must be more issues with the piston and/or rings as it was ceased well below the damaged area. The piston is still on the conrod and I have not had a very good look at it yet. I have not yet stripped the left one either. I have uploaded some pictures.

20170809 180757 20170809 180727
I have found an article "How to identify the cylinder bores of roundfin Guzzis" by Pete Roper on another site. Based on this, my cylinder appears to have a nicasil lined bore. The lining is magnetic, there is virtually no "lip" above the top ring line, it is not very shiny, there is no mark at the bottom of the stroked area and there are still honing marks visible in the bore. But according to the workshop manual that I got with the bike, it is supposed to have a chrome bore so I am not sure. It has the same cylinders that came with the bike when I bought it 35 years ago.

Can anybody confirm if this is in fact a nicasil lining and not a chrome one?
Have others experienced similar failures?

Any what to do next:

- Dress out the damaged part and put the cylinder back? Most of it is above the top ring line - but I doubt this will work.

- Find a 2nd hand cylinder or two? I am not sure where to look but the must be some out there.

- Get the old one(s) repaired? There are suppliers who advertise that they repair cylinders with nicasil coatings.

- Buy new barrels, pistons and rings? These seem to be "no longer available" on most of the on-line spares suppliers that I have looked at.

Thanks

Ian
 
Hi Ian, based on this wiki info "Nikasil was very popular in the 1990s. It was used by companies such as BMW, Ducati, Jaguar and Moto Guzzi in their new engine families" -- and based on what I can tell, it is NOT nikasil. Nikasil fractures... it doesn't flake off like that.
I would recommend having both sides bored around new V65 pistons if you can, and Nikasil'ed.
 
I have stripped the 2nd cylinder. It is undamaged and looks to be in good condition. The top ring on the piston off the corroded cylinder is frozen into the top groove.

Both cylinder bores are magnetic. A small magnet will stick to the bore. I have also found this Wikipedia reference (in Dutch, but Google will translate it) which claims my V50 MKII, electronic ignition, has a Nicasil bore: https://nl.wikipedia.org/wiki/Moto_Guzzi_V_50-serie#V_50_II. Can anybody confirm that a known chrome bore is not magnetic?

Assuming my bore is Nicasil, it may be worth looking for a 2nd hand cylinder in a similar condition to my other one, or getting just one cylinder reconditioned. I will most likely need new rings, and it is probably a good idea to replace the pistons. Next step is to try get that frozen ring out and measure bores and pistons.

Ian
 
I have a V50 Mk2 which had been sitting for a while when I bought it. It still had it's original hard-chromed cylinders and one of them was starting to peel at the top of the bore above the top ring. It looked very much like your photos.
If you can find someone who can remove the hard chrome, you could rebore and have a nikasil coating put on. I could put you onto a company in New Zealand who can do it for you if you can't find anyone closer to home. If you are going to do it, do both as hard chrome will eventually flake, go through the engine and ruin it.
My solution was to buy new cylinders and pistons/rings from MotoKiwi in NZ. I don't know if he has any more but it may be worth an email.
 
Thank for the feedback injundave

Do you still have your old barrels lying around? If so, do me a favour and test them with a magnet, and let me know if they are magnetic?

Was it the left or the right one that failed?

I have a quote from a local company who can refurbish and reline the bore with nicosil. This is a good option for me, but a 2nd hand cylinder would be another option. My only decisions are whether to do both cylinders or just one. The guy at the refurbish company thinks I only need to do the one. He also confirms that his nicosil bores are magnetic.

Then whether or not to replace the pistons. My current feeling is two new pistons, but just recon one bore.

I have a lot of other work to do on the bike. Both brakes had seized and so had the clutch. I have managed to fix the rear and linked front brake (blocked brake lines), but the hand brake master cylinder may need an overhaul. I have not looked at the clutch yet. I am working on a shopping list of parts that I will need to import, then I will try get them all in one order. Shipping is likely to come close to US$100 so I want to make sure I get everything I need in one shipment.

But it we are having fun and there is no deadline to get it going.
 
Myself personally I never liked a part overhaul job. My problem is that you will get the new cylinder to seal up perfectly and likely not as good on the untouched one. Always ended up costing me more money when I had to do it twice than if I did it right the first time. I would look for a used complete engine .
 
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