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 Was planning on doing a Beetlemap, but now...

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FlatTappeter
Squinternotto
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PostSubject: Was planning on doing a Beetlemap, but now...   Wed Oct 10, 2018 4:39 pm

My bike has a scored barrel, so will also need a new piston and rings  Shocked.

This was the report I had yesterday from the Guzzi service agent, when they investigated low compression on the left pot.  I would still be none the wiser had I not asked them at its recent service, about the amount of fresh oil collecting in the airbox drain pipe.  A compression check indicated the left cylinder was 70psi down compared to the right, and a leakdown test showed the crankcase was being pressurised (which might account for the extra oil in the drain pipe).

As I'm not a mechanic, could the compression imbalance have been responsible for extra vibes when accelerating?  This is one of the things I noticed following the tappet conversion done (by a different MG service agent) last year.  It also seemed slightly less eager to rev.  As I said, not being a mechanic I assumed these to be natural characteristics of the roller conversion, and I didn't question them further after the agent could shed no light.  Note, this had been the first tappet conversion done by the agent.

One comment made by the agent following the conversion has always bugged me, and that is when they first started the bike it made a bit of a racket.  Would they have needed to remove the cylinders to do the conversion (using a 'C' kit)?  It's by no means conclusive that they screwed up somewhere, as in spite of everything the bike has still been running remarkably well, but I would be grateful if anyone here can suggest potential causes for the existing cylinder damage.  The bike's not yet done 30k miles.

Still hoping to try a Bettlemap to address low-speed running, once the engine is back to rude health and I've figured out how to pay for this little lot pale.
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Oz1200Guzzi
Don Abbondio
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PostSubject: Re: Was planning on doing a Beetlemap, but now...   Wed Oct 10, 2018 5:43 pm

Sheesh - bad indeed. Sounds like "something" was adrift in the cylinder when it was reassembled. The question is where is it now? This part is important... Ask them if they found anything that would have caused this - unless the previous shaved apes did it in their process, in which case a broken ring, cir-clip from the gudgeon pin, or plain old stupidity may be to blame. Ask questions, lots.

This would certainly contribute to extra vibes - of the wrong sort.
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Pete Roper
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PostSubject: Re: Was planning on doing a Beetlemap, but now...   Wed Oct 10, 2018 5:48 pm

I would suggest that before going any further a bit more investigation would be in order.

Firstly I'd double check the cam timing. Does it 'Go flat' at about 6,000rpm? That's a classic sign. It will also result in weird compression readings on the badly timed cylinder and although it wouldn't explain the leak down it would explain the weird vibes and loss of power throughout the range.

Before shelling out for a new barrel and piston kit, (£287 from TLM. edit I think that's a second hand one!) it would definitely be worth pulling the head or even just looking in through the plug hole with a borescope. I'd pull the head, it's only half an hour and then any scoring would be evident and the valves checked for damage.

Incidentally I have at least two bikes worth of 1200 barrels and pistons in good condition so if you'd be happy with a second handy I can supply for half the cost of a new kit.

Oh, and the barrels don't have to come off during rollerisations unless they didn't unload the cam chain tensioner plunger before unhooking the sprocket so they shouldn't of been able to get *anything* into the bore???

Pete
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FlatTappeter
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PostSubject: Re: Was planning on doing a Beetlemap, but now...   Thu Oct 11, 2018 3:07 am

Many thanks for your quick responses and suggestions.

I'm guessing they may have already popped the head and found the scoring.  Would it still be possible for them to tell if the cam timing was out?

I was only detecting a very slight loss of revy-ness and gain in vibes, and it still had plenty of go if I dropped down a gear to overtake.  Only very lately did it seem unusually flat when I gassed it, but I had full luggage and was in a high gear at about 75mph and so not near 6000.

Pete, thanks, I may yet come back to you on the subject of s/hand barrel and piston.  Could you give me an idea of the total cost inc. shipping to the UK?
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Pete Roper
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PostSubject: Re: Was planning on doing a Beetlemap, but now...   Thu Oct 11, 2018 3:36 am

If they didn't check it as the cambox was coming off, (If it's off yet?) then likely no. The cam timing marks are linked to TDC and should be checked at disassembly if there is a problem but to me it sounds like they have done a compression and leak down test and that's that so the top end may still be intact.

It may well be bore damage, but without fully exploring you won't know. Indicators show it's probably bore damage, but you don't make a decision until the fat lady sings and that requires taking it to bits and looking. Once the head is off you can see the bore and 99% of the time this sort of damage will be painfully obvious. You can also test the valves for leakage and look for the, (Very unlikely.) signs of gasket blow-by.

I'll look into the shipping costs.

Pete
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FlatTappeter
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PostSubject: Re: Was planning on doing a Beetlemap, but now...   Thu Oct 11, 2018 7:23 am

The compression and leakdown tests were done on a previous visit. The head is now off, and there is scoring around the whole circumference of the barrel.

It seems the tech was working in a vacuum of information that didn't get passed on by the reception guy Rolling Eyes.  Now that they understand rollerisation was done last year and by someone else they'll check everything thoroughly. I've had no regrets about work they've done previously.

Unfortunately they won't provide a warranty if I want them to use s/hand parts. (Anticipated as much, them being a Guzzi official dealer.)  Not sure how I feel about that, so will have to cogitate on a happy pill.
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motor-timothy
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PostSubject: Re: Was planning on doing a Beetlemap, but now...   Thu Oct 11, 2018 11:12 am

FlatTappeter wrote:

Unfortunately they won't provide a warranty if I want them to use s/hand parts. (Anticipated as much, them being a Guzzi official dealer.)  Not sure how I feel about that, so will have to cogitate on a happy pill.

In my experiences, most shops will evade responsibility anyway when something breaks, claiming it has nothing to do with their work even when its really obvious that its their fault.
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