Evening Gent’s,
My 1000s lost power in a noisy fashion mid summer, Â just got around to pulling it to bits, turns out it’s eaten the lefthand head gasket, Â somehow about an inch of the metal inner ring part of the gasket has ended up in the combustion chamber marking the head+piston, I’m not too concerned about the head, (it’s cleaned up nicely), but there are two small indents on the outer edge of the piston…clean them up and reuse or replace? No marks on bore, valves unharmed, Â (inverted the head + filled combustion chamber with fuel, no leaks past valves).
Are the pistons forged or cast?
Would you reuse or replace?

Guy and me would re use…

I concur.

Reuse it is :smiley:,

Pretty sure they’ll be cast.

Good result Phil. Was the cam chain tensioner ok or are you renewing it anyway as you mentioned?

Cheers Daz

Good result indeed Daz,
motors tip top, the original cam chain tensioner is fine, I suppose that raises another question, would you leave it alone or change it to a blade type? (I’ve got the parts), to my eye it looks like the aftermarket blade type exerts more pressure, Â any comments welcome,Â

If your in there Phil, i would be tempted to change it.

Cheers Daz

So far as I understand it the rubber block type so-called ‘tensioner’ is NOT a tensioner, it merely stops the longest run of the chain flapping about.

If you try tightening it up to apply ‘tension’, it just rips the surface off the block so you end up with bits of black rubber in the sump.

Haynes manual says turn engine over to find the position where the longest run is at its tightest, then push the block across to contact it, and do up the bolts there.

That’s much more than what my kosher MG workshop manual has to say about adjusting it, which is sweet bu99er all.

The later plastic spring loaded slipper shoe type again exerts no appreciable pressure (I’ve got one), again it is just to stop the chain flailing.


Only time I replaced a Tonti type block tensioner for a fancy sprung blade, the spring came adrift, jammed in the chain, ripped the oil pump out and made for a very unpleasant 7 hour wait for the RAC at Oxford services. You have been warned. Cheers, Gerry.


But, yes.

Tensioner that’s in is the standard flapper spring type, looks like new in there even tho’ the bike’s 23 years old, big valve, b10 motor 20odd thousand miles, been ran on mobil fully synthetic 20/50 for the last 10 years,
 (contrary to popular belief no oil leaks from the seals).
So leave the standard set up alone or blade it?

I’ve changed my mind Phil. If it aint broke… :slight_smile:

Only way to go with a Guzzi.

Will leave in the flapper, it was an earlier conversation with Daz that got me thinking :smiley:
Thanks for the replies,

I too would stick to the flapper style tensioner, put it this way, would you trust something that moto guzzi has developed and have used successively for years or trust something that has been badly engineered and looks like it has been manufactured in someones shed!

The reason i say badly engineered is because of several design faults, one of which is when the blade tensioner is fitted the vertical spring on the tensioner presses hard horizontally against a lug on the engine casing causing the spring to bow, this will either fracture the tensioner spring due to it having a horizontal force placed on it or the spring will eat into the engine casing, neither of which is desirable.

The other reason is the excessive tension it generates, causing excessive radial force on the oil pump which has a  small diameter shaft supported by very small needle roller bearings housed in a delicate cage, and is clearly not designed to take this amount of force, resulting in accelerated pump ware.

 But hey, thats just my opinion! good luck with it all!

Good point Mr gates, definitely going along the “if it aint broke…don’t fix it” route.
Any recommendations on a piston ring compressor ?
 I’ve used the band of tin+jubilee clip method with success in the past, but it’s a fiddle.

Sorry but I don’t have any recommendations on a ring compressor as most of the ones on the market just seem to get in the way so I normally end up using your meathod with someone supporting the bore to make the process a little easier.

A piston ring compressor?
I’ve only ever reringed one bike, my Mk111 Le Mans about 10 years ago and we did it by hand, no tools. Whole job took less than an hour with one of us on either side.

Fancied a bit of luxury as I’m on me tod and the engine’s loose on the bench.