Nice jugs! 1973 V7 Sport Bore Pics...

[FrankenGuzzi]

Just picked up an original-looking 1973 V7 Sport w/22k miles. Bike came with zero history/documentation. I tried the "magnet trick" on the bores through the spark plug holes, but test was inconclusive (couldn't feel if the magnet was sticking or not). Sooo...purchased an Amazon endoscope and snapped some pics. I looked around and found nothing that appears to be flaking/peeling. Finish seemed consistent throughout. The outside finish of the cylinders seem to be newer than the surrounding case/heads. Can anyone determine from the photos if these are chrome or other bores? (White line through the pic(s) is the light reflecting)







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[Dave Swanson]

The pictures appear to show evidence of micro pitting, but is not enough evidence to convict.  Further investigation is warranted. 

It is normal that the barrels and heads will have different outer casting appearance.  They are cast most likely at different casting houses. 

The chrome will not stick to a magnet at all.  Nikasil will hold onto a magnet weakly.  You should be able to tell the difference.  If not it is certainly worthwhile on such a valuable machine to remove the heads and barrels to perform a thorough investigation. 

Over 20 years ago I was in your position.  I had acquired a '73 V7 Sport with 900 miles with original chrome barrels looked absolutely pristine, except under magnification the micro pits were very evident.  I had drained the toy fund to buy the bike, and was hesitant to spend $$$ on Gilardonis, but I was given a stern lecture on this very forum to not destroy my V7 Sport.  I am glad I followed their advice. 

If all is good with your bike you are only out the expense of a top end gasket set.  If it is not good you can end up with an engine that would make a good base for a coffee table. 

[FrankenGuzzi]

The pictures appear to show evidence of micro pitting, but is not enough evidence to convict.  Further investigation is warranted. 

It is normal that the barrels and heads will have different outer casting appearance.  They are cast most likely at different casting houses. 

The chrome will not stick to a magnet at all.  Nikasil will hold onto a magnet weakly.  You should be able to tell the difference.  If not it is certainly worthwhile on such a valuable machine to remove the heads and barrels to perform a thorough investigation. 

Over 20 years ago I was in your position.  I had acquired a '73 V7 Sport with 900 miles.  The chromed barrels looked pristine, but under magnification you could see the micro pits.

Thank you.

I'll have to try the magnet test again with the aid of the endoscope. Couldn't do it by feel.

Is there a visible difference between chrome bores and nikasil?

[Gliderjohn]

Also if the motor has not been used regularly and the bike has sat for long periods of time tends to weaken the chrome. If the rest of the bike is nice I would not not risk running it at all until the cylinders are replaced with nikasil or relined with it. Not worth the risk of destroying an classic engine. My 2.5 cents worth.
GliderJohn

[Dave Swanson]

Thank you.

I'll have to try the magnet test again with the aid of the endoscope. Couldn't do it by feel.

Is there a visible difference between chrome bores and nikasil?

Can't tell by appearance.  I recommend a top end teardown to fully investigate.

If all is good with your bike you are only out the expense of a top end gasket set.  If it is not good you can end up with an engine that would make a good base for a coffee table

[Antietam Classic Cycle]

Thank you.

I'll have to try the magnet test again with the aid of the endoscope. Couldn't do it by feel.

Is there a visible difference between chrome bores and nikasil?

Your photos show what I call "starry night" - the lighter color alloy casting of the cylinder showing through the chrome plating which has been worn thin.

If they were "Nikasil", there would be cross-hatching showing, from the bore being honed. Most likely they would have the name "GILARDONI" cast into them at the outside bottom of the cylinders. 

[FrankenGuzzi]

Your photos show what I call "starry night" - the lighter color alloy casting of the cylinder showing through the chrome plating which has been worn thin.

If they were "Nikasil", there would be cross-hatching showing, from the bore being honed. Most likely they would have the name "GILARDONI" cast into them at the outside bottom of the cylinders.

Yes, checked for the Gilardoni...not there.

So...if I have to change the jugs, what's involved in installing a big-bore kit? Go big or go home... 

[Dave Swanson]

Yes, checked for the Gilardoni...not there.

So...if I have to change the jugs, what's involved in installing a big-bore kit? Go big or go home... 

IMO a V7 Sport is such a historically significant machine it would not be appropriate to go with a big bore.  A big bore will bring along a lot of other complexities in the engine build also.

Keep it a 750 you will pat yourself on the back in years to come.  Your best option is to have the current barrels plated.  While it is apart for plating it will be a good idea to inspect the bottom end also and check and clean the crank sludge trap.

[Antietam Classic Cycle]

Yes, checked for the Gilardoni...not there.

So...if I have to change the jugs, what's involved in installing a big-bore kit? Go big or go home... 

I agree with Dave. But since you asked...

https://hmb-moto.de/Engine-upgrade-V7-V7-Sport-750-S-750-S3

[FrankenGuzzi]

IMO a V7 Sport is such a historically significant machine it would not be appropriate to go with a big bore.  A big bore will bring along a lot of other complexities in the engine build also.

Keep it a 750 you will pat yourself on the back in years to come.  Your best option is to have the current barrels plated.  While it is apart for plating it will be a good idea to inspect the bottom end also and check and clean the crank sludge trap.

Sounds like good advice...and less expensive/troublesome.

Thanks again. 

[cliffrod]

The replacement V7 Sport cylinder kits from Moto Guzzi in the early 1990’s had nikasul plated bores with no external markings to differentiate them from original chrome plated cylinders.  That’s what I installed on mine back then. 

It’s not cheap but properly servicing this matter on your bike, as thoroughly as it needs to be, is the smart move.  Start being a  suspender-snapping cheapskate later, not now.

[dguzzi]

  Is sleeving not a consideration? Or why not a cast iron sleeve?

[Antietam Classic Cycle]

  Is sleeving not a consideration? Or why not a cast iron sleeve?

It was a good way to go... "back in the day", but time moves on. "Nikasil" allows tighter piston to cylinder clearances, so better ring seal and heat transfer, less friction. By the time one buys iron liners, and has them installed and sized, the cost is more than replating in "Nikasil" in my experience.