Gregory Bender

2015 February 15: Remove pistons and cylinders


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This entry is extracted from a series of email exchanges between myself, Charlie Mullendore of Antietam Classic Cycle and Gordon Kline of MG Cycle. Both Charlie and Gordon were very supportive and helpful.

Hi Gordon and Charlie,

Defeated, I gave up on any other solution to solve my excess blow-by problem. This morning I pulled the pistons and cylinders from my Convert.

I measured the clearance between each ring and the piston groove and then referenced the Guzzi workshop manuals. According to Guzzi, the clearance must be 0.0011 inch0.0024 inch. Here are my results:

Ring Left piston Right Piston
Top compression ring 0.004 inch 0.006 inch
Second compression ring 0.0025 inch 0.0025 inch
Scraper 0.002 inch 0.002 inch
Oil ring 0.002 inch 0.002 inch

Scraper and oil ring are probably fine, but the other two are out of spec (especially the top compression ring).

Gordon, I know a long time ago you mentioned ring flutter when pushing the engine hard as a possible cause of my excess blow-by. Seems to me that I may have just exactly that. Thoughts????

To reiterate my problem – the Convert does great except when I push it hard and fast uphill or do extended high speed interstate runs. Then it pushes massive oil out the breather.

My engine block is from the original V1000 I-Convert. My crankshaft is from the original V1000 I-Convert. Seems like now would be a good time to fit 1,000 cc piston/cylinder kits.

As always, your thoughts welcome and appreciated.


Gregory Bender

Charlie's reply to Gregory

That could definitely cause issues IMO. How are ring end gaps?

Yeah - may be time to just bite the bullet and fit 88 mm Gilardonis...


Gordon's reply to Gregory

Hey Greg and Charlie,

I'd say finding that is is a heck of a lot better than finding nothing, which I remember was a concern. It's *got* to be the problem. I wonder if those pistons had ever been run in cylinders that had a ridge forming at the top of the stroke. You know, where the top ring rides on the cylinder wall and changes direction and digs it's little pit.


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