Scooterotica

My Avanti has now clocked up well over 2000 miles now and has been running very well throughout the summer but seemed to be showing signs of running a bit weak and was also leaking oil onto the stator. The bottom end has done over 5000 miles having had 2 previous barrels on it. So, time for a strip down and rebuild ready for 2014.

First thing I noticed was that there was only about 400 mls of oil in the gearbox The next thing was that the exhaust stub was loose and the gasket had been blowing The stator seemed relatively clean though. Oh well new bearings and seals are on the cards and I'll probably get the big end renewed as well.

Here's some picks of the top end, the head is just as I removed it, completely spotless Never had that before The bore seems ok with a just discernible wear ridge at the top (I ran it unfiltered for the first 1000 or so miles) and some slight wear on the exhaust bridge but otherwise great. I haven't measured the ring gap but you can see that it has just started to blow by the top one.







Any comments?

unsymetrical combustion son!

fastfrog wrote:unsymetrical combustion son!

I was wondering about that, I thought the swirl marks from the transfers would be on both sides I should point out that the fuel consumption has always been on the high side (32 mpg best recorded) so any thoughts along those lines would be appreciated.

I had an Augusto fitted and strobbed the motor to retard to 16 degrees BDC, 30 PHBH, JL3, Squish was 1.5.

fastfrog wrote:unsymetrical combustion son!

How can you tell?

The flow patterns that show themselves in the carbon deposits on the piston crown.

Adam

half bat print on top of the piston

New set o rings and off you go....maybe a reed valve for MPG improvement

Yep, crown patterns can easily differ from side to side and, whilst perhaps not the 'pattern' that you might wish for, the most important factor is how the motor performs.

Adam

fastfrog wrote:half bat print on top of the piston

Please explain more, is it bad or good, us mere mortals are trying to learn

psychedelicropcircle wrote:New set o rings and off you go....maybe a reed valve for MPG improvement

New rings for certain, not sure about the reed valve though, I'm thinking it might require a bit of gouging out of the barrel (finger port?) unless the Avanti boost ports make that unnecessary? I do have an MB reed conversion manifold at my disposal though.