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Hey Skip,
Your (and other's) comments on how Guzzi increased the stroke got me
thinking. I understand that by increasing the journal height on the
cranksaft, that you will naturally increase stroke. |
| | However, it doesn't make sense to me that repositioning the wrist pin on
the piston would would effect stroke at all. Regardless of the wrist pin
location, the piston would still travel the same distance within the
cylinder. |
cylinder with a 700/750 crank and you put it on an 850 crank (using the
same rod) that caused the piston to go down furthur, but also go up
further, what would happen? The piston would not stop at the top of the
cylinder, but would continue up the extra distance caused by the extra
crank stroke. The wrist pin was relocated to keep the piston from going
up past the top of the cylinder.
| | Perhaps the wrist pin was relocated to accomodate the greater connecting
rod angle that was imposed by the increased journal height? (So that the
connecting rod would not come into contact with the side of the piston)
Also, V700 pistons had 4 rings (one below the wrist pin), Ambo pistons
had 4 rings (all above the wrist pin), and Eldo pistons had 3 rings (all
above the wrist pin). Perhaps the wrist pin relocation was simply an
artifact of the piston redesign? |
| | Another thought: My Chilton manual states that the V700 and Ambo had 9:1
compression ratios, while the Eldo had 9.2:1 compression ratio (I don't
know how accurate these numbers are). Could the wrist pin relocation
increase the compression ratio? However, I would tend to think that
other changes would have a greater impact on compression than this. |
pistons and the 850's were more flat top the heads stayed basically the
same, this counts for the different compression ratio.
| | Finally, I took a few minutes to look up part numbers for the various
connection rods and associated parts. In sum, all part numbers are
identical for the V700 and Ambo, but the Eldo part numbers are different
for all parts except the big end half bearings. Unfortunately, my parts
books do not provide part numbers for the connecting rod itself
(separate from the other parts). These differences in part numbers lead
me to believe that although the connecting rods are interchangeable
between the various models (as reported by others on this forum), that
Guzzi may have beefed up or modified the associated parts for the 850.
That being said, I do not have any of the parts in front of me to
provide direct comparisons.
SMALL END BUSHING
Model Part Number
V700 9111 2124
Ambo 9111 2124
Eldo 9111 2122
NUT FOR THE BIG END BOLT
Model Part Number
V700 9275 0082
Ambo 9275 0082
Eldo 9273 1090
LOCK PLATE FOR THE BIG END BOLT
Model Part Number
V700 1206 2300
Ambo 1206 2300
Eldo Not listed separately and not pictured in parts book
BIG END BOLT
Model Part Number
V700 1206 2200
Ambo 1206 2200
Eldo 1406 2201
HALF BEARING FOR BIG END
Model Part Number
V700 1206 2000/01/02/03/04
Ambo 1206 2000/01/02/03/04
Eldo 1206 2000/01/02/03/04
CONNECTING ROD COMPELTE WITH BUSHING, BOLT, NUTS AND LOCK PLATES
Model Part Number
V700 1206 1500
Ambo 1206 1500
Eldo 1406 1501
This turned out to me more long-winded than I originally planned...
Regards,
Greg Bender
1971 Ambassador
2000 Quota
http://www.thisoldtractor.com/gtbender
Skip & Jane wrote:
| | the 750 & 850 rods were the same. The stoke difference was in the
position
of the crank journal and the wrist pin height on the piston. I don't
know
why gauzy did it like this. You think it would have been cheaper to
just
change the rods rather than the crank and pistons. Maybe they had a
bunch
of rods they needed to get rid of. |
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