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How Big Can You Get?

Tonerjockey

Tonerjockey

High Miler
GT Contributor
Joined
Oct 28, 2008
Messages
788
Location
San Jose
Hey Fellow Guzzi Mavens,

I wanna get big.... REALY BIG...

What's the max bore you've experienced on a round fin? I'm lookin to 95mm.

This engine will run for about 2 minutes at a time. WOT.

Anybody have experince with 95mm bore jobs on say... a 76 Lemans or some other "young" round fin?

Crank magnaflux, good crank bearings, Carrillo rods, custom pistons, ringed cylinder tops for copper gaskets, higher grade studs and all that jazz.

Among my concerns, besides paying for all this nonsense :whistle: , are:

Any meat left between the stud hole and piston hole
I haven't looked yet but will there be any skirt left
Sleeve vs. Nikasil
Will these things withstand 12:1 compression
and so forth.

Whatcha think?

Alex
 
I would start with a Norge/Sport 1200 motor, and have the cylinders and heads machined round... that starts you at 1163cc. :huh:
Moto Int. once offered a big bore piston for the 1064cc motors, in which the cases needed to be bored to accept. I can't remember what cc it got you to, but it didn't seem worth it to me at the time. The limitations are indeed the studs and pushrod tunnel locations.
 
People have taken 'em to 92 but if you're going to be running on dope with that sort of CR I'd be cagey about even going that big.

I take it this is some sort of drag-bike project? If so perhaps a chat with the likes of bill Ross is in order.

Pete
 
Interesting.

Gotta stick with the old round fin case, carbs etc.... it's the class I'm in (P-PP).

Land Speed Racing... similar to drag but only interested in top speed at 3 mile marker.

Bill sounds like a good resource. I'll contact Mike R. also to see what he thinks.

Thanks for the notes guys.

Alex
 
Years ago I had a friend running 95mm Fiat pistons in iron liners in his V700 ambassador. You could see the liners in between the cooling fins but it worked....
 
WOW

That sounds extreme.

I once bored out a couple VHB30's to 33mm. Hadda JB Weld the holes. After that fell out I used gas tank epoxy. Waisted 2 carbs.

I dunno about the iron liner thing... Sounds like the limit though. Thanks for the note!

Alex
 
Hey Alex, Not sure what your class goal is :huh: if you go 92 or larger you will have to go with a really short custom crank to keep it under 750cc for 750cc P-PP rules. If you bored the cases and somehow made 95`s fit, you would have a 992 cc rev monster motor with the stock crank. See you at Elmo October 25th ? Bill
 
Yo Bill,

Musing a 76 Lemans 850 with a short crank in 1000P-PP class.

Seems I can't loose enough weight to make 750 giddyup... maybe a high reving overbored Lemons with a facacta cam might do something. AND it has something of a fairing heh heh .

BonnevilleWorldFinals.jpg


I think I need to work some more on my tuck...

C ya on the dirt next weekend.

Al
 
This really is a very male forum ... and yet you're talking about bore instead of ...

oh, ok, I'm :arrow: :arrow: :arrow:



:ugeek:
 
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