Author Topic: Let's Go BIG 1000cc or more (Read 7090 times)

gschuld · « **Reply #25 on:** November 29, 2015, 05:57:17 PM »

For those who would enjoy some light reading from the archives:

December, 1973, Big Bike magazine: (3yrs before the big "Cobra" article came out)

Enjoy,

George

gschuld · « **Reply #26 on:** November 29, 2015, 05:58:12 PM »

2nd page

gschuld · « **Reply #27 on:** November 29, 2015, 05:58:57 PM »

gschuld · « **Reply #28 on:** November 29, 2015, 05:59:42 PM »

gschuld · « **Reply #29 on:** November 29, 2015, 06:00:16 PM »

gschuld · « **Reply #30 on:** November 29, 2015, 06:00:55 PM »

Bill/BentON Racing · « **Reply #31 on:** November 29, 2015, 06:42:05 PM »

I tried @ 5:30. It just moves from one compression stroke to the next! Crazy. It was laughing at me!!

,Bill

gschuld · « **Reply #32 on:** November 30, 2015, 04:03:46 AM »

Billy,

Are those 73mm pistons 12.5:1 in the Cobra motor?

George

BPellerine · « **Reply #33 on:** November 30, 2015, 10:25:11 AM »

Quote from: Bill/BentON Racing on November 29, 2015, 06:42:05 PM

I tried @ 5:30. It just moves from one compression stroke to the next! Crazy. It was laughing at me!! ,Bill
you got some heavy compression there Bill!!! how did it sound when it laughed.haha billp

Jerry Rxman Griffin aka MuthaF'er · « **Reply #34 on:** November 30, 2015, 06:59:25 PM »

Curious minds want to know. OK George, here you go ;-) No drooling or begging allowed!

Doesn't this make this a real 1080 and not a 1055/1060?

Sleeve thickness is 1.2mm. Kinda thin to win.

Bill/BentON Racing · « **Reply #35 on:** November 30, 2015, 08:16:54 PM »

Last time I did the math, I believe it takes 73.75 to actually get 1080 cc, send all that this way, Bill

Jerry Rxman Griffin aka MuthaF'er · « **Reply #36 on:** November 30, 2015, 08:48:46 PM »

Buncha posers!! There you go begging again LOL. I've already denied George's request. NOS to boot ;-)

Wonder if these are the same as in your Cobra Bill?

Bill/BentON Racing · « **Reply #37 on:** December 01, 2015, 04:46:00 AM »

Why, send them to me and I'll gladly compare!

gschuld · « **Reply #38 on:** December 01, 2015, 07:15:56 AM »

Nice stuff Jerry. You might have to build something with that someday

Interesting piston design. I have never seen a big bore piston that was cast and machined like that. Venolia was the exclusive piston maker for RC until about 1974, then Arias took over. The RC Arias pistons in the later 70s that I have or have seen all had specific markings cast in the mold in the underside of the piston. Like the RC 70s below:

Your pistons have a very different shape and casting design. Frankie has a 1989 vintage Arias set of 73s and his are similar to their earlier RC versions. I wonder what the deal is with those 73.75s. Perhaps Arias used a totally different piston blank for custom piston sizes beyond 73mm. Maybe Arias didn't make them...

Any idea when these pistons were originally purchased?

George

kmb69 · « **Reply #39 on:** December 01, 2015, 07:31:33 AM »

Quote from: Jerry Rxman Griffin aka MuthaF'er on November 30, 2015, 06:59:25 PM

.....
Doesn't this make this a real 1080 and not a 1055/1060?
.....

Almost.
73.75 ~~Pistons~~ Cylinders = 1076.50
74.00 ~~Pistons~~ Cylinders = 1083.81

Fixed it. Thanks, Turbo.

TurboD · « **Reply #40 on:** December 01, 2015, 08:03:56 AM »

What happens when we add .0025 clearance in each cylinder...

teebee67 · « **Reply #41 on:** December 01, 2015, 08:59:16 AM »

Can anyone tell me the actual stroke of the RC Eng big bore kits? I have one fitted and we are required to provide the stroke in mm for noise testing.

gschuld · « **Reply #42 on:** December 01, 2015, 09:10:11 AM »

63mm is stock. Plus 1/4"

George

Jerry Rxman Griffin aka MuthaF'er · « **Reply #43 on:** December 01, 2015, 09:37:55 AM »

George, not too sure of the background. I picked these up a number of years ago from a member in Texas.

It IS an RC box, that I am sure of ;-)

teebee67 · « **Reply #44 on:** December 01, 2015, 11:03:14 AM »

Thanks George - that would work out at 6.35mm = 69.35 then?

gschuld · « **Reply #45 on:** December 01, 2015, 12:03:49 PM »

Sounds about right.

George

KayOne · « **Reply #46 on:** December 01, 2015, 03:29:29 PM »

Not to highjack the thread, but thanks for posting the Big Bike article George. The pictures verify that the header that came on my K1 Chopper is a RC

gschuld · « **Reply #47 on:** December 01, 2015, 03:41:14 PM »

No problem. RC pipes have a unique 1/3 2/4 collector pattern and gentler than typical bends in the header pipes. The early ones did not have any ID markings on them.

Glad you liked the article. It's all about big bore motors

George

bear · « **Reply #48 on:** December 02, 2015, 01:29:55 AM »

A bit more big bore stuff for you.
These barrels where cast for us many years ago.
No oil leaks with these.

Retro Rocket · « **Reply #49 on:** December 02, 2015, 03:46:58 AM »

Quote from: bear on December 02, 2015, 01:29:55 AM

A bit more big bore stuff for you.
These barrels where cast for us many years ago.
No oil leaks with these.

Good looking Block there Brian... If you don't mind me asking, how many kidneys did they cost you...

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Author Topic: Let's Go BIG 1000cc or more (Read 7090 times)