motor info:

[john fretschl]

can someone explain to me when did they started to put Bonneville motors in Chiefs? Also what are the differences between the stock 74Ci. ?

[bstevens479]

Hi John 1940-1948 pistons different, slightly higher compression, heavier valve springs,more aggressive cams & followers special carb. mods.

[someozybloke]

I have seen a sales brochure from 1939 that lists the Bonneville option.

339 "B" - $405.00
339 "M" - $425.00
339 "BM" - $450.00

might have seen it on another forum.. just remember seeing the prices.

[Lonewolf_51]

Magneto, larger cylinder head depth, high lift cams, 350 and up carb, or BONN Carb.

[T. Cotten]

A mystery Folks,

Is why the 1940 Motorcycle Parts Catalog lists Bonneville carburetor parts, when apparently Schebler didn't produce any.

Any fossil evidence would be greatly appreciated!

....Cotten

[someozybloke]

Grabbed a couple of images from the 1936 - 1942 parts Catalog that I have.

Bonneville Parts were offered for

1939-1942 Chief 74"
1939-1942 SS 45"
1940-1942 45"

Here are some of the screenshots

Bonneville Cylinders.JPGBonneville Heads.JPGBonneville Manifold.JPGBonneville Pistons 74.JPGBonneville Heads SS.JPG

They offered a Bonneville replacement for the Marvel Carb as well.

Has anyone got a Bonneville Manifold, how different is it from the standard manifold.

Mike

[someozybloke]

Missed the attachment for the Carb

Bonneville Marvel Carbs.JPG

[T. Cotten]

Someozybloke!

That carb listing is similar to the '40 book (attached);
The mystery is why there were Bonne carbs listed for '39-only twins before Linkerts were introduced for Indians in '41.

Nobody seems to have ever encountered a Schebler stamped 'Bonne', and I have never encountered a 1 1/8" Schebler venturi.
Listing in the '42 catalog as "replacements" is not such a mystery.

I have never found much of a difference (other than cast iron vs aluminum) in Chief manifolds.
Sport Scouts do vary greatly in porting, however.

You confuse me about the 'Bonne' Marvel, as I do not see the '36-only Four model listed.
( But I have encountered those with differing jets... for what that's worth.)

.....Cotten
PS: All Bonnes I have encountered appeared to be typical for Linkert's '40 or later productions. If a '39 Indian Bonne Linkert exists, it would be nickel, with the "4-line script" on the side.

[someozybloke]

Thanks for the update Cotten, it fascinates me that a company has such poor record keeping, or I guess a lot of it was lost or throw out when the company ceased trading.

It's like doing a jigsaw that is missing some of the pieces and you have no picture to work from, so really don't know what is missing anyway.

Mike

[T. Cotten]

Forensics is our task, Mike!

Parts books from many marques are questionable upon specifics, and the Indian '36-'42 is often cited for blatant flaws.

Once again, if anyone has examples from the 'fossil record' about pre-'41 Bonne's, please post us with clear photos.
As a student, I will greatly appreciate it.

....Cotten

[Lonewolf_51]

I have found eight factors that comprise a Bonneville Indian. Plus, much higher top speed than the Standard Chief with 92 mph.
1. Magneto ignition
2. Cam measurement-Lobe Height=1.575" (standard=1.510")
Base Circle Dia=1.100" (standard=1.110")
3. Cam Lifters and Followers.
4. Heads-3/4" reach to spark plug (standard-1/2")
5. Kickstarter pedal-11 tooth (standard 10 tooth). Kickstarter Gear-28 tooth (standard 32 tooth).
6. Linkert Carburetor-Stamped M-BONN, and I believe is larger than Standard Indian Chief. Linkert Stamped 350-352 will also work.
7. Heavier Valve Springs.
8. Bonneville Cylinders intake measurement different than standard Chief.